BACKGROUND

Human to human interaction is responsible, in large measure, for the transmission of the SARS-CoV-2, or CO VID-19 virus during the current pandemic. COVID-19 and other viruses are spread through airborne transmission. More specifically, it has been found that COVID-19 and other viruses transmit readily via droplets or aerosols generated and spread by coughing, sneezing, talking, and breathing. Thus, it has become important to enact measures to reduce or eliminate the potential for human-to-human transmission of the virus where people work, eat, and travel together, and otherwise interact in close proximity to each other.

Although the requirement for face masks has been imposed strictly by places, face masks are not fully effective at preventing transmission of COVID- 19. For example, many people refuse or neglect to wear face masks, or wear face masks in an improper manner. Also, unless a face mask meets the N95 standard, the face mask will not prevent the wearer from being exposed to aerosolized COVID-19.

Social distancing is another means for reducing transmission of COVID- 19. It is difficult, however, to administer and enforce social distancing norms at all times, especially in public places and other common areas. Also, in most public or semi-public places, it is not practical to consistently detect whether, and when the minimum social distance, i.e., the minimum separation between two or more people needed to reduce the potential for transmission of the virus, has been violated or breached. And research has indicated that the minimum social distance is not fixed, but instead depends on multiple variables, including the surrounding environmental and meteorological conditions. More specifically, it is believed that the minimum social distance can vary between about five and about nine feet, depending on the ambient temperature and relative humidity, and the level of particulates in the ambient air.

It is known that maintaining good air circulation and low particulate levels within indoor spaces are some of the most effective ways to reduce the risk for humans to become infected by such viruses. Since the beginning of the COVID- 19 pandemic, hundreds of products have been released in the market with the goal of achieving greater indoor air circulation and fdtering, based on the assumption that these factors will lead to a virus-free airspace. Virus particles ejected from the human body by sneezing and exhaling, however, can have a relatively high velocity that makes it difficult to efficiently and effectively remove all of the particles from an indoor air space. Also, while air filtration can reduce the airborne levels of COVID-19 and other pathogens, air filters generally do not provide purified air to the specific locations at which it is most needed, i.e., around two or more individuals separated by less than the minimum social distance. For example, stand-alone air filters often are placed in comers or other non-central locations at which the air filter cannot purify the air immediately around individuals breaching the minimum social distance. Centralized air filtration systems incorporated into the ventilation systems of homes and building typically have the same drawback. Also, air filtration systems, in general, do not have any means for knowing whether, and to what extent, an airborne viral load is present in the immediate vicinity of the air filter, and thus cannot respond automatically to the presence (or absence) of a viral load.

Chemical or ion-based air purification devices can present logistical and safety -related challenges, because these types of systems can be harmful to human health and thus can be used only when humans are not present. SUMMARY

In one aspect, the disclosed technology relates to a system that includes interconnected components that can both sense and cleanse an airborne viral load quickly and efficiently, minimizing the probability of human infection in the presence of a virus such as COVID-19. The system can include a biosensing or viral load sensing system configured to measure an airborne viral load and probability of infection from the viral load; and an air purification device configured to effectively neutralize the virus in the adjacent space. The system also can include an alarm hub. The alarm hub can be a local server/hub that is wirelessly connected to the viral load sensing system and the air purification device; and can house strong visual and/or audible alarms to make the user aware of any breach of the social distancing protocol, and/or a high airborne viral load.

In another aspect, the disclosed technology relates to an intelligent air-sensing and cleaning system configured to detect the presence of aerosol close to a user. The system is configured to calculate a social distance and maximum viral concentration level that produce a low probability of infection, based on the density of the aerosolized particles, humidity, present airborne viral load, and ambient temperature in the immediate vicinity of the system. The system is configured to automatically activate the air purification device whenever the airborne virus is detected in the vicinity of the device, or when the detected level of the airborne virus exceeds a particular level. Since the safe social distance changes significantly with the level of aerosolized particles and the humidity of the ambient air, the system incorporates a proximity sensor to estimate whether the user’s personal airspace, i.e., the airspace in the immediate vicinity of the system, requires local filtration or not. If local filtration is required, as determined by the dynamic calculation of social distance and the presence of another person who is not maintaining the required social distance from the user, or if the detected viral load exceeds a predetermined level, the air purification device starts automatically, and sucks particulates and aerosols present in the immediate vicinity of the system. Such aerosolized particles can include virus particles emitted as projectiles from the mouth of an infected individual. Also, the system can alert the user to the presence of an airborne viral load, so that the user can quickly take precautions like social distancing and masking; and the system can eliminate the viruses automatically (similar to a fire alarm and sprinkler system) and efficiently in the vicinity of the user, allowing the user to quickly resume normal activity.

In another aspect, the disclosed technology relates to an air purification device. The air purification device includes a casing; a fan system mounted within the casing and configured to circulate ambient air through the casing; and a filter mounted within the casing and configured to filter the ambient air circulated though the casing. The air purification device also includes a first sensor configured to determine a characteristic of the ambient air around the system; a second sensor configured to detect the presence of two or more people proximate the system; and a control unit communicatively coupled to the fan system, the first sensor, and the second sensor.

The control unit is configured to: calculate a minimum separation distance needed to reduce a potential for human-to-human transmission of airborne pathogens to a predetermined level, based at least in part on an input from the first sensor; estimate an actual distance between the two or more people based on an input from the second sensor; and activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect of the disclosed technology, the air purification device further includes a second and a third sensor each being communicatively coupled to the control unit. The first sensor is a temperature sensor configured to sense a temperature of the ambient air. The second sensor is a humidity sensor configured to sense a humidity of the ambient air. The third sensor is a particulate matter sensor configured to sense a concentration of particles in the ambient air. The control unit is further configured to calculate the minimum separation distance based at least in part on inputs from the first, second, and third sensors.

In another aspect of the disclosed technology, the air purification device further includes a display mounted on the casing and communicatively coupled to the control unit. The control unit is further configured to activate a visual warning feature on the display when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect of the disclosed technology, the control unit is further configured to activate an audible warning feature on the display when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect of the disclosed technology, the visual warning feature includes an illuminated light.

In another aspect of the disclosed technology, the air purification device further includes an ultraviolet light mounted within the casing and communicatively coupled to the control unit. The fan system is further configured to circulate the ambient air past the ultraviolet light. The ultraviolet light is configured to illuminate the ambient air with ultraviolet radiation. The control unit is further configured to activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect of the disclosed technology, the air purification device further includes a negative ion generator mounted within the casing and communicatively coupled to the control unit.

The fan system is further configured to circulate the ambient air through the casing. The negative ion generator is configured to impart a negative charge to particles in the ambient air. The control unit is further configured to activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect of the disclosed technology, the air purification device further includes a corona discharge chamber in fluid communication with the negative ion generator.

In another aspect of the disclosed technology, the air filter includes a high efficiency particulate air filter.

In another aspect of the disclosed technology, the control unit is configured to continually update the minimum separation distance at least in part on the ambient temperature, the ambient humidity, and the concentration of particles in the ambient air.

In another aspect of the disclosed technology, the ultraviolet light is configured to illuminate the ambient air with ultraviolet radiation having a wavelength of about 265 to about 272 nm.

In another aspect of the disclosed technology, the fan system has an air flow rate of about 15- 30 cubic feet per minute.

