Field of the invention

The present invention relates generally to the field of devices, systems and methods for sanitizing or disinfecting rooms or spaces or the like, and more specifically to a method for disinfecting a room by fogging a hydrogen peroxide mixture, and a device and a computer program that performs such a method, and a system comprising such a device.

Background of the invention

Methods and devices for disinfecting or sterilizing rooms by circulating a gas stream comprising hydrogen peroxide to kill microorganisms such as e.g. viruses, bacteria, fungi, spores and yeasts are known in the art.

EP0774263(Al) and EP2952475(A1) describe such methods and devices.

There is always room for improvements or alternatives.

Summary of the invention

It is an object of the present invention to provide a method for disinfecting a room or space or the like.

It is also an object of the present invention to provide a device and a computer program that performs such method, and a system comprising such a device.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that can achieve killing of a broad spectrum of microorganisms, e.g. as specified in standard EN17272.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that can achieve killing of a broad spectrum of microorganisms, e.g. as specified in standard EN17272, in a reduced time span (counted from the start of the disinfection cycle until the room is made available again for normal use).

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program with good or improved reliability, e.g., indicating that an intended disinfection process can/cannot be performed reliably, and/or has been performed, under given conditions (e.g., temperature and humidity) and with the available means.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program having a relatively simple structure (e.g., simple hardware), and/or relatively simple complexity (e.g., without complex motor control).

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that accurately controls the amount of disinfectant (e.g., even if the flow rate is not constant). It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that efficiently manages the amount of hydrogen peroxide mixture, e.g. that uses less or as little hydrogen peroxide mixture as possible to achieve a predetermined kill rate.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program with which a disinfection cycle can be performed in a controlled manner, even if at least one of the reservoirs with hydrogen peroxide mixture is not completely filled.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that poses a low or reduced safety risk to the user and his/her immediate environment.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that is simple to use and/or that is user-friendly.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that allows a room or a space or a hall (e.g., a meeting room) with a volume of up to about 100 or up to about 145 m ³ to be reliably sterilized.

It is an object of embodiments of the present invention to provide a method, a device, a system and a computer program that allows a room or a space or a hall (e.g., a meeting room) with a volume of up to about 450 or up to about 750 m ³ to be reliably sterilized.

These and other objects are achieved by a method, a device, a system and a computer program according to embodiments of the present invention.

According to a first aspect, the present invention provides a method of disinfecting a room, e.g. to achieve killing of microorganisms, e.g. according to standard EN17272, by fogging a hydrogen peroxide mixture carried out by a fogging device (e.g. which may be referred to as, or which may comprise, a fogger, nebulizer, atomizer, disperser, ...) with connecting means for at least one replaceable reservoir with a hydrogen peroxide mixture, and with means for fogging this hydrogen peroxide mixture in the room, the method comprising the following steps: a) increasing a gas-phase hydrogen peroxide concentration in the room by (e.g., continuously) fogging a first amount of the hydrogen peroxide mixture during a first phase of a disinfection process using a first fixed-speed pump which provides air circulation through the fogging device; b) maintaining the gas-phase hydrogen peroxide concentration in the room by intermittently fogging a second amount of the hydrogen peroxide mixture during a second phase of the disinfection process by repeatedly turning the pump ON and OFF; wherein the hydrogen peroxide mixture is a silver-stabilized hydrogen peroxide mixture comprising 4.5 to 13.0 wt% hydrogen peroxide; and wherein the hydrogen peroxide concentration is maintained during the second phase at a value in the range from 45 to 180 ppm for a period in the range from 15 to 120 minutes, e.g. in the range from 45 to 120 minutes.

For example, even though the concentration may reach higher peak values locally, such as, for example, up to 250 ppm H2O2 in specific points (e.g., in local maxima, or "hot-spots," of the spatial concentration distribution), under normal use, the average H2O2 concentration in the room (e.g., averaged over at least three points in the room to which the method is applied, m.m. where the apparatus according to embodiments of a further aspect of the invention is operational, as further described below) will typically remain in the range of 45 to 180 ppm.

It will also be apparent that for a relatively small chamber, a shorter treatment time may be sufficient, and a larger chamber may potentially require a longer treatment time. As an example, a 35 m ³ chamber may possibly already be sufficiently disinfected in only 15 minutes of the substantially stabilized H2O2 (spatially averaged) concentration, i.e. in a duration time, of the second phase referred to above, of approx. 15 minutes. A larger chamber may possibly require a longer treatment, such as e.g., at least 30 minutes, or at least 60 minutes, or even up to 120 minutes.

Apart from this, it will also be clear that, for sizeable rooms (e.g., a large hallway, long corridor, industrial workshop, greenhouse, ....), it may possibly be advantageous to apply this mode of operation from multiple positions simultaneously, e.g., by operating multiple nebulizing devices in parallel from (sufficiently dispersed) positions in the room. The latter approach may be advantageous to distribute the concentration more evenly (and keep it stable) in the room, and thus may potentially reduce somewhat the required treatment time, even for a large volume to be treated (e.g., in a predetermined range as mentioned above).

Tests have shown that the kill rate is many times greater when a silver-stabilized hydrogen peroxide mixture is used (e.g. the product "Huwa-San TR-12,5", commercially available from Roam Technologies), compared to a hydrogen peroxide mixture without silver stabilization. For some microorganisms, the difference is even more than a factor of 10 or a factor of 100 times greater.

Surprisingly, testing has also shown that a maintenance period (i.e. the duration of the second phase) of approximately 15 to 120 minutes, e.g. 45 to 120 minutes, is sufficient to achieve a kill rate according to standard EN17272.

It is also an advantage of a silver-stabilized hydrogen peroxide mixture that it is much more stable, i.e. decomposes less quickly than a hydrogen peroxide mixture without silver stabilization, (e.g. the product "Huwa-San TR-12,5", commercially available from Roam Technologies, has a shelf life of approximately 2 years, compared to only a few months for similar products without silver stabilization).

It is further an advantage to use a hydrogen peroxide mixture with a hydrogen peroxide concentration of only 4.5 to 13.0 wt%, as opposed to mixtures comprising up to 30 wt% or even higher, because the product is much safer to use (less corrosion and less risk of explosion).

It is further a very great advantage to maintain the hydrogen peroxide concentration during the second phase at a value in the range from 45 to 180 ppm, or in the range from 90 ppm to 150 ppm, or in the range from 90 ppm to 130 ppm, or in the range from 90 ppm to 120 ppm, (as opposed to a gasphase H2O2 concentration of 400 ppm or even higher), because (i) it takes less time to reach such a value (shorter phasel), (ii) because such a value is achievable with a hydrogen peroxide mixture with a relatively low hydrogen peroxide concentration (safer), (iii) because such values are often achievable without conditioning the room (time savings, simpler equipment, no heater and/or dehumidifier required), (iv) because it takes much less time to lower this value back to a safe level (in a third phase), and (v) because sufficient killing can still be guaranteed, as specified in standard EN17272.

Fogging in the first phase is preferably continuous (or uninterrupted) fogging, i.e. the first pump that circulates air through the fogging device is continuously ON during the first phase.

The fogging in the second phase is an intermittent fogging, i.e. the first pump is switched ON and OFF repeatedly during the second phase, preferably at least 5 times.

Preferably, the hydrogen peroxide mixture is not heated (called "cold fogging"). This drastically reduces the risk of explosion.

A control unit of the fogging device may furthermore be provided (and adapted) to update the amount of hydrogen peroxide mixture in the at least one replaceable reservoir, taking into account a variable flow rate of the liquid mixture, in which the flow rate depends on the remaining amount of hydrogen peroxide mixture in the at least one reservoir.

The first amount of hydrogen peroxide mixture, atomized into the chamber during the first stage, and the second amount of hydrogen peroxide mixture, atomized into the chamber during the second stage, may be determined (in part) on the basis of the time that liquid is withdrawn from the at least one reservoir, and e.g. based on a linear or nonlinear relationship between the time (the total time in which liquid was already, previously, withdrawn from the reservoir) and the remaining (or, equivalently, the cumulatively consumed) amount of hydrogen peroxide mixture in the at least one replaceable reservoir, as tracked and repeatedly updated by the control unit.

It was found that this relationship can be considered linear in first approximation, but begins to deviate substantially therefrom when the reservoir contains progressively less residual product (in light of a decreasing flow rate). Therefore, another advantage of embodiments is that the required time can be estimated more accurately by taking this nonlinear deviation into account.

The nonlinear relationship between the cumulatively consumed amount of hydrogen peroxide mixture taken from the reservoir and the accumulated fogging time may correspond, specifically, to a monotonously increasing, but sublinear, function of the cumulatively consumed amount (from the reservoir) as a function of time (i.e., the total time that hydrogen peroxide mixture was withdrawn from the reservoir), or, equivalently, a superlinear function of time as a function of the consumed amount of mixture.

Such a function can be expressed, or approximated, by a polynomial. For example, the nonlinear relationship may correspond to a polynomial of at least second degree expressing total fogging time as a function of cumulative consumed quantity, preferably such a polynomial of at least fourth degree, or even more preferred, a polynomial of fourth degree. For example, the nonlinear relationship may be expressed as a polynomial of fourth degree T(M) CI+C2M+C3M ² +C4M ³ +CSM ⁴ , where T refers to time (cumulative fogging time), M to the cumulative consumption quantity (e.g., expressed in units of mass, e.g., grams), and ci to cs to predetermined coefficients of the polynomial, which may be determined experimentally (e.g., by numerical regression methods). Optionally, of course, the constant term ci can be set equal to zero.

In an embodiment, the product of the gaseous hydrogen peroxide concentration in the room and the time that this concentration is present is at least a predetermined factor, e.g., 6000. For example, at least 60 minutes x at least 100 ppm, or at least 50 minutes x at least 120 ppm, or at least 40 minutes x at least 150 ppm, or at least 75 minutes x at least 80 ppm, or at least 80 minutes x at least 75 ppm, or at least 90 minutes x at least 67 ppm, or at least 100 minutes x at least 60 ppm, or at least 120 minutes x at least 50 ppm.

In an embodiment, the integral of the gaseous hydrogen peroxide concentration in the room over time is at least 6000. This can be mathematically approximated by: (eg * AT) >6000, where eg is the gaseous hydrogen peroxide concentration in the room (expressed in ppm), and AT is the duration of a period during which this concentration was measured (expressed in minutes).

In an embodiment, the factor (6000 in the above example) is operator adjustable.

In an embodiment, killing of microorganisms is achieved according to standard EN17272.

In an embodiment, a ratio of the weight percent hydrogen peroxide to the weight percent silver ions is a value in the range from 1500 to 2000, preferably in the range from 1600 to 1900.

Such a ratio ensures very good killing of microorganisms.

In an embodiment, the hydrogen peroxide mixture consists of hydrogen peroxide and demineralized water and silver ions.

This mixture therefore does not comprise any other substances such as chlorine or peracetic acid.

In an embodiment, the silver-stabilized hydrogen peroxide mixture consists of a mixture of 12.1 to 12.5 wt% hydrogen peroxide, and 0.0059 to 0.0079 wt% silver as a stabilizer, and demineralized water (the remaining wt%); Such a product is commercially available from "Roam Technologies" under the product name "Huwa-San TR-12,5".

In an embodiment, the silver-stabilized hydrogen peroxide mixture consists of 7.5 to 7.9 wt% hydrogen peroxide, and 0.0042 to 0.0053 wt% silver as stabilizer, and demineralized water (the remaining wt%). Such a product is commercially available from "Roam Technologies" under the product name "Huwa-San TR-7,9".

In an embodiment, the silver-stabilized hydrogen peroxide mixture consists of 11.5 to 11.9 wt% hydrogen peroxide, and 0.0057 to 0.0074 wt% silver as stabilizer, and demineralized water (the remaining wt%). Such a product is commercially available from "Roam Technologies" under the product name "Huwa-San TR-11,9". In an embodiment, the silver-stabilized hydrogen peroxide mixture consists of 4.5 to 4.9 wt% hydrogen peroxide, and 0.0027 to 0.0035 wt% silver as stabilizer, and demineralized water (the remaining wt%). Such a product is commercially available from "Roam Technologies" under the product name "Huwa-San TR-5".

In an embodiment, the method further comprises the following steps: i) collecting data regarding the hydrogen peroxide mixture and regarding the room to be disinfected; ii) verifying whether the collected data meets certain conditions in order to be able to successfully carry out the fogging process; and if the certain conditions are not met, giving an error message; and if all conditions are met, continuing with step a).

The data or parameters related to the hydrogen peroxide mixture may comprise one or more of the following values: the volume of the hydrogen peroxide mixture available in one or more reservoirs connected to the fogging device, its composition, expiration date or date of manufacture.

The data or parameters related to the room to be disinfected may comprise one or more of the following values: the temperature of the air in the room, the relative humidity of the air in the room, the volume of the room.

"Be able to successfully carry out" is understood to mean that the preconditions are met to achieve an intended kill, e.g. a LOG4 or LOG5 kill of certain bacteria, e.g. as specified in the EN17272 standard.

In an embodiment, the collecting step comprises: c) determining or receiving a volume of the room to be disinfected (and possibly also a text string associated with the room, e.g. a name of the room); d) determining the concentration of hydrogen peroxide in the hydrogen peroxide mixture in the at least one replaceable reservoir; e) estimating an amount of hydrogen peroxide mixture required to obtain (during the first phase) and maintain (during the second phase) said gaseous hydrogen peroxide concentration; f) determining how much hydrogen peroxide mixture is available in the at least one replaceable reservoir; g) giving an error message if the amount of hydrogen peroxide mixture present is less than the required amount of hydrogen peroxide mixture (to successfully complete the disinfection process, e.g. according to standard EN17272).

The hydrogen peroxide concentration of the hydrogen peroxide mixture may, for example, be entered by an operator via a touch screen, or may, for example, be read from an (optional) RFID tag, if present on the at least one reservoir.

The available amount of hydrogen peroxide mixture in the at least one replaceable reservoir can, for example, be entered by an operator via a touch screen, or can, for example, be read from the optional RFID tag, if present.

It is an advantage that it is checked in advance whether a "successful disinfection cycle" can be carried out before actually starting the cycle. This allows an operator to e.g. replace a fairly empty reservoir with a full reservoir, or to preheat the room (e.g. by using an external air heater), etc. In an embodiment, the required amount of hydrogen peroxide mixture in step e) is determined based on the following formula: NH = KV * A, where NH is the required amount of hydrogen peroxide mixture (expressed in ml), and where KV is the volume of the room (expressed in cubic meters), and where A is a predetermined value (expressed in ml/m ³ ) which depends on the hydrogen peroxide concentration in the hydrogen peroxide mixture.

In an embodiment, the required amount of hydrogen peroxide mixture in step e) is determined based on the following formula: NH = KV * A, where NH is the required amount of hydrogen peroxide mixture (expressed in ml), and where KV is the volume of the room (expressed in cubic meters), and where A is a value (expressed in ml/ m ³ ) that is calculated based on the hydrogen peroxide concentration in the hydrogen peroxide mixture, and on one or more of the following parameters: Troom, RHroom, and Vroom, where Troom is the temperature of the room, RHroom is the relative humidity of the room, and Vroom is the volume of the room.

