FIELD OF THE INVENTION

The invention relates to ultraviolet radiation based disinfection. The invention relates to an illumination device comprising a light source for emitting ultraviolet light for disinfecting a volume of air, and a sensor unit for determining a concentration of a particle in the volume of air. The invention further relates to such an illumination device comprising an air purification device. The invention further relates to such an illumination device comprising an ionizer. The illumination device may for example be an upper air ultraviolet disinfection luminaire. The invention further relates to an illumination system. The invention further relates to a method of emitting ultraviolet light for disinfecting a volume of air. The invention further relates to a corresponding computer program product.

BACKGROUND OF THE INVENTION

The COVID-19 pandemic has been shaking the world in 2020. Said pandemic has already shown that it may catalyze economic recession, and that it may disrupt the mental wellbeing of people as a consequence of social distancing measures. However, irrespective of COVID-19, the health and wellbeing of people and/or animals has been contested periodically with other viruses and bacteria outbreaks already, such as for example the seasonal symptomatic influenza A/B outbreak, SARS, MERS, H1N1 and Bird Flu (Avian Influenza). Seasonal symptomatic influenza A/B has for example proven to be a returning economic burden. Future outbreaks, mutations, epidemics, and pandemics are not excluded.

Consequently, to prevent economic loss and to improve health and wellbeing of people and animals, a clear need exists for health and wellbeing in for example the office domain, the domestic space, the public space and/or agriculture. Such a need may be met by an ultraviolet (UV) radiation based disinfection device.

For example, it is known that UV-C radiation has a strong germicidal effect. UV-C radiation is thereby absorbed by DNA / RNA, and consequently destroys the DNA / RNA structures, while inactivating (where applicable) the corresponding cells. Microorganisms such as viruses, bacteria, yeasts and fungi may therefore be rendered harmless when exposed to UV-C radiation. Low-pressure mercury discharge lamps may for example be an efficient source for generating ultraviolet light. Namely, low-pressure mercury discharge lamps may on average convert 35% of their respective input watts to UV-C watts (for example rendering radiation at 254 nm). The use of LED lighting also becomes increasingly more efficient and common in UV disinfection applications.

Such UV-C radiation based disinfection devices may however, in operation, generate an unpleasant smell. People may characterize such unpleasant smell as “Fried Chicken”, or even mistakenly as “Ozone Stink”, while no chicken is fried, and no ozone is produced at all. Hence, the generated unpleasant smell is a clear disadvantage. Even further, the more a space has been occupied by people, the stronger may be the smell. Such unpleasant smell may affect the wellbeing, health and comfort of people. Such unpleasant smell generation may even limit the possibility to apply such disinfection devices in populated spaces, where such disinfection may be needed most.

SUMMARY OF THE INVENTION

Internal studies have found the source of the unpleasant smell caused by ultraviolet radiation based disinfection devices, particularly by UV-C radiation disinfection devices. The source appears to be a certain high concentration of human skin cells in dust, which is particularly present in indoor spaces with high human presence and/or traffic. For example: offices, subway stations, stadiums, hospitals, but also indoor spaces associated with certain human activities, such as working out or cutting hair. More specifically, ultraviolet light transforms the relatively high levels of keratin and cysteine in dust particles into ‘unpleasantly smelling’ sulfur comprising thiols. For example, mercaptan.

It is therefore an object of the invention to provide an improved illumination device, which at least alleviates the problems and disadvantages mentioned above, such as providing ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith. Thereto, the invention provides an illumination device comprising: a light source configured to emit ultraviolet light for disinfecting a volume of air; a sensor unit configured to determine a concentration of a particle in the volume of air, wherein the particle is biogenic dust; a controller configured to determine a condition in which the concentration of the particle is below a predefined threshold value, and when said condition is determined, to control the light source to emit the ultraviolet light. Thereby, in an embodiment, the controller may be configured to control, when said condition is determined, the light source to emit the ultraviolet light at a first light intensity during a first period of time.

Hence, the controller of the illumination device according to the invention controls the light source to emit the ultraviolet light, e.g. at a first intensity during a first period of time, when the concentration of the particle is below a predefined threshold value. This advantageously reduces an unpleasant smell during the process of UV disinfection, because the volume of air comprises a lesser concentration of said particle. In other words: UV disinfection is applied at conditions when the air may be classified as more ‘pure’ or ‘clean’, thereby mitigating the possible generation of chemical components causing unpleasant smell. Said illumination device may be mounted in a space. Said space may be comprising the volume of air.

Throughout the application, said illumination device may alternatively be phrased, and/or classified as, a disinfection device. Throughout the application, said ‘concentration’ may be an average concentration of a particle in the volume of air.

Said particle may alternatively be phrased as ‘type of particle’. Said particle may be associated with an unpleasant smell. As partly mentioned, said particle may be dust. Said dust may for example be phrased as domestic dust and/or airborne dust. As mentioned, said particle may be biogenic dust. Such biogenic dust may be produced by living organisms, such as dust comprising (dead) human skin cells which are shed, or desquamated from the human body. More specifically, in an embodiment, said biogenic dust may comprise human skin cells. Said particle may thereby be human skin cells. More specifically, in an embodiment, said biogenic dust may comprise at least one of: cysteine particles and keratin particles. Said particle may therefore be cysteine particles and/or keratin particles. Said particle, or biogenic dust, may alternatively be classified as PM10.

Said first light intensity may be phrased as, or associated with, a disinfection light intensity. For example, said first light intensity may be the light source turning on. For example, when said condition is determined, the controller may be configured to control the light source to start emitting the ultraviolet light. For example, said first light intensity may be an intensity in the range between 1-100%. For example, when said condition is determined, the controller may be configured to control to increase emitting the ultraviolet at a first light intensity during a first period of time. For example, when determining said condition, the light source may be controlled to increase emitting the ultraviolet light with an intensity of at least 20%. Since the volume of air comprises a lesser concentration of the particle, the ultraviolet light may be emitted at a higher intensity, so as to improve the germicidal effect while having a reduction of the unpleasant smell (at least compared to the condition if the concentration was determined higher). Said first light intensity may be expressed as a percentage of the maximum light output of the ultraviolet light source (i.e. the maximum being 100%). In aspects, said first light intensity may be phrased as first light dim level. Such terminology are known for a skilled person in the art of lighting.