In another aspect of the disclosed technology, the second sensor is a proximity sensor group.

In another aspect of the disclosed technology, the proximity sensor group includes a plurality of passive infrared sensors.

In another aspect of the disclosed technology, each of the passive infrared sensors has a field of view of about 140 degrees.

In another aspect of the disclosed technology, the proximity sensor group includes five of the passive infrared sensors arranged in side by side about an entire outer perimeter of the proximity sensor group.

In another aspect of the disclosed technology, the control unit is further configured to estimate the actual distance between the two or more people based on inputs from one or more of the passive infrared sensors. In another aspect of the disclosed technology, the control unit is further configured to deactivate the fan system when the estimated actual distance between the two or more people is greater than the minimum separation distance.

In another aspect of the disclosed technology, the control unit is mounted within the casing.

In another aspect of the disclosed technology, at least a portion of the control unit is located remote from the casing.

In another aspect of the disclosed technology, the fan system includes a plurality of fans arranged in series.

In another aspect of the disclosed technology, the system also includes an application executable on a mobile computing device in communication with the control unit. The application is configured to cause the mobile computing device to display one or more of a temperature, a relative humidity, a carbon monoxide level, and a nitrogen dioxide level as measured by the system.

In another aspect of the disclosed technology, the system also includes a copper mesh located within the corona discharge chamber.

In another aspect of the disclosed technology, the system also includes a fifth and a sixth sensor each being communicatively coupled to the control unit. The fifth sensor is a carbon dioxide sensor configured to sense a level of carbon dioxide in the ambient air; and the sixth sensor is a nitrogen dioxide sensor configured to sense a level of nitrogen dioxide in the ambient air.

In another aspect of the disclosed technology, an air purification device includes a casing; a fan system mounted within the casing and configured to circulate ambient air through the casing; and a filter mounted within the casing and configured to filter the ambient air circulated though the casing. The air purification device also includes a first sensor configured to determine a characteristic of the ambient air around the system; a second sensor configured to detect the presence of two or more people proximate the system; and a computing device. The computing device is configured to: calculate a minimum separation distance needed to reduce a potential for human-to-human transmission of airborne pathogens to a predetermined level, based at least in part on an input from the first sensor; and estimate an actual distance between the two or more people based on an input from the second sensor. The air purification device further includes a control unit mounted within the casing and communicatively coupled to the fan system, the first sensor, the second sensor, and the computing device. The control unit is configured to activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect, the disclosed technology addresses drawbacks of present air purification systems by accurately determining whether a space contains a detectable level of virus particles, thereby helping to identify the location and origin of an infection or potential infection. The systems and techniques also can be used to determine whether an air purification system is working effectively, by continually checking whether the airborne viral load in a space decreases following the sudden introduction of a virus into the space caused by the entrance of an infected person. Also, because airborne viruses can be spread via breathing and sneezing, an Internet of Things (loT) based system such as that disclosed herein can be used to inform occupants throughout a building or other living space whether any part of the building or living space is sensing a higher viral load, and thus can act both as a locator of virus-spreading sources, and a warning system. Even if no air filtering or purification system is present in a particular space, which is common in public gatherings, the detection of viral loads by the disclosed system can be highly useful information because it can identify the need to disperse the gathering for safety -related reasons.

In another aspect of the disclosed technology, an air sensing and purification system, includes a virus detection subsystem configured to detect the presence of an airborne viral load; and an air purification device. The air purification device includes a casing; a fan system mounted within the casing and configured to circulate ambient air through the casing; and a filter mounted within the casing and configured to filter the ambient air circulated though the casing. The air purification device also includes a first sensor configured to determine a characteristic of the ambient air around the system; and a second sensor configured to detect the presence of two or more people proximate the system.

The air purification device also includes a computing device communicatively coupled to the fan system, the first sensor, the second sensor, and the virus detection subsystem. The computing device is configured to: calculate a minimum separation distance needed to reduce a potential for human-to-human transmission of airborne pathogens to a predetermined level, based at least in part on an input from the first sensor; estimate an actual distance between the two or more people based on an input from the second sensor; and activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance and/or when the detected airborne viral load is above a threshold.

In another aspect of the disclosed technology, the air sensing and purification system further includes an alarm hub having at least one of an audible and visual warning device communicatively coupled to the computing device, wherein the computing device is configured to activate the at least one of an audible and visual warning device when the estimated actual distance between the two or more people is less than the minimum separation distance and/or when the detected airborne viral load is above the threshold.

In another aspect of the disclosed technology, the virus detection system includes a first volume of a liquid, the first volume having particles sampled from the airspace absorbed therein. The virus detection system also includes a second volume of the liquid; a first and a second conductivity probe.

The virus detection system further includes a first frequency generator communicatively coupled to the first conductivity probe and configured to apply a first alternating voltage to the first conductivity probe while the first conductivity probe is immersed at least in part in the first volume, the first alternating voltage causing a first alternating current to flow between the first conductivity probe and the first frequency generator. The virus detection system also includes a second frequency generator communicatively coupled to the second conductivity probe and configured to apply a second alternating voltage to the second conductivity probe while the second conductivity probe is immersed at least in part in the second volume, the second alternating voltage causing a second alternating current to flow between the second conductivity probe and the second frequency generator;

The virus detection system also includes a differential frequency detector communicatively coupled to the first and second frequency generators and configured to determine a difference between the frequencies of the first and second alternating currents; and a computing device communicatively coupled to the differential frequency detector and configured to determine a viral load in the first volume based on the difference between the frequencies of the first and second alternating currents.

In another aspect of the disclosed technology, the computing device is further configured to calculate the minimum separation distance needed to reduce the potential for human-to-human transmission of airborne pathogens to the predetermined level based in part on the detected airborne viral load.

In another aspect of the disclosed technology, the computing device is further configured to calculate the minimum separation distance needed to reduce the potential for human-to-human transmission of airborne pathogens to the predetermined level based in part on a correlation between the airborne viral load and the minimum separation distance needed to reduce the potential for human- to-human transmission of airborne pathogens to the predetermined level.

In another aspect of the disclosed technology, the air purification device includes the computing device.

In another aspect of the disclosed technology, the alarm hub includes the computing device.

In another aspect of the disclosed technology, the air purification device further includes a third and a fourth sensor each being communicatively coupled to the computing device. The first sensor is a temperature sensor configured to sense a temperature of the ambient air; the third sensor is a humidity sensor configured to sense a humidity of the ambient air; and the fourth sensor is a particulate matter sensor configured to sense a concentration of particles in the ambient air. The computing device is further configured to calculate the minimum separation distance based at least in part on inputs from the first, third, and fourth sensors.

In another aspect of the disclosed technology, the air purification device further includes an ultraviolet light mounted within the casing and communicatively coupled to the control unit. The fan system is further configured to circulate the ambient air past the ultraviolet light; the ultraviolet light is configured to illuminate the ambient air with ultraviolet radiation; and the computing device is further configured to activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance. In another aspect of the disclosed technology, the air purification device further includes a negative ion generator mounted within the casing and communicatively coupled to the control unit. The fan system is further configured to circulate the ambient air through the casing; the negative ion generator is configured to impart a negative charge to particles in the ambient air; and the computing device is further configured to activate the fan system when the estimated actual distance between the two or more people is less than the minimum separation distance.