It is an advantage of this embodiment that the value of A can be further refined by also taking into account the temperature and relative humidity of the room. As a result, the time of the disinfection cycle can possibly be shortened somewhat, and/or some hydrogen peroxide mixture can be saved, without compromising the disinfection process.

In an embodiment, the method further comprises a step of: c) actively reducing or passively decreasing the gas-phase hydrogen peroxide concentration in the room to a predetermined value of not more than 1.0 ppm, during a third phase, before indicating or reporting that the disinfection process is complete.

In other words, step c) is completed when the gas-phase hydrogen peroxide concentration in the room has dropped to a value equal to or less than 1.0 ppm.

It is an advantage to actively extract hydrogen peroxide from the air of the room, because in this way the H2O2 concentration in the room can be reduced more quickly, and the room can be released again more quickly. Typically, this reduces the time of the third phase by a factor of about two compared to passively decreasing the hydrogen peroxide concentration.

In an embodiment, step c) comprises actively reducing the gas-phase hydrogen peroxide concentration in the room using a catalyst.

For example, the catalyst may be a metal catalyst, e.g., a platinum/alumina catalyst, or a ruthenium/alumina catalyst, but the invention is not limited thereto, and another suitable catalyst may also be used.

In an embodiment, step c) comprises actively reducing the hydrogen peroxide concentration using a scrubber.

The scrubber may, for example, comprise an activated carbon filter. In an embodiment, the method comprises the use of both a scrubber and a catalyst. In this way, the duration of the third phase can be further shortened. Of course it is also possible to provide several scrubbers, spread over the room.

In an embodiment, the method comprises a third phase, with a first part of passively decreasing the gas-phase hydrogen peroxide concentration in the room for a predetermined period of time (e.g. 15 minutes, or 30 or 45 or 60 or 75 or 90 minutes); and with a second part of: actively reducing the gasphase hydrogen peroxide concentration in the room to a predetermined value of not more than 1.0 ppm, before indicating or reporting that the disinfection process is complete. In this way, the contact time can be slightly extended in order to achieve a higher kill rate.

In an embodiment, the method further comprises the step of: iv) reporting and/or displaying that the disinfection process has been completed.

This notification means that the room may be re-entered without personal protective measures such as a gas mask. The notification can be an announcement or a message or a communication sent or displayed by a control unit of the fogging device performing the method, and/or by a hydrogen peroxide sensor, and/or by a laptop that is communicatively connected to the sensor and with the fogging device, e.g. a text message, a GPRS message, a UMTS message, a message on the screen of a remote control unit, or on the screen of a laptop or a smartphone that is communicatively connected to the fogging device.

In an embodiment, the method further comprises the step of: v) reporting and/or displaying whether or not the disinfection process has been carried out successfully, e.g. by checking whether a power interruption has occurred while the disinfection process was active, or e.g., in the case of control in "closed loop," by verifying whether an abnormal amount of hydrogen peroxide mixture had to be fogged to achieve the target gas-phase concentration (e.g., 100 ppm). Such an abnormally high value can, for example, be the result of a window that was open, or a door that was open.

In embodiments where the gaseous hydrogen peroxide concentration in the room is not only measured, but also transmitted to a central server (e.g., as shown in FIG. 5B), preferably together with a timestamp, the determination of whether the disinfection process has been successfully carried out may be determined by the central server, e.g., by statistical analysis of the measured concentrations and timestamps for the specified room conditions and the disinfectant used.

In an embodiment, the fogging device comprises a first fluid circuit, having a first pump, and having a first inlet for receiving a first gas stream from the room, and having a connection to the at least one replaceable reservoir with the hydrogen peroxide mixture, and means for adding droplets (e.g. 20 to 30 microns in average diameter) of the hydrogen peroxide mixture to this first gas stream, and having a first outlet for delivering this first gas stream containing these droplets to the room; and the first fluid circuit is provided to add the droplets of hydrogen peroxide mixture to the first air stream by means of a liquid pump or on the basis of the Venturi principle. If a liquid pump is used, it preferably has a constant speed and a constant flow rate, so that its control comprises simply activating or switching off this liquid pump. This allows to determine the amount of the mixture by the time that the first pump and the liquid pump are both active.

When the liquid mixture is sucked up based on the Venturi effect, a liquid pump can be avoided, which contributes to the simplicity of the fogging device.

A disadvantage of this is that the flow rate of the liquid flow is not constant but depends on the actual amount of liquid in the reservoir. However, it is possible to calculate this amount starting from a known initial amount (e.g. when a user enters the initial amount in the reservoir via the touchscreen, or when the reservoir contains an RFID tag. However, the latter is not strictly necessary. In either case, a control unit of the fogging device can repeatedly update the amount of fluid, storing it in a local memory (e.g. RAM), and/or non-volatile memory (e.g. Flash or EEPROM), and/or write it to the RFID tag if present.

In a preferred embodiment, the velocity of the first gas stream is a velocity of 50 to 70 m/s (e.g. about 60 m/s), and the suction channel of the liquid mixture has an internal diameter of 5 to 7 mm (e.g. 6 mm ).

In an embodiment, the first pump has a fixed speed, and the fogging device control unit is arranged to switch the first pump either ON or OFF.

It is an advantage that the first pump has a fixed speed, and that the control unit does not have to regulate speed. This requires less complex hardware and software of the fogging device.

In an embodiment the first fluid circuit is provided to add the droplets of hydrogen peroxide mixture to the first air stream based on the Venturi principle; and a control unit of the fogging device is provided to update the amount of hydrogen peroxide mixture in the at least one replaceable reservoir, taking into account a variable flow rate of the liquid mixture (due to the Venturi effect), wherein the flow rate depends on the amount of hydrogen peroxide mixture still present in the at least one reservoir.

In a preferred embodiment, the flow rate of the liquid drawn from the reservoir varies by a factor of at least 1.5 (150%) between a substantially full reservoir and a substantially empty reservoir, or by a factor of at least 160%, or by a factor of at least 170%, or by a factor of at least 180%, or by a factor of at least 190%.

It is not trivial to accurately calculate the amount of liquid remaining in the reservoir for a suction based on the Venturi principle, but an accurate estimation of the amount remaining is important to obtain an optimal compromise between: i) being able to guarantee sufficient killing, ii) wasting as little hydrogen peroxide mixture as possible (or in other words: using the amount of hydrogen peroxide mixture present as optimally as possible), iii) performing the shortest possible disinfection cycle, iv) maintaining a constant or substantially constant hydrogen peroxide concentration during the second phase (the "contact phase"), e.g. in open-loop control.

In an embodiment, the remaining amount of hydrogen peroxide mixture in the at least one reservoir is calculated iteratively, taking into account the initial contents and assuming that the instantaneous rate of flow changes linearly as a function of the amount of hydrogen peroxide mixture in the at least one reservoir between a first flow rate value associated with a substantially full reservoir, and a second flow rate value associated with a substantially empty reservoir.

This implies that the amount of mixture in the reservoir varies non-linearly as a function of the time that liquid is drawn from the reservoir.

FIG. 6 shows a measurement of the flow rate of a prototype fogging device. In this example, the first value (corresponding to a full reservoir) is about 62 ml/min, and the second value (corresponding to a substantially empty reservoir) is about 30 ml/min.

FIG. 7 and FIG. 8, derived from FIG. 6, show that the flow rate and the volume of liquid mixture remaining in the reservoir change non-linearly as a function of the time that liquid mixture is drawn from the reservoir.

FIG. 8 also shows that the time required to withdraw 500 ml of liquid mixture from a substantially full reservoir (in the example 500 sec) differs very strongly from the time required to withdraw the same amount of liquid mixture from a substantially empty reservoir (in the example: 790 sec).

In practice, this can be implemented by using a lookup table with at least two columns, where one column comprises the cumulative time that liquid mixture is drawn from the reservoir (or in other words: that the first pump is active, and the relevant valve is open), and a second column comprising the remaining amount of hydrogen peroxide mixture. For example, the table can comprise values for discrete time intervals of multiples of 10 seconds, or multiples of 20 seconds, or multiples of 30 seconds, or multiples of 1 minute, but of course a table with other intervals can be used. Optionally, values from the table can be interpolated. Alternatively, it is also possible to calculate the variable flow rate and/or the remaining amount of liquid using mathematical formulas.

In an embodiment, the first amount of hydrogen peroxide mixture that is fogged into the room during the first phase of the disinfection process and the second amount of hydrogen peroxide mixture that is fogged into the room during the second phase of the disinfection process are determined based on the time that liquid is drawn from the at least one reservoir.

When the hydrogen peroxide mixture is drawn based on the Venturi principle, only the time that the first pump is active is relevant. When the liquid mixture is drawn from the reservoir by means of a liquid pump, the time that both the first pump and the liquid pump are active should be considered.

This method uses a so-called "open loop" control. In this method, it is not necessary for the fogging device to contain a hydrogen peroxide sensor or to be communicatively connected to it, but it is sufficient to control the first pump based on known characteristics of the device and known parameters of the room, e.g. using tables generated during calibration testing, possibly supplemented by information obtained from fogging devices "in the field" when connected to a central server (e.g., as shown in FIG. 5B). When the fogging device is communicatively connected to a central server (as in FIG. 5B), the necessary time information (e.g. the duration of the first phase and the second phase for certain room parameters and for a certain hydrogen peroxide mixture) may also be retrieved to the server. Based on statistical analysis of data received from multiple fogging devices, the server can determine the necessary times to disinfect rooms of various sizes and under various combinations of temperature and relative humidity.

In an embodiment, the fogging device further comprises or is communicatively connected to at least one hydrogen peroxide sensor; and the method further comprises repeatedly receiving a measured value from this sensor, and the method comprises controlling the first pump taking into account the measured values.

The communicative connection may be a cable connection (e.g. USB, Ethernet, RS232, etc.) or may be a wireless connection, e.g. an RF connection (e.g. Bluetooth, Wi-Fi), or an optical connection (infrared).

In this way, the fogging device knows the actual gas-phase hydrogen peroxide concentration in the room, and the first pump can be controlled more precisely, e.g. no longer than necessary to allow the hydrogen peroxide concentration in the room to rise to a value in the intended range (e.g. 100 to 120 ppm) during the first phase and second phase, and to start and stop the first pump in a timely manner during the second phase so that hydrogen peroxide concentration in the room remains in the target range (e.g. 100 to 120 ppm).

In an embodiment, the fogging device further comprises or is communicatively connected to at least two hydrogen peroxide sensors; and the method further comprises repeatedly receiving a measured value from these sensors, and the method comprises controlling the first pump, taking into account the measured hydrogen peroxide concentration values, a minimum of the at least two measured values being considered an effective value during the first and second phase of the disinfection process, and where a maximum of the at least two measured values is considered an effective value during the third phase of the disinfection process.

In an embodiment, the fogging device further comprises an RF communication module (e.g. WiFi or Bluetooth or Zigbee) and/or a mobile data communication module for transmitting data via mobile internet, e.g. via a 3G or a 4G or a 5G network, e.g. via SMS or GPRS or UMTS, and the method further comprises the following steps: detecting an abnormal rise in the gaseous hydrogen peroxide concentration in the room during the first phase of the disinfection process; and if an abnormal rise is detected, sending an alarm message via the RF communication module and/or via the mobile data communication module.

Detecting an abnormal rise may comprise, for example, measuring a current gaseous hydrogen peroxide concentration in the room, and comparing it to an alarm value. The alarm value can e.g. be calculated as a function of the cumulative time that the first pump was activated, taking into account the parameters of the room to be disinfected (e.g. volume, temperature, relative humidity), or can be determined based on a predetermined table. By sending such an alarm message, an operator can be notified as quickly as possible, and accidents can be avoided, e.g. to bystanders who were in the vicinity of the room of which e.g. a door was accidentally left open.

In an embodiment, the fogging device further comprises an RF communication module (e.g. WiFi or Bluetooth or Zigbee) and/or a mobile data communication module for transmitting data via mobile internet, e.g. via a 3G or a 4G or a 5G network, e.g. via SMS or GPRS or UMTS, and the method further comprises the following steps: sending to a central server, by the fogging device, the collected data regarding the hydrogen peroxide mixture and regarding the room to be disinfected; sending to the central server, by the fogging device, a plurality of measured values of gaseous hydrogen peroxide concentration in the room, preferably together with a timestamp; the receipt by the central server of the collected data and the measured values, and the storage by the central server of this data on a storage medium (e.g. a hard disk or a network disk); analyzing, by the central server, the received data and values, in order to detect an abnormality; (e.g. an abnormal rise in hydrogen peroxide concentration under the given conditions); and reporting a result of the analysis to the fogging device.

It is an advantage (for the manufacturer) that a lot of statistical information can be collected in this way, which can be used for drawing up tables, and/or for improving process parameters, and/or for giving advice to users of the fogging device.

It is also an advantage (for the user/operator) that their process is monitored (if desired), and they receive quick feedback if an abnormality is detected, e.g. a report that the fogging device or a sensor unit or the like is not functioning as expected. In this way, the reliability of the disinfection process can be further increased, as well as the safety of the users of the fogging device and bystanders.

If necessary, a "name of the room" will also be sent. Optionally, the initial and final amount of hydrogen peroxide mixture in the at least one reservoir is also sent along, from which the consumed amount of hydrogen peroxide mixture can be derived.

In an embodiment, the second phase of the disinfection process is divided into a predetermined number (N) of intervals; and a substantially equal amount of hydrogen peroxide mixture is fogged in each of these intervals (e.g. accurate to ±5%).

Preferably, the number of intervals is two to fifteen intervals.

The intervals may be of equal duration (e.g., as illustrated in FIG. 15A or FIG. 15B), or may be of unequal duration. This amount corresponds to "the second amount" divided by the number of intervals "N."

It is not trivial to inject equal amounts of the liquid mixture into the room, if the Venturi principle is used, because the flow rate is not constant, but depends on the fill factor of at least one reservoir, but it is technically possible by keeping track of this fill factor and updating it repeatedly, as described above. In an embodiment, the at least one reservoir carries an RFID tag that stores data comprising at least an amount of the hydrogen peroxide mixture; and the fogging device further comprises at least one RFID reader/writer communicatively connected to the control unit, and the control unit is configured to read data from the RFID tag of the at least one reservoir; and the method further comprises the step of: writing to the RFID tag repeatedly to update the amount of hydrogen peroxide mixture on the RFID tag of the at least one reservoir.

It is a great advantage if the replaceable reservoir comprises an RFID tag, and if the fogging device comprises an RFID reader/writer, as this way information about the hydrogen peroxide mixture can be passed to the device without human intervention, thus with a reduced risk on errors.

The RFID tag makes it possible, among other things, to check whether the reservoir comprises the correct contents, or in other words, to detect whether a reservoir with a wrong mixture has been connected.