Said first period of time may be phrased as, or associated with, a disinfection period of time. Said period of time may be a pulse. For example, said period of time may be a pulse of at least 0.1 second, a pulse of at least 0.5 seconds, or a pulse of at least 1 second.

Said period of time may for example be a period of at least 1 second, a period of at least 2 seconds, a period of at least 10 seconds, or a period of at least 10 minutes. The period of time may be dependent on the operation of the illumination device, and e.g. the specific requirements for disinfection as known in the art.

As mentioned, the invention may provide an illumination device comprising: a light source configured to emit ultraviolet light for disinfecting a volume of air; a sensor unit configured to determine a concentration of a particle in the volume of air; a controller configured to determine a condition in which the concentration of the particle is below a predefined threshold value, and when said condition is determined, to control the light source to emit the ultraviolet light at a first light intensity during a first period of time.

In an embodiment, the predefined threshold value may be a concentration of at most 3000 pg per cubic meter (m ³ ), preferably at most 1000 pg per cubic meter (m ³ ), most preferably at most 100 pg per cubic meter (m ³ ). For example, said predefined threshold may be a concentration of at most 1000 pg of biogenic dust per cubic meter (m ³ ).

For example, said predefined threshold value may be a concentration within the range of 50-1000 pg per cubic meter (m ³ ), as such concentrations (of dust, e.g. PM10) may be typical for indoor domestic or people-occupied spaces, and that may still render the undesired smell as mentioned.

In examples, said sensor unit may be separate from the light source. For example, said sensor unit may be standalone and separate from the light source. Although part of the illumination device, the sensor unit may be separate. For example, the sensor unit may thereby be positioned in a space comprising at least part of the volume of air. The sensor unit may be portable.

The light source is configured to emit, in operation, ultraviolet light for disinfecting a volume of air. The light source may comprise a conventional light source. The light source may additionally or alternatively comprise an LED light source. The light source may additionally or alternatively comprise a laser-based light source.

In an embodiment, the ultraviolet light may comprise at least one of: Ultra Deep UV light in the range of 100 -190 nm, Deep UV light in the range of 190-220 nm, UV- C light in the range of 220-280 nm, UV-B light in the range of 280-315 nm, UV-A light in the range of 315-400 nm, UV light at 254 nm. Such spectral distributions are known for their germicidal effect.

In an embodiment, the illumination device may be arranged in the volume of air. Hence, the volume of air to be disinfected is substantially external to the illumination device. Thus, the illumination device is configured to disinfect the volume of air external to the illumination device. Thereby, the light source of the illumination device may be arranged open to the ambient or environment (in which the illumination device is installed).

In an embodiment, the illumination device may be an upper air disinfection luminaire. In aspects, the illumination device may be an UV disinfection robot. In aspects, the illumination device may be an UV disinfection ceiling tile and/or panel luminaire. Said upper air disinfection luminaire may be characterized by the light source, in operation, being directed upwards relative to gravity. Said upper air disinfection luminaire may be characterized by the light source, in operation, being directed towards a surface of a space bounding at least part of the volume of air. Said upper air disinfection luminaire may be mounted to a ceiling of a space, which space may comprise said volume of air.

In an embodiment, the illumination device may be an robotic apparatus. For example, the illumination device may be an ultraviolet illumination based disinfection robot. Said robotic apparatus may be mobile, so as to be able to disinfect various different spaces effectively and dynamically.

Said sensor unit may be configured, in aspects, to measure a concentration of a particle in the volume of air. The sensor unit may be a sensor bundle, said sensor bundle may be comprising multiple sensors. In an embodiment, the sensor unit may comprise at least one of: an Air Quality Sensor, a Volatile Organic Component (VOC) sensor, a light sensor, a camera, a Radiofrequency receiver. Such an Air Quality Sensor and Volatile Organic Component (VOC) sensor may for example measure a concentrations of the particle (e.g. biogenic dust) directly. Said light sensor and camera may measure a concentrations of the particle (e.g. biogenic dust) indirectly.

The light sensor may for example measure light intensity indicative of a dust concentration in the volume of air. The light sensor may e.g. monitor light reflections on a surface comprising an accumulation of dust, which may be indicative of a dust concentration in the volume of air.

The camera may for example determine biogenic dust accumulation and/or biogenic dust levels in a space associated with the volume of air. The camera may thereby determine the concentration of biogenic dust in the volume of air. The camera may determine a cleaning status of a space associated with the volume of air. Thereby, the camera may determine a concentration of the particle in the volume of air based on said determined cleaning status. For example, the camera may detect a cleaning apparatus in said space, thereby correlating the presence of the cleaning apparatus to a particular concentration of the particle in the volume of air. Even though direct concentration measurements are most accurate, such indirect determinations may be cheaper in hardware but still sufficiently accurate.

The radiofrequency receiver may determine the concentration of the particle in the volume of air via radiofrequency based sensing. Alternatively, said radiofrequency receiver may obtain data indicative of the concentration of the particle via another device. Hence, in examples, the controller may be configured to retrieve or receive said concentration of the particle from an external control device; wherein the external control device is one of: a user input device, a building management server, a cleaning robot, a memory, an external sensor device.

The predefined threshold value may be prestored in the controller according to the invention. Said predefined threshold value may be factory set, or provided during commissioning of the illumination device at the installed location. Alternatively, in aspects, the controller may be configured to retrieve or receive said predefined threshold value from an external control device; wherein the external control device is one of: a user input device, a building management server, a cleaning robot, a memory, an external sensor device. For example, said predefined threshold value may be set by a user input device, such as e.g. a tablet, smartphone, commissioning device, a remote control, a computer, a building management device.