In another aspect of the disclosed technology, the air purification device further includes a corona discharge chamber in fluid communication with the negative ion generator.

In another aspect of the disclosed technology, the computing device is further configured to continually update the minimum separation distance needed to reduce the potential for human-to- human transmission of airborne pathogens to the predetermined level based in part on the detected airborne viral load.

In another aspect of the disclosed technology, the ultraviolet light is configured to illuminate the ambient air with ultraviolet radiation having a wavelength of about 265 nm to about 272 nm.

In another aspect of the disclosed technology, the fan system has an air flow rate of about 15 to about 30 cubic feet per minute.

In another aspect of the disclosed technology, the second sensor includes a proximity sensor group.

In another aspect of the disclosed technology, the proximity sensor group includes a plurality of passive infrared sensors.

In another aspect of the disclosed technology, each of the passive infrared sensors has a field of view of about 140 degrees.

In another aspect of the disclosed technology, the proximity sensor group includes five of the passive infrared sensors arranged in side by side about an entire outer perimeter of the proximity sensor group.

In another aspect of the disclosed technology, the computing device is further configured to estimate the actual distance between the two or more people based on inputs from one or more of the passive infrared sensors. In another aspect of the disclosed technology, the computing device is further configured to deactivate the fan system when the estimated actual distance between the two or more people is greater than the minimum separation distance.

In another aspect of the disclosed technology, the air sensing and purification system further includes an application executable on a mobile computing device in communication with the alarm hub. The application is configured to cause the mobile computing device to display one or more of a temperature, a relative humidity, a carbon monoxide level, and a nitrogen dioxide level as measured by the system.

In another aspect of the disclosed technology, the air purification device further includes copper mesh located within the corona discharge chamber.

In another aspect of the disclosed technology, the air purification device further includes a fifth and a sixth sensor each being communicatively coupled to the computing device. The fifth sensor is a carbon dioxide sensor configured to sense a level of carbon dioxide in the ambient air; and the sixth sensor is a nitrogen dioxide sensor configured to sense a level of nitrogen dioxide in the ambient air.

In another aspect of the disclosed technology, a system for detecting the presence of a virus in an airspace includes a first volume of a liquid, the first volume having particles sampled from the airspace absorbed therein; a second volume of the liquid; and a first and a second conductivity probe.

The virus detection system also includes a first frequency generator communicatively coupled to the first conductivity probe and configured to apply a first alternating voltage to the first conductivity probe while the first conductivity probe is immersed at least in part in the first volume, the first alternating voltage causing a first alternating current to flow between the first conductivity probe and the first frequency generator;

The virus detection system further includes a second frequency generator communicatively coupled to the second conductivity probe and configured to apply a second alternating voltage to the second conductivity probe while the second conductivity probe is immersed at least in part in the second volume, the second alternating voltage causing a second alternating current to flow between the second conductivity probe and the second frequency generator; The virus detection system also includes a differential frequency detector communicatively coupled to the first and second frequency generators and configured to determine a difference between the frequencies of the first and second alternating currents; and a computing device communicatively coupled to the differential frequency detector and configured to determine a viral load in the first volume based on the difference between the frequencies of the first and second alternating currents.

In another aspect of the disclosed technology, the second volume of the liquid is free of virus particles.

In another aspect of the disclosed technology, the liquid has the characteristic of becoming polarized in the presence of a virus.

In another aspect of the disclosed technology, the first frequency generator is further configured to generate a first output representing the first alternating current; the second frequency generator is further configured to generate a second output representing the first alternating current; and the differential frequency detector is further configured to determine the difference between the frequencies of the first and second alternating currents based on the first and second outputs.

In another aspect of the disclosed technology, the first and second conductivity probes each include a first and a second electrode.

In another aspect of the disclosed technology, the computing device is further configured to correlate the viral load in the first volume with a viral load in the airspace.

In another aspect of the disclosed technology, the computing device is further configured to generate and send a notification when the viral load in the airspace is determined to be greater than a predetermined value.

In another aspect of the disclosed technology, the virus detection system further includes a visual altering device communicatively coupled to the computing device. The computing device is further configured to generate an output when the viral load in the airspace is determined to be greater than a predetermined value; and the visual alerting device is configured to generate a visual alert in response to the output of the computing device. In another aspect of the disclosed technology, the virus detection system further includes an audible altering device communicatively coupled to the computing device. The computing device is further configured to generate an output when the viral load in the airspace is determined to be greater than a predetermined value; and the audible alerting device is configured to generate an audible alert in response to the output of the computing device.

In another aspect of the disclosed technology, the computing device is an edge-cloud server.

In another aspect of the disclosed technology, the virus detection system further includes a particle collector in fluid communication with the airspace and configured to separate the particles from a sample of the airspace.

In another aspect of the disclosed technology, the particle collector includes a coarse filter configured to remove from the sample of the airspace particles having a size greater than a predetermined value.

In another aspect of the disclosed technology, the coarse filter is configured to remove from the sample of the airspace particles having an aerodynamic diameter greater than about ten microns.

In another aspect of the disclosed technology, the particle collector further includes a particle separator configured to remove from the sample of the airspace the particles sampled from the airspace.

In another aspect of the disclosed technology, the virus detection system further includes a fan in fluid communication with the particle collector and configured to direct the sample the airspace from the airspace to the particle collector.

In another aspect of the disclosed technology, the liquid includes one of deionized water, distilled water, isopropyl alcohol, and disodium laureth sulfosuccinate solution.

In another aspect of the disclosed technology, the differential frequency detector is configured to determine the difference between the frequencies of the first and second alternating currents using one of a homodyne and a heterodyne detection technique.

In another aspect of the disclosed technology, a process for detecting the presence of a virus in an airspace includes providing a first volume of a liquid, the first volume having particles sampled from the airspace absorbed therein; providing a second volume of the liquid; immersing a least a portion of a first conductivity probe in the first volume; and immersing a least a portion of a second conductivity probe in the second volume.

The process further includes applying an alternating voltage to the first probe and the second probe; determining a difference between: a frequency of an alternating current produced in the first electrode in response to the application of the alternating voltage to the first electrode, and a frequency of an alternating current produced in the second electrode in response to the application of the alternating voltage to the second electrode; and determining a viral load in the first volume based on the frequency difference.

In another aspect of the disclosed technology, the process further incudes maintaining the first and second volumes at substantially the same temperature.

In another aspect of the disclosed technology, the process further includes correlating the viral load in the first volume with a viral load in the airspace.

In another aspect of the disclosed technology, determining a difference between: a frequency of an alternating current produced in the first electrode in response to the application of the alternating voltage to the first electrode, and a frequency of an alternating current produced in the second electrode in response to the application of the alternating voltage to the second electrode includes determining the frequency difference using a homodyne detection technique.

In another aspect of the disclosed technology, the process further includes generating and sending a notification when the viral load in the airspace is determined to be greater than a predetermined value.

In another aspect of the disclosed technology, the process further includes removing from a sample of the airspace particles having a size greater than a predetermined value.

In another aspect of the disclosed technology, the process further includes removing from the sample of the airspace the particles sampled from the airspace.

In another aspect of the disclosed technology, determining a viral load in the first volume based on the frequency difference includes determining the viral load in the first volume based on the frequency difference using an edge-cloud server. In another aspect of the disclosed technology, determining a viral load in the first volume based on the frequency difference includes determining the viral load in the first volume based on a predetermined relationship between the viral load in the first volume and the frequency difference.