It is an advantage that the RFID tag comprises the initial amount of hydrogen peroxide mixture (e.g. 1000 ml, or 3000 ml), and that the control unit is equipped to repeatedly update this amount, or keep it up-to-date, so that the RFID tag indicates the remaining amount of the hydrogen peroxide mixture in the reservoir at any time. In this way, the fogging device can check whether there is sufficient hydrogen peroxide mixture present before starting a (new) disinfection cycle. In this way, the RFID tag can therefore help to successfully complete a disinfection cycle and waste as little hydrogen peroxide mixture as possible.

Although it is in principle possible to update the contents of the reservoir only once at the end of a disinfection cycle, it is an advantage to update the contents repeatedly, e.g. periodically, e.g. at least once per minute, or at least once every 30 seconds, or at least once every 15 seconds, or at least once every 10 seconds, because this drastically reduces the risk of a large deviation between the actual amount of the hydrogen peroxide mixture on the one hand, and the amount as indicated on the RFID tag on the other hand, even in the event of a power failure.

It is an advantage to communicate contactlessly (via RFID) as opposed to galvanic contact, due to the corrosivity of the mixture.

The use of an RFID tag also ensures that a user cannot use a product that the device is not familiar with, or with which the device cannot perform proper disinfection, e.g. a hydrogen peroxide mixture of too low a concentration (e.g. with only 3 wt% H2O2 concentration).

The use of an RFID tag on the reservoir also ensures that if a user were to place a half-full reservoir in another similar fogging device, the device would automatically recognize that this reservoir is only half full.

The RFID tag also allows a device with at least two reservoirs to start a disinfection cycle with a reservoir that is not completely filled. Thus, the user does not have to throw away hydrogen peroxide mixture (economical, or efficient use), or decant it (safety), and yet the device is able to introduce the correct amount of hydrogen peroxide into the room (reliability). This is particularly non-trivial for a device without a liquid pump, but where the liquid is drawn from the reservoir by the Venturi principle.

In an embodiment, the data on the RFID tag indicating the amount of hydrogen peroxide mixture in the at least one reservoir is updated at least once per minute that fluid is drawn from the respective reservoir, preferably at least 2x or at least 3x or at least 5x per minute that the first pump (and/or the liquid pump, if present) is active, and the first or second valve is open.

Of course, the amount is not updated if the first pump is OFF, or if the third reservoir is used (for rinsing).

In an embodiment, the data on the RFID tag of the at least one reservoir also comprises a value of a concentration of hydrogen peroxide in the hydrogen peroxide mixture; and the method further comprises the step of: reading this concentration value stored on the RFID tag.

This value can e.g. be used to calculate the required amount of hydrogen peroxide mixture to be fogged in the first and second phase to disinfect a certain room. This value can also be used during the disinfection cycle itself, e.g. to determine the duration T1 of the first phase, and/or to determine the duty cycle of the second phase.

By storing the hydrogen peroxide concentration of the hydrogen peroxide mixture on the RFID tag, the fogging device can optimally take into account the hydrogen peroxide mixture. This greatly increases the flexibility of the device, as it can work with different hydrogen peroxide mixtures.

In an embodiment, the data on the RFID tag of the at least one reservoir further comprises an expiration date of the hydrogen peroxide mixture, and the method further comprises steps of: determining (e.g. requesting or retrieving) a current date, and comparing the expiration date with the current date, and giving an error message if the expiration date has passed.

Determining the current date can be done, for example, by requesting it from an external device such as a smartphone or a laptop, or by reading a local clock, or by retrieving the date from a website, or the like.

By checking the expiration date of the reservoir, or if several reservoirs are present, of each reservoir, the reliability of effective disinfection or killing of microorganisms such as viruses, bacteria, fungi, spores and yeasts can be increased.

In an embodiment, the data on the RFID tag of the at least one reservoir further comprises a date of manufacture; and the method further comprises the step of: adjusting the concentration of the hydrogen peroxide mixture read from the RFID tag based on the date of manufacture and the current date.

It is known that the hydrogen peroxide concentration in the hydrogen peroxide mixture decreases spontaneously with time (although this decrease is much smaller in the case of a silver- stabilized hydrogen peroxide mixture). In this embodiment, this decrease is taken into account in order to be able to guarantee the effect of sufficient killing, or at least approach it as closely as possible. In an embodiment, the fogging device further comprises a first valve for selectively connecting a first replaceable reservoir to the first fluid circuit, and further comprises a second valve for selectively connecting a second replaceable reservoir with a second hydrogen peroxide mixture to the first fluid circuit; and the second reservoir comprises a second RFID tag storing data comprising at least an amount of the second hydrogen peroxide mixture; and the method further comprises the step of: repeatedly updating the RFID tag of each reservoir from which hydrogen peroxide mixture is drawn.

It is a great advantage to use a fogging device with connection for two reservoirs, because in this way it is possible to avoid losing hydrogen peroxide mixture (or rather: leaving it unused), and because it avoids the need for a user to decant hydrogen peroxide mixture, with all the risks that this entails. This also makes it possible to disinfect a larger room (or space).

By using two reservoirs, the control unit can switch from the first to the second reservoir, or vice versa, at a convenient time, in order to lose as little hydrogen peroxide mixture as possible (leave it unused).

In a fogging device according to the present invention, the two reservoirs are not used simultaneously to fog hydrogen peroxide mixture, but either the first reservoir or the second reservoir. The first and second valves allow choosing which of the two reservoirs is connected to the nozzle (or nozzles). These valves are controlled by the control unit. The RFID tag of the reservoir that is fluidly connected is updated repeatedly.

In an embodiment the fogging device comprises a first RFID reader/writer arranged to communicate only with the RFID tag of the first replaceable reservoir; and the fogging device comprises a second RFID reader/writer arranged to communicate only with the RFID tag of the second replaceable reservoir; and the method further comprises the step of: communicating with the RFID tag of the first reservoir via the first RFID reader/writer (e.g., repeatedly when fluid is drawn from the first reservoir), and communicating with the RFID tag of the second reservoir via the second RFID reader/writer (e.g. repeatedly when fluid is drawn from the second reservoir).

It is an advantage to use two separate RFID reader/writers, one for each reservoir, because the control unit can then determine for itself how much liquid each of the reservoirs comprises, without human intervention. In this way, the risk of human error is reduced or completely eliminated, thus increasing the reliability of a successful disinfection cycle.

In an embodiment, the fogging device further comprises electromagnetic shielding to prevent the first RFID reader/writer from communicating with the RFID tag of the second reservoir, and vice versa, or to reduce interference.

The RFID tag is preferably a passive RFID tag, operating at a frequency of 13.56 MHz.

Testing has shown that such an RFID tag is effective over a sufficient distance from the reservoir and can provide sufficient power to read and write data reliably, at a sufficiently high read/write speed.

The RFID tag preferably has a memory of at least 512 bytes, or at least 1024 bytes. Although not all bytes are available for the fogging device, such an RFID tag is very suitable for the current application. Preferably an RFID tag with an EEPROM memory is used because it allows to overwrite the "amount of mixture," although this is not strictly necessary, and it is also possible to work with an RFID tag of which not every byte can be individually overwritten without erasing an entire sector. The latter would be considerably more complex in terms of software.

In an embodiment, the data on the RFID tag is encrypted, and the method further comprises the steps of: decrypting data read from the RFID tag, and encrypting data written to the RFID tag.

It is an advantage to encrypt the communication with the RFID tag to prevent the data on the reservoir from being accidentally changed or deleted by an unauthorized user. This helps to guarantee the reliability of a "successful disinfection cycle."

It should be noted that it is not necessary for all information to be encrypted. For example, the invention would still work if one or more of the values selected from the group consisting of the product name, concentration, and expiration date were unencrypted on the RFID chip. For example, this would allow an employee with a smartphone (or other device that supports NFC communication) to read the RFID tag of a reservoir before inserting it into the fogging device.

In a specific embodiment, at least one of: the product name, the concentration, and the expiration date are stored both encrypted and unencrypted on the RFID tag.

According to a second aspect, the present invention also provides a fogging device comprising: at least one replaceable reservoir with a hydrogen peroxide mixture; and a control unit; and means for fogging the hydrogen peroxide mixture, the control unit being arranged to carry out a method according to the first aspect.

According to a third aspect, the present invention also provides a fogging system comprising: a fogging device according to the second aspect; and one or more external devices selected from: a hydrogen peroxide sensor, a temperature sensor, a relative humidity sensor, a remote control unit, a fan or a ventilator, an air heater, a dehumidifier, an external scrubber, a laptop, a tablet or a smartphone, a central server, the external device being communicatively connected with the control unit of the fogging device.

According to a fourth aspect, the present invention also provides a computer program product for disinfecting a room, the computer program product comprising executable instructions which, when executed on the control unit of a fogging device according to the second aspect or of a fogging system according to the third aspect, cause the fogging device to perform a method according to the first aspect.

Particular and preferred aspects of the invention are set out in the appended independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims. These and other aspects of the invention will become apparent and elucidated with reference to the embodiments described below.

Brief description of the drawings

FIG. 1A shows a first example of a fogging device according to an embodiment of the present invention, also referred to herein as a "small fogger", in perspective view. A reservoir with a hydrogen peroxide mixture is connected to the fogging device. The reservoir optionally comprises an RFID tag with therein a field that displays the amount of hydrogen peroxide in the reservoir. The fogging device optionally has an RFID reader/writer provided to keep this amount up to date.

FIG. IB shows the reservoir of FIG. 1A with an RFID tag. The RFID tag is also shown magnified with increased contrast.

FIG. 2A shows a block diagram of a possible embodiment of the fogging device of FIG. 1A, wherein liquid is drawn from the at least one reservoir based on the Venturi principle.

FIG. 2B shows a block diagram of a variant of the fogging device of FIG. 2A, wherein liquid is drawn from the at least one reservoir by means of a liquid pump.

FIG. 3A shows a second example of a fogging device according to an embodiment of the present invention, also referred to herein as a "large fogger", in perspective view. Space is provided in the device for at least two reservoirs with hydrogen peroxide mixture. Each reservoir optionally has an RFID tag with therein a field that represents the amount of hydrogen peroxide in the respective reservoir. The fogging device optionally comprises two RFID reader/writers, each adapted to communicate with one RFID tag. The device is optionally provided to keep the amounts indicated in the RFID tags up to date.

FIG. 3B and FIG. 3C show an example of a reservoir that may be used in conjunction with the fogging device of FIG. 3A. The RFID tag is also shown magnified with increased contrast.

FIG. 4A shows a block diagram of a possible embodiment of the fogging device of FIG. 3A, wherein liquid is drawn from the at least one reservoir based on the Venturi principle.

FIG. 4B shows a block diagram of a variant of the fogging device of FIG. 4A, wherein liquid is drawn from the at least one reservoir by means of a liquid pump.

FIG. 5A shows a fogging system comprising a fogging device according to an embodiment of the present invention, and one or more external devices selected from: a hydrogen peroxide sensor, a temperature sensor, a relative humidity sensor, a remote control unit, at least one fan or ventilator, an air heater, a dehumidifier, an external scrubber, a laptop or a tablet or a smartphone, the external device being operationally and/or communicatively connected to the control unit of the fogging device.

FIG. 5B shows a variant of the fogging system of FIG. 5A, with a hydrogen peroxide sensor, and with a central server, communicatively connected to the fogging device, e.g. via an internet connection.

FIG. 6 shows an illustrative curve representing the flow rate of the liquid hydrogen peroxide mixture from the reservoir as a function of the fill factor of the reservoir, as applicable in fogging devices according to the present invention that utilize the Venturi effect. FIG. 7 shows another representation of the curve of FIG. 6, showing the fluid flow rate as a function of the cumulative time of the emptying of a reservoir.

FIG. 8 shows a curve representing the contents of a 3000 ml reservoir, as a function of the cumulative time, corresponding to the fluid flow rate of FIG. 6, illustrating, for example, that it takes much less time to withdraw 500 ml of liquid mixture from a full reservoir than from one that is substantially empty. This curve shows that, in order to obtain a good estimate of the flow rate of the liquid mixture, a good knowledge of the contents of the reservoir is necessary. In other words, this curve shows that a good knowledge of the contents of the reservoir is necessary to make a good estimate of the time it takes to withdraw a certain amount of mixture from the reservoir.

FIG. 9A shows three curves representing the maximum gaseous hydrogen peroxide concentration that can be achieved by so-called "cold fogging" (i.e., fogging without heating the liquid mixture), as a function of ambient temperature and relative humidity in a room.

FIG. 9B shows a curve illustrating minimum room temperature as a function of relative humidity to achieve a gaseous hydrogen peroxide concentration of 100 ppm in the room by "cold fogging" of a hydrogen peroxide mixture comprising substantially 87.5 wt% water and substantially 12.5 wt% hydrogen peroxide.

FIG. 10 to FIG. 13 illustrate a method according to the present invention.

FIG. 14A is an illustrative representation of an ideal course of the concentration of gaseous H2O2 in the room during a disinfection process.

FIG. 14B is an illustrative representation of a possible course in practice of the concentration of gaseous H2O2 in the room, during a disinfection process according to a method proposed by the present invention, which is carried out by a fogging device in "open-loop" control, i.e. without measurement of the gaseous H2O2 concentration in the room.

FIG. 14C is an illustrative representation of a possible course in practice of the concentration of gaseous H2O2 in the room, during a disinfection process according to a method proposed by the present invention, which is carried out by a fogging device in "closed-loop" control, i.e. with measurement of the gaseous H2O2 concentration in the room.

FIG. 15A shows an example of "intermittent fogging" with a fixed interval time and a fixed duty cycle.

FIG. 15B shows an example of "intermittent fogging" with a fixed interval time and a variable duty cycle.

FIG. 16 shows an illustrative graph of cumulative fogging time as a function of cumulative consumption of the hydrogen peroxide mixture in the reservoir, for the sake of illustrating embodiments of the present invention.

Detailed description of illustrative embodiments The present invention will be described with respect to particular embodiments and with reference to certain drawings, but the invention is not limited thereto but only by the claims. The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not necessarily correspond to actual reductions to practice of the invention.

Furthermore, the terms "first," "second" and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

It is to be noticed that the term "comprising," used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "In an embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of illustrative embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects are in less than all the features of a single prior disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some, but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those skilled in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

In this document, "fogging device" is also referred to as "fogger," "disinfection device" and "sterilization device."

In this document, the term "room" is used for an enclosed space. For example, this term can refer to a hospital room, a meeting room in a company, etc.

References in this document to "humidity" or "degree of humidity," without reference to absolute humidity or relative humidity, mean the relative humidity of the room air.

In this document the terms "liquid mixture" and "hydrogen peroxide mixture" are used synonymously.

In this document, the terms "disinfection cycle" and "disinfection process" are used synonymously.

When referring to "hydrogen peroxide concentration in the room" in this document, it means the hydrogen peroxide concentration in gaseous form, unless explicitly stated otherwise, or unless clear from the context that something else was intended.

In this document, when referring to "hydrogen peroxide concentration in the mixture," the liquid phase hydrogen peroxide concentration is meant, unless explicitly stated otherwise, or unless clear from the context that something else was intended.

The present invention relates to devices, systems and methods for sanitizing or disinfecting rooms or spaces or the like, and more specifically to a method for disinfecting a room by fogging a silver- stabilized hydrogen peroxide mixture, and a device and a computer program that performs such a method, and a system comprising such a device.

