FIELD OF THE INVENTION

The field of the invention generally relates to systems for purifying and improving air quality within a closed space. More particularly, the invention relates to a system for regulating thCeO ₂ concentration in the air adjacent to each individual operating computer within a closed space based on his own biological measured parameters.

BACKGROUND OF THE INVENTION

A person operating a computer (hereinafter, also referred to as "user" or "computer user") typically spends many continuous hours sitting in front of the computer's screen. This user' s activity is usually performed in a closed space at work or home. In offices and workplaces, there are many cases where a plurality of computer users share the same room or space .

While the state of awareness of an individual depends on various parameters (for example, on the duration he slept at night, if and when he ate lunch, on his emotional state, etc. ) , it is well known that a high concentration ofCO ₂ in the breathing air (above some threshold) reduces awareness and current cognitive capabilities of a human being. In the case of a working environment, this reduction of awareness results in lower productivity, even with unnecessary errors .

On average, the concentration ofCO ₂ in the open air is about 400ppm. However, this concentration frequently increases within a closed space, even above 2000ppm. Any increase ofCO ₂ , typically above lOOOppm, causes one or more phenomena like reduced awareness, higher breathing rate, fatigue, headache, increased heartbeat rate, increased movements, and more.

Employers highly invest in HVAC systems (or similar) to improve their workers' comfort and increase productivity. However, these systems are indifferent to the level ofCO ₂ in the air and cannot affect this level.

US 2016/0334124 and EP 3376343 disclose systems for controlling an air conditioner based on data acquired from a wearable device. However, the operation of an air conditioner does not affect the level ofCO ₂ within the closed environment. Moreover, while operating an air conditioner based on data accumulated from an individual, the systems of US 2016/0334124 and EP 3, 376, 343 equally affect the entire space, irrespective of the number of individuals or characteristics of each individual located therein. Furthermore, only a small portion of the population possesses or uses a wearable device. Therefore other solutions become necessary.

US 2017/0154517 discloses an air quality alert system that indicates a necessity for (fully or partially) opening a window to the external environment based on air quality measurement within the closed space. However, opening a window is not always applicable when a significant temperature or wind difference exists between the external environment and the internal space or when the external environment is noisy. As such, any window opening reduces the effect of the air conditioner. Moreover, the air quality of the external environment may be lower than the air within the internal space (particularly in large cities) , resulting in an opposite effect than desired. Finally, offices in high towers are frequently not provided with windows; therefore, a window' s opening is entirely irrelevant. US 2017/0154517 also suggests combining its system with a conventional domestic (HEPA-based) air purifier. However, a conventional air purifier containing a HEPA filter is designed to capture particles (e.g., dust, carbon particles, etc. ) but cannot reduce the concentration ofCO ₂ in gas form. Therefore, neither HVAC nor a conventional domestic air purifier can increase the awareness of a computer user in a closed space suffering from a high concentration ofCO ₂ . Moreover, the prior art systems cannot affect an individual computer user working in an area containing a plurality of users while considering his specific state of awareness.

In another aspect, Infineon Ltd. has developed a 60GHz radar sensor for advanced sensing that, according to its marketing brochures, is designed, among others, for heart monitoring.

In still another aspect, US 2018/0132043 (VocalZoom Systems, Ltd. ) discloses a laser-based microphone. The laser microphone includes a transmitter for transmitting an outgoing laser beam to a human speaker. The laser transmitter also acts as a self-mix interferometry unit that receives the optical feedback signal reflected from the face (or throat, or neck, or another body part) of the human speaker and generates an optical self-mix signal by selfmixing interferometry of the laser beam and the received optical feedback signal.

In still another aspect, heating, ventilation, and air conditioning (HVAC) systems used in homes and offices facilitate the accumulation of air pollutants within airregulated closed spaces. For example, a central HVAC system that operates in an office building accumulates outdoor air, regulates its temperature and moisture, and circulates the regulated air within spaces of the building. However, the air brought from the outdoors to the system is, in many cases, polluted, resulting in a conveyance of micro-particles of, for example, dust, smoke, smog, chemicals, and the like into the closed space, and additional micro-particles are added from within the spaces themselves. The situation is similarly problematic in the air-conditioning of apartments and homes, where the indoor air is circulated in a closed loop without even adding outdoor refreshing air into the loop. Both cases (i.e., office buildings, apartments, and homes) accumulate solid particles and gases, such as dust, smoke, smog, and bio-hazards, such as viruses and bacteria, within the air-regulated spaces. These micropollutants impair health and productivity.

A variety of stand-alone domestic air purifiers (hereinafter, also referred to as "home-purifiers" or "room purifiers") that are used in individual rooms at homes, offices, hospitals, medical clinics, waiting rooms, and the like) that are supplementary to existing HVAC systems have been developed to reduce the accumulation of polluting particles in closed spaces. These stand-alone devices typically include a silent blower and a set of one or more fine filters. These air purifiers are designed to circulate the room's air through a set of fine filters, thereby capturing particles larger than 1pm to 10pm. For example, lpm particles generally originate from smoke and smog, 2.5pm particles originate from motor-vehicle exhausts and woodburning fires, and 10pm and larger particles originate from general dust. Unfortunately, while capturing up to 99% of those micro-sized particles, these traditional air purifiers are not effective against high concentrations of CO2, nor a multitude of chemical and biological contaminants, alongside Volatile Organic Compounds (VOCs) (e.g., formaldehyde) , allergens, bacteria, viruses, and the like .

One type ofCO ₂ -reducer is disclosed, for example, in KR 10-2182242. TheCO ₂ -reducer includes twoCO ₂ adsorbing units, each containing aCO ₂ adsorbing material (Zeolite) . The two adsorbing units alternately operate inCO ₂ adsorbing andCO ₂ desorbing modes. Air sucked from the room is maneuvered into one of thCeO ₂ adsorbing units (the unit that at this specific time operates inCO ₂ adsorbing mode) , discharging air with reduceCdO ₂ into the room. At the same time, the other unit may operate in a desorbing mode. This type of CO ₂ -reducer is referred to herein as a "dry" (or solid-based) CO ₂ -reducer, as it utilizes a solid adsorbing material .

An aqueous alkali hydroxide/H ₂ C>2 solution (i.e., an alkali hydroxide solution to which H2O2 is added, hereinafter also referred to as "MOH/H2O2 reagent"; M stands for the alkali metal, e.g., sodium, potassium or a mixture thereof) has been previously reported as a generator of the superoxide radical anion (O2~*) . In a series of publications (e.g., WO 2013/093903; Stoin, U. et al. ChemPhysChem, 2013, 14, 4158 and WO 2015/170317) , it was shown that the aqueous MOH/H2O2 reagent is a powerful oxidizer that could be used to serve several valuable purposes. A "liquid" type ofCO ₂ -reducer utilizing the above aqueous alkali hydroxide/H ₂ 02 solution with the addition of H2O2 is described herein.

It is an object of the invention to provide a real-time system configured for each computer user located within a closed space designed to reducCeO ₂ within that user' s breathed air surroundings, thereby increasing his awareness and current cognitive capabilities.