In another aspect of the disclosed technology, the process further includes calculating a minimum separation distance needed to reduce a potential for human-to-human transmission of airborne pathogens, based on an estimate of distance the particles will travel upon being exhaled as determined using the temperature and relative humidity of the airspace, and the particle concentration in the airspace.

In another aspect of the disclosed technology, the process further includes validating the determination of the viral load based at least in part on a carbon dioxide level, a particulate matter level, and the presence or absence of people in the airspace.

BRIEF DESCRIPTION OF THE DRAWINGS

The following drawings are illustrative of particular embodiments of the present disclosure and do not limit the scope of the present disclosure. The drawings are not to scale and are intended for use in conjunction with the explanations provided herein. Embodiments of the present disclosure will hereinafter be described in conjunction with the appended drawings.

FIG. 1A is a diagrammatic illustration of an embodiment of an air sensing and purification system.

FIG. 1 is a top perspective view of an air purification device of the air sensing and purification system shown in FIG. 1A. FIG. 2 is a schematic view of an air sanitizer and a fan system of the air purification device shown in FIG. 1.

FIG. 3 is a schematic view of electrical components of the air purification device shown in FIGS. 1 and 2.

FIG. 4 is a schematic view of a control unit of the air purification device shown in FIGS. 1-3. FIG. 5 A is a top view of a proximity sensor group of the air purification device shown in

FIGS. 1-4.

FIG. 5B is a side view of the proximity sensor group shown in FIG. 5A, FIGS. 6 and 7 are schematic views of the air purification device shown in FIGS. 1-5B, with the system in an activated state in response to two individuals proximate the system being separated by a distance less than a minimum social distance.

FIG. 8 is a schematic illustration depicting various factors affecting a spreading distance of aerosolized particles emitted by a human.

FIG. 9 is a schematic illustration of a mobile computing device equipped with an application of the system shown in FIGS. 1-7.

FIG. 10 is a diagrammatic illustration diagram of a virus detection system of the air sensing and purification system shown in FIG. 1A.

FIGS. HA and 1 IB are flow charts depicting operation of the virus detection system shown in FIG. 10.

FIG. 12A is a diagrammatic illustration of a coarse filter of a particle collector of the virus detection system shown in FIG. 10.

FIG. 12B is a diagrammatic illustration of an alternative embodiment of the coarse filter shown in FIG. 12 A.

FIG. 13A is a diagrammatic illustration of an aerosol sampler the particle collector of the virus detection system shown in FIG. 10.

FIG. 13B is a diagrammatic illustration of an alternative embodiment of the aerosol sampler shown in FIG. 13 A.

FIG. 13C is a diagrammatic illustration of another alternative embodiment of the aerosol sampler shown in FIG. 13A.

FIG. 13D is a diagrammatic illustration of another alternative embodiment of the aerosol sampler shown in FIG. 13A.

FIG. 13E is a diagrammatic illustration of another alternative embodiment of the aerosol sampler shown in FIG. 13A.

FIG. 14 is a diagrammatic illustration of various electrical components of the virus detection system shown in FIG. 10, with a graphical representation of various frequency measurements made using the components. FIG. 15A is a graph depicting the relationship between the frequency of an alternating current through a first conductivity probe of an embodiment of the virus detection system shown in FIG. 10, as a function of the viral load in a solution in which the probe is immersed.

FIG. 15B is a graph depicting the difference between the alternating current frequency depicted in FIG. 15 A, and the frequency of an alternating current through a second conductivity probe immersed in a solution that does not contain a viral load, as a function of the viral load in which the first probe is immersed.

FIG. 16 is a diagrammatic illustration diagram of an alarm hub of the air sensing and purification system shown in FIG. 1A.

DETAILED DESCRIPTION

The inventive concepts are described with reference to the attached figures, wherein like reference numerals represent like parts and assemblies throughout the several views. The figures are not drawn to scale and are provided merely to illustrate the instant inventive concepts. The figures do not limit the scope of the present disclosure or the appended claims. Several aspects of the inventive concepts are described below with reference to example applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the inventive concepts. One having ordinary skill in the relevant art, however, will readily recognize that the inventive concepts can be practiced without one or more of the specific details or with other methods. In other instances, well-known structures or operation are not shown in detail to avoid obscuring the inventive concepts.

The figures depict an air sensing and purification system 10 for reducing the potential for human-to-human transmission of pathogens via droplets or aerosols. The system 10 includes an air purification device 11, a virus detection system or subsystem 12, and an alarm hub 13. The air purification device 11, virus detection system 12, and alarm hub 13 can be internet of things (loT) enabled, and are communicatively coupled via a suitable wireless means such as Wi-Fi, BLUETOOTH, a cellular network, etc. The air purification device 11, virus detection system 12, and alarm hub 13 can by communicatively coupled via a suitable wired connection in alternative embodiments. The virus detection system 12 is an intelligent system that can detect an airborne viral load, and can communicate the viral-load data wirelessly to any connected hub or cloud, such as the alarm hub 13. The alarm hub 13 can function as a local server/hub for the air purification device 11 and virus detection system 12. The alarm hub 13 a computing device configured to perform the logical operations disclosed below. The computing device can be, for example, an edge-cloud server 246 as depicted in FIG. 16; other types of computing devices can be used in lieu of the edge-cloud server 246 in alternative embodiments. The edge-cloud server 246 is communicatively coupled to the virus detection system 12 and the air purification device 11 by a suitable wireless means, such as Wi-fi, BLUETOOTH, a cellular network, etc. The edge-cloud server 246 can be communicatively coupled to the virus detection system 12 and the air purification device 11 by a wired connection in alternative embodiments.

The alarm hub 13 houses strong visual and audio alarms to alert the user of any breach of a safe social distance between the user and another individual, and of the detection of a high airborne viral load int the immediate vicinity of the user. The air purification device 11 efficiently uses a multiple sensor stack and multiple effective viral denaturing technologies to neutralize COVID-19 or other enveloped viruses present in the ambient environment around the air purification device 11.

Upon startup of the system 10, the air purification device 11, virus detection system 12, and alarm hub 13 are powered on and begin to communicate with each other. Once the air purification device 11, virus detection system 12, and alarm hub 13 have established communication with each other, they begin to share useful data and perform the tasks described below.

The alarm hub 13 acts as a local hub/server for the air purification device 11 and the virus detection system 12. Also, the alarm hub 13 will alert the user if there is a breach in the required social distancing, as provided by the air purification device 11, and/or upon the detection of an unacceptable viral load by the virus detection system 12. Immediately after the alarm is activated, the air purification device 11 starts to automatically clear substantially all the aerosolized particles from the airspace around the air purification device 11, and operates until the viral load as detected by the virus detection system 12 reaches zero, or a predetermined level; and/or until the minimum social distance is re-established between the user and other individuals in the vicinity of the user as determined by the air purification device 11.

Alternative embodiments of the system 10 can include more than one air purification device 11 and/or more than one virus detection system 12 communicatively coupled to the alarm hub 13, i.e., one alarm hub 13 can service more than one air purification device 11 and more than one virus detection system 12.

Air Purification Device

The air purification device 11 includes an outer casing 14. The casing 14 can be formed from a durable, impact-resistant material such as high-impact plastic.