It is known in the art that hydrogen peroxide (chemical formula: H2O2) is suitable for killing microorganisms such as viruses, bacteria, fungi, spores and yeasts. In practice, a mixture is generally used where hydrogen peroxide (H2O2) is dissolved in demineralized water (H2O), and the fogging device must ensure that "appropriate amounts" of this mixture are introduced into the room. Much less known is how much that "appropriate amount" must be to achieve a certain kill rate (e.g. LOG5). Different manufacturers offer different solutions. For example, the concentration of hydrogen peroxide (H2O2) varies from about 5 wt% to about 35 wt% relative to the mixture. Some manufacturers fog the mixture without heating it ( cold fogging ), other manufacturers heat or vaporize the mixture. However, the latter can be dangerous.

It is also known that the relative humidity and temperature of the room to be disinfected play an important role in the disinfection process. In general, the higher the temperature and the lower the relative humidity, the more water and hydrogen peroxide can be added to the air in the room. For this reason, some manufacturers of fogging devices build a heating component and/or an air dehumidifier into their device to condition the room before starting fogging. This allows a higher concentration of hydrogen peroxide to be introduced into the room, but the disinfection process will take much longer.

However, the prior art is much less clear about exactly how much hydrogen peroxide is needed to achieve a certain kill rate. Some manufacturers recommend raising the hydrogen peroxide level in the room to at least 400 ppm, and preferably much higher, e.g. at least 900 ppm. However, this has several drawbacks: (1) reaching such a high value is only possible if the room has a sufficiently high temperature and a sufficiently low humidity, which in practice means that the room has to be conditioned, which requires extra hardware, and costs extra time and energy; (2) it takes longer to bring the hydrogen peroxide level in the room to this level (see e.g. phase 1 in FIG. 14A); and (3) it takes much longer to reduce the hydrogen peroxide level in the room back to a safe level (see e.g. phase 3 in FIG. 14A), which again takes additional time.

The inventors of the present invention had several objectives in mind, including: above all they wanted to offer a reliable solution, a solution that kills sufficiently (e.g. at least L0G5 as specified in the EN17272 standard), preferably with hardware that is as simple as possible, preferably with as little waste of hydrogen peroxide mixture as possible, and preferably by performing a process that is safe for the user that takes as little time as possible (the total time, counting from the start of the disinfection, up to and including the release of the room), and preferably two or more of these objectives.

According to a first aspect, the present invention provides a method of disinfecting a room by fogging a hydrogen peroxide mixture. This method is carried out by a fogging device which has connecting means for at least one replaceable reservoir with a hydrogen peroxide mixture, and which has means for fogging this hydrogen peroxide mixture in the room. The method comprises the following steps: a) increasing a gas-phase hydrogen peroxide concentration in the room by (e.g., continuously) fogging a first amount of the hydrogen peroxide mixture during a first phase of a disinfection process; b) maintaining the gas-phase hydrogen peroxide concentration in the room by intermittent fogging of a second amount of the hydrogen peroxide mixture during a second phase of the disinfection process. The hydrogen peroxide mixture is a silver-stabilized hydrogen peroxide mixture comprising 4.5 to 13.0 wt% hydrogen peroxide. The hydrogen peroxide concentration during the second phase is maintained at a value in the range from 45 to 180 ppm, or in the range from 90 to 120 ppm, or in the range from 100 to 120 ppm, for a period of time in the range from 45 up to 120 minutes, e.g. from 50 to 70 minutes, e.g. from 55 to 65 minutes, e.g. of about 60 minutes. Preferably, the product of the gaseous hydrogen peroxide concentration in the room and the time that this concentration is present is at least a factor of 6000. For example, at least 60 minutes x at least 100 ppm, or at least 40 minutes x at least 150 ppm, or at least 100 minutes x at least 60 ppm, or at least 120 minutes x at least 50 ppm. This can be mathematically approximated by: (eg * AT) >6000, where eg is the gaseous hydrogen peroxide concentration in the room (expressed in ppm), and AT is the duration of a period during which this concentration was measured (expressed in minutes).

In particular, the fogging device comprises a first fluid circuit with a first inlet "INI" for receiving a first gas stream from the room, and with means for adding droplets (e.g., having an average diameter of 20-30 microns) of the hydrogen peroxide mixture to this first gas stream, and with a first outlet "OUT1" for supplying this first gas stream with these droplets to the room. The first fluid circuit comprises a first pump 205, 405 to circulate air through the first circuit. The fogging device further comprises a control unit 215, 415 (e.g., a programmable microprocessor) for controlling the first pump 205, 405, e.g., to turn this pump on and off. The fogging device is further adapted to connect to the first circuit of at least one replaceable reservoir 202, 402a, 402b with the silver-stabilized hydrogen peroxide mixture therein.

It is a great advantage to use a silver-stabilized hydrogen peroxide mixture because tests have shown that the kill rate is many times greater when a silver-stabilized hydrogen peroxide mixture is used (e.g. the product "Huwa-San TR-12,5", commercially available from Roam Technologies), compared to a hydrogen peroxide mixture without silver stabilization. For some microorganisms, the difference is even more than a factor of 10 or a factor of 100 times greater.

Surprisingly, testing has also shown that a maintenance period (i.e. the duration of the second phase) of approximately 45 to 75 minutes is sufficient to achieve a kill rate according to standard EN17272.

It is also an advantage of a silver-stabilized hydrogen peroxide mixture that it is much more stable, i.e. decomposes less quickly than a hydrogen peroxide mixture without silver stabilization, (e.g. the product "Huwa-San TR-12,5", commercially available from Roam Technologies, has a shelf life of approximately 2 years, compared to only a few months for similar products without silver stabilization).

It is further an advantage to use a hydrogen peroxide mixture with a hydrogen peroxide concentration of only 4.5 wt% to 13.0 wt%, as opposed to mixtures comprising up to 30 wt% or even higher, because the product is much safer to use (less corrosion and lower risk of explosion).

It is further a very great advantage to maintain the hydrogen peroxide concentration during the second phase at a value in the range from 90 to 180 ppm, or in the range from 90 ppm to 150 ppm, or in the range from 90 ppm to 130 ppm, or in the range from 90 ppm to 120 ppm, (as opposed to a gasphase H2O2 concentration of 400 ppm or even higher), because (i) it takes less time to reach such a value (phasel shorter), (ii) because such a value is achievable with a hydrogen peroxide mixture with a relatively low hydrogen peroxide concentration (safer), (iii) because such values are often achievable without conditioning the room (time savings, simpler equipment), (iv) because it takes much less time to lower this value back to a safe level (in a third phase), and (v) because sufficient killing can still be guaranteed, as specified in standard EN17272.

Fogging in the first phase is preferably continuous fogging, i.e. the first pump that circulates air through the fogging device is continuously ON during the first phase.

The fogging in the second phase is an intermittent fogging, i.e. the first pump is switched ON and OFF repeatedly during the second phase, preferably at least 5 times. This offers the advantage that (i) the risk of condensation decreases, and (ii) that the hydrogen peroxide concentration is not raised unnecessarily high, which would require more liquid mixture, and (iii) which would require much more time later (in the third phase) to bring this concentration back down to a safe value before the room is accessible again without a respirator.

Furthermore, information (e.g. a stored data record) on the remaining (or, equivalently, already consumed) amount of hydrogen peroxide mixture, during/after each use, may be updated, taking into account a variable flow rate of the mixture, in which the flow rate depends on the remaining amount of hydrogen peroxide mixture in the reservoir.

The dispersed amount of hydrogen peroxide mixture (first and second phases) may be determined based on time that liquid is withdrawn from the at least one reservoir and on a linear or nonlinear relationship between the cumulative fogging time and the cumulatively consumed (or, equivalently, the remaining) amount of hydrogen peroxide mixture in the reservoir.

This relationship is initially linear, but may deviate substantially therefrom as the reservoir contains progressively less residual product (in light of a decreasing flow rate). The nonlinear relationship between the cumulative atomization time and the cumulative amount of hydrogen peroxide mixture consumed in the reservoir may correspond, specifically, to a monotonously increasing, sublinear function of the cumulative amount consumed as a function of the cumulative atomization time (or vice versa, the total time of active use of the reservoir increases superlinearly as the amount consumed increases).

This nonlinear function can be expressed, or approximated, by a polynomial. For example, the nonlinear relationship may correspond to a polynomial of at least second degree, preferably at least fourth degree, e.g., a fourth degree polynomial, which expresses the cumulative fogging time as a function of the amount consumed. For example, the nonlinear relationship can be expressed as a fourthdegree polynomial, wherein the coefficients of the polynomial can be determined empirically (e.g., with numerical regression methods), e.g., for a specific model of reservoir and fogging device. It was confirmed experimentally that such a 4th degree polynomial can approximate the empirically determined gradient with sufficient accuracy for practical applications, i.e. can model the deviation from a simple linear relationship with sufficient accuracy. These are the main underlying principles of the present invention. Further embodiments and variants are described in more detail below.

Optionally, the hydrogen peroxide mixture is drawn from the at least one reservoir using the Venturi principle, but this is not strictly necessary, and it is also possible to use a liquid pump.

Optionally, the at least one reservoir carries an RFID tag 103, 303, storing data comprising at least an amount of the hydrogen peroxide mixture, and the fogging device further comprises at least one RFID reader/writer communicatively connected to the control unit, and the control unit is provided to read data from the RFID tag, and write to the RFID tag repeatedly, e.g. to keep the amount of mixture in the at least one reservoir up to date, but an RFID tag is not strictly necessary for the present invention, and the initial amount may also be entered manually by an operator, and kept up-to-date in the fogging device (e.g. in RAM).

Optionally, the fogging device is communicatively connected to one or more external devices (e.g. with at least one hydrogen peroxide sensor), and/or to an external server, and the disinfection process is controlled in "closed loop," i.e. using the values read from the hydrogen peroxide sensor, but this is not strictly necessary, and it is also possible to control the disinfection process in "open loop," based on time.

Referring to the figures,

FIG. 1A shows a first example of a fogging device 100, also referred to herein as a "small fogger", in perspective view. A reservoir 102 with a hydrogen peroxide mixture is connected to the fogging device 100. As can be seen, the reservoir 102 is located on the outside of the "small fogger". Preferably, the reservoir 102 comprises an RFID tag (see FIG. IB) with a non-volatile memory (e.g., flash memory or EEPROM), containing a field (e.g., one byte or two bytes in size) comprising a value corresponding to the amount of hydrogen peroxide that is (still) present in the reservoir 102.

The fogging device 100 has a control unit 215 (also referred to herein as "controller"), e.g., a programmable processor, and preferably also an RFID reader/writer 204 connected to this processor, (not visible in FIG. 1A, but see FIG. 2), so that the control unit can read data stored in the RFID tag, e.g. the initial amount of hydrogen peroxide mixture, but optionally also other data such as e.g. one or more values selected from the group consisting of: the date of manufacture of the hydrogen peroxide mixture, an expiration date, the concentration of hydrogen peroxide in the (liquid) hydrogen peroxide mixture.

In some embodiments of the present invention, the fogging device 100 is provided to keep the value of this field in the RFID tag (corresponding to the amount of liquid mixture) up-to-date, e.g. by updating the value of this field repeatedly, e.g. periodically when liquid is drawn from the reservoir 202. Preferably, this field is updated at least once every 20 seconds that the first pump 205 and/or the liquid pump 219 is active, e.g. at least once every 10 seconds, or at least once every 8 seconds, or at least once every 6 seconds, or at least once every 5 seconds, or at least once every 4 seconds. The more often this value is updated, the more closely the content of the field corresponds to the actual amount of fluid in the reservoir. By updating the field repeatedly (as opposed to just once at the end of a disinfection cycle), it can be assumed that this field correctly reflects the actual contents of the reservoir, even if the disinfection cycle was interrupted prematurely by e.g. a power failure.

FIG. IB shows the reservoir with the hydrogen peroxide mixture 102 of FIG. 1A, and with an RFID tag 103. The RFID tag is also shown magnified with increased contrast.

FIG. 2A shows a block diagram of a possible embodiment of the fogging device 100 of FIG. 1A, wherein liquid is drawn from the at least one reservoir 102 based on the Venturi principle.

As already mentioned above, the fogging device 200 comprises a first fluid circuit with a first inlet "INI" for receiving a first gas stream from the room to be disinfected in which the device is located, and has means for adding small droplets (e.g., having an average diameter of 10 to 50 microns, e.g. from 20 to 40 microns, or from 20 to 30 microns) of a hydrogen peroxide mixture to this first gas stream, and with a first outlet "OUT1" for supplying this first gas stream with these droplets to the room, and with a first pump 205 for circulating air through the first fluid circuit.

In FIG. 2B, a variant of the fogging device will be shown that comprises a fluid pump 219 to pump fluid from the at least one reservoir 202 and add it to the first air stream, but the fogging device 200 of FIG. 2A preferably does not comprise a liquid pump, but liquid is added from the at least one reservoir 202 via a tube or hose 206 that is inserted into the reservoir 202, along which liquid is drawn by means of the Venturi principle, caused by the velocity of the first gas stream.

Preferably, the first pump 205 has a predetermined (non-adjustable) speed. The first pump 205 and the diameter of the pipes of the first fluid circuit can be dimensioned such that the velocity of this air stream is, for example, 40 m/s to 80 m/s, or a value in the range from 50 m/s to 70 m/s, e.g. approximately equal to 60 m/s. This allows the liquid mixture to be sucked out of the reservoir at a flow rate of about 30 to 60 ml/min, as will be further explained in FIG. 6.

The fogging device 200 further comprises a control unit 215, also referred to as controller, e.g. a programmable microprocessor, as well as working memory (RAM) and non-volatile memory (e.g. flash memory or EEPROM or the like), which can be located internally or externally of the processor. The nonvolatile memory preferably comprises a computer program comprising instructions that can be executed by the controller 215. Preferably, this computer program performs a method 1000 as described in FIG. 10 to FIG. 13. This computer program is provided, inter alia, for controlling the first pump 205, e.g. to switch the pump ON or OFF, e.g. by means of a relay. Such circuits are well known and therefore need not be described in detail.

The fogging device 200 further comprises facilities for connecting to a replaceable reservoir 202 with a hydrogen peroxide mixture, e.g. via a screw cap connection and hose 206. The fogging device 200 further comprises a user interface, e.g., a display, (e.g., an LCD screen) and buttons, or a touch screen 212, or the like, communicatively connected to the control unit 215. In this way, the control unit can exchange information with the user, e.g. retrieve data, and/or display data.