In an embodiment, the predefined threshold value may be determined based on an installation property of the illumination device; wherein the installation property may be installation height of the illumination device relative to a floor. Such an embodiment may be advantageous. Namely, the present invention reduces unpleasant smell, which may be controlled by the value of predefined threshold value. Setting the predefined threshold value based on an installation property may thus enable that the reduction of unpleasant smell may be adapted to (or dependent on) the context of how and where the illumination device is installed (or e.g. currently moving in case of the illumination device being a robotic apparatus).

As partly mentioned before, it is an object of the invention to provide ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith. A pre-treatment of the volume of air may be advantageous.

Therefore, in aspects, the illumination device comprises: an air purification device configured to reduce, in operation, the concentration of the particle in the volume of air during a second period of time. The second period of time may be phrased as, or associated with, a purification period of time. In an embodiment, the second period of time may be before the first period of time. In an embodiment, the second period of time may at least partly overlap the first period of time.

The air purification device may for example be an air purifier. Said air purifier may comprise a filter, a conduit and a fan, wherein the fan is configured to convey air of the volume of air through the conduit of the air purifier, wherein the filter is arranged at least partly in the conduit, wherein the filter is arranged to reduce, in operation, the concentration of the particle in the volume of air during the second period of time. Said filter may e.g. be an activated carbon filter, or a HEPA filter. Such filters may e.g. reduce a concentration of thiol particles in air.

The air purification device may be an ionizer. Therefore, in an embodiment, the illumination device comprises: an ionizer configured to reduce, in operation, the concentration of the particle in the volume of air during a second period of time. The second period of time may be phrased as, or associated with, a purification period of time. In an embodiment, the second period of time may be before the first period of time. In an embodiment, the second period of time may at least partly overlap the first period of time.

Such embodiments and aspects may be advantageous, because the air purification device and/or ionizer of the illumination device reduces, in operation, the concentration of the particle in the volume of air, such that the concentration (or even amount) of particles being a source for the unpleasant smell are reduced, before and/or during ultraviolet light based disinfection is applied by the illumination device. Hence, the illumination device, in operation, provides ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith.

Yet in further aspects, the illumination device comprises: an air purification device configured to reduce, in operation, the concentration of the particle in the volume of air during a second period of time, wherein the air purification device comprises comprising an ionizer and/or an air purifier. The second period of time may be phrased as, or associated with, a purification period of time. In an embodiment, the second period of time may be before the first period of time. In an embodiment, the second period of time may at least partly overlap the first period of time.

An ionizer generates, in operation, a concentration and/or density of ionized molecules in air (i.e. ionization cloud). The ionized molecules in air will namely be generated, and be consequently present, in the near vicinity of an ion generating source. The ionized molecules are thereby either negatively or positively charged. Ionized molecules in air may also be referred to as an ionization cloud throughout the application. An ionization cloud may moreover be defined as a cloud of ionized molecules in air having a particular concentration and/or density. Said particular concentration and/or density may be suitable for purification of a volume of air from particles, such as the particle(s) according to the invention.

Moreover, it may be advantageous to purify at least part of the volume of air with the ionizer before said volume of air is subjected to UV disinfection. An ionization cloud around the illumination device may facilitate this, because all air of the volume of air, which is being subjected to UV disinfection, may require to pass the illumination cloud first. Hence, in an embodiment, the ionizer may be configured to ionize at least one region of air in the volume of air; wherein said at least one region may be adjacent to the illumination device and within a distance of two meters from the illumination device. Further examples may be envisioned, in which the at least one region is within a meter from the illumination device.

As partly mentioned before, it is an object of the invention to provide ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith. A post-treatment of the volume of air may be advantageous. Therefore, in an embodiment, the sensor unit may be configured to determine a concentration of a second particle in the volume of air; wherein the controller is configured to determine a second condition in which the concentration of the second particle is above a second predefined threshold value, and when said second condition is determined, to control the ionizer to reduce the concentration of the second particle in the volume of air. Thereby, the second particle may be the source of the unpleasant smell. Namely, in an embodiment, said second particle may be a reaction product of the particle when exposed to ultraviolet light. Moreover, in examples, said second particle may be one of the group of Thiols. For example, thiols that are generated by dust, or biogenic dust, exposed to ultraviolet light. Such embodiments are advantageous, because the ionizer may also be utilized, in operation, to reduce any unpleasant smell still being present and caused by the reaction product of the particle according to the invention when exposed to ultraviolet light, thereby noting that said reaction product may be referred to as the second particle.

In aspects, the sensor unit may comprise a further sensor, wherein said sensor may also keep track for how long the UV light has been actuated in the space and thereby infer how long the particle has been exposed to ultraviolet light. This may for example allow computing how many of said particle may be broken down into smaller molecules.

It is further an object of the invention to provide an improved illumination system, which at least alleviates the problems and disadvantages mentioned above, such as providing ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith. Thereto, the invention provides an illumination system comprising: a light source configured to emit ultraviolet light for disinfecting a volume of air; a sensor unit configured to determine a concentration of a particle in the volume of air; a controller configured to determine a condition in which the concentration of the particle is below a predefined threshold value, and when said condition is determined, to control the light source to emit the ultraviolet light at a first light intensity during a first period of time. The advantages and/or embodiments applying to the illumination device according to the invention may also apply mutatis mutandis to the illumination system according to the invention.

In embodiments, said sensor unit, controller, and/or light source may be integrated in a single device. Yet alternatively, in embodiments, said sensor unit, controller and/or light source may be separate devices. The sensor unit may thereby for example be a portable device. The controller may be arranged separately, but in wired or wireless communication with the sensor unit and/or light source. Such embodiments may provide more freedom and flexibility in housing separate parts of the illumination system.

It is a further object of the invention to provide an improved method, which at least alleviates the problems and disadvantages mentioned above. Thereto, the invention provides a method of emitting ultraviolet light for disinfecting a volume of air, wherein the method may comprise: a sensor unit determining a concentration of a particle in the volume of air; a controller determining a condition in which the concentration of the particle is below a predefined threshold value; the controller controlling, when said condition is determined, a light source to emit ultraviolet light at a first light intensity during a first period of time. The advantages and/or embodiments applying to the illumination device according to the invention may also apply mutatis mutandis to the method according to the invention.

In an embodiment, the method may comprise: an ionizer reducing, in operation, concentration of the particle in the volume of air during a second period of time; wherein the second period of time is before the first period of time. Alternatively, the second period of time may at least partly overlap the first period of time.

Said ionizer may mutatis mutandis be any other air purification device, such as an air purifier as mentioned before.

In an embodiment, the method may comprise: the sensor unit determining a concentration of a second particle in the volume of air; wherein the controller determining a second condition in which the concentration of the second particle is above a second predefined threshold value, and when said second condition is determined, controlling the ionizer to reduce the concentration of the second particle in the volume of air. In an embodiment, said second particle may be a reaction product of the particle when exposed to ultraviolet light. Moreover, in examples, said second particle may be one of the group of Thiols.

The invention further relates to a computer program product. Hence, the invention provides a computer program product for a computing device, the computer program product comprising computer program code to perform a method according to the invention when the computer program product is run on a processing unit of the computing device.

Thus, aspects of the invention may be implemented in a computer program product, which may be a collection of computer program instructions stored on a computer readable storage device which may be executed by a computer. The instructions of the present invention may be in any interpretable or executable code mechanism, including but not limited to scripts, interpretable programs, dynamic link libraries (DLLs) or Java classes. The instructions can be provided as complete executable programs, partial executable programs, as modifications to existing programs (e.g. updates) or extensions for existing programs (e.g. plugins). Moreover, parts of the processing of the present invention may be distributed over multiple computers or processors.

In alternative aspects, the invention provides an illumination device, said illumination device comprising: a light source configured to emit ultraviolet light for disinfecting a volume of air; a sensor unit configured to determine a concentration of a third particle in the volume of air; a controller configured to determine a third condition in which the concentration of the third particle is above a third predefined threshold value, and when said third condition is determined, to control the light source to emit the ultraviolet light at a third light intensity during a third period of time. Such an example may be advantageous, as the third particle may be causing another unpleasant smell, which is not related to UV disinfection, and the illumination device may be operated whenever such another unpleasant smell is present in the volume of air anyway. Thus, only operate the disinfection function of the illumination device, when another unpleasant smell is already present.

In aspects, the invention provides an illumination device comprising: a light source configured to emit ultraviolet light for disinfecting a volume of air; a sensor unit configured to determine a concentration of a particle in the volume of air; wherein the light source is configured to emit the ultraviolet light if the concentration of the particle is below a predefined threshold value. Said particle being for example biogenic dust. The advantages and/or embodiments applying to the illumination device according to the invention may also apply mutatis mutandis to this aspect according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further elucidated by means of the schematic non-limiting drawings:

Fig. 1 depicts schematically an embodiment of an illumination device according to the invention;

Fig. 2 depicts schematically an embodiment of an illumination device according to the invention comprising an ionizer in a first situation;

Fig. 3 depicts schematically an embodiment of the illumination device depicted in figure 2 in a second situation;

Fig. 4 depicts schematically an embodiment of an illumination system according to the invention.

Fig. 5 depicts schematically an embodiment of a method according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As mentioned, UV-C radiation based disinfection devices may, in operation, generate an unpleasant smell. People may characterize such unpleasant smell as “Fried Chicken”, or even mistakenly as “Ozone Stink”, while no chicken is fried, and no ozone is produced at all. Hence, the generated unpleasant smell is a clear disadvantage. Internal studies have found the source of the unpleasant smell caused by ultraviolet radiation based disinfection devices, particularly by UV-C radiation disinfection devices. The source appears to be a certain high concentration of human skin cells in dust, which is particularly present in indoor spaces with high human presence and/or traffic. For example: offices, subway stations, public transport passenger cabins, stadiums, hospitals.

More specifically, ultraviolet light transforms the relatively high levels of keratin and cysteine in dust particles into ‘unpleasantly smelling’ sulfur comprising thiols. The present invention enables ultraviolet radiation based disinfection, while reducing any unpleasant smell associated therewith. The present invention does this, amongst others, by intelligently controlling the ultraviolet light source based on determining a particle concentration within the volume of air to be UV disinfected, which particle concentration is associated with the origin of the unpleasant smell (e.g. dust); and/or by intelligently timing the use of an ionizer to either purify the volume of air to be disinfected from undesired particles (e.g. dust) beforehand, or to purify the volume of air afterwards from particles resulting from the UV disinfection and causing the unpleasant smell.

Even more specifically: Humans may describe the smell originating from UV disinfection systems as ‘the burning of hair’ or as ‘an odor resembling rotten eggs or garlic’. Burning of hair produces a sulfurous odor smell, because hair may contain large amounts of the sulfur-containing amino acid cysteine. Rotten eggs or garlic smell is characteristic of the thiol mercaptans. Both skin and hair contain around 5% of sulfur. Human hair may e.g. contain 14% of cysteine.

Exposing skin and/or hair to an UV photon ‘bombardment’ breaks skin and hair particles into thiol molecules such as Methyl Mercaptan, Ethyl Mercaptan, or even Hydrogen Sulfide. It may be known in the art that airborne dust, as present in indoor environments occupied by humans, may contain up to 80% of dead human skin and squamous hair, wherein the remaining 20% may comprise pollen, textile & paper fibers, minerals from outdoor soil, and many other micron size materials found in the local environment. In a typical indoor environment, airborne dust may be in the range of 100 and 10.000 pg/m ³ . ASHRAE specifies a maximum acceptable level for total dust of 10.000 pg/m ³ and 3.000 pg/m ³ for PM10 indoor air quality standard.

Considering a typical dust concentration of 100 pg/m ³ , and operating a 254nm UV disinfection system, this may translate into a concentration of mercaptans of about 2 ppb. The smell threshold level for mercaptans may typically be 1 ppb. Hence, the implementation of UV disinfection in a room may result in undesirably ‘smell’ levels, threatening health and wellbeing of people and/or animals within said room.

Figure 1 depicts schematically, by non-limiting example, an illumination device 10 according to the invention. The illumination device 10 is arranged within a space 20. Said space 20 requires disinfection. For example, to disinfect the space 20 from airborne viral matter. The space 20 comprises a volume of air 21. Thereby, in the present embodiment, the illumination device is arranged in the volume of air. The volume of air 21 that is to be disinfected is thus substantially external to the illumination device 10. Said disinfection is provided by ultraviolet radiation based disinfection. Said illumination device 10 may alternatively be phrased, and/or classified as, a disinfection device.

Therefore, the illumination device 10 comprises a light source 1. The light source 1 is configured to emit, in operation, ultraviolet light 4 for disinfecting the volume of air 21. Ultraviolet light is known for its germicidal effect. Here, the light source 1 is a set of low-pressure mercury discharge lamps. The low-pressure mercury discharge lamps generate, in operation, UV-C radiation at 254 nanometer. Alternatively, the ultraviolet light may comprise at least one of: Ultra Deep UV light in the range of 100 -190 nm, Deep UV light in the range of 190-220 nm, UV-C light in the range of 220-280 nm, UV-B light in the range of 280-315 nm, UV-A light in the range of 315-400 nm.

Alternatively, said light source may be another conventional light source. Alternatively, said light source may be a LED light source. Alternatively, said light source may be a semiconductor light source. Alternatively, said light source may be a laser-based light source.

More specifically, in the present embodiment, the illumination device 10 is an upper air disinfection luminaire. The light source 1 is arranged such that the emitted ultraviolet light 4 remains bounded to a particular disinfection region with said space 20, namely a ceiling region of the space 20. Other examples may similarly be envisioned, and the invention is not limited thereto. The illumination device may in further possible options comprise mounting means (not depicted) to mount said illumination device to a surface in said space. Alternatively, said illumination device may be any other type of luminaire. Alternatively, said illumination device may be a robotic apparatus, such as an ultraviolet disinfection robot. Such a robot may be mobile, and in operation autonomously disinfect said space with ultraviolet radiation.

Referring to figure 1, the illumination device comprises a sensor unit 2. The sensor unit 2 is configured to determine, in operation, a concentration of a particle 5 in the volume of air 21. Said particle may alternatively be phrased as ‘type of particle’. More specifically, the particle 5 is biogenic dust. Such biogenic dust may be produced by living organisms, such as dust comprising (dead) human skin cells which are shed, or desquamated from the human body. As mentioned, said biogenic dust 5 is associated with an unpleasant smell caused by ultraviolet radiation based disinfection, because biogenic dust may comprise skin cells. Said particle 5 may thereby also be phrased as (human) skin cells instead of biogenic dust. Skin cells may comprise at least one of: cysteine particles and keratin particles. Ultraviolet radiation may for example turn said cysteine and keratin particles in the biogenic dust into unpleasantly smelling thiols.

Here, the sensor unit 2 comprises an optical dust sensor. The optical dust sensor measures the concentration of the particle 5 in the volume of air 21. Alternatively, the sensor unit may comprise at least one of: an Air Quality Sensor, a Volatile Organic Component (VOC) sensor, a light sensor, a camera, a Radiofrequency receiver. Such an Air Quality Sensor and Volatile Organic Component (VOC) sensor may for example measure a concentrations of the particle (e.g. biogenic dust) directly. Said light sensor and camera may measure a concentrations of the particle (e.g. biogenic dust) indirectly.

Namely, in alternative embodiments, such a light sensor and/or camera may measure a light intensity and/or an image indicative of a concentration of the particle in the volume of air (e.g. indicative of the biogenic dust). The light sensor may e.g. monitor light reflections on a surface comprising an accumulation of dust, which may be indicative of a dust concentration in the volume of air. The camera may determine a concentration of the particle in the volume of air based on a determined image of the space, which may be indicative of the cleanliness. Moreover, the camera may even detect a cleaning apparatus in said space, thereby correlating the presence of the cleaning apparatus to a particular concentration of the particle in the volume of air.

Said radiofrequency receiver may determine the concentration of the particle in the volume of air via radiofrequency based sensing. Alternatively, said radiofrequency receiver may obtain data indicative of the concentration of the particle via another device.

For example, a cleaning robot or an external sensor device.

Still referring to figure 1, the illumination device 10 comprises a controller 3. The controller 3 is, in operation, in communication with the sensor unit 2 and the light source 1. The controller 3 may for example control the light source 1. The controller 3 may for example control and/or communicate with the sensor unit 2. Here, the light source 1, the sensor unit 2, and the controller 3 are embodied in a same housing (not referenced in the figure) of the illumination device 10. Hence, the light source 1, the sensor unit 2, the controller 3 are co-located and part of the housing of the illumination device 10. Alternatively, the light source, the sensor unit, and/or the controller may be arranged separately or remotely from each other. The illumination device may thereby be an illumination system with separate standalone parts in communication with each other to provide ultraviolet radiation based disinfection of said space.

Still referring to figure 1, the sensor unit 2 measures the concentration of the particle 5 in the volume of air 21. The controller 3 is thereby configured to determine a condition 6 in which the concentration of the particle 5 is below a predefined threshold value. Said condition 6 is schematically depicted in figure 1 in the controller 3. In the present embodiment, the predefined threshold value is an (average) concentration of at most 100 pg particles of biogenic dust per cubic meter (m ³ ). Alternatively, this may be an (average) concentration of at most 50 pg particles of biogenic dust per cubic meter (m ³ ). Here, the predefined threshold value is factory set, and thereby prestored in the controller 3, such that the predefined threshold value is available to the controller 3 to determine said condition 6. Here, the predefined threshold value is constant, but may alternatively be dynamic, such as the predefined threshold value being dependent on the time of day. The predefined threshold value may alternatively be dependent on a light setting applied by the light source emitting the ultraviolet light.

Alternatively, the predefined threshold value may be retrieved or received from an external location. For example, the controller may be configured to retrieve or receive said predefined threshold value from an external device, such as an external control device. Such an external control device may for example be one of: a user input device, a building management server, a cleaning robot, a memory, an external sensor device. Hence, the predefined threshold value, based on which the condition is to be determined, may be provided by an external source, and may be dynamic in time (i.e. the predefined threshold value may be variable depending on different spatial or temporal contexts, wherein said temporal context may e.g. a planned occupancy of a room, or planned visit of a space, such as breaks during an event). For example, the predefined threshold value may change during the time of day, or type of space, or light setting applied by the light source. Hence, yet alternatively, the predefined threshold value may be determined based on an installation property of the illumination device. For example, the installation property may be installation height of the illumination device relative to a floor. Still referring to figure 1, as mentioned, the controller 3 is configured to determine a condition 6 in which the concentration of the particle 5 is below the predefined threshold value. The controller is further configured to control, in operation, the light source to emit the ultraviolet light 4. The ultraviolet light 4 may thereby be emitted according to a light setting. Or phrased differently: the ultraviolet light may comprise a lighting characteristic.

Namely, according to the invention, the controller 3 is configured to control, when said condition 6 is determined, the light source 1 to emit the ultraviolet light 4 at a first light intensity during a first period of time.

Hence, the controller 3 of the illumination device 10 controls the light source 1 to emit the ultraviolet light 4 at a first intensity during a first period of time, when the concentration of the particle 5 is below a predefined threshold value. This advantageously reduces an unpleasant smell during the process of UV disinfection, because the volume of air 21 comprises a lesser concentration of said particle 5. In other words: UV disinfection is applied at conditions when the air may be classified as more ‘pure’ or ‘clean’, thereby mitigating the possible generation of chemical components causing unpleasant smell.

Said first period of time may be phrased as, or associated with, a disinfection period of time. Said first light intensity may be phrased as, or associated with, a disinfection light intensity. Here, the first light intensity of the ultraviolet light 4 is characterized as the light source 1 turning on when said condition 6 is determined, and turning on for a duration of at least one minute, so as to provide ultraviolet radiation based disinfection to the space 20. The first period of time and the first light intensity may be optional parameters to the invention, dependent on the disinfection task at hand.

Such light intensity and duration may be envisioned differently in alternative embodiments. For example, when said condition is determined, the controller may control the light source to start emitting ultraviolet light for a duration of one second, or as repetitive pulses of one second. For example, when said condition is determined, the controller may control the light source to increase the intensity of the ultraviolet light from 40% to 80% intensity for a duration of at least 10 minutes. Similar embodiments may be envisioned accordingly.

As mentioned, referring to the embodiment depicted in figure 1, the volume of air 21 that is to be disinfected is thus substantially external to the illumination device 10. In alternative aspects, the invention may provide an illumination device according to the invention, but wherein the volume of air is conveyed to an internal cavity of the illumination device, in which internal cavity the ultraviolet light of the light source disinfects said conveyed volume of air.

Figure 2 and figure 3 depict, by non-limiting example, an embodiment of an illumination device 30 according to the invention, which is at least partly similar to the embodiment depicted in figure 1, but additionally comprises an ionizer 38. The ionizer 38 is not operational in the situation depicted in figure 2. The ionizer 38 is operational in the situation depicted in figure 3.

Alternatively, said ionizer may be any other air purification device, such as an air purifier (or an ionizer and an air purifier). Said air purifier may comprise a filter, a conduit and a fan, wherein the fan is configured to convey air of the volume of air through the conduit of the air purifier, wherein the filter is arranged at least partly in the conduit, wherein the filter is arranged to reduce, in operation, the concentration of the particle in the volume of air during the second period of time. Said filter may e.g. be an activated carbon filter, or a HEPA filter.

More specifically, said illumination device 30 is a luminaire arranged in a space 40. The space 40 comprises a volume of air 41. The luminaire 30 is configured to disinfect, in operation, at least part of the space 40 and associated volume of air 41 by means of ultraviolet radiation (i.e. illumination). Said illumination device 40 may alternatively be phrased, and/or classified as, a disinfection device. Said disinfection is provided by ultraviolet radiation based disinfection.

Therefore, the illumination device 30 comprises a light source 31. The light source 31 is configured to emit, in operation, ultraviolet light 34 for disinfecting the volume of air 41. Ultraviolet light is known for its germicidal effect. Here, the light source 31 is a LED panel. The LED panel is configured to provide UV-C light in the range of 220-280 nm, but may alternatively provide other ranges of ultraviolet light, such as UV-B light in the range of 280-315 nm, UV-A light in the range of 315-400 nm. Alternatively, said light source may be another LED and/or conventional light source.

Referring to figure 2 and figure 3, the illumination device 30 comprises a sensor unit 32. The sensor unit 32 is configured to determine, in operation, a concentration of a particle 35 in the volume of air 41. Said particle may alternatively be phrased as ‘type of particle’. More specifically, the particle 35 is biogenic dust. Such biogenic dust may be produced by living organisms, such as dust comprising (dead) human skin cells which are shed, or desquamated from the human body. As mentioned, said biogenic dust 35 is associated with an unpleasant smell caused by ultraviolet radiation based disinfection, because biogenic dust may comprise skin cells. Said particle 35 may thereby also be phrased as (human) skin cells instead of biogenic dust. Skin cells may comprise at least one of: cysteine particles and keratin particles. Ultraviolet radiation may for example turn said cysteine and keratin particles in the biogenic dust into unpleasantly smelling thiols. Here, the sensor unit 32 comprises an Air Quality sensor. The Air Quality sensor may e.g. be a Volatile Organic Component sensor suitable for measuring dust. Here, the Air Quality sensor measures the concentration of the particle 35 in the volume of air 41.

Still referring to figure 2 and figure 3, the illumination device 30 comprises a controller 33. The controller 33 is, in operation, in communication with the sensor unit 32, the light source 31 and the ionizer 38. The controller 33 may for example control the light source 31 and/or the ionizer 38. The controller 33 may for example control and/or communicate with the sensor unit 32.

Here, the light source 31, the sensor unit 32, the ionizer 38, and the controller 33 are embodied in a same housing (not referenced in the figure) of the illumination device 30. Hence, the light source 31, the sensor unit 32, the ionizer 38 and the controller 3 are co located and part of the housing of the illumination device 30. Alternatively, the light source, the sensor unit, the ionizer and/or the controller may be arranged separately or remotely from each other. The illumination device may thereby be an illumination system with separate standalone parts in communication with each other to provide ultraviolet radiation based disinfection of said space.

Still referring to figure 2 and figure 3, the sensor unit 32 measures the concentration of the particle 35 in the volume of air 41. The controller 33 is thereby configured to determine a condition in which the concentration of the particle 35 is below a predefined threshold value. The controller 33 is further configured to control, in operation, the light source 31 to emit the ultraviolet light 34. The ultraviolet light 34 may thereby be emitted according to a light setting. Or phrased differently: the ultraviolet light may comprise a lighting characteristic.

Here, the predefined threshold value is an (average) concentration of at most 50 pg particles of biogenic dust per cubic meter (m ³ ). Here, the predefined threshold value is factory set, and thereby prestored in the controller 33, such that the predefined threshold value is available to the controller 33 to determine said condition 6. As mentioned in present application, said predefined threshold value may alternatively be received or retrieved by the controller from other devices, and/or may be dynamically adapted by the controller, e.g. based on time of day or a lighting characteristic applied by the light source. According to the invention, the controller 33 is configured to control, when said condition is determined, the light source 31 to emit the ultraviolet light 34 at a first light intensity during a first period of time. However, in the present embodiment, as depicted in figure 2, and in a situation when the ionizer 38 is not yet operational, said condition cannot be determined by the controller 33, because the concentration of the particle 35 is not below, but above the predefined threshold value. Hence, in the situation depicted in figure 2, the controller 33 is not controlling the light source 31 to emit the ultraviolet light 34 for ultraviolet radiation based disinfection.

However, as mentioned, the illumination device 30 comprises an ionizer 38. The ionizer 38 is configured to generate, in operation, negatively charged ionized molecules (not depicted) in the volume of air 41. Alternatively, positively charged ionized molecules may be generated. The negatively charged ionized molecules 36 may purify the volume of air 41 from the particle 35, i.e. the biogenic dust. Said negatively charged ionized molecules may be characterized as an ionization cloud 36, which ionization cloud 36 may encircle the illumination device 30. For example, in alternative and optional examples, the ionizer 38 is configured to ionize at least one region of air in the volume of air 41, wherein said at least one region is adjacent to the illumination device 30 and within a distance of two meters from the illumination device.

Therefore, now referring to figure 3 in particular, the ionizer 38 is operated during a second period of time, and the ionizer thereby 38 reduces the concentration of the particle 35 in the volume of air 41 during the second period of time. The second period of time may be phrased as, or associated with, a purification period of time. Since it is an object of the invention to provide ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith, the ionizer 38 provides a pre-treatment of the volume of air 41. This may be advantageous.

As a consequence, the volume of air 41 comprises a substantially lower concentration of the particle 35. As mentioned, the controller 33 is configured to determine a condition in which the concentration of the particle 35 is below a predefined threshold and configured to control, when said condition is determined, the light source 31 to emit the ultraviolet light 34 at a first light intensity during a first period of time. Referring to figure 3, said condition is determined, because the concentration of the particle 35 is below a predefined threshold. Therefore, the ultraviolet light 34 is provided by the light source 31 of the illumination device 30, so as to disinfect at least part of the volume of air 41 and the space 40. Here, the first period of time occurs after the second period of time. Alternatively, the second period of time at least partly overlaps the first period of time.

This embodiment may be advantageous, because the ionizer of the illumination device 30 reduces, in operation, the concentration of the particle 35 in (at least part of) the volume of air 41, such that the concentration (or even amount) of particles being a source for the unpleasant smell are reduced, before and/or during ultraviolet light based disinfection is applied by the illumination device 30. Hence, the illumination device 30, in operation, provides ultraviolet radiation based disinfection while reducing any unpleasant smell associated therewith.

In an alternative embodiment, not depicted, an illumination device as depicted in figure 2 and figure 3 is provided, but wherein a post-treatment is provided to reduce the unpleasant smell originating from ultraviolet radiation based disinfection. Namely, in such an embodiment, the sensor unit is configured to determine a concentration of a second particle in the volume of air. The controller is further configured to determine a second condition in which the concentration of the second particle is above a second predefined threshold value. The second particle is a reaction product of the particle when exposed to ultraviolet light. Namely, a thiol as a reaction product of exposing biogenic dust to ultraviolet light. Furthermore, when said second condition is determined, to controller controls the ionizer to reduce the concentration of the second particle in the volume of air. Such an embodiment reduces said unpleasant smell as well.

In further alternative embodiments, the controller may control the ionizer to perform the mentioned pre-treatment according to the invention (i.e. purifying the air before providing ultraviolet radiation based disinfection) and said post-treatment (i.e. purifying the reaction products of the biogenic dust exposed to ultraviolet light, i.e. the unpleasant smell particles itself) at a particular degree relative to each other, so as to achieve an overall target of particles in the volume of air rendering the unpleasant smell. For example, a part of the biogenic dust may be purified, such that ultraviolet radiation based disinfection may occur based on controlling the ultraviolet light source to turn on, but that it may still result in particles rendering the unpleasant smell, but to a lesser degree. The ionizer may then be used to reduce the unpleasant smell further to the desired target or degree. Hence, the controller may actively and dynamically control said ionizer and light source based on the sensor unit sensing both the particle as well as the second particle according to the invention.

Figure 4 depicts, by non-limiting example, an embodiment of an illumination system 50 according to the invention. Said illumination system 50 may alternatively be phrased as a disinfection system. The illumination system 50 is arranged in a space 60 comprising a volume of air 61. Said space 60 may e.g. be a room, a corridor, an office space, a subway space, a hospital space, a retail environment, etc. Said space 60 requires disinfection, e.g. from microbiological species. This disinfection is provided by means of ultraviolet radiation based disinfection, by the illumination system 50. The space 60 comprises a volume of air 61.

Namely: the illumination system 50 comprises a sensor unit 52. The sensor unit 52 is arranged within the space 60. More specifically, the sensor unit 52 comprises three separate dust sensors 521, 522, 523 arranged within the space 60. The dust sensors 521, 522, 523 are wirelessly connected to each other, though said dust sensors may at least partly be wiredly connected as well in alternative examples.

The dust sensors 521, 522, 523 collectively measure a concentration of dust particles 55 in the volume of air 61. Hence, the sensor unit 52 is configured to determine the concentration of dust particles 55 in the volume of air 61. Said dust particles may alternatively be phrased as biogenic dust particles. Said dust may alternatively be another particle in said space. The sensor unit may alternatively comprise an Air Quality Sensor, a Volatile Organic Component (VOC) sensor, a light sensor, a camera, a Radiofrequency receiver. The sensor unit 52 may be configured to determine the concentration of a particle, such as a dust particle, in particular regions in the volume of air.

Furthermore, the illumination system 50 comprises a light source 51 and a controller 53. The light source 51 and the controller 53 are arranged, or embodied, in a robotic apparatus 54. Namely, said robotic apparatus 54 is a UV disinfection robot. The UV disinfection robot 54 comprises the light source 51 and the controller 53. The light source 51 is configured to emit, in operation, ultraviolet light for disinfection, such as for disinfecting at least part of the volume of air 61.

Said ultraviolet light (not depicted in figure 4, as the light source is not operational in the depicted situation) may comprise one of: Ultra Deep UV light in the range of 100 -190 nm, Deep UV light in the range of 190-220 nm, UV-C light in the range of 220- 280 nm, UV-B light in the range of 280-315 nm, UV-A light in the range of 315-400 nm, UV light at 254 nm. Such spectral distributions of light may render a germicidal effect.

For example, the light source may be a UV tower mounted on a wheeled standing plate of the UV disinfection robot. The light sources may thereby be tubular lights. The light source may optionally comprise a reflector or a collimator means for concentrating the ultraviolet light, in operation, towards an area to be disinfected. The controller 53 is arranged for controlling the light source 51. The controller 53 further comprises a wireless transceiver for communicating with the sensor unit 52, and/or each individual dust sensor 521, 522, 523 of the sensor unit 52. The controller 53 is thereby configured to receive the determined concentration of dust particles 55 in the volume of air 61.

Still referring to figure 4, the controller is configured to determine a condition in which the concentration of the dust particles 55 is below a predefined threshold value, and when said condition is determined, to control the light source 51 to emit ultraviolet light. The ultraviolet light may thereby be emitted at a first light intensity during a first period of time. The predefined threshold value is stored in the controller 53. In examples, the predefined threshold value may be received wirelessly from a user input device.

Hence, the controller 53 of the illumination system 50, as part of the UV disinfection robot 54, controls the light source 51 to emit the ultraviolet light 54, e.g. at a first intensity during a first period of time, when the concentration of the dust particles 55 is below the predefined threshold value. Ultraviolet disinfection is therefore only provided when the dust particles are below the predefined threshold value. This advantageously reduces an unpleasant smell during the process of UV disinfection, because the volume of air 61 comprises a lesser concentration of said dust particles 55. In other words: UV disinfection is applied at conditions when the air may be classified as more ‘pure’ or ‘clean’, thereby mitigating the possible generation of chemical components causing unpleasant smell.

Similar embodiments may be envisioned in which the light source, controller and/or sensor unit are separate or combined in various types of hardware, such as lighting devices, robotic apparatuses, building management systems, etc.

In alternative embodiments, the illumination system may further comprise an ionizer. The ionizer may thereby be configured to reduce, in operation, the concentration of the dust particles in the volume of air during a second period of time. The second period of time may be classified as a purification period of time. The second period of time may be before the first period of time in which the ultraviolet disinfection is provided by the light source.

Figure 5 depicts schematically, by non-limiting example, an embodiment of a method 70 of emitting ultraviolet light for disinfecting a volume of air. The method 70 may be provided by an illumination device according to the invention. The method comprises a step 72 of a sensor unit determining a concentration of a particle in the volume of air. Here, said particle is biogenic dust comprising human skin cell particles. Hence, the sensor unit determines the concentration of biogenic dust in the volume of air, or alternatively the concentration of human skin particles in the volume of air, or yet alternatively the concentration of cysteine or keratin particles in the volume of air.

The method further comprises a step 73 of a controller determining a condition in which the concentration of the particle is below a predefined threshold value. Here, the predefined threshold value is prestored in the controller, but may alternatively be received or retrieved by the controller from another device. The predefined threshold value may be a concentration of at most 100 pg particles of a type of particles / m ³ .

The method further comprises a step 74 of the controller controlling, when said condition is determined, a light source to emit ultraviolet light, e.g. at a first light intensity, during a first period of time. Said first period of time may be phrased as, or associated with, a disinfection period of time The light source is thereby configured to emit ultraviolet light, in operation, for disinfecting the volume of air. The ultraviolet light comprises at least one of: Ultra Deep UV light in the range of 100 -190 nm, Deep UV light in the range of 190-220 nm, UV-C light in the range of 220-280 nm, UV-B light in the range of 280-315 nm, UV-A light in the range of 315-400 nm, UV light at 254 nm.

The method 70 comprises an optional step 71 of an ionizer reducing, in operation, a concentration of a particle in the volume of air during a second period of time. The second period of time may be phrased as, or associated with, a purification period of time. The second period of time occurs before the first period of time, or alternatively at least partly overlapping the first period of time.

The method 70 may further, optionally, comprise a step 75 of the sensor unit determining a concentration of a second particle in the volume of air, and a step 76 of the controller determining a second condition in which the concentration of the second particle is above a second predefined threshold value, and a step 77 of controlling, when said second condition is determined, an ionizer to reduce the concentration of the second particle in the volume of air. Thereby, the second particle is a reaction product of the particle when exposed to ultraviolet light. Namely, said second particle may be one of the group of Thiols, which may result from exposing biogenic dust to ultraviolet light.