The air purification device 11 also includes a sensor group 16; an air sanitizer 18; a fan system 19; a proximity sensor group 20; a display 22; and a computing device in the form of a control unit 24. The air purification device 11 receives electric power by way of a universal serial bus (USB) port 25. Alternative embodiments of the air purification device 11 can be powered by internal rechargeable battery. The sensor group 16 comprises various sensors that sense the ambient environmental conditions around the air purification device 11. The proximity detector 20 senses the presence of people in proximity to the air purification device 11. The control unit 24 is configured to determine a minimum person-to-person spacing, or minimum social distance, needed to minimize the potential for transmission of pathogens, such as the COVID- 19 virus, under the specific environmental conditions sensed by the air purification device 11.

Upon determining that the minimal social distance is not being maintained between two or more individuals proximate the air purification device 11, the control unit 24 activates the fan system 19 and the various electrical components of the air sanitizer 18. The control unit 24 also activates the fan system 19 and the various electrical components of the air sanitizer 18 upon receiving an input from the virus detection system 12, via the alarm hub 13, indicating that an excessive, i.e., unacceptable, airborne viral load has been detected. The threshold for characterizing the viral load as unacceptable can be zero, or some other level above which the risk of infection is considered unacceptable. The fan system 19, upon activation, draws ambient air into the air purification device 11, where the air is filtered and disinfected by the air sanitizer 19. The purified air then is discharged back into the ambient environment around the air purification device 11, thereby reducing the potential for transmission of pathogens between the individuals located proximate the air purification device 11. The air purification device 11 can be made compact enough to be placed close to the individual(s) being protected. For example, the exemplary embodiment of the air purification device 11 disclosed herein can be placed on a typical table of a restaurant or cafe.

Referring to FIG. 3, the sensor group 16 comprises a temperature sensor 50; a humidity sensor 52; a particulate matter sensor 54; a nitrogen dioxide sensor 56; and a carbon dioxide sensor 58. The temperature sensor 50; humidity sensor 52; particulate matter sensor 54; nitrogen dioxide sensor 56; and carbon dioxide sensor 58 are mounted within the casing 14; and are communicatively coupled to the control unit 24. The casing 14 is depicted in FIG. 1.

The temperature sensor 50 and the humidity sensor 52 provide the control unit 24 with inputs representing the temperature and relative humidity, respectively, of the ambient air around the air purification device 11. The particulate matter sensor 54 provides the control unit 24 with three separate inputs, PM 1.0, PM 2.5 and PM 10, representing the concentrations of particulate matter in the ambient air, where: PM 1.0 refers to the density of particles which are smaller than or equal to about 1pm in size, suspended in the air; PM 2.5 refers to the density of particles which are smaller than or equal to about 2.5 pm in size, suspended in the air; and PM 10 refers to the density of particles which are smaller than or equal to about 10 pm in size, suspended in the air. The nitrogen dioxide sensor 56 and carbon dioxide sensor 58 provide the control unit 24 with inputs representing the concentrations of nitrogen oxide and carbon dioxide, respectively, in the ambient air.

Referring to FIG. 4, the control unit 24 comprises a processor 62, such as a microprocessor; a memory device 64 communicatively coupled to the processor 62 via an internal bus 66; and computer-executable instructions 68 stored on the memory device 64 and executable by the processor 62. The control unit 24 also comprises an input-output bus 70; an input-output interface 72 communicatively coupled to the processor 62 by way of the input-output bus 70, and a transceiver 73 communicatively to the input-output interface 72. The computer-executable instructions 68 are configured so that the computer-executable instructions 68, when executed by the processor 62, cause the control unit 24 to carry out the various logical functions described herein. The above details of the control unit 24 are presented for illustrative purposes only. The control unit 24 can have components in addition to those described above, and can have an internal architecture other than that descried above.

The virus detection system 12 also can include a wireless gateway 252a. The wireless gateway 252a is communicatively coupled to the control unit 24 by way of the transceiver 73, and facilitates communication between the controller 223, the edge-cloud server 246 of the alarm hub 13, and other devices on which the air-sampling results, environmental data, and warnings can be displayed, processed, and/or stored. For example, the above noted information displayed on a display 251 of the alarm hub 13; on a mobile device 79; and/or on a desktop computer 256 of the alarm hub 13. The display 251, mobile device 79; and desktop computer 256 are depicted in FIG. 16. Also, data can be further processed and/or stored on the edge-cloud server 246 or other computing devices. Communication between the wireless gateway 252a and the above-noted devices can be facilitated by any suitable means, such as the internet, a cellular network, Wi-Fi, a local area network, a wide area network, BLUETOOTH, etc.

The control unit 24 can share the environmental data generated by the sensor group 16 with the edge cloud server 246, and can receive the dynamic social distance calculated by the edge cloud server 246, via the transceiver 73 and the wireless gateway 252a. Also, the control unit 24 can receive software updates via the transceiver 73 and the wireless gateway 252a; and can share diagnostic information and information regarding when, and how often the minimum social distance has been breached, via the transceiver 24 and the wireless gateway 252a. The transceiver 73 can communicate with the wireless gateway 252a via a wireless means such as WiFi, BLUETOOTH, a cellular network, etc. The transceiver 73 can communicate via wired means in alternative embodiments.

The edge-cloud server 246 of the alarm hub 13 is configured to determine, and constantly update, a dynamic social distance, based on the ambient environmental conditions as measured by the sensor group 16 and the viral load as measured by the virus detection system 12. In particular, the edge-cloud server 246 can be programmed with algorithms that, when executed by the edge-cloud server 246, calculate a dynamic social distance at a given time based on the measured temperature and humidity of the ambient air; the concentration and size distribution of particles in the ambient air; and the viral load in the ambient air as determined by the virus detection system 12.

It is believed that the size of the droplet nuclei resulting from sneezing, coughing, and talking is a function of the process by which the droplets are generated, and the environmental conditions. For example, sneezing can generate around 40,000 droplets in the 0.5 micron to 12 micron range, which most likely are aerosolized. Also, studies have shown that talking for five minutes can generate the same number of droplet nuclei as a cough, i.e., about 3,000 droplet nuclei. The actual size distribution of the droplets is dependent on parameters such as the exhaled air velocity, the viscosity of the fluid, and the flow path.

Human-to-human transmission of pathogens such as the COVID-19 virus takes place via droplets, or aerosol transportation, from one individual to another. After being exhaled by an infected person, respiratory droplets with various sizes travel and simultaneously evaporate in the ambient air. The droplets begin to exchange heat and mass with the ambient air while moving under the influence of various forces such as gravity, buoyancy, and air drag. It is believed that the respiratory droplets evolve into two categories, large and small-sized droplets, depending on their initial diameter. Largesized droplets can reach limited distance, whereas small-sized droplets dry to form a cloud of aerosol particles that can remain suspended in the air for a significant amount of time. It is believed that the size of the droplet nuclei resulting from sneezing, coughing, and talking is a function of the process by which the droplets are generated, and the environmental conditions. For example, it is believed that sneezing can generate approximately one million droplets of up to 100 pm in diameter, plus several thousand larger particles formed predominantly from saliva in the frontal part of the mouth. Also, studies have shown that talking for five minutes can generate the same number of droplet nuclei as a cough, i.e., about 3,000 droplet nuclei. The actual size distribution of the droplets is dependent on parameters such as the exhaled air velocity, the viscosity of the fluid, and the flow path.

Human-to-human transmission of pathogens such as the COVID-19 virus takes place via droplets, or aerosol transportation, from one individual to another. After being exhaled by an infected person, respiratory droplets with various sizes travel and simultaneously evaporate in the ambient air. The droplets begin to exchange heat and mass with the ambient air while moving under the influence of various forces such as gravity, buoyancy, and air drag. This phenomenon is depicted schematically in FIG. 8. It is believed that the respiratory droplets evolve into two categories, large and small-sized droplets, depending on their initial diameter. Large-sized droplets can reach limited distance, whereas small-sized droplets dry to form a cloud of aerosol particles that can remain suspended in the air for a significant amount of time.

The time of flight and distance traveled by exhaled particles depend upon the transport characteristics of the ambient air, i.e., the viscosity, temperature, specific heat capacity, and thermal conductivity of the ambient air. The transport characteristics vary with the ambient temperature and relative humidity, and hence can change the minimum social distance required to minimize the potential for person-to-person transmission of pathogens carried by exhaled particles. The following set of equations can be used to estimate the distance an exhaled particle will travel, using the temperature and relative humidity of the air through which the particle will travel, and the concentration of particles in the air:

Because the minimum social distance is related to the distance an exhaled particle will travel, the above equation set can be used to estimate the minimum social distance based on the ambient temperature and relative humidity, and the particle concentration in the ambient air.

The parameters used in the above equation set are air transport characteristics at different temperatures and different relative humidity (RH) values, where r _p = Radius of the droplet

T _p = Temperature of the droplet

V _p = Velocity of the droplet X _p = Distance traveled by the droplet

The edge-cloud server 246 is configured to perform a Runge Kutta Fourth Order Method to solve the above differential equations for the distance traveled by the droplet under the specific conditions existing at a particular time. The distance traveled by the droplet represents the minimum separation distance for that particular point in time. The edge-cloud server 246 calculates and constantly updates the minimum social distance using the above technique.

Once the minimum social distance has been determined, it is modified using the actual airborne viral load as measured by the virus detection system 12. Specifically, the minimum social distance is modified by applying a predetermined correlation between the viral load, and the minimum social distance, i.e., the minimum separation between two individuals needed to maintain the risk of one of the individuals becoming infected by an airborne virus carried by the other individual at an acceptable level. The minimum social distance is adjusted based on the actual airborne viral load as measured by the virus detection system 12, and the predetermined correlation, to yield a dynamic social distance that represents the minimum social distance modified to account for the actual airborne viral load.

In alternative embodiments, calculation of the minimum social distance and/or the dynamic social distance can be performed by the control unit 24 of the air purification device 11, instead of the edge-cloud server 246.

The air purification device 11 constantly monitors the surrounding area for the presence of humans, using the proximity detector 26. Referring to FIGS. 5A and 5B, the proximity detector 26 comprises five passive infrared sensors (PIRs) 76. The PIRs 76 are equally spaced along the outer circumference of the proximity detector 26. Each PIR 76 has a detection angle of about 140 degrees. Thus, the five PIRs 76 have a combined field of view of 360 degrees around the air purification device 11. The combined field of view extends outward to a radius of about three meters to about 7 meters from the centerline of the air purification device 11.

The PIRs 76 are communicatively coupled to the control unit 24. Each PIR 76 is configured to generate a discrete output signal in response to a changes in the temperature field within its field of view. Such temperature changes can occur when a human enters the field of view of the PIR 76. Thus, each PIR 76 responds to the entry of a human into its field of view by generating a discrete output signal that is provided to the control unit 24.

The proximity detector 26 can have configurations other than the above -de scribed configuration, in alternative embodiments. For example, alternative embodiments of the proximity detector 26 can detect the presence of humans using a sensing means other than infrared radiation.

The computer executable instructions 68, executed on the processor 62, cause the control unit 24 to perform the following logical operations to determine whether the minimum social distance is being violated at any point in time. The control unit 24 constantly samples the output of each PIR 76. Upon receiving inputs from two or more PIRs 76 indicating that two or more humans have entered the respective fields of view of the PIRs 76, the control unit 24 determines the distance between the two individuals. More specifically, the control unit 24 determines the position of each individual based on the relative locations of the particular PIRs 76 registering the presence of the individual, using a conventional triangulation (geometric) technique. The control unit then calculates the distance between the two or more individuals. If the control unit 24 determines that the individuals are separated by a distance less than the minimum social distance calculated at that particular time, the control unit 24 generates outputs that activate the fan system 19, the air sanitizer 18, and the audible and visual warnings associated with the display 22. The control unit 24 maintains the fan system 19 and the air sanitizer 18 in an activated state until the control unit 24 determines that the individuals are separated by a distance greater than the minimum social distance. The logical operations to determine whether the minimum social distance is being violated can be performed by the edge cloud server 246, instead of the control unit 24, in alternative embodiments.

FIGS. 6 and 7 schematically depict the air purification device 11, and two humans located proximate the air purification device 11 and being separated by a distance “R” that is less than the calculated minimum social distance “R _o ” for that particular point in time. Because the control unit 24 has determined that the actual separation of the two persons (R) is less than the minimum social distance (R _o ), the control unit 24 has activated the fan system 19 and the air sanitizer 18. As depicted schematically in FIG. 6, the air purification device 11 draws in unpurified ambient air, and discharges purified air toward the people near the air purification device 11. Thus, the potential for the transmission of airborne pathogens, such as COVID- 19, from one of the individuals to the other is substantially reduced.

The fan system 19 is mounted in the casing 14, proximate the upper end of the casing 14. The fan system 19 is communicatively coupled to the control unit 24, and is activated and deactivated in response to inputs from the control unit 24. The fan system 19 generates airflow through the air sanitizer 18. The air purification device 11 has an internal airflow passage 78, depicted schematically in FIG. 2. The fan system 19 is located at the exit of the passage 78. The inlet of the passage 78 communicates with the environment around the air purification device 11 via inlet openings 80 in the casing 14. Upon activation, the fan system 19 generates a suction force within the passage 78. The suction force causes ambient air from around the air purification device 11 to be drawn into the passage 78 by way of the inlet openings 80. After entering the passage 78, the air is drawn through the air sanitizer 18. The purified air subsequently passes through the fan system 19, which forces the purified air out of the air purification device 11 by way of outlet openings 82 in the top of the casing 14.

The fan system 19 comprises a plurality of individual fans 85. The fans 85 are arranged in series; and are located in the airflow passage 78, near the outlet openings 82. The fans 85 collectively create a relatively high suction around the entire air purification device 11, so as to quickly draw ambient air from around the air purification device 11, along with any droplets or particulates suspended in the ambient air, into the airflow passage 78. This suction effect, in conjunction with the discharge of purified air from the top of the air purification device 11, creates a localized volume of purified air around the user, as depicted schematically in FIG. 6. The localized volume of purified air, in turn, substantially reduces the potential for the transmission of pathogens between the two or more individuals proximate the air purification device 11. The airflow rate of the fan system 19 can be, for example, about 15 to about 30 cubic feet per minute. It is believed that a fan system 19 having this flowrate can create a “safe zone” around the air purification device 11, i.e., a volume in which the potential for person-to-person transmission of pathogens is substantially reduced. Fan systems having an airflow rate greater, or less than about 15 to about 30 cubic feet per minute can be used in alternative embodiments.

Referring to FIG. 2, the air sanitizer 18 includes four separate means for purifying the air passing through the air purification device 11. In particular, the air sanitizer 18 includes an air filter 84, an ultraviolet (UV) light 86, a negative ion generator 88, and a corona discharge chamber 90.

The UV light 86 is positioned within the casing 14 so that the UV light 66 illuminates that airflow traveling through the air purification device 11 upon entry of the airflow into the internal airflow path within the casing 14. The UV light 86 is communicatively coupled to the control unit 24, and is activated and deactivated in response to inputs from the control unit 24. The UV light 86 comprises a plurality of high-intensity light emitting diodes (LEDs) that emit UV radiation within a wavelength range of about 265 nm to about 272 nm. Based on currently -available scientific evidence, it is believed that exposing the COVID-19 virus to UV radiation within this range of wavelengths has the potential to neutralize the virus with maximum efficiency relative to other wavelengths. The UV light 86 can have other configurations in alternative embodiments.

The negative ion generator 88 is located in the airflow path 78. The airflow through the air purification device 11 passes through the negative ion generator 88 after being sanitized by the UV light 86. The negative ion generator 88 is communicatively coupled to the control unit 24, and is activated and deactivated in response to inputs from the control unit 24.

The negative ion generator 88 comprises sharp electrodes that generate an high electrostatic potential on particles passing by the electrodes. As a result of this high electric potential, air breakdown occurs and the formation of negative ions takes place. The resulting negative ions pass into the corona discharge chamber 90, which is located downstream of the negative ion generator 88. The corona discharge chamber 90 maintains a high concentration of the negatively -charged particles, in the range of about 10 ⁶ ions/cc. A copper mesh 91 positioned within the corona discharge chamber 90 makes the interior of the corona discharge chamber 90 alkaline in nature, resulting in the production of OH" ions in great numbers. Based on currently-available scientific evidence, it is believed that the highly -concentrated negatively-charged particles act as an air detergent that neutralizes pathogens, including the COVID-19 virus, within the corona discharge chamber 90. Also, the negative charge imparted to the particles by negative ion generator 88 causes the charged particles to be attracted to the surfaces of the air filter 84 located downstream of the corona discharge chamber 90. Any charged particles not captured by the air 84 filter, after being discharged from the air purification device 11, will tend to be attracted to, and adhere to exposed surfaces in the vicinity of the air purification device 11, further reducing the potential for the airborne transmission of pathogens between individuals located proximate the air purification device 11.

The air filter 84 performs the final stage of air purification within the air purification device 11. The airflow within the air purification device 11 passes through the air filter 84 after exiting the corona discharge chamber 90. The air filter 84 is a high efficiency particulate air (HEP A) filter with the capability to filter out particles larger than 0.3 pm, an efficiency of about 99.95 percent. It is believed that about 99.9 percent of the viral load transmitted by respiratory means is carried by particles larger than 0.3 pm. Thus, the air filter 84 can substantially reduce the potential for the air exiting the air purification device 11 to transmit COVID-19 and other viral pathogens. Alternative embodiments of the air purification device 11 can be configured with a filter 84 other than a HEPA filter. In other alternative embodiments, the air filter 84 can include a pre-filter and an activated charcoal layer located upstream and downstream of the HEPA layer, respectively.

After passing through the airflow filter 84, the airflow within the air purification device 11 is discharged to the ambient environment by way of the outlet openings 82. As this point, the potential for the air exiting the air purification device 11 to transmit pathogens, such as the COVID-19 virus, has been substantially reduced due to the above-noted steps of filtration, neutralization through exposure to negative ions, and UV disinfection. As a result of the high flow-rate of the fan system 19, the purified air exiting the air purification device 11 quickly displaces the ambient air proximate the air purification device 11 as the air purification device 11 in the potentially contaminated air around the air purification device 11. Also, the powerful suction generated by the fan system 19, in conjunction with the ability to place the compact air purification device 11 close to the individual(s) being protected, allows droplets and aerosolized particles containing pathogens to be removed from the ambient air immediately after being emitted by an infected individual proximate the air purification device 11. The display 22 is mounted on the top of the casing 14. The display 22 can be mounted at other locations on the casing 14 in alternative embodiments. The display 22 can be, for example, a light emitting diode (LED) display having a length of about 2.86 inches. The display 22 is communicatively coupled to the control unit 24. The display 22 continually displays the dynamic social distance being calculated by the 10, to apprise those in the vicinity of the air purification device 11 of the minimal social distance at any given time. The display 50 also comprises a plurality of warning lights 86 that are activated by the control unit 24 when the control unit 24 determines that two or more individuals are separated by a distance less than the minimum safe social distance. The warning lights 52 are located above a legend “Social Distance Compromised.” The display 52 can have other configurations in alternative embodiments. Also, the display 22 is configured to continually display the minimum social distance as calculated by the control unit 24,

Also, the control unit 24 generates an output that, when received by the alarm hub 13, causes the alarm hub 13 to activate audible and visual warnings as discussed below, to clearly alert the individuals near the system 10 that the local airborne viral load is at a dangerous or otherwise unhealthy level, and that each individual immediately needs to increase his or her distance from the other individuals. Thus, potential for human-to-human transmission of pathogens carried by droplets and other aerosolized particles emitted by the individuals proximate the air purification device 11 can be reduced substantially by the air purification device 11.

The air purification device 11, and the system 10 in general, can be used in conjunction with a mobile device 97 such as a smartphone, depicted in FIG. 16. The mobile device 97 can be equipped with an application 98 that permits the mobile device 97 to communicate with the air purification device 11 and the virus detection system 12 via the alarm hub 13, and to display information such as the calculated dynamic social distance at any given time; whether the system 10 is in an “alarm” state; whether the air sanitizer 18 is activated; the actual airborne viral load as measured by the virus detection system 12, etc.

The application 98 also permits the mobile device 97 to display the environmental and meteorological parameters measured by the air purification device 11. For example, as shown in FIG.

9, in addition to displaying the ambient temperature and relative humidity and the particulate concentration in the ambient air, the mobile device 97 can display the carbon dioxide and nitrogen dioxide levels measured by the carbon dioxide sensor 58 and the nitrogen dioxide sensor 56. These parameters can be displayed to make the user aware of the quality of the air in the immediate vicinity of the air purification device 11. For example, higher concentrations of carbon dioxide can indicate poor ventilation of the surrounding area; and higher concentrations of nitrogen dioxide can indicate levels of high air pollution, i.e., unhealthy air quality, in the surrounding area. The mobile device 97 can display the actual levels of carbon dioxide and nitrogen dioxide, as well as the recommended limits for both parameters, to provide the user with a readily discernable scale against which to judge the air quality.

Virus Detection System

FIGS. 10 and 12A-14 depict the virus detection system 12 for detecting the airborne virus load. The virus detection system 12 uses alternating current (AC) conductivity measurement to determine the viral load in a liquid medium into which particulate matter sampled from the monitored spaced has been introduced. The virus detection system 12 also uses a reference solution that is maintained at substantially the same environmental conditions as the solution containing the sampled particles, and does not include any virus particles.

An alternating voltage is applied across the electrodes of a first probe immersed in the sample solution, i.e., the solution into which the sampled particulate matter has been introduced. A substantially identical alternating voltage is applied across the electrodes of a second probe immersed in the reference solution. The voltage potential across the electrodes of the first and second probes causes an alternating current to flow through each probe. The difference between the frequencies of the respective alternating currents is determined using a homodyne detection technique. In alternative embodiments, the difference between the frequencies of the respective alternating currents is determined using a heterodyne detection technique. The difference in frequency can be used to estimate the viral concentration, including very low viral concentrations, in the sample solution. More specifically, the presence of a viral load in the sample solution affects the electrochemical characteristics of the solution, which in turn affects the electrical conductivity and dielectric properties of the solution. The change in electrical conductivity and dielectric properties affect the frequency of the alternating current passing between the electrodes of the probe immersed the sample solution by a very small, but detectable, amount. The difference between the frequency response of the alternating currents in the probes immersed in the sample and reference solutions thus can be correlated to the presence and magnitude of the viral load in the reference solution.

Also disclosed are mechanical methods for introducing the virus particles into the liquid solution; and a dopant that, when added to the liquid, enhances the Zeta potential and Debye radius of the resulting colloidal solution in which charged virus particles have been trapped, thereby enhancing the overall sensitivity of the detection of the viral load. With the disclosed combination of mechanical, electrical, signal processing, and algorithmic features, the virus detection system 12 has been shown to be sensitive enough to detect small viral loads in the range of 10-50 particle/100 mL of air with a high degree of reliability and repeatability.

The virus detection system 12 can be characterized as including, without limitation, three core component groups: an aerosol classification and bio-sampling group; a viral detection group that detects the presence and magnitude of a viral load based on changes in electrical properties of the liquid in which viral particles are suspended; and an edge computation and loT platform group that facilitates validation of the acquired data, and generation of notifications and warnings when an airborne virus is detected.

In aerosol sampling, air quality generally is determined by: (i) determining the density of airborne particles of different sizes; (ii) determining the “health” of breathing space, i.e., whether the breathing space is too densely populated, and (iii) determining the air properties to scientifically calculate the air transport characteristics.

FIGS. HA and 1 IB are flow charts depicting operation of the virus detection system 12. The initial portion of the virus detection process performed by the virus detection system 12 comprises collecting air from throughout the room or other space in which the air quality is to be monitored; and isolating particles that potentially are the most conductive to causing an infection and spreading the virus.

A person infected with a respiratory virus typically emits a variety of aerosols that can be classified in accordance with their aerodynamic diameter. The aerodynamic diameter of a particle is defined as the diameter of a sphere of density lg/cm ³ which suspends or settles in still air at same velocity as the particle. An infected person, in general, can emit aerosolized particles having aerodynamic diameters in the range of 1 micron to 200 microns. The particles having an aerodynamic diameter greater than 100 microns are much less likely to remain airborne than smaller diameter particles, and settle to the nearby ground very quickly after being emitted. Such particles, therefore, are highly unlikely to cause virus spread.

Aerosolized particles having an aerodynamic diameter in the range of ten microns to 100 microns are characterized as inhalable fractions. Such particles typically become trapped in the nose and mouth, and therefore are unlikely to cause an infection by way of the respiratory system.

Aerosolized particles with an aerodynamic diameter in the range of four microns to ten microns are characterized as thoracic fractions. These types of particles readily can reach the throat and upper respiratory duct, and therefore are likely to result in infection and spreading of the virus.

Aerosolized particles having an aerodynamic diameter less than four microns are characterized as respirable fractions. These types of particle generally are considered the most dangerous, because such particles can reach the finest parts of the lungs. Respirable particles, therefore, are responsible to a large extent for the spread of illnesses due to airborne viral pathogens.

Thoracic and respirable particles are believed to make up a major portion of the viral load in a typical space in which the COVID- 19 virus is spread. And as noted above, these types of particles, if inhaled, are highly likely to cause an infection. Hence, the virus detection system 12 is configured to target thoracic and respirable particles when estimating the viral load, to help maximize the detection of potentially infectious particles, and decrease false readings based on the detection of larger particles.

The virus detection system 12 comprises a fan 222, depicted schematically in FIG. 10. The fan 222 is configured to draw ambient air from the space or volume of air being monitored for a viral load (step 100 in FIG. HA). In one possible embodiment, the fan 222 can be configured to generate a suction that draws air from every direction around the fan 222, and from a distance of up to 12 feet away from the fan 222, to help maximize the area of coverage and the operational efficiency of the virus detection system 12. The fan 222 is communicatively coupled to a controller 223 of the virus detection system 12, as shown in FIG. 10. The controller 223 is configured activate and deactivate the fan 222 at the start and end of each sampling period.

Each sampling period can have a duration of, for example, about ten to about 100 seconds. The controller 223 can be configured to obtain a sample at predetermined intervals, such as about every one to ten minutes. The virus detection system 12 can be configured so that the sampling period and sampling intervals can be varied by the user via inputs provided through a suitable input device communicatively coupled to the controller 223. The virus detection system 12 can be further configured so that the user can initiate a sampling period on demand, by entering a command though the alarm hub 13 or the mobile device 97.

The controller 223 can be any type of computing device capable of performing the logical operations described therein. As a non-limiting example, the controller 223 can be a microcontroller comprising, in relevant part, a microprocessor; a memory communicatively coupled to the microprocessor; and computer executable instructions stored in the memory. The computer executable instructions are configured so that, upon execution by the microprocessor, the computer executable instructions cause the microcontroller to perform the logical operations disclosed herein.

The system further comprises a particle collector 224, depicted schematically in FIG. 1. The particle collector 224 is in fluid communication with the fan 222, and is located downstream from the fan 222 so that the particle collector 224 receives the ambient air entrained by the fan 222. The particle collector 224 is configured to collect aerosolized virus particles likely to result in an infection, and to separate and eliminate aerosolized particles of no interest, i.e., particles that are unlikely to result in infection.

Referring to FIGS. 12A and 12B, the particle collector 224 comprises a coarse filter that filters out, or eliminates particles having an aerodynamic diameter greater than about ten microns (step 102 in FIG. 11A). As discussed above, virus particles characterized as inhalable fractions, i.e., particles with an aerodynamic diameter greater than ten microns, are highly unlikely to produce an infection. Thus, these particles are eliminated in the initial, or coarse filtration portion of the aerosol sampling process. The coarse filter can use any suitable technique to eliminate the inhalable fractions.

For example, the coarse filter can comprise a filter mesh 226, shown in FIG. 12A, that captures particles larger than ten microns. Alternatively, the coarse filter can comprises a cyclonic filter 227, shown in FIG. 12B, having a cut-off particle diameter of ten microns.

Referring to FIGS. 13A-13E, the particle collector 224 further comprises an aerosol sampler. The air sample is directed to the aerosol sampler following removal of the inhalable fractions in the coarse filter. The aerosol sampler is configured to separate the thoracic and respirable fractions from the air flow after the larger particles have been removed by the coarse air filter (step 102 in FIG. HA). The aerosol sampler can use any suitable technique to perform this function. For example, as shown diagrammatically in FIG. 13A, the aerosol sampler can comprise an impinger 270 configured to capture aerosolized particles having an aerodynamic diameter of less than ten microns.

Alternatively, as shown diagrammatically in FIG. 13B, the aerosol sampler can comprise a cyclonic filter 272 configured to capture aerosolized particles having an aerodynamic diameter of less than ten microns.

Alternatively