Although not strictly necessary, the reservoir 202 preferably carries an RFID tag 103 with a nonvolatile memory in which data is stored. This data comprises at least the amount of the hydrogen peroxide mixture, e.g. in the case of the reservoir 102 for the "small fogger" the initial amount is approximately equal to 1000 ml, in the case of the reservoir 302 for the "large fogger" the initial amount is approximately equal to 3000 ml. And, while not strictly necessary, the fogging device 200 preferably comprises a RFID reader/writer 204, which is positioned in proximity to the reservoir's RFID tag when the reservoir is connected to the fogging device. The RFID reader/writer 204 has an antenna (not explicitly shown in FIG. 2) that allows it to communicate wirelessly with the RFID tag 203 of the reservoir 202. The RFID reader/writer is communicatively connected to the control unit 215 so that the control unit 215 can read and/or write data from/to the RFID tag 203. Preferably, the RFID tag of the reservoir is repeatedly written to when hydrogen peroxide mixture is drawn from the reservoir, i.e. when the first pump 205 is active, to keep the amount of hydrogen peroxide mixture up to date. Preferably, the memory field comprising the initial amount of hydrogen peroxide mixture is repeatedly overwritten, but the present invention is not limited thereto, and it is also possible to provide multiple fields to be written or overwritten sequentially.

In embodiments where the reservoir does not carry an RFID tag, and/or where the fogging device does not comprise an RFID reader/writer, the user can manually enter, e.g. via user interface 212 how much hydrogen peroxide mixture is still present in the at least one reservoir (see e.g. step 1010 of FIG. 10, and step 1016 of FIG. 11) and the fogging device may update e.g. in RAM this amount during a disinfection cycle.

The fogging device 200 further comprises a timing circuit 217, e.g. a timer and/or a real-time clock. "Real-time clock" refers to a chip or module, optionally with a battery, which keeps track of not only the time, but also the date. However, the latter is not strictly necessary, and it is sufficient that the control unit 215 can measure the time.

Preferably, the fogging device 200 also comprises a buzzer 213, or a loudspeaker or the like, capable of generating an acoustic signal. In this way, the control unit 215 can, for example, indicate that an operator must leave the room and/or may not enter the room yet. In this way the safety of the operator can be increased.

Optionally, the fogging device 200 also comprises an RF communication module 211, e.g., a Bluetooth module or a Wi-Fi module, to communicate with one or more external devices, e.g., with a remote control unit. This aspect will be further explained in FIG. 4 and FIG. 5 but is not strictly necessary for the operation of the fogging device. 1

Optionally, the fogging device 200 also comprises a mobile data communication module 218, e.g. an SMS transceiver, or a GPRS transceiver, or a UMTS transceiver, or other suitable transceiver module for a 3G or 4G or 5G network, e.g. to communicate with a central server 560 over the internet. This aspect will be further explained in FIG. 5B and FIG. 13 but is not strictly necessary for the operation of the fogging device.

With this, the main hardware components of the fogging device 100 of FIG. 1A have been described, which can be seen as a "minimum embodiment", but of course the present invention is not limited thereto, and one or more components may be added, e.g. internal to the fogging device, or external to the fogging device, or both, as will be described further (e.g., in FIG. 4A to FIG. 5B).

In FIG. 10 to FIG. 13 a method will be described which can be performed by the fogging device 200 to disinfect a room, in "open loop" (without hydrogen peroxide sensor), or in "closed loop" (with hydrogen peroxide sensor), but before such a method is explained, a second embodiment of a fogging device will first be described with reference to FIG. 3A to 5B. For now, it suffices to know that an operator can enter certain parameters (e.g. temperature and relative humidity and volume) of the room to be disinfected via the user interface, and that the controller 215 can check (e.g. via the RFID tag) how much hydrogen peroxide mixture is available in the reservoir 202, and that the controller 215 can check (and display) whether the available amount of hydrogen peroxide mixture is sufficient to adequately sanitize the room (and optionally whether the expiration date has expired). If the user decides to proceed, a disinfection cycle can be started, after which the controller 215 will generally generate an acoustic signal to indicate that the operator should leave the room, after which the controller 215 will actuate the first pump 205 to run a disinfection cycle, e.g. based solely on time information ("open loop"). If a hydrogen peroxide sensor is present, this can be used, and a "closed-loop" disinfection cycle can be completed. This will be further explained in more detail with reference to FIG. 6 to FIG. 15B.

FIG. 2B shows a block diagram of a fogging device 250 which can be viewed as a variant of the fogging device 200 of FIG. 2A, with the main difference being that the fogging device 250 of FIG. 2B comprises a liquid pump 219 to draw hydrogen peroxide mixture from the reservoir. In this embodiment, the fluid flow rate is preferably constant, and the graphs of FIG. 6 to FIG. 8, and FIG. 15A and FIG. 15B are therefore not applicable. If the flow rate is constant (variant of FIG. 6 and FIG. 15A and FIG. 15B), the contents of the reservoir will change linearly as a function of time (variant of FIG. 7 and FIG. 8).

FIG. 3A shows a second example of a fogging device 300 according to an embodiment of the present invention, also referred to herein as a "large fogger", in perspective view. This device can be viewed as a variant of the fogging device 100 of FIG. 1A, and aside from the differences, what was described above for the "small fogger" also applies here, mutatis mutandis. The fogging device 300 (the large fogger ) is larger and heavier than the fogging device 100 (the "small fogger") of FIG. 1A, and the chassis therefore preferably includes four wheels 331, 332 and a handle 334 for moving the device. In the example shown, for practical reasons the device comprises two non-swiveling wheels 331 located on the side of the handle, and two swiveling wheels 332 with wheel brake 333 on the opposite side, but this is of course not essential to the invention. In the exam ple of FIG. 3A, the non-swivel wheels 331 have a larger diameter than the swivel wheels 332, but again this is not essential, and the invention would work even if the device had four similar wheels, swivel or nonswivel, with or without wheel brake.

The fogging device 300 further comprises a user interface 312, in the example in the form of an LCD touchscreen, where information can be displayed to the operator, and where the operator can enter certain values (e.g. room temperature, relative humidity of the room, volume of the room), and/or can select or set certain parameters, and/or can start the disinfection process, etc. Instead of a touch screen 312, an ordinary display can of course also be used (e.g. LCD screen without input option) and one or more push-buttons and/or rotary knobs or the like.

It should be noted that the fogging device 300 preferably has a communication module 411, e.g., an RF communication module (e.g., Bluetooth or Wi-Fi). This is not visible in FIG. 3A, but is shown in FIG. 4A, FIG. 4B, FIG. 5A and FIG. 5B, which means that the presence of a user interface 312, 412 on the fogging device 300 itself is not strictly necessary, since communication with the operator could also take place via an external device, e.g. a remote control unit 540 or a laptop 541 or a smartphone. But the presence of a user interface 312, 412 on the device itself is useful, and allows the fogging device 300 to work stand-alone (by itself), without external devices.

Within the fogging device 300, space is provided for two reservoirs 402a, 402b, each containing 3 liters of hydrogen peroxide mixture. To connect a new reservoir and/or replace an existing reservoir, an operator must open the top lid 336 by means of a handle or hand grip 337. Alternative embodiments can accommodate more than two reservoirs with hydrogen peroxide mixture, e.g. three or four reservoirs, or two reservoirs with a capacity greater or less than 3 liters. As with the "small fogger" of FIG. 1A and FIG. 2, each reservoir 402a, 402b with hydrogen peroxide mixture preferably has an RFID tag 403a, 403b with data, including a field representing the amount of hydrogen peroxide in the respective reservoir; and preferably the fogging device 300 of FIG. 3A comprises two RFID reader/writers 404a, 404b (see FIG. 4), each provided to communicate with one RFID tag. The antennas of the RFID reader/writers are dimensioned in such a way (relatively small) that they can only communicate with the reservoir over a relatively short distance, and in such a way that communication with another reservoir that does not belong to the RFID reader/writer in question is avoided. It is of course also possible to provide electromagnetic shielding, but this is not strictly necessary.

As explained above for the "small fogger," the fogging device 300 comprises a controller 415, e.g., a programmable microcontroller, provided with a software program containing routines to perform a method as shown in FIG. 10. If the device comprises RFID reader/writers 404, and if the reservoirs are provided with RFID tags 403, then the software program preferably comprises routines to keep the value of the amount of liquid mixture in each reservoir, on each RFID tag, up to date, and update it repeatedly when fluid is drawn from a reservoir.

Visible in FIG. 3A are also two nozzles 301a, 301b, which form the outlet OUT1 of the first fluid channel, along which the air with droplets of hydrogen peroxide mixture are blown into the room. Also visible in FIG. 3A are two openings IN2 of the second fluid channel. Unlike the "small fogger" of FIG. 1A, the "large fogger" of FIG. 3A actually has an active filter for removing hydrogen peroxide from the room during a third phase of the fogging process. This active filter may comprise an activated carbon filter, or may comprise a metal catalyst, or both. The output OUT2 of the second fluid channel is not visible in FIG. 3A but located at the bottom of the device.

FIG. 3B shows an example of a reservoir 302 that may be used in conjunction with the fogging device 300 of FIG. 3A. The reservoir of FIG. 3B can comprise 3000 ml of hydrogen peroxide mixture, but of course the invention will also work with larger or smaller reservoirs.

Certain tests (with a relatively narrow range of room volume, temperature and relative humidity) have shown that under certain conditions approximately 7 to 10 ml of mixture per cubic meter of room volume of silver-stabilized hydrogen peroxide mixture with a hydrogen peroxide concentration in the liquid mixture of 12.5 wt%, was sufficient to obtain a disinfection that complies with the EN17272 standard. That amount is sufficient to create a gas-phase hydrogen peroxide concentration of about 100 to about 120 ppm in the room. This amount can be calculated using the following formula:

NH = KV * A where NH is the required amount of hydrogen peroxide mixture (expressed in ml), and where KV is the volume of the room (expressed in cubic meters), and where A is a predetermined value (expressed in ml/ m ³ ).

In an embodiment, the value of A is a number in the range from 7 to 10 ml/m ³ , but the invention is not limited thereto, and values of A in the range from 5 to 25 ml/m ³ , or in the range from 5 to 20 ml/m ³ , or in the range from 5 to 15 ml/m ³ , or in the range from 8 to 25 ml/m ³ , or in the range from 8 to 20 ml/m ³ , or in the range from 8 to 15 ml/m ³ , are also possible. Optionally, this value is adjustable by the operator.

Optionally, the RFID tag comprises not only the amount of hydrogen peroxide mixture in the reservoir, but also the value of the hydrogen peroxide concentration in the liquid mixture, and the fogging device is provided to retrieve (read) this value from the RFID tag, and to take this into account when determining the amount of the hydrogen peroxide mixture to be introduced into the room. Preferably, before effectively starting the cycle, the device will first check whether there is sufficient hydrogen peroxide mixture in the two reservoirs together, and will give an error message, if there is insufficient hydrogen peroxide mixture. This will be discussed further at the method of FIG. 10 to FIG. 13.

Preferably, the device will also request the temperature and relative humidity of the room from the operator or measure it itself (if it comprises the necessary sensors, or if it has contact with external sensors), and the device will also check whether the target hydrogen peroxide concentration is achievable based on the given room conditions and will generate an error message if the target concentration is not achievable. This will be further discussed in FIG. 9A and FIG. 9B.

As an illustrative example, but the invention is not limited thereto, a fogging device according to the present invention with a full reservoir of 1 liter (1000 ml) silver-stabilized hydrogen peroxide mixture having a hydrogen peroxide concentration of 12.5 wt%, can disinfect a room or space of about 100 m ³ by introducing approximately 450 ml of the mixture into the room during a first phase (see FIG. 14B) of about 8 or 9 minutes, thereby raising the hydrogen peroxide concentration in the room to around 100 to 120 ppm and then, during a second phase lasting for about 60 minutes, introducing the remaining 550 ml of the mixture into the room by "intermittent fogging" with an appropriate duty cycle, so as to achieve a total maintenance period of around 60 minutes. The total time of phasel and phase2 is therefore approximately 68 to 69 minutes in this example.

As an illustrative example, but the invention is not limited thereto, a fogging device according to the present invention with one full reservoir of 3 liters (3000 ml) of silver-stabilized hydrogen peroxide mixture having a hydrogen peroxide concentration of 12.5 wt%, can disinfect a room or space of about 300 m ³ by introducing approximately 1350 ml mixture into the room during a first phase (see FIG. 14B) of about 24 to 27 minutes, thereby raising the hydrogen peroxide concentration in the room to about 100 to 120 ppm, and then, during a second phase of approximately 60 minutes, introducing an additional 1650 ml of said mixture (e.g. from the same reservoir and/or from the other reservoir) into the room by "intermittent fogging" with an appropriate duty cycle so as to achieve a total maintenance period of around 60 minutes. The total time of phasel and phase2 is therefore approximately 84 to 87 minutes in this example.

These are of course only examples, and since the large fogger has two reservoirs of 3 liters each, it can also be used to disinfect a room larger than 300 m ³ .

FIG. 3C shows one side (designated by the letter "X") of the reservoir of FIG. 3B on which an RFID tag 303 is applied. The RFID tag is also shown enlarged with increased contrast, but as mentioned above, the presence of the RFID tag is not necessary. FIG. 4 shows a block diagram of a possible embodiment of the fogging device 300 of FIG. 3A. This block diagram (of the "large fogger") is a variant of the block diagram of FIG. 2 (of the "small fogger"). The basic function of the "large fogger" 300 is the same as that of the "small fogger" 100, which is to disinfect a room, but there are a number of differences, including:

(i) that this fogging device accommodates two reservoirs 402a, 402b with hydrogen peroxide mixture, and optionally also a third reservoir 420 of sterilized water, for an optional rinse of the device after phase 1 and phase 2, for cleaning the pipes or conduits;

(ii) that each reservoir can be individually and selectively connected to or disconnected from the nozzle by means of an associated valve VI, V2, V3. These valves are controlled (e.g., opened or closed) by the controller 415;

(iii) that the valves VI, V2, V3 are connected to a joint pipe leading to the nozzle 401, in the example via a manifold 422;

(iv) that this fogging apparatus optionally comprises two RFID reader/writers 404a, 404b, one for each reservoir with an RFID tag, and with a hydrogen peroxide mixture;

(v) that this fogging device further has means for actively removing hydrogen peroxide from the ambient air, in the example a scrubber 421 with an activated carbon filter. The scrubber 421 is part of a second fluid circuit having a second inlet IN2 and a second outlet OUT2 and has a second pump "POMP2" for circulating a stream of air through the second fluid circuit. This second pump can be selectively turned ON or OFF by the controller 415, e.g. during a third phase F3 of the disinfection process (see FIG. 14A to FIG. 14C).

In an alternative embodiment, the activated carbon filter is replaced with a catalyst to remove hydrogen peroxide H2O2 from the room. It is also possible to use both an activated carbon filter and a catalyst.

These differences allow the fogging device 300 ("the large fogger") to disinfect a larger room, and the third phase F3 will take less time, so that the room can be released more quickly. It also offers the advantage that (for rooms smaller than about 300 m ³ ) it can use the hydrogen peroxide mixture more economically, because it can first empty one reservoir before starting a new reservoir. With this device it is therefore not necessary to always start a new cycle with new reservoirs, and it can also be avoided that liquid has to be decanted, which benefits the safety of the operator.