It is still another object of the invention to provide within this system a dry or liquid-based CO ₂ -reducer capable of reduciCnOg ₂ in the immediate environment of each computer' s user based on individual measurements collected from this user.

It is still another object of the invention to provide a contactless laser-based or radar-based measurement unit configured to collect relevant real-time data related to the user. "Radar-based" is meant herein to be a radar unit operating in the RF spectrum.

It is still another object of the invention to regulate the flow of CO ₂ -reduced air supplied to the proximity of each computer user based on said user' s awareness signals gathered from that user.

It is still another object of the invention to combine the operation of the CO ₂ -reducer with other systems targeted to improve users' comfort and health.

Other objects and advantages of the invention become apparent as the description proceeds.

SUMMARY OF THE INVENTION

The invention relates to a system for increasing awareness of one or more computer users located within a closed space, comprising: (a) one or more contactless sensing units each directed respectively to a user and configured to acquire a measurement signal indicative of a distance and distance change from the user over time; and (b) a CCh-reducer comprising collecting and analyzing unit configured to (i) receive said indicative signal separately for each user, and determine parameters comprising at least the user's heartbeat rate and one or more of the breathing rate or user's movement; (ii) determine from said parameters a user awareness level; and (iii) based on said determined user's awareness level and predefined awareness reference values for the same user, regulate, in association with a managing unit, a supply of CO ₂ -reduced air to the proximity of the user via a respective outlet channel dedicated to that user.

In an embodiment of the invention, the CO ₂ -reducer comprises a predefined database containing reference threshold values for each individual user within a closed space, said threshold values relating to the user's heartbeat rate and one or more of the breathing rate or movement in normal or lowCO ₂ conditions.

In an embodiment of the invention, the analyzing unit comprising bandpass filters for separating said indicative signal to a heartbeat signal and one or more of breathing rate signal, or motion signal.

In an embodiment of the invention, the sensing unit is in communication with the user's computer, which in turn communicates the measurement signals, or contents thereof to the CO ₂ -reducer or to a cloud system which is in communication with said CO ₂ -reducer.

In an embodiment of the invention, the CO ₂ -reducer comprises a solid-based or liquid-based reactor. In an embodiment of the invention, the sensing unit is laser-based or radar-based unit .

In an embodiment of the invention, the sensing unit is laser-based, comprising a self-mixing interf erometery of the laser beam and a received optical feedback signal .

In an embodiment of the invention, the air regulation involves for each user whether to is sue a supply ofCO ₂ reduced air, the air flow rate , and period of supply .

In an embodiment of the invention, the air is supplied to a proximity of les s than 2 meters horizontally from each user utilizing dedicated air channels leading air from the CO ₂ -reducer .

In an embodiment of the invention, the reactor is further configured to reduce additional chemical and biological pollutant s , and said CO ₂ -reduced air is also purified from said additional pollutant s .

In an embodiment of the invention, the predefined reference values are specific for each user or average for several users known to be located in proximity .

In an embodiment of the invention, the reference values are determined by applying the sensing unit and analyzing the user ' s indicative signals during the user ' s concentration in solving a challenge within a low CO ₂ concentration air, and wherein said challenge is conveyed to a screen of the user from a computer .

In an embodiment of the invention, the managing unit regulates the CO ₂ -reduced air to each user via a distribution unit , which in turn controls , respectively, one or more air channels leading to each individual user .

In an embodiment of the invention, the CCp-reducer is liquid-based and further comprising : ( a ) an inlet air channel ; (b ) one or more air-sucking component s configured to direct air from the closed space into said inlet channel , and to direct the air via said inlet channel into a perforated membrane mounted in a chemicalbased CCp-reducing reactor ; and ( c ) one or more outlet air channels configured to receive CCp-reduced air from the reactor ; wherein the reactor comprises : ( i ) a reservoir configured to contain a purifying aqueous alkali hydroxide/H202 solution ; wherein during thCeO ₂ - reducer ' s operation, said perforated membrane is positioned below a surface level of the solution such that air pas sing through the perforated membrane is converted into bubbles that travel through the solution and towards said outlet channel ; and wherein thCeO ₂ - reducer further comprising a removable storage unit positioned above the reactor, said removable storage unit is configured to contain and supply alkali hydroxide , hydrogen peroxide , and optionally water to said reactor .

In an embodiment of the invention, the inlet air channel conveys air in a downwards direction, the inlet air channel pas ses through an opening in said perforated membrane towards an air compartment located below the perforated membrane .

In an embodiment of the invention, each perforation at the membrane has a diameter in the range of between 40pm and 1200pm . In an embodiment of the invention, the perforated membrane has perforations with top and bottom openings , respectively, at top and bottom surfaces of the perforated membrane , the diameter of said top opening is larger than a diameter of said bottom opening .

In an embodiment of the invention, each of the perforations is divided into two sections in cros ssection, a lower section having a cylindrical shape , and an upper section having a f rustoconical shape .

In an embodiment of the invention, the storage unit comprises an alkali hydroxide container, a H2O2 container, and optionally a water container .

In an embodiment of the invention, the CO ₂ -reducer has an es sentially cylindrical shape , wherein said alkali hydroxide container, said H2O2 container, and said water container are arranged concentrically within the storage unit .

In an embodiment of the invention, the alkali hydroxide container is configured to contain alkali hydroxide tablet s in a releasable arrangement .

In an embodiment of the invention, the alkali hydroxide container comprises a plurality of cylindrical columns , each column is configured to store alkali hydroxide tablet s .

In an embodiment of the invention, the alkali hydroxide container is configured to angularly revolve , thereby to position a single column above an opening to a pas sage leading to said solution reservoir, thereby to allow a periodical feeding of the solution by hydroxide tablets.

In an embodiment of the invention, the CO ₂ -reducer further comprising a blower and a HEPA filter fitted in an air inlet of the CO ₂ -reducer.

In an embodiment of the invention, the system further comprising a sensor for measuring a concentration ofCO ₂ at the room-air, and wherein a schedule and a period of operation of the device is further based onCO ₂ measurements by said sensor.

In an embodiment of the invention, the CO ₂ -reducer is a mobile autonomous apparatus .

In an embodiment of the invention, the mobile system comprising: a docking station which is configured to: (a) host a mobile, CO ₂ -reducer; (b) receive each user's awareness level, and determine when a user awareness falls below a level of predefined awareness threshold; and (c) communicate with said mobile CO ₂ -reducer, and at least send to it an indication of proximity of the user for which the awareness has fallen below the awareness threshold; and (d) said mobile CO ₂ -reducer, which is configured to: (e) communicate with said docking station, and at least receive from it an indication of the proximity of the user in which the awareness below threshold threshold has been determined; and (f) upon receipt of said indication, navigate to the proximity of the user, operate there to supply CO ₂ -reduced air, and upon completion, return to the docking station. In an embodiment of the invention, the CO ₂ -reducer further purifies one or more chemical and biological contaminant s .