Although not strictly necessary to perform a disinfection cycle with high reliability, the fogging device 300 preferably comprises an RF communication module, e.g. with Bluetooth and/or with Wi-Fi, and the fogging device is arranged to communicate with a "remote control unit" 540 (see FIG. 5). This remote control unit can be an existing tablet or a smartphone, with an appropriate application (app), and can optionally have a touchscreen. In a simple implementation, the remote control unit application may be provided to start the fogging device remotely, e.g. after an operator has entered the necessary data via the touchscreen 412 on the fogging device itself; or to remotely stop the device, and the controller 415 will start or stop the device accordingly as if the user had given this command via the touchscreen 412. However, the present invention is not limited thereto, and it is also possible to implement a more extensive application on the remote control unit, which is provided to display the same information as appears on the display 412 of the fogging device 400, and to send input data (e.g. temperature of the room, volume of the room, relative humidity of the room), entered on the remote control unit, to the controller 415. The controller 415 in this case will be configured to process both commands or data entered through the local user interface 412, or through the remote control unit 540. The great advantage of using a remote control unit is that it allows an operator to operate the fogging device remotely, and/or monitor the status, e.g. while they are located outside the room. After all, it is very dangerous to enter the room without personal protective measures such as a respirator, as long as the gaseous hydrogen peroxide concentration in the room exceeds a predetermined safe value, typically 1.0 ppm. The development and/or manufacture of such remote control unit 540 (hardware and/or software) is known in the art, and thus needs no further explanation. Communication with a remote control unit is also possible via a mobile data communication module 418 if present.

For the sake of completeness, it is noted that, in a practical implementation of the block diagram of FIG. 4 the "first fluid channel" can be implemented e.g. as two physical channels in parallel, each with its own input, its own pump, and its own nozzle, but this is not essential, and such details therefore need not be explained further.

FIG. 4B shows a block diagram of a fogging device 450 which can be viewed as a variant of the fogging device 400 of FIG. 4A, with the main difference being that the fogging device 450 of FIG. 4B comprises a liquid pump 419 to draw hydrogen peroxide mixture from the reservoir. In this embodiment, the fluid flow rate is preferably constant, and the graphs of FIG. 6 to FIG. 8, and FIG. 15A and FIG. 15B are therefore not applicable. If the flow rate is constant (variant of FIG. 6 and FIG. 15A and FIG. 15B), the contents of the reservoir will change linearly as a function of time (variant of FIG. 7 and FIG. 8).

FIG. 5 shows a fogging system 590 that comprises a fogging device 500 according to an embodiment of the present invention (e.g., a "small fogger" as shown in FIG. 1A or a "large fogger" as shown in FIG. 3A), and one or more external devices selected from:

- one or more hydrogen peroxide sensors 531 for measuring a gas-phase hydrogen peroxide concentration, at one or more locations in the room. If present, these hydrogen peroxide sensors can be used, e.g., in steps 1021 to 1023 of the method of FIG. 13, corresponding to phase 3 of FIG. 14A to FIG. 14C, in particular to perform a "closed-loop" process;

- one or more temperature sensors 532 for measuring an ambient temperature at one or more locations in the room. If present, they can be used e.g. in step 1011 or 1012 of the method of FIG. 11; - one or more relative humidity sensors 533 for measuring a relative humidity at one or more locations in the room. If present, they can be used e.g. in step 1011 or 1012 of the method of FIG. 11;

- one or more fans or ventilators 551 for distributing the air with droplets in the room, and thus to make the hydrogen peroxide concentration in the room more uniform. If present, these fans can be used e.g. in steps 1021 to 1023 of the method of FIG. 13,

- one or more air heaters 552 for heating the air in the room to condition the room. If present, these air heaters can be used e.g. in step 1011 of the method of FIG. 11;

- one or more air dehumidifiers 553 to lower the relative humidity of the air in the room by extracting water vapor from the air to condition the room. If present, these air dehumidifiers can be used e.g. in step 1011 of the method of FIG. 11;

- one or more external scrubbers 554 to reduce the gaseous hydrogen peroxide concentration present in the air of the room. If present, these scrubbers can be used e.g. in step 1023 of the method of FIG. 13, corresponding to phase 3 of FIG. 14A to FIG. 14C, to further reduce the duration of the third phase, thus further accelerating the overall decontamination process, so that the room can be released more quickly, but without sacrificing the reliability of killing.

- a remote control unit 540. This has already been discussed above.

- a laptop 541 or a tablet or a smartphone or the like. It can perform the function of the remote control unit 540 and possibly more, such as e.g. logging data (e.g. of measured values of Temperature and/or Relative Humidity and/or gaseous hydrogen peroxide concentration. These can also be used, for example, to adjust parameters or settings, or even the entire software program of the fogging device.

Preferably, any of these external devices, if present, can be communicatively connected to the control unit 415 of the fogging device, e.g. via the RF communication module, or optionally via a cable connection (not shown), e.g. RS232, USB, etc., or via the mobile data communication module (e.g. over a 3G, 4G or 5G network).

The hydrogen peroxide sensor 531, and the temperature sensor 532 and the relative humidity sensor 533 may possibly be integrated into one sensor device 530. This sensor device 530 may further comprise a controller 539 for controlling and/or reading the sensors and may comprise a port (not shown) for connecting a cable (e.g., RS232, USB, etc.), and/or may comprise an RF communication module 538 to transmit data wirelessly.

In a specific embodiment, the fogging system 590 comprises the fogging device 500 with two hydrogen peroxide reservoirs 402a, 402b and with a third reservoir 420 of sterilized water (to rinse the conduits), and a laptop 541 with both Bluetooth and Wi-Fi capabilities, and an external sensor device 530 which comprises at least a hydrogen peroxide sensor 531, an RF communication module 538 with Bluetooth, and a controller 539. In such a system, the controller 515 of the fogging device can communicate with the controller 539 of the sensor device 530 via the laptop, which acts as a gateway. In such an arrangement, the laptop can also be used to log data to a local storage medium 542 (e.g., hard disk), or to a network drive (not shown), or to the cloud 543 or the like.

In another or further embodiment, the fogging system 590 comprises the air heater 552 and the air dehumidifier 553, which are preferably automatically controlled by the controller 515 of the fogging device 500, e.g. via a cable (not shown), or via a wireless connection (e.g. Bluetooth or Wi-Fi). These devices 552, 553 allow the room to be conditioned if the temperature and/or the humidity do not meet the necessary conditions to fog the intended amount of hydrogen peroxide (e.g. about 100 to 120 ppm) in the room.

In another or further embodiment, the fogging system 590 comprises at least two hydrogen peroxide sensors 531, preferably arranged at different locations in the room; and the fogging device 500 is arranged to receive a value from each of these at least two hydrogen peroxide sensors, and to consider during the first phase (phasel) and the second phase (phase2) of the disinfection cycle (see FIG. 14A to FIG. 14C) a minimum of this plurality of values as the relevant gas-phase hydrogen peroxide concentration in the room (by ensuring, e.g., that the minimum value is at least 100 ppm), and to consider during the third phase (phase3) of the disinfection cycle (see FIG. 14A to FIG. 14C) a maximum of this plurality of values as the relevant gas-phase hydrogen peroxide concentration in the room (by ensuring, e.g., that the maximum value falls below 1.0 ppm). In this way, on the one hand, the probability is increased that the hydrogen peroxide concentration everywhere in the room comprises at least the predetermined value (e.g. about 100 ppm), in order to achieve sufficient killing everywhere in the room (e.g. according to standard EN17272), and on the other hand to reduce the risk that the hydrogen peroxide concentration anywhere in the room is higher than the predetermined safe value (e.g. 1.0 ppm) before releasing the room again.

Of course, many other combinations are possible of the fogging device 500 with one or more of the aforementioned external devices, shown in dotted line in FIG. 5.

For the sake of completeness, it is noted that it is also possible to incorporate one or more of these devices, e.g., temperature sensor, humidity sensor, air heater, air dehumidifier, fan into the fogging device 500 itself, and it is also possible to use both an internal device (e.g., a first, internal scrubber), as well as an external device (e.g., a second scrubber).

FIG. 5B shows a fogging system 595 that can be viewed as a variant of the fogging system 590 of FIG. 5A. The fogging system 595 comprises a hydrogen peroxide sensor 531, which may or may not be integrated into a sensor module 530, communicatively connected to the controller of the fogging device 561, e.g. directly via a Wi-Fi connection, or indirectly via a Bluetooth connection to a laptop, and via a Wi-Fi connection to the fogging device. In such a system, the actual gaseous hydrogen peroxide concentration in the room can be measured repeatedly, and the disinfection process can be performed in "closed-loop" control, e.g., as illustrated in FIG. 14B. Preferably, the fogging device is also communicatively connected to a central server, e.g. via an RF communication module 411 (e.g. via Wi-Fi), and/or via a mobile data communication module 418, e.g. via an internet connection.

The controller may further be provided to receive data about the room to be disinfected (e.g. initial temperature, initial relative humidity, volume), and data about the hydrogen peroxide mixture (e.g. hydrogen peroxide concentration in the liquid mixture, initial volume, intermediate volumes, preferably together with a timestamp), and to forward the measured hydrogen peroxide values, or a subset thereof, preferably together with a timestamp, to the central server 560. The latter can then check, based on the data received, whether the disinfection process has been carried out successfully, e.g. by statistical analysis of the measured concentrations and timestamps for the specified room conditions and the disinfectant used.

It is noted that the presence of a hydrogen peroxide sensor and/or a connection to the central server are not necessary to perform a reliable disinfection cycle. Indeed, it is perfectly possible to carry out a disinfection cycle in so-called "open loop" control. In this case, it suffices to control the first pump (and possibly the liquid pump) based on known characteristics of the device and known parameters of the room, e.g. using tables established during calibration tests. In this case, a number of safety margins can possibly be taken, e.g. introducing a slightly higher than average amount of hydrogen peroxide mixture into the room (e.g. during the first and/or second phase), in order to guarantee sufficient killing, and/or waiting a slightly longer than average time (e.g. during the third phase) to guarantee sufficient reduction of the gas-phase hydrogen peroxide concentration in the room. Such a safety margin can optionally be set by the operator.

FIG. 6 shows an illustrative curve representing the flow rate of the liquid hydrogen peroxide mixture from the reservoir as a function of the fill factor of the reservoir, as applicable in fogging devices according to the present invention that utilize the Venturi effect. This curve is mainly determined by the speed of the air stream in the first fluid channel, as well as by the shape and size of the nozzle.

As can be seen, the relationship between the fluid flow rate (of the hydrogen peroxide mixture) and the amount of liquid in the reservoir is substantially linear. This graph was measured for a 3000 ml reservoir with a height of approximately 25 cm, measured in a prototype "large fogger" of FIG. 3A. In the specific example of FIG. 6, the fluid flow rate can be calculated or approximated based on the following formula:

VD [ml/min] = 30.8 [ml/min] + 0.31*VG [in %] [1] where VD is the fluid flow rate (expressed in ml/min), and

VG is the fill factor of the reservoir (expressed in %), but of course this can be different for a different fogging device. So in the example of FIG. 6, the fluid flow rate is about 30.8 + 31.0 = 61.8 ml/min for a full reservoir (VG=100%), and the fluid flow rate is about 30.8 + 0.31 = 31.1 ml/min for a substantially empty reservoir (VG=1%). That is almost a factor of two difference between a full reservoir and a substantially empty reservoir. It will be appreciated that this must be taken into account in order to introduce and/or maintain an accurate concentration of hydrogen peroxide in the room (e.g. during the second phase of FIG. 14A to FIG. 14C). This will be further discussed in FIG. 15A and FIG. 15B.

The fluid flow rate in a prototype of the "small fogger" of FIG. 1A is similar, but the measurement points are slightly shifted. For the sake of completeness, it is noted that the specific curve of FIG. 6 was measured in an 81 m ³ test room.

FIG. 7 shows another representation of the curve of FIG. 6, showing the fluid flow rate as a function of the cumulative time, starting from a full 3000 ml reservoir. This graph can be derived from the graph of FIG. 6, or based on formula [1], using the following formulas:

AVfluid [in ml] = VD [in ml/min] * AT [in min] [2] where AVfluid is the liquid volume that is drawn from the reservoir for a short time AT, VD is the aforementioned fluid flow rate (expressed in ml/min), and AT is the time span (expressed in minutes). It should be noted that this graph is not linear.

In the example of FIG. 7, AT was chosen as a period of 10 seconds, and every 10 seconds the amount of liquid remaining in the reservoir was calculated, as well as the corresponding fluid flow rate. These values can be calculated iteratively or can be stored in a table. If AT = 10 seconds, then a table of about 408 items is sufficient. Such a table can easily be stored in a non-volatile memory of the device. But of course the invention is not limited to this, and it is also possible to store other tables, or to store the curve in a different way, e.g. by storing the coordinates of a piecewise linear approximation.

FIG. 8 shows a curve 891 representing the contents of a 3000 ml reservoir as a function of the cumulative time fluid is drawn from the reservoir (i.e., the cumulative time the first pump is ON), corresponding to the fluid flow rate of FIG. 6 and FIG. 7. The curve 891 is clearly non-linear (it lies below the dotted line). The area under the curve 891 also illustrates that it takes, for example, much less time (in the example 500 seconds versus 790 seconds) to withdraw 500 ml of liquid mixture from a full reservoir (e.g. from a contents of 3000 ml to 2500 ml) compared to a reservoir that is substantially empty (e.g. from a contents of 1000 ml to 500 ml).

In practice, a lot of hydrogen peroxide mixture would be wasted if one had to start from a completely filled reservoir each time. Thus, in order to allow the fogging device to operate with a reservoir that is not fully filled, a correct knowledge of the remaining contents of the hydrogen peroxide mixture in the reservoir is desirable to properly estimate the time required to draw a given amount of mixture from the reservoir (in the example: 500 ml, but this is only an example). This is especially important for an open-loop method, i.e. a method in which the gaseous hydrogen peroxide concentration in the room is not measured effectively (e.g. because no hydrogen peroxide sensor is present), but is estimated based on time, and using the table mentioned above, or mathematical formulas and iterative calculations prepared based on the results of various tests with varying values of temperature, humidity and room size in which the gaseous hydrogen peroxide concentration in the room was measured in a test setup.

During the experiments, the inventors also found that the gaseous hydrogen peroxide concentration in the room cannot be increased indefinitely, but that it is limited to a ceiling value. They also found that this ceiling value mainly depends on temperature and relative humidity in the room. Further investigation led to the graph of FIG. 9A.

FIG. 9A shows three curves representing the maximum gaseous hydrogen peroxide concentration achievable by so-called "cold fogging" (i.e. fogging without heating of the liquid mixture), as a function of the ambient temperature (T) and relative humidity (RH) in a room. These curves apply to a hydrogen peroxide mixture with a liquid phase hydrogen peroxide concentration of approximately 12.5 wt% in demineralized water. In general, it can be said that the higher the temperature and the lower the relative humidity of the room to be disinfected, the higher the maximum hydrogen peroxide concentration achievable with this mixture.

In preferred embodiments of the present invention, the target gas-phase hydrogen peroxide concentration is about 100 ppm. As shown in FIG. 9A, this value is achievable in:

- a room with relative humidity = 49% and Temperature of at least 15°C,

- a room with relative humidity = 60% and Temperature of at least 19°C,

- a room with relative humidity = 70% and Temperature of at least 21.5°C, etc.,

If the temperature and relative humidity of the room meet one of these conditions, then it does not need to be "conditioned," i.e. the temperature does not have to be raised, and/or the relative humidity lowered before a disinfection cycle can be started (this means e.g. that step 1011 of FIG. 11 can be skipped). The specific curves of FIG. 9A were measured in the 81 m ³ test room mentioned above.

Similar curves can be prepared for hydrogen peroxide mixtures with a different hydrogen peroxide concentration different from 12.5 wt%.

FIG. 9B shows a curve derived from FIG. 9A, and which represents the minimum room temperature as a function of the relative humidity, or vice versa, which indicates the maximum relative humidity for a given temperature, in order to achieve a gaseous hydrogen peroxide concentration of 100 ppm in the room by "cold fogging" of a hydrogen peroxide mixture comprising substantially 87.5 wt% demineralized water and substantially 12.5 wt% hydrogen peroxide, and preferably also 0.006 to 0.008 wt% silver ions. Such hydrogen peroxide mixture is commercially available from Roam Technologies under the product name: "Huwa-San TR-12,5" or "Huwa San 12,5 MD".

For example, using the curve of FIG. 9B, the fogging device can determine that a target gaseous hydrogen peroxide concentration of, e.g., 100 ppm by fogging of "Huwa-San TR-12,5" is not achievable if the relative humidity is 80%, and the temperature in the room is below 23.5°C at the start of the disinfection cycle. Such a test can be performed, e.g., in step 1020 of FIG. 10 or FIG. 12.

Similar curves can be prepared for other gas-phase hydrogen peroxide concentrations, different from 100 ppm, and/or using a hydrogen peroxide mixture with a hydrogen peroxide concentration different from 12.5 wt%.

FIG. 10 shows a flowchart of a method 1000 that can be performed by a fogging device as illustrated in FIG. 1 to FIG. 4, and/or by a fogging system 590, 595 as illustrated in FIG. 5A and FIG. 5B, with one or more external devices. Different variants of the method are possible, depending on which facilities are available, e.g.:

- If the fogging device comprises a temperature sensor and/or a humidity sensor or has communicative access to an external temperature sensor 532 and/or an external humidity sensor 533, then the device can measure the temperature and relative humidity of the room to be disinfected itself. Alternatively, the operator can measure the temperature and/or relative humidity and enter the values via the display 412 of the device or via the remote control unit 540 (if present), before starting a disinfection cycle.

- If the fogging device has an air heater and/or an air dehumidifier or has communicative access to an external air heater 552 and/or an external air dehumidifier 553, then the fogging device can optionally increase the temperature in the room, and/or lower the relative humidity in the room. Alternatively, if an external air heater 552 and/or an air dehumidifier 553 are present in the room, but are not communicatively connected to the fogging device, an operator can optionally operate these devices manually before starting a disinfection cycle. But as explained above (see e.g. FIG. 9A and FIG. 9B), the presence of an air heater and/or an air dehumidifier is not strictly necessary, and it is often possible to start a disinfection cycle without preconditioning the room, if the temperature and the relative humidity meet the conditions e.g. shown in FIG. 9B.

- If the fogging device comprises a hydrogen peroxide sensor internally, and/or has communicative access to an external hydrogen peroxide sensor 531, then the fogging device can measure the gas-phase hydrogen peroxide concentration in the room, and dynamically adjust the process parameters (e.g. the duration of phasel of FIG. 14C; starting and stopping the so-called intermittent fogging during phase2, and releasing the room after phase3), taking into account the measured values, in a so-called "closed-loop" control. If the fogging device does not have access to a hydrogen peroxide sensor, the fogging device can perform a fogging process with so-called open-loop' control, based on time, taking into account the current fill factor of the reservoir(s).

The method 1000 of FIG. 10 as proposed by the present invention actually involves four major steps: i) collecting 1010 data for performing a fogging process in a particular room; ii) checking 1020 whether the collected data meets certain conditions in order to successfully carry out the intended fogging process, and if not all conditions are met, issuing 1030 an error message, and if all conditions are met, proceeding to step 1040; iii) performing 1040 the fogging process; iv) optionally reporting 1051 that the disinfection process is complete; v) optionally reporting 1052 whether or not the fogging process has been carried out successfully, e.g. by checking whether a power interruption has occurred while the disinfection process was active, or e.g., in the case of "closed-loop" control, by verifying whether an abnormal amount of hydrogen peroxide mixture had to be fogged to achieve the target gas-phase concentration (e.g., 100 ppm). Such an abnormally high value can, for example, be the result of a window that was open.

FIG. 11 shows a possible refinement of the first major step i) of FIG. 10, regarding the collection of data on the room, and may comprise one or more of the following steps: b) determining 1012 conditions of the room, including the temperature and relative humidity of ambient air in the room to be disinfected. As described above, this step may comprise an automatic reading of relevant sensors, if these are built into the fogging device, or external to it, but communicatively connected to it. Alternatively, this step may comprise, e.g., receiving data input on the user interface 212, 412 of the fogging device. If the room was conditioned by means of an air heater and/or an air dehumidifier, in step 1011, then step 1012 may be skipped; c) determining 1013 the volume of the room to be disinfected (e.g. the number of cubic meters). This step may comprise, e.g., receiving the appropriate value via the user interface 212, 412 of the fogging device, or may comprise, e.g., receiving a length, a width, and a height of the room, after which the fogging device will calculate the volume of the room. Optionally, this volume can be stored in a nonvolatile memory of the device, e.g. together with a "name" (e.g. a character string) of the room in question, so that it can be retrieved later. d) determining 1014 the hydrogen peroxide concentration of the liquid mixture in the reservoir. For example, this step may comprise receiving the appropriate value via the user interface 212, 412 of the fogging device, or may comprise automatic reading of the appropriate value from the RFID tag by the controller 215, 415 (if the RFID tag comprises this value); e) estimating 1015 the amount of hydrogen peroxide mixture required to introduce a predetermined concentration (e.g. 100 ppm) of gas-phase hydrogen peroxide into the room during a first phase (phasel) and to maintain this concentration for a predetermined maintenance period (e.g. about 60 min) during a second phase (phase2). These predetermined values (e.g. the concentration of 100 ppm, and the maintenance period of 60 minutes) can be predetermined in the software of the fogging device, or can optionally be set or adjusted by the operator via the user interface 212, 412;

The amount of hydrogen peroxide mixture required to increase the predetermined gas-phase hydrogen peroxide concentration (during a first phase) and to maintain it for a certain "maintenance period" (during a second phase), can be determined e.g. on the basis of the following formula: NH = KV * A, where NH is the required amount of hydrogen peroxide mixture (expressed in ml), and where KV is the volume of the room (expressed in cubic meters), and where A is a predetermined value (expressed in ml/m ³ ). The value A depends on the concentration of hydrogen peroxide in the hydrogen peroxide mixture, and possibly also on the room conditions (e.g. temperature and relative humidity), and possibly also on the room volume. This can be represented mathematically by the following formulas:

A = fl(H2C>2 concentration in the hydrogen peroxide mixture), or:

A = f2(H2C>2 concentration in the hydrogen peroxide mixture, Troom, RHroom), or:

A = f3(H2C>2 concentration in the hydrogen peroxide mixture, Troom, RHroom, Vroom), where Troom, RHroom and Vroom are the (initial) temperature, relative humidity and volume of the room before the start of the disinfection process, respectively. One or more of these functions can e.g. be stored in tabular form in a non-volatile memory 216, 416 of the fogging device, but the present invention is not limited to this, and the process parameters may also be optionally queried from a networked application running in the cloud, after transmitting the above-mentioned parameters.

As an example, for a room volume of approximately 50 m ³ , and using a silver-stabilized hydrogen peroxide mixture with a hydrogen peroxide concentration of 12.5 wt%, and an (initial) room temperature of approximately 20°C and a relative humidity of approximately 65%, A is preferably a value in the range from 7 to 10 ml/m ³ .

NH thus represents the total amount of hydrogen peroxide mixture to be fogged during the first and second phase. The ratio of the amount of hydrogen peroxide mixture to be fogged during the first phase and the second phase can be a value of about 45%, or a value in the range from 40% to 50%, or a value in the range from 35% to 55%, or a value in the range from 30% to 60%. In an embodiment, this ratio is a constant value, e.g. 45%, but the invention is not limited thereto, and in other embodiments, this ratio may be a function of one or more of the following parameters: the hydrogen peroxide concentration in the hydrogen peroxide mixture, Troom, RHroom, Vroom, where Troom, RHroom and Vroom are the (initial) temperature, relative humidity and volume of the room before the start of the disinfection process, respectively. f) determining 1016 how much hydrogen peroxide mixture is available in the at least one reservoir. This step may comprise, e.g., reading the appropriate value from the RFID tag(s), or retrieving the fill factor of the reservoir(s) via the user interface 212, 412. If several reservoirs are connected, the amounts must be added up.

FIG. 12 shows a possible refinement of the second major step ii) of FIG. 10, regarding verifying that the collected data meets certain conditions for the successful completion of the fogging process, and may comprise one or more of the following steps: h) calculating the required amount of hydrogen peroxide mixture, in particular to achieve a fogging process with a target gas-phase hydrogen peroxide concentration in the room; and j) verifying that the temperature and relative humidity of the room meet a predetermined criterion (e.g., as shown in FIG. 9B) to achieve the target gas-phase concentration; and k) checking whether the available amount of hydrogen peroxide mixture in the at least one reservoir is greater than the required amount of mixture.

As shown in FIG. 10, if all conditions are met, the fogging device can continue to perform 1040 the fogging process, (possibly after a certain waiting time during which an audible signal is produced so that the operator can leave the room); and if not all conditions are met, giving 1030 an error message.

In another or further embodiment, the RFID tag 103, 303 on the at least one reservoir also comprises an expiration date of the hydrogen peroxide mixture, and the control unit 215, 415 is further provided to determine a current date, (e.g. by reading a real-time clock 217, 417 in the device, or retrieving the current date from an external device, e.g. from a laptop communicatively connected to it, or retrieving it from the internet), and the control unit (as an additional test) also verifies whether the expiration date has expired (i.e., is beyond the current date). If the expiration date has passed, an error message may be given in step 1030. If the expiration date has not yet passed, the control unit may proceed to step 1040.

FIG. 13 shows a possible refinement of the third major step iii), which involves performing the fogging process, and may comprise one or more of the following steps: m) adding air with droplets of hydrogen peroxide mixture to the room (herein also called "fogging"), to increase the gas-phase hydrogen peroxide concentration in the room; and optionally updating the amount of hydrogen peroxide mixture in each reservoir repeatedly (e.g., in RAM and/or on the RFID tag); and optionally sending measured H2O2 values (if a hydrogen peroxide sensor is present) and timestamps to a central server 560. This step m) corresponds to a first phase "phasel" Fl of the fogging process (see FIG. 14A to FIG. 14C). * This increasing can be done in open-loop control , e.g. if no hydrogen peroxide sensor is present, in which case the (predicted) increase of the gas-phase hydrogen peroxide in the room is based on time, for example the cumulative time the first pump was active, and taking into account the variable flow rate in case the device uses the Venturi principle; or based on the cumulative time that the first pump and the liquid pump are active together, if the device uses a liquid pump.

* This increasing can also be done in "closed-loop control," e.g. if a hydrogen peroxide sensor is present, in which case the actual amount of gas-phase hydrogen peroxide in the room can be measured, and the time the first pump (and optionally also the liquid pump) is active can be dynamically adjusted based on the measured value. In particular, the first pump (and optionally also the liquid pump) can be activated and remain activated until the measured value exceeds the target gas-phase hydrogen peroxide concentration (e.g. 100 ppm). n) maintaining the hydrogen peroxide concentration in the room for a predetermined period of time (e.g., 60 min); and optionally updating the amount of hydrogen peroxide mixture in each reservoir repeatedly (e.g., in RAM and/or on the RFID tag); and optionally sending measured H2O2 values (if a hydrogen peroxide sensor is present) and timestamps to a central server 560. This step n) corresponds to a second phase "phase2" F2 of the fogging process (see FIG. 14A to FIG. 14C).

* Maintenance of the hydrogen peroxide concentration can be carried out in open-loop, e.g. by activating the first pump 405 (and optionally also the liquid pump) repeatedly with a certain duty cycle, e.g. every 5 minutes, switching the first pump ON for 1 minute, and OFF for 4 minutes, until the predetermined period (e.g., 60 min) is over, (e.g., as shown in FIG. 15A); or e.g., activate the first pump every 5 minutes for a variable time (e.g., "actl") to periodically add a certain amount of hydrogen peroxide mixture to the room (e.g., as shown in FIG. 15B);

* Maintenance can also be carried out in "closed loop" if a hydrogen peroxide sensor is present, in which case the first pump 405 (and optionally also the liquid pump) e.g. can be switched ON whenever the measured value of the gas-phase H2O2 concentration is lower than the predetermined value (e.g. 100 ppm), and can be switched OFF whenever the measured value exceeds a certain threshold (e.g. 110 ppm or 120 ppm), until the predetermined contact period (e.g. 60 min) is over. o) actively reducing or passively decreasing the hydrogen peroxide concentration in the room until a predetermined value has been reached ("closed loop"), (e.g. less than 1.0 ppm), or for a predetermined time ("open loop"); and optionally sending measured H2O2 values (if a hydrogen peroxide sensor is present) and timestamps to a central server 560.

* If a scrubber or catalyst is present in the device (as e.g. with the "large fogger" of FIG. 3A and FIG. 4), then the second pump (in the scrubber 421) will be activated during the third phase F3, in order to allow an air stream to flow through the second fluid channel; * If no scrubber or catalyst is present in the device (as e.g. with the small fogger of FIG. 1A), nor externally connected to it, and if no hydrogen peroxide sensor is present, this step comprises "passively waiting for a certain period".

* If a hydrogen peroxide sensor is communicatively connected to the controller 415, it can be read repeatedly to determine when the gaseous hydrogen peroxide concentration in the room has dropped sufficiently before releasing the room. If no hydrogen peroxide sensor is communicatively connected to the controller 415, then of course this is not possible, and then only a predetermined time can be passively waited.

* As an example, without a scrubber and without a catalyst, for a particular room it may take e.g. 12 to 15 hours to drop the gaseous hydrogen peroxide concentration in the room from 100 ppm to 1.0 ppm. Thanks to the scrubber 412 with activated carbon filter, this time can typically be halved.

* In a relatively simple embodiment of a fogging device with an activated carbon scrubber, but without connection to an external hydrogen peroxide sensor, the duration of the third phase F3 can be estimated using the following formula:

T3 (in seconds) = A3 + B3* Vroom [3] where A3 is a predetermined time, e.g. 900 s, and where B3 is a value of 100 s/m ³ , and where Vroom is the volume of the room (expressed in m ³ ). But, of course, this is just an example, and the present invention is not limited thereto.