In an embodiment of the invention, the mobile CO ₂ -reducer comprises : ( a ) an inlet air channel ; (b ) one or more air sucking component s configured to suck air from the close space into said inlet channel , and to direct the air via said air channel into a perforated membrane mounted at a CO2 elimination reactor ; and ( c ) an outlet air channel configured to receive treated air from the reactor, and to direct the treated air to a proximity of individual for which awarenes s below a predefined threshold value has been determined; wherein theCO ₂ elimination reactor comprising : ( d) a reservoir configured to contain a purifying aqueous alkali hydroxide /H202 solution ; wherein during the purifier operation said perforated membrane is positioned below a surface level of the solution such that air pas sing through the perforated membrane is converted into bubbles that travel through the solution and towards said outlet channel ; and wherein thCeO ₂ - reducer further comprising a removable storage unit , said removable storage unit is configured to contain and supply alkali hydroxide , hydrogen peroxide , and water to said reactor .

In an embodiment of the invention, the component s of the CO ₂ -reducer are divided into two component groups positioned in two rooms , respectively, and wherein a wall separates between said two rooms .

In an embodiment of the invention, the CO ₂ -reducer comprises a plurality of reactors positioned in a tandem structure . In an embodiment of the invention, the CO ₂ -reducer is based on a solid sorbent (e.g., packed in a column) . Suitable sorbents are based on materials possessing high specific surface area and porous structure, such as activated carbon [including activated carbon which was surface-modified to incorporate functional groups with basic character, that is, nitrogen-containing functionalities, as described in Journal of Analytical and Applied Pyrolysis 89 (2010) , p. 143-151) ] , carbon fibers, graphene-based adsorbing material, zeolites, molecular sieves, metal organic frameworks, highly porous polymers and amine-incorporated clay minerals and polymers, used in a granular or pellet forms (e.g., mm size) , supported on grids and sometimes covered by a mesh, e.g., single or multilayer structure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings :

- Fig. 1 generally illustrates the structure of the present invention' s system in a top view block diagram form;

- Fig. 2 illustrates in a block diagram form the general structure of the collecting/analyzing unit, according to an embodiment of the invention;

- Fig. 3a shows an example of a radar-based sensor suitable for operation with the system of the invention;

- Fig. 3b shows signals accumulated by the invention's system from one user using a single-based laser unit;

- Fig. 4 shows how the laser' s signal is separated into three feature signals by bandpass filters;

- Fig. 5 demonstrates pre-training stages performed according to an embodiment of the invention; - Fig. 6 generally illustrates the real-time operation of the system of the invention in a block diagram form;

- Fig. 7 illustrates a reward procedure according to an embodiment of the invention;

- Fig. 8 further illustrates the procedure for increasing the user' s awareness, according to an embodiment of the present invention;

- Figs. 9a-9p illustrate a structure of a CCt-reducer (homepurifier) according to an embodiment of the invention. Figs. 9b and 9c are schematic diagrams. Figs. 9h, 9i, and 9j provide partial illustrations, respectively, of the home-purifier. Figs. 9e, 9f, and 9g provide cross- sectional views of the home-purifier. Figs. 9k-9n describe the structure of the perforated membrane of the home-purifier, and Figs. 9o and 9p describe the improved effect of bubble creation obtained by the perforated membrane of the invention, compared to a conventional perforated membrane;

- Fig. 10 shows a mobile CCt-reducing system, according to another embodiment of the invention;

- Fig. 11 shows an exemplary configuration of thCeO ₂ reduction system of Fig. 10 for the elimination or reduction of CO ₂ (and optionally bio-hazards) ;

- Fig. 12 shows an exemplary docking station and a mobile CO ₂ purifier;

- Fig. 13 shows experimental set-up;

- Fig. 14 graphically shows experimental results;

- Fig. 15 shows additional experimental results;

- Figs. 16a - 16c illustrate a structure of a high-power CCt-reducer, which is particularly adapted to a large room;

- Fig. 17 shows still another high-power CCt-reducer which includes n reactors in tandem; - Figs. 18a and 18b show a home purifier (CCt-reducer) in which the functionality of the purifier is divided between two rooms .

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As stated, a level ofCO ₂ (above some threshold) in the breathing air highly affects the awareness and current cognitive state of a user working on a computer. Therefore, it is highly desired to maintain thCeO ₂ level in the air breathed by the user as low as possible. Unfortunately, neither existing HVAC systems (typically operating in a closed air loop) nor existing purifying systems based on HEPA filters can resolve this problem.

Researches show that a human's breathing rate and heartbeats are increased when the concentration ofCO ₂ in the breathed air increases above about lOOOppm. Moreover, a computer user' s movements on his chair in terms of rate and amplitude increase. The breathing rate, heartbeat, and user' s movement are also referred to herein as the user' s "parameters" .

Fig. 1 generally illustrates the structure of the present invention's system in a top-view block diagram form. A computer user, 1023, sits on chair 1017 while working on his computer 1019. The screen 1022 and keyboard 1021 are positioned conventionally on desk 1024 in front of the user. Additional computer users may similarly exist within the same closed space 1030. CO ₂ -reducer 1010 is positioned somewhere within the closed space 1030. When used herein, the term "CCh-reducer" refers to an apparatus that sucks air from a room, treats the air, and outputs into the room air with reduceCdO ₂ (and optionally reduced from additional pollutants) . Specifically, the CO ₂ -reducer is a dry-type or liquid-based apparatus. The CO ₂ -reducer is configured to reduce at least CO2 from the air sucked via its inlet 1012. Dry or liquidbased reactor 1011 sucks contaminated room's air via inlet 1012 and processes it to reduce at least the concentration ofCO ₂ (and optionally other pollutants, such as Volatile Organic Compounds (VOCs) , formaldehyde, viruses, bacteria, etc. ) . TheCO ₂ -reduced air is conveyed via the reactor's outlet channel 1029a into distribution unit 1013. The distribution unit, in turn, maneuvers theCO ₂ -reduced air 1029a to one or more outlet channels 1016, each conveying CO2-reduced air 1029b to the proximity of a respective user located within the closed space 1030 ("proximity" means 2 meters or less horizontally from the users location. The actual distance from the user may be longer, if the air supply is provided from the ceiling) . The managing unit 1014 controls the operation of the distribution unit 1013. More specifically, it defines for the distribution unit if, when, and in what volume and flow rate to distribute the CO ₂ -reduced air via individual channels 1029b leading to the proximity of each respective user 1023.

A (laser-based or radar-based) sensing unit 1020, which, for example, is attached to the screen 1020 of each user (or positioned on desk 1024) , is directed to the user and wired or wirelessly communicates with the user' s computer 1019. By utilizing the sensing unit 1020, computer 1019 accumulates signals relative to at least the user' s heartbeat rate and one or more of breathing rate and/or movement (typically, movements are considered in conjunction with one or the two other parameters) . Each computer 1019 conveys the respective accumulated signals to collect ing/analyzing unit 1015 located, for example, within the CO ₂ -reducer 1010 . The collecting/analyzing unit 1015 may alternatively be located in the cloud, where data from many users ( and pos sibly many locations ) is accumulated to improve considerations and decisions of the managing unit 1014 of the CO ₂ -reducer 1010 . Based on these signals , the collecting/analyzing unit 1015 determines if and when the concentration ofCO ₂ within the breathed air by a user 1023 exceeds a maximum defined threshold for that user . An exces s of theCO ₂ concentration level is concluded from said user' s heartbeat rate , and one or more of the user' s breathing rate , and/or movement ( or optionally additional parameters , as found relevant ) . All said determinations are made based on comparison either with the same user' s reference parameter in normal conditions or with reference average users ' parameters determined based on normal conditions , as stored in storage 1015a . Typically, collective consideration of more than one parameter is preferable .

The collecting/analyzing unit 1015 may reside within purifier 1010 , computer 101 9 , or the cloud .

Fig . 2 illustrates in a block diagram form the general structure of the collecting/analyzing unit 1015 , according to an embodiment of the invention . Database 1015a (the database of only userl is shown in Fig . 2 ) contains a collective threshold value for each user, for example , based on pre-training . The pre-training, performed within a low- CO2 environment , defines a reference cumulative threshold value based on the user heartbeat and one or more of the user' s breathing rate and/or motion rate . When the collective measurement s for the user exceed the threshold value , it is concluded that theCO ₂ concentration in the user' s immediate environment exceeded a maximum concentration value defined for that user, which should be lowered . Based on the collective user threshold, respectively, and on the real-time signals 1018 received from the respective computer, analyzer 1015b determines for that user if and when an exces s of threshold occurs , and therefore whether a supply ofCO ₂ reduced air to the immediate environment of the user becomes neces sary . Thi s analyzer' s determination is conveyed to the managing unit 1014 as a control signal 1031 .

It should be noted that the individual analysis and respective individual supply of CO ₂ -reduced air, as disclosed herein, is preferable due to the expected scarcity and given the purchase and operation high cost s ofCO ₂ - reducers .

In a first embodiment of the invention, the sensing unit 1020 is a contactles s radar-based circuit ("radar-based" is meant for an apparatus operating in the RF electromagnetic spectrum) suitable of measuring at least the heartbeat rate , the breathing rate , and the user' s movement s . For example , the BGT 60TR13C manufactured and marketed by Infineon was tested and found suitable . The BGT 60TR13C is a 60GHz radar sensor with integrated antennas . It is also supplied with software for contactles s measurement of at least the heartbeat and the breathing rate . As shown in Fig . 3a, the IC of the BGT 60TR13C includes one transmitting antenna and three receiving antennas . Thanks to the L-shaped antenna array of the circuit , horizontal and vertical angular measurement s can be measured . Moreover, the Antenna in Package (AIP ) concept of the radar device eliminates the complexity of the antenna design at the user end, and the PCB can be designed with standard FR4 materials . When applying the BGT 60TR13C, for example , the radar-based sensing unit 1020 acquires real-time raw data that , when proces sed by the collecting/analyzing unit 1015 , enables real-time estimates for the breathing rate , the heartbeat rate , and movement s of the closest human target . Additionally, the application returns the continuous timedomain reference signals for heart and breathing patterns .

The Applicant has tested the applicability of this circuit for the system' s requirement s and found it suitable for use within the system of the invention, as demonstrated by Experiment 1 .

Experiment 1

The following Table 1 provides several parameters of the radar IC : Table 1

The following reference device was used to verify the applicability and performance of BGT60TR13C:

Name: Capnograph and Oximeter Model: PC-900B;

Measuring Interval: 4s (5s in Radar) ;

Respiration rate accuracy: ±1% of reading or ±1% breaths/min whichever is greater;

Pulse rate accuracy: ±2% for PR range from 30-250bpm;

TEST PROCEDURE:

The Infineon radar device was placed on a table. A participant sat in front of it. For accuracy testing, the reference device was connected to the participant and activated simultaneously with the radar.

The following tests were performed:

Test 1 - Distance: The participant sat in front of the sensor. The radar was placed on the table at varying distances. At each distance, the radar and the reference device were activated simultaneously.

Test 2 - Finding the maximal effective angle:

The participant sat in front of the sensor. The radar was placed on the table at a distance of 0.5m and turned to different directions. At each distance, the radar and the reference devices were activated simultaneously.

RESULTS :

Testi - Effect of Distance: The following distances were determined as the maximum and minimum distances at which the HR (heartbeat rate ) and RR ( respirat ion/breathing rate ) were detected :

Table 2

Test2 - Ef fect of Angles : Azimuth (horizontal ) angles :

The following angles were determined as the maximal left and maximal right angles at which the HR and RR were still detected :

Table 3

Azimuth (horizontal ) angles :

The following angles were determined as the max upper and lower angles at which the HR and RR were still detected :

Table 4

Experiment conclusions : a . It has been found that at least a range up to 85cm is applicable , while 60cm was determined as an optimal range; b. An average of 3bpm error has been observed for HR (heartbeat rate) ; c. An average of 3bpm error has been observed for HR (heartbeat rate) ; d. When tested during movement, the following increases of errors were observed: (i) HR: error increased by ~3 bpm (3 vs. 6) ; (ii) RR: error increased by ~3 bpm (3 vs. 6) ; e. It was therefore concluded that a radar-type (RF) sensor is applicable for use in the system of the invention.

In another embodiment of the invention, the sensing unit 1020 has the form of the optical microphone described in US 2018/0132043.

However, while in US 2018/0132043 the optical microphone is directed to the throat of the user' s body, in the system of the present invention, the microphone' s laser beam is directed most conveniently to the user' s chest, where the breathing vibrations are noticeable. For the invention, a low-energy laser unit with minimal distance sensitivity below 10 microns can determine breathing and heartbeat rates. Such an optical microphone is manufactured and distributed, for example, by VocalZoom Systems Ltd. The user' s movement can be determined by the same or another laser unit. However, when a single laser microphone is used, the minimal sensitivity of 10 microns satisfies all the invention's requirements. The breathing, heartbeat, and user movements are translated to distance change affecting the phase and/or the frequency of the beam reflected from the user to the degree that allows the determination of their respective rates. The laser beam's wavelength and power are selected to be non-damaging to the human body, particularly the eyes. A variety of such laser sources are well known. Moreover, the laser beam should preferably be directed to a bare portion of the user' s body to allow the most accurate heartbeat measurement .

While the use of self-interferometry within the laser-type sensing unit 1020 is preferable (as it enables carrying out the invention by a single laser rather than separate transmission and decoding lasers) , a sensing unit utilizing a separate laser transmitter and laser decoder (in addition to a beam splitter) is within the invention's scope.

Fig. 3b shows signals 1018 accumulated by the invention's system from one user using a single-based laser-type sensing unit manufactured by VocalZoom Systems Ltd. It can be seen that both the breathing rate (typically 12 to 20 breaths per minute) and the heartbeats (60 to 100 heartbeats per minute) can be observed in the signals and can be visually distinguished. These signals can be separated, for example, by subjecting them to two different bandpass filters. In addition, the user' s movement can be seen as an increased "noise" on the signal. Therefore, based on the above signals (in real-time compared to the reference value) , the system of the invention can conclude whether it is necessary to supply CO ₂ -reduced air to each specific user and at what volume rate. It should be noted that while a continuous supply of CO ₂ -reduced air to all users is possible, this continuous distribution regime is not preferable as it unnecessarily consumes power and the chemical ingredients of the CO ₂ -reducer.

As noted, one or more threshold values selected from breathing rate, beat rate, and movement are predefined for each user and included within the database 1015a, respectively. In real-time, respective signals 1018 are measured by sensing unit 1020 and analyzed by analyzer 1015b to determine whether to provide CO ₂ -reduced air to that specific user and the air volume necessary.

Fig. 8 further illustrates the procedure for increasing the user' s awareness, according to an embodiment of the present invention. For the sake of simplicity, the procedure refers to a single user. In step 1101, pre-training is performed. The database 1015a (Fig. 2) , which includes each user' s threshold definitions, is prepared during the pre-training. In stage 1102, the sensing unit 1020 is directed to the user and activated. In stage 1103, a signal is extracted from within the sensing element (laser or radar) . Then, signal processing is performed to reduce noise. In stage 1104, the signal is separated into one or more of the feature signals 1018a-1018c (Fig. 4) and digitized. Stage 1105 analyzes each signal to determine the respective breathing rate, movement rate, and heartbeat. The results are weighted and combined to determine a cumulative awareness value. The cumulative awareness value is then compared with the respective pre-trained awareness threshold for that user to determine if and what volume to activate a supply of CO ₂ -reduced air to the specific user from CO ₂ -reducer 1010.

Experiment 2

The inventors have tested the applicability of the lasertype sensing unit of the invention. A laser sensing unit (eye-safe) , manufactured by VocalZoom Systems Ltd., including a built-in interferometer and signal processor with a distance sensitivity of a few pm (less than 5pm) , was used. The VocalZoom' s sensor utilized a self-mixing laser to obtain such a sensitivity, whereas the laser' s transmitter also acted as a self-mix interferometer. The interferometer received a reflected optical signal from the user' s chest. The user was located less than one meter (about 50cm) from the sensor. The interferometer self-mixed the returned signal with a sample of the transmitted signal within the same laser to produce a self-mix optical signal of the laser beam. While the user was stationary, signals, such as shown in Fig. 3b, were obtained. A user' s movement (above some level) was observed at the signal as increased "noise". A user' s movement, even lateral relative to the laser beam, significantly affects the signal given the roughness of the user' s shirt and the distance sensitivity of the laser unit (as said, below 20pm) . Therefore, it was concluded that a breath rate, heartbeat rate, and user' s motion could be distinguished. However, while it was found that all three signals can be measured and distinguished, the invention can be satisfied, for example, with the measurements of the breathing rate and movements.

In another embodiment of the invention, the collect ing/analysis unit may utilize machine learning modules to determine breathing rates, heartbeat rates, and movements, (a) A breathing rate of a specific person can be measured by a conventional breathing rate measuring sensor (for example, a sensor inserted into the person's nose) , simultaneously with a collection of signals by the laser unit of the invention directed to the same person. Then, given a classified database of the person' s measured breathing rate synchronized with collected signals by the laser unit, the breathing-rate machine learning module can be taught to determine this breathing rate by submission to classified signals into it. Repeating this procedure with a plurality of different breathing rates can teach the breathing rate module to determine and distinguish between various breathing rates. Then, in real time, this module can be used to measure breathing rates. (b) A similar procedure can be utilized to create a heartbeat measuring module (however, using a physically touched heartbeat sensor rather than the breathing rate sensor used in step (a) ) . Then, in real time, this module can be used to measure heartbeat rates, (c) A similar procedure can be utilized to create a movement measuring module (however, using a physically touched acceleration sensor rather than the breathing rate sensor used in step (a) ) .

Experiment 3

A breathing rate measurement module based on machine learning was built utilizing about 1000 signal samples. First, 500 samples were used to train the module, and then 500 samples were used to test the module. Reasonable accuracy of measurement has been found.

Fig. 4 shows how the laser sensor's signal 1018 is separated into three feature signals by the set of bandpass filters 1015f. Once these signals are available to the collect ing/analyzing unit 1015, the respective breathing rate, heartbeat, and motion can be determined. In an embodiment of the invention, weights are predefined for each feature measurement, resulting in a cumulative determination of each user' s awareness (cognitive) state.

During the pre-training state, it is vital to ensure that the user' s reference measurements are performed while he is in a high-awareness state and within an environment of low CO2 concentration. In one embodiment, the user is given a specific challenge to solve, ensuring that he is in a high- awareness state during the pre-training. The user concentrates on solving the challenge, ensuring a concentration state. The challenge and the training measurements typically prolong a period of a few minutes (for example, 1-3 minutes) and may be performed only once. Fig. 5 demonstrates the pre-training stages. First, in step 1120, a challenge is displayed to the user on the screen (for example, solving a math problem, puzzle, etc. ) . Then, in step 1130, while ensuring that the user concentrates on solving the challenge, the movement, heartbeat, and breathing rate measurements are performed in step 1140. Finally, in step 1150, the measurements are recorded and analyzed to determine an "envelope" (baseline) for an awareness state for that specific user. Then, the pretraining is repeated separately for each additional user.

Fig. 6 generally illustrates the system's real-time operation (for a single user) in a block diagram form. In step 1220, a user' s measurements are accumulated by sensing unit 1020 and conveyed to computer 1019 and collect ing/analyzing unit 1015 (shown in Fig. 1) . In step 1230, the measurements are recorded at the collect ing/analyzing unit 1015 and analyzed to determine a cumulative value. In step 1240, the cumulative value is compared with the predetermined envelope for that user (as determined in step 1150 - Fig. 5) . If the comparison of step 1240 shows that the cumulative value is within the predefined envelope (threshold) , nothing happens, and the procedure returns to step 1220 for new real-time measurements. The new real-time measurements of step 1220 are performed periodically, and steps 1230 and 1240 are repeated. If, however, it is determined in step 1240 that the user' s measurements are out of the predefined envelope, it is concluded that the user' s awareness has been reduced, therefore managing unit 1014 (Fig. 1) instructs the distribution unit 1032 to increase the supply of CO ₂ -reduced air to the user.

The invention may also be used to provide an "award" indication to the user (or remotely to his parent, in the case of a child user) regarding a continuous prolonged period (i.e., a duration above a predefined period) of awareness. The procedure of Fig. 7 is similar to the procedure of Fig. 6 (similar references reflect similar functions) . In addition, in stage 1360, the system verifies whether a predefined period of, e.g., 30 minutes, has excessed without determining a state of reduced user awareness. When an excess of the period is determined, in step 1370 an "award" indication is sent (e.g., in the form of a pop-up) to the user' s screen 1022, to his parent (as a message) , or both. Such a procedure provides a measurable value regarding the duration of high awareness and encourages the user to maintain high awareness.

In still another embodiment, an interactive program within computer 1019 may be used to fine-tune the references (as determined in the pre-training stage) , and better associate the measurements with the user's proper awareness state (and regulate the air in the room accordingly) . Periodically (for example, every 20 minutes) , a message such as "it seems that you are somewhat tired - please type: 'correct' or 'incorrect'" or "you are in a good awareness state - please type: 'correct' or 'incorrect'" is displayed to the user. The message is issued based on real-time measurements and analysis determination, as concluded by comparing the realtime measurements with the user's predetermined references. The user' s feedback assists in fine-tuning the baseline for that user.

The system may utilize additional sensors to optimize its operation. For example, aCO ₂ sensor may be provided outdoors to measure the outdoor air quality. When a situation of higChO ₂ is determined at the user' s proximity, the system may advise the user to open a window (when applicable) instead of supplying reduced-CCh air to the user's proximity. In addition, machine learning techniques may be applied within the collect ing/analyzing unit 1015. The system may also include or be combined with other purifying (for example, ionizer) or comfort relates devices and sensors to improve the comfort and awareness of the user .

As shown, the invention provides a system for increasing the awareness of a computer user working within a close space. Increasing awareness means increasing the user's cognitive state, resulting in higher productivity and fewer errors. The increase in awareness is obtained by regulating the operation of a CO ₂ -reducer based on real-time measurement of the user's cognitive state.

Several embodiments of a liquid-based CO ₂ -reducer suitable for operation with the system of the invention are now described in more detail. Figs. 9a-9p illustrate a structure of a liquid-baCOse ₂ d - reducer (for use at offices and homes, hereinafter also referred to as "home-purifier") 800, that can be used in conjunction with the invention. Figs. 9b and 16c are schematic diagrams. Figs. 9h, 9i, and 9j provide partial illustrations, respectively, of the CO ₂ -reducer. Figs. 9e, 9f, and 9g provide cross-sectional views of theCO ₂ - reducer. Figs. 9k-9n describe a structure of a perforated membrane of the CO ₂ -reducer 800, and Figs. 9o and 16p describe the improved effect of bubble creation obtained by the perforated membrane of the invention compared to a conventional perforated membrane.

Fig. 9a shows the external shape of the CO ₂ -reducer 800 (this external shape is provided as an example for illustration only) . Fig. 9b generally illustrates the operation of the reactor Ra of the home-purifier 800. The air inlet 824 of reactor Ra is positioned at the top of the CO ₂ -reducer. The contaminated air is received at top inlet 824 and conveyed downwards via air pipe 827 into sump 837. Air pipe 827 arrives at the sump via a central opening at the perforated membrane 836. The contaminated air is pressurized within the sump, passing bottom-up through the perforated membrane 836, causing bubbles within the solution 838. The bubbles interact with the reservoir's liquid 838 and are enriched with oxygen. The oxygen-enriched air is then returned via a demister and carbon filter (not shown) to the room asCO ₂ reduced air 877 via outlet 832.

Fig. 9c schematically illustrates the structure of purifier 800. Blowers Bi and B ₂ simultaneously suck contaminated air from the room via inlet 824. After passing a Hepa filter 842, the airflow is divided into air channels 819 and 829, respectively. Air channel 819 returns HEPA-f iltered air to the room similarly to a conventional filtering device (via blower Bl) , while air channel 829 conveys air into reactor Ra (via blower B2) for purification. The contaminated air, which is top-to- bottom conveyed into sump 837 (see Fig. 9b) , passes from the sump in an upward direction via the perforations of perforated membrane 836, creating bubbles within solution 838, performiCnOg ₂ reduction following interaction between the bubbles and the solution. Purification of biohazards may also be performed. Solution 838 occupies a portion of the space of the reactor compartment (above the solution, there is a gas space) . Following the purification, the purified air passes first through demister 846, which removes from the purified air residues of aerosol and droplets of the reactive liquid that the airflow may carry. From the outlet of demister 846, the CO ₂ -reduced air is conveyed to optional carbon filter 849, which removes smells from the air. From the outlet of the carbon filter, the purified airflow merges with the Hepa- filtered airflow 819 to form a unified airflow 819a, which is conveyed to outlet 832 (i.e., back to the room) . Cartridge A (alkali hydroxide, e.g., sodium or potassium hydroxide) is provided in tablet form; each tablet is individually dropped into solution 838 by a tablets- feeder 841. A liquid (hydrogen peroxide) contained within cartridge B is fed into solution 838 utilizing (peristaltic) first pump 839. The feeding of the cartridges' contents into the solution may be performed, respectively, either periodically or every predefined period of the reactor operation. The purifier further includes a clean/wastewater container 847. Initially, cleaned water is filled into container 847 and conveyed into reactor Ra to form solution 838. Periodically, or after a predefined period of operation, solution 838 is pumped utilizing second pump 857 into container 847 for removal from the device and solution refreshment. The Hepa filter 842, clean/wastewater container 847, carbon filter 849, cartridge A 826, and cartridge B 828 are removable/ replaceable components. The entire system is controlled by controller 801.

Fig. 9d shows the general assembly structure of purifier 800. The purifier generally has a cylindrical configuration, and it includes (from bottom to top) a reactor unit 850, operational unit 860, and storage unit 870. Also shown are Hepa filter 842, main blower Bl, and cover 851.

Reference is now made particularly to Figs. 9e, 9h, and 9j . The storage unit 870 is removable, containing the solution ingredients, such as (a) tap water, (b) alkali hydroxide (potassium hydroxide or sodium hydroxide, respectively) in a solid form (or otherwise) , and (c) H ₂ C>2 (hydrogen peroxide) in liquid form. The storage unit (in this specific example) includes 3 concentric containers, as follows: Cartridge A container 826 for the alkali hydroxide (NaOH, KOH or both) , (in a tablet form) , water container 847, and H2O2 container (cartridge B) 828. Cartridge A is divided into a plurality of column cylinders 826a, each containing a plurality of tablets. In an embodiment of the invention, the plurality of hollowed column cylinders 826a are arranged in a revolving drum 826. To add a tablet to solution 838, a motor (not shown) rotates the drum 845 to angularly position a tablets' column 626a above opening 859 (best shown in

Fig. 9g) , permitting one tablet to fall into solution 838 gravitationally. The structure of the reactor is shown mainly in Figs. 9e, 9f, and 9i, and the structure of the perforated membrane 836 is shown mainly in Figs. 9k, 91, and 9n .

For example, the weight of each tablet may be about 5 to 100g, e.g., from 15 to 30g, and 2 to 100 tablets may be included within cartridge 826. The water container may contain 1 to 10, e.g., 2 to 6 liters, and the hydrogen peroxide container may include between 250ml and 10 liter. Initially, the user removes the storage unit using handle 863 and fills it with the solution ingredients. Upon filling the water container with tap water, and filling cartridges A 826 and B 828 with tablets and liquid, respectively, and remounting the storage unit at the purifier, the device is ready for operation. The water is poured down to the reactor via pipe 853, and one tablet (or more, if necessary) is dropped down to the solution via opening (and respective pipe) 859. A dose of the hydrogen peroxide is conveyed periodically into proximity of the perforated membrane utilizing pump 839, pipe 855 (one or more pipes may be used) , and respective perforations (not shown) on tube 855a (Fig. 9f) . It has been found that supplying the hydrogen peroxide near the outlets of the membrane-perforations 836a is preferable, as it significantly reduces, even eliminates clogging of the membrane perforations due to carbonates that accumulate in the solution during the process. Membrane 836 is positioned slightly above the bottom-internal surface of the device, creating a sump 837 (see Figs. 9b and 9e) below the membrane. The contaminated airflow, as sucked from the room by blower B2 (Fig. 9c) is conveyed via intake pipe 829, arriving at sump 837 via central opening 836b of membrane 836. During the process, air from the sump penetrates solution 838 via the membrane's 836 perforations, creating bubbles that interact with the solution as described above. The bubbles leave the solution as a purified air. The purified air passes through demister 846, which removes from the purified air residues of aerosol and droplets of the reactive liquid that the airflow may carry. The outlet of the demister includes a funnel (not shown) , which is connected to a pipe (not shown) leading to the carbon filter 849.

After some period of operation, the effectiveness of solution 838 reduces to a degree requiring entire replacement by fresh water and ingredients from cartridges A and B, respectively. When such a necessity arose, pump 857 pumps and conveys the entire liquid content of compartment 820 (Fig. 9b) to the waste/clean water container 847. The "waste" liquid is typically rich in potassium carbonate (not a hazardous material) . The user may then remove the storage unit 870 and may either: (a) use the "waste" liquid to fertilize his garden; (b) pour the liquid into the sewerage; or (c) return the liquid to the ingredients' supplier for further processing .

The invention' s process is optimized when as small as possible and as many as possible bubbles are simultaneously created. This configuration maximizes the overall interaction surface between the bubbles and solution 838. However, it has been found that a membrane with too close perforations results in vast merges of proximate bubbles, as illustrated in the prior art membrane 896 of Fig. 9o. The inventors have found that the dif ficulty that individual bubbles face ( in prior art membranes ) when trying to separate from the membrane top facet towards the solution increases the size of the bubbles , leading to a merge between proximate bubbles . This delay of separation increases the size of individual bubbles to a situation where proximate bubbles merge .

Fig . 9n shows a cros s-section of membrane 836 , resolving the above problem of the merge between bubbles . In contrast to a cylindrical perforat ion ' cros s-section, as existing in typical membranes , each perforation of the invention ' s membrane includes two sections , a lower cylindrical section 836c and an upper f rustoconical section 836d expanding towards the top surface of the membrane . More specifically, the bottom-to-top airflow first faces a small-diameter cylindrical perforation, and then the perforation diameter expands towards the top surface of the membrane . Such a perforation configuration eases the separation of each bubble from the perforation , thereby significantly reduces merges between bubbles for a given perforation-dimension and perforations density . Fig . 9p illustrates such an improved result compared to the cylindrical configuration of Fig . 9o . As shown, in the cylindrical configuration of Fig . 9o, proximate bubbles 836g tend to merge before their release to the solution . On the contrary to the cylindrical configuration of Fig . 9o, in the combined cylindrical- f rustoconical configuration of Fig . 9p, the occurrence of merges between bubbles 936g is reduced, even eliminated .

In some cases , the height of the lower cylindrical section of the perforation is reduced ( compared to the upper conical section ' s height ) . In some other cases , the lower cylindrical section of the perforation may be eliminated, resulting in a truncated cone cross-section. Fig. 9k shows a top view of membrane 836, Fig. 91 shows the membrane in perspective view, and Fig. 9m shows a bottom view of the membrane. As can be seen, each perforation at the bottom side of the membrane has a smaller diameter compared to its respective diameter at the top side. For example, the diameter at the bottom surface of the membrane may be between 0.08-lmm. The perforation's diameter at the top surface may be 1.3 to 2.0 larger than the bottom diameter. The distance between individual perforations is in the range of 2-50 of the perforation's diameter at the upper surface of the membrane. The above-described flat perforated membrane, with the combined geometry of perforation shaped as cylindrical sections joining f rustoconical sections, forms another aspect of the invention. It can be produced by 3D printing. CO ₂ -reducer 800 may be stationary, mobile (in similarity to embodiment 700 described below) , or manually carried from one room to another.

Fig. 10 shows a mobile CO ₂ -reducing system, according to another embodiment of the invention. The system includes a mobile CO ₂ -reducer 710, a docking station 712, a plurality of room sensing units 714, a home Wi-Fi router 716, and an optional application in a user's smartphone 720. Each sensing unit 714 (for example, laser unit 1020 of Fig. 1) is installed in a single room of the house (or directed to a single user) , measuring the individual state of awareness (as described above) orCO ₂ level within that room. In addition, the measured level may relate to an undesired amount of any gas, particles, airborne biohazards, etc., and these levels of contaminants may either be measured directly or deduced indirectly based on any given conversion method. Each sensing unit reports, for example, via a Wi-Fi network, the user's awareness (or the level ofCO ₂ and optionally additional contaminants) it measures to the docking station 712, which in turn collects these measurements, and compares them to one or more predefined user's thresholds. The docking station includes predefined rules for activating the mobilCeO ₂ - reducer. These rules may apply to all users (or rooms) , or specific rules may apply to each individual user or room. The mobile CO ₂ -reducer 710 includes a navigation system, enabling the purifier to automatically navigate to any of the rooms based on commands received from the docking station. For example, the docking station may convey a command to the mobile purifier to move to proximity with a first user, work there for several minutes, and then return to the docking station. Following the reception of such command, the mobile CO ₂ -reducer automatically navigates to proximity of a user, as necessary, operates for the prescribed duration, and returns autonomously to the docking station. The docking station may also define for the mobile CO ₂ -reducer any specific mode of operation based of the different users' thresholds, and may also send commands to the CO ₂ -reducer while in operation. The docking station may also serve as a recharger for the mobile purifier's 710 battery. The CO ₂ -reducer may include, in addition to aCO ₂ (and optionally additional bio-hazards) reactor, one or more types of purification filters, such as, for example, one or more HEPA filters as described above.

Fig. 11 shows an exemplary configuration of thCeO ₂ reduction system of Fig. 10 for the elimination or reduction ofCO ₂ (and optionally bio-hazards) . The mobile CO ₂ -reducer 710 is preferably made as compact as practically possible. Therefore, mobile CO ₂ -reducer 710 may include a minimal amount of purification solution within a compact-size reservoir 738. The docking station may include one or more tanks for water and reagents A (MOH) and B (H2O2) , for draining the purification reservoir 738, and refilling it from the tanks. In the exemplary configuration presented in Fig. 11, the docking station includes a filling tank 742 for water and a filling tank 744 for reagent A (MOH) . Thanks to its small volume, tank 746 of reservoir B (H2O2) is entirely contained within the mobilCeO ₂ ~reducer 710.

A single mobile device having a single reduceCdO ₂ outlet may replace a plurality of individual outlet air channels 1029b, each leading to a single user. The mobile device is activated based on instructions from the collect ing/analyzing unit 1015.

Periodically, or based on any other definition, the docking station 712 is activated to drain the existing liquid from reservoir 738 of the mobile CO ₂ -reducer into sewage tank 748, and refill reservoir 738 with new liquids (or solids, as is applicable) from tanks 742, 744, and 746 (in predetermined proportions) . The docking station and the mobile CO ₂ -reducer include additional components, such as pumps, valves, etc., to perform these tasks. The mobile CO ₂ -reducer also includes a blower for circulating air into the reservoir (in the form of bubbles, as described) and release it into the room.

The components that are required for the navigation may be divided between the mobile CO ₂ -reducer and the docking station in various possible configurations. In one embodiment, the mobile CO ₂ -reducer 710 maintains a full navigation capability (i.e., map of the house, etc. ) . The docking station can indicate the targeted room, and based on this indication, the mobile CO ₂ -reducer navigates autonomously to the targeted room. In another configuration, the navigation capabilities are maintained within the docking station 712, while it sends real-time direction commands, such as right, left, forward, backward, move, stop, etc., to the mobile CO ₂ -reducer.

The system may also include a remote control (for example, user smartphone 720) . The remote control may define various parameters of the system.

As noted, the mobile system preferably utilizes the WiFi router of the house for communication between all its components. Other types of wireless networks may be used. Moreover, a central computer, which may be separate from the docking station, may be utilized to receive user or sensors' data and send commands to the mobile device. In such a case, the docking station serves only as a recharging station for the mobilCeO ₂ -reducer.

Fig. 11 shows a configuration that is specifically designed to reducCeO ₂ (and optionally airborne biohazards) . This configuration also includes an optional HEPA filter 752. In other embodiments, the mobilCeO ₂ - reducer 710 may include onlCyO ₂ reducing capabilities.

Fig. 12 shows an exemplary docking station 712 and a mobile purifier 710. The relative dimensions may vary.

Figs. 16a - 16c illustrate a structure of a high-power CO ₂ -reducer, which is particularly adapted to a large room, for example, a meeting room. The waste container 971 is located at the bottom of the purifier, and may include wheels for easy mobility. The hydroxide container 972, and the hydrogen peroxide container 973 (for example, in 1: 6 volume ratio) are positioned above the waste container 971. The utility chamber 979 is located above the containers 972 and 973. First pump 974 conveys, when necessary, refreshing hydroxide from container 972 via a tube to one or more nozzles that spread the hydroxide into reactor 984. Second pump 975 conveys, when necessary, refreshing peroxide from container 973 via a tube to other nozzles that spread the peroxide into reactor 984. Third pump 976 conveys, periodically, or when necessary, used liquid from the reactor 984 into the waste container 971. Purifier 900 also includes a power supply 978, a control unit 977, a communication unit 990 (for optionally communicating with a mobile phone having a dedicated application) . The communication unit also communicates with computer 1019 (Fig. 1) to receive the individual's cognitive state measurements (i.e., breathing rate, movement, heartbeat rate) and optionally with additional sensors within the close space 1030. The purifier also includes a control panel 989 for operational and display purposes. The contaminated air is sucked into the purifier by bellow 980, and passes via a HEPA filter (to prevent entry of particles) , before introduction into the reactor 984 via the reactor's membrane. In this specific case, the membrane is cylindrical, with a side inlet. From the reactor, the CO ₂ -reduced air is returned to the room via outlet 986.

Fig. 17 shows still another high-power CO ₂ -reducer 900a. Purifier 900a has a structure similar to the structure of the CO ₂ -reducer 900 of Figs. 20a-20c. However, purifier 900a includes n reactors in tandem (4 are shown in Fig. 17) , each reactor has its own pumps. The CO ₂ -reduced air may be directed to the same outlet or to n different outlets 986.

In still another embodiment shown in Figs. 18a and 18b, the functionality of the purifier may be divided between two rooms, having a separation wall 991 between them. While the waste container 971, the two liquid cartridges 972 and 973, and the utility chamber are included within a "service room" in one side of wall 991, the other components of the purifier, such as the reactors may be contained in the "main room" . Other separation options may apply. For example, the entire purifier may be positioned within the "service room", while only the inlet and outlet may be positioned within the "main room" .

Example

Treatment of low concentration C02~bearing air by absorption to aqueous solution of sodium hydroxide and hydrogen peroxide

The goal of the study was to test the ability of the aqueous NaOH/H ₂ C>2 reagent to removCeO ₂ from air that is passed/bubbled through the reagent, when the air is loaded with lowCO ₂ concentrations, challenging characteristic CO2 indoor loading and maintaining adequaCtOe ₂ conversion rates over a couple of hours.

The experimental set-up is shown in Fig. 13. TheCO ₂ source was a commercial 100%CO ₂ held in gas cylinder (1) . Pumps (3) madeCO ₂ from cylinder (1) and air from cylinder (2) to flow and mix to create a combined stream of 1200 ppm-CC>2 bearing air, which was directed to reactor (4)

(as previously described) at a flow rate of 13L/min, where the NaOH/H ₂ C>2 reagent was held (the reagent was charged to the reactor by first adding 250ml of 30 wt% of NaOH solution, and slow continuous addition of hydrogen peroxide solution (10%) at a flow rate of O.lml/min over the test period. A pair ofCO ₂ detectors (5 - BGA-EDG-MA, Emproco Ltd., Israel) connected to the incoming (1200 ppm-CC>2 bearing air) and outgoing (purified) streams were used to measure the concentration ofCO ₂ , respectively.

CO2 levels in the incoming and outgoing streams were recorded continuously over forty minutes. The results are presented graphically in Fig. 14. It is seen that high conversion percentage ofCO ₂ was maintained over the forty minutes test period, reaching 90-100%.

Reaction ofCO ₂ with alkali hydroxide alone would merely result in formation of the corresponding carbonate, as shown by the following reaction equatioCOn ₂ : + 2MOH M ₂ CO ₃ + H ₂ O

In contrast, reaction of carbon dioxide with the superoxide leads to formation of oxygen: 2MO ₂ + CO ₂ -+ M2CO3 + 1.5O ₂

Hence, the involvement of the superoxide radical in decomposing ofCO ₂ is demonstrated by evolution of O ₂ . That is, enrichment of the outgoing air stream with oxygen. Oxygen levels in the incoming and outgoing streams recorded over forty minutes indeed indicate oxygen evolution and creation of oxygen-rich outgoing air stream, as shown by the O ₂ concentration versus time plot of Fig. 15, indicating from 22% to 28% oxygen level.

Therefore, throughout this application, the term "CO2- reducer" may relate either to an apparatus that only reduces CO ₂ , or to an apparatus adding oxygen to the air, in addition to reducingCO ₂ .