* In a somewhat more complex embodiment, the time T3 depends not only on the volume of the room, but also on one or more of the following parameters: the hydrogen peroxide concentration in the hydrogen peroxide mixture used, the initial temperature in the room, the initial relative humidity in the room. This can be written mathematically as:

T3 = f4(H2C>2 concentration in the hydrogen peroxide mixture, Troom, RHroom, Vroom),

This function can e.g. be established by performing tests under various conditions and can e.g. be stored in tabular form in a non-volatile memory 216, 416 of the fogging device.

FIG. 14A is an illustrative representation of an ideal course of the concentration of gaseous hydrogen peroxide in the room during a disinfection process. It should be noted that these graphs are not drawn to scale. The course comprises three phases:

- in a first phase Fl, hydrogen peroxide mixture in fogged form is injected into the room via the nozzle, or via two nozzles 301a, 301b in the example of FIG. 3A. If the relative humidity of the air in the room is less than 100%, these droplets will evaporate, and the water (H2O) from these droplets and the hydrogen peroxide (H2O2) from these droplets will be released in gaseous form. Tests have shown that the concentration of hydrogen peroxide in gaseous form in particular is decisive for the killing of microorganisms. Tests have also very surprisingly shown that the kill rate is many times greater when a silver-stabilized hydrogen peroxide mixture is used (e.g. the product "Huwa-San TR-12,5", commercially available from Roam Technologies), compared to a hydrogen peroxide mixture without silver stabilization. For some microorganisms, the difference is even more than a factor of 10 or a factor of 100 times greater;

- in a second phase F2, the gaseous hydrogen peroxide concentration in the room is kept substantially constant for a predetermined period (typically 60 minutes), also called "maintenance period"; or rather, it is ensured that the gaseous hydrogen peroxide concentration remains at least 100 ppm during this period. In practice, however, the hydrogen peroxide concentration will slowly decrease unless new droplets are injected into the room (see FIG. 14B and FIG. 14C). At the end of the second phase, the intended killing of the microorganisms has been achieved.

- in a third phase F3, the gaseous hydrogen peroxide concentration in the room must be reduced to a value of no more than 1.0 ppm before entering the room without a respirator. As described above, a scrubber and/or a catalyst is preferably used during this third phase F3 in order to accelerate the decrease of the gaseous hydrogen peroxide concentration.

Although not shown in FIG. 14A to FIG. 14C, a rinse with demineralized water can optionally be performed at the beginning of the third phase F3 to clean the conduits and the nozzle, so that less corrosion occurs. This is not necessary for the fogging process or the killing process, but it will benefit the life of the device. The third reservoir 420 in the block diagram of FIG. 4A and FIG. 4B, and the third valve V3 serve this purpose. Typically there is a 1 minute "rinse", i.e. the first pump is activated, and air with water droplets is sprayed into the room, but the time to rinse can also be longer than 1 minute, or shorter than 1 minute.

The amount of hydrogen peroxide mixture required for the first and second phase together has already been described above. As a rule of thumb, it can be said that typically 40% to 60% of this is introduced into the room during the first phase, and the remaining amount in the second phase. The optimal ratio between the amount introduced in the first and second phases depends mainly on the volume of the room and the maintenance period, but also on the initial temperature and relative humidity of the room. This ratio can again be stored in tabular form in a non-volatile memory of the fogging device.

FIG. 14A shows the ideal or theoretical course, but in practice the increase in hydrogen peroxide concentration during the first phase is not linear, among other things, not only because of the decreasing liquid flow rate in fogging devices without liquid pump (see FIG. 7), but also and especially because the evaporation of the droplets becomes more difficult as the process progresses, and more water vapor enters the room. In other words, during the first phase not only does the gaseous hydrogen peroxide concentration increase, but also the relative humidity. When the relative humidity in the room has reached 100%, the air is saturated and the hydrogen peroxide concentration in the room cannot increase any further.

FIG. 14B shows an example of a course that could occur in practice when using open-loop control. Taking into account that the hydrogen peroxide concentration will decrease spontaneously during the second phase, it is preferable to blow slightly more liquid mixture into the room than in the ideal case, so that a point A' is reached which is slightly higher than the point A of FIG. 14A. During the second phase, the pump can be run intermittently, e.g. with a certain duty cycle, e.g. as shown in FIG. 15A or FIG. 15B, where the course of the hydrogen peroxide concentration (see FIG. 14B) is not perfectly flat in practice but will show a kind of sawtooth. When the predetermined duration (e.g. 60 min) of the second phase has elapsed, a short rinse of the conduits will optionally be done with demineralized water from the third reservoir 420, after which the hydrogen peroxide concentration in the room will decrease spontaneously or forced. Since FIG. 14B illustrates an "open loop" control, i.e. without effective measurement of the gaseous hydrogen peroxide concentration, it is not known exactly when the hydrogen peroxide concentration has fallen below 1.0 ppm. Therefore, in this case it is best to build in a safety margin before releasing the room.

FIG. 14C shows an example of a course that could occur in practice when using closed-loop control. In this case, the course will also show a sawtooth, but the first pump (and optionally also the liquid pump) can be selectively activated and deactivated repeatedly based on the measured hydrogen peroxide concentration, in order to bring this value as close as possible to the target value (of e.g. 100 ppm), or to keep this value within a certain range (e.g. within the range from 100 ppm to 120 ppm). Thanks to the hydrogen peroxide sensor, it can also be determined exactly when the hydrogen peroxide concentration in the third phase F3 has dropped below 1.0 ppm, after which the room can be released.

In a variant (not shown) of the method of FIG. 10, the third phase consists of a first part of a predetermined duration (e.g. 30 minutes or 60 minutes or 90 minutes or 120 minutes), in which no active means (e.g. scrubber and/or catalyst) are used to actively reduce the gas-phase hydrogen peroxide in the room; and a second part, in which active means (e.g. scrubber and/or catalyst) are used to reduce the gas-phase hydrogen peroxide in the room. In this way, the "contact time' with a relatively high concentration of hydrogen peroxide gas can be deliberately extended, in order to achieve greater killing.

FIG. 15A shows an example of an "intermittent fogging" method, which may be applied during the second phase phase2 of the "open-loop" control fogging process, performed by a fogging device that fogs a liquid mixture using the Venturi principle. In this example, a maintenance period T2 of 60 minutes is assumed, which is divided into 12 periods or intervals of 5 minutes each (N=l to 12). Each interval comprises an active portion during which the first pump is turned ON to fog, and a passive portion during which the first pump is turned OFF. In the example it is assumed that a residual volume of "Vrest" of the mixture still has to be fogged. Depending on the fill factor at the beginning of the second phase, the fogging device can calculate how long the first pump (and optionally also the liquid pump) needs to be activated to fog this amount. Suppose that 500 ml is to be fogged in the second phase, and that the fill factor is 100% (e.g. because the second reservoir is used). As shown in FIG. 8, the pump must be activated cumulatively for 500 s to fog this amount of mixture. In the example of FIG. 15A this time will be divided by 12, and the first pump will be turned ON every 5 minutes for 500/12 = approximately 41.7 seconds. By applying this time schedule (with fixed duty cycle), the same amount of mixture will not be blown into the room in each period, but only approximately, because the flow rate in the first period is approximately 62 L/min, and for the twelfth period about 55 ml/sec.

FIG. 15B shows a second example of an "intermittent fogging" method which may be applied during the second phase phase2 of the "open-loop" fogging process. In this example, a maintenance period T2 of 60 minutes is again assumed, which is divided into 12 intervals of 5 minutes each (N=l to 12), and it is assumed that another 500 ml should be fogged. But in the schedule of FIG. 15B (with variable duty cycle), the active time of each time slot is selected so that the same amount of mixture is introduced into the room in each time slot, in the example 500 ml/12 = approximately 41.7 ml. To achieve this effect, the first pump will need to be switched ON for a little less time in the first period and switched ON a little longer in the twelfth period.

Of course these are just examples, and in practice other values can be used for e.g. the amount of mixture to be maintenance period (e.g.: 500 ml), the maintenance period (e.g.: 60 min), and the number of periods (e.g.: 12).

However, the invention is not limited to an intermittent fixed period time schedule as shown in FIG. 15A or FIG. 15B, (in the example: 60min / 12 = 5min), but it is also possible to choose the duration of the intervals differently, and in such a way that the first pump will run for the same amount of time in each interval (as in FIG. 15A), butthat the "injections" are distributed in such a way that a more regular H2O2 concentration profile is obtained. In such a time schedule, in the event that the liquid is drawn by the Venturi principle, the first interval will be somewhat longer than that of FIG. 15A, and the last interval somewhat shorter, inversely proportional to the amount of liquid that will be fogged in the respective interval, in other words, proportional to the fluid flow rate.

In the example of FIG. 15A and FIG. 15B, hydrogen peroxide mixture was introduced into the room at the beginning of each period, but this is of course not strictly necessary, and it is e.g. also possible to introduce hydrogen peroxide mixture at the end of each period, or in the middle of each period.

FIG. 16 shows an illustrative graph of cumulative fogging time as a function of cumulative consumption of the hydrogen peroxide mixture in the reservoir, for the sake of illustrating embodiments of the present invention. When the remaining volume of hydrogen peroxide mixture in the reservoir decreases, the flow rate of extraction of the product from the reservoir will also decrease, so that this relationship exhibits a superlinear behavior (of time as a function of quantity consumed). However, the decrease in flow rate is not perfectly linear with the amount of consumed (or, equivalently, remaining) product.

To disperse a given volume of the hydrogen peroxide mixture, the fogging time should increase as the flow rate (or, equivalently, the residual amount in the reservoir) decreases. Thus, it is possible to accurately estimate the time required to disperse a given amount of product by characterizing this relationship, e.g., with experimental tests.

As an example, a fogging device as described hereinabove was placed in a test chamber. The reservoir placed in this device was initially filled with 3000 g of the Huwa-San TR-12.5 product. As a reference, the total weight of the filled reservoir (but without cap) was measured. The nebulizer was then activated for a predetermined time (700 s) to nebulize the Huwa-San TR-12.5. By repeatedly weighing the reservoir (in the same manner) and activating the device again for the predetermined time, the amount of product consumed as a function of cumulative fogging time (and therefore also vice versa) could be determined. This process was repeated until the reservoir was completely emptied, specifically, in this experiment, after nine repetitions.

FIG. 16 shows this cumulative consumption of the product (from 0 g consumed to substantially 3000 g, i.e., complete emptying).

It was found that this relationship can be characterized with sufficient accuracy using a fourthdegree polynomial. This thus allows, according to embodiments of the present invention, to store this empirically determined relationship (without limitation thereto, e.g., similar results can also be achieved, e.g., by accurate modeling of the fluidomechanical system) for use by the device control software and/or controller.

This can be done, for example, by storing the coefficients of this polynomial in a digital memory, but implementations entirely in hardware are therefore not necessarily excluded (e.g., by translation of the functional relationship into a digital circuit, or even an analog equivalent).

Even though, in embodiments according to the present invention, the time that liquid must be withdrawn from the reservoir to disperse the desired amount of product is determined based on a linear (in first approximation) or nonlinear relationship (such as the polynomial described above) between the total atomization time (i.e. cumulative over all previous reservoir uses since filling) and the cumulative amount of hydrogen peroxide mixture consumed from or remaining in the reservoir, it will be clear that this is not necessarily done by directly evaluating the relevant polynomial (or other) expression. Thus, in a particularly simple way, a nonlinear relationship can be stored and used by using a table of values (a look-up table, LUT). Many variations are known in the art for encoding and applying such a correlation. For example, hereinabove, the empirically determined correlation was analyzed by determining its best fitting expression in a polynomial expression (of predetermined degree, being 4 in this example). It is known that alternative basis functions (i.e. alternative to the polynomial series expansion in the basis 1, x, x ² ,...) can be used equally. In addition, nonlinear behavior can also be modeled by other means, such as a piecewise continuous linear function (e.g., a linear progression between certain tipping points, which would be substantially equivalent to linear interpolation based on a LUT, without limitation thereto, e.g. non-linear interpolation approaches may equally be used when using a LUT).

FINALLY,

Although the invention has mainly been described with reference to a number of specific parameters, or combinations of specific parameters, e.g. at least 100 ppm as the target gas-phase hydrogen peroxide concentration over a period of at least 60 minutes; not more than 1.0 ppm as the target gas-phase hydrogen peroxide concentration at the end of phase3; the present invention is of course not limited thereto, and other values are also possible.

Although the invention was primarily described for a silver-stabilized hydrogen peroxide mixture, commercially available under the name "Huwa-San TR-12,5", consisting of a mixture of 12.1 to 12.5 wt% hydrogen peroxide, 0.0059 to 0.0079 wt% silver as a stabilizer, and demineralized water (for the remaining wt%), the present invention is not limited thereto, and other silver-stabilized hydrogen peroxide mixtures can also be used, such as, for example, but not limited to: the product, commercially available under the name "Huwa-San TR-7,9", consisting of 7.5 to

7.9 wt% hydrogen peroxide, and 0.0042 to 0.0053 wt% silver as stabilizer, and demineralized water (for the remaining wt%); or the product, commercially available under the name "Huwa-San TR-11,9", consisting of 11.5 to

11.9 wt% hydrogen peroxide, and 0.0057 to 0.0074 wt% silver as stabilizer, and demineralized water (for the remaining wt%); or the product, commercially available under the name "Huwa-San TR-5", consisting of 4.5 to 4.9 wt% hydrogen peroxide, and 0.0027 to 0.0035 wt% silver as stabilizer, and demineralized water (for the remaining wt%).

For the sake of completeness, the following combinations of parameters are explicitly stated:

Which of these combinations is used depends on the hydrogen peroxide mixture used but may also depend on the conditions of the room. For example, tests have shown that while it is possible to achieve a hydrogen peroxide concentration of 80 ppm by fogging a hydrogen peroxide mixture with 4.5 wt% hydrogen peroxide, in a room with an initial temperature of 20°C and an initial relative humidity of 48%, it is not possible to achieve 100 ppm in gas phase without preconditioning the room to a higher temperature or lower humidity.

In an embodiment with "closed loop" control, the fogging device is provided to detect that the gas-phase hydrogen peroxide concentration does not rise to the predetermined value (e.g., 100 ppm), but only rises to a lower value (e.g. 80 ppm), and will dynamically adjust the predetermined time of the second phase (e.g., 60 minutes, because 100 * 60 = 6000) (e.g., to a value of 75 minutes, because 80 * 75 = 6000), so that the above-mentioned factor of 6000 (or another value, set by the operator) is still achieved.

For the sake of completeness, it is noted that external hydrogen peroxide sensors for measuring gaseous hydrogen peroxide are commercially available. For example, the following sensor can be used: "DragerSensor® H2O2 LC - 6809705" in embodiments of the present invention. This sensor can accurately measure the gas-phase hydrogen peroxide concentration both during the first and second phase (where a value of e.g. approximately 100 ppm is targeted), as well as during the third phase (where a value of e.g. approximately 1.0 ppm is targeted). While individual features have been illustrated in various drawings and in various embodiments of the present invention, it is contemplated that features of various embodiments may be combined, as would be obvious to those skilled in the art upon reading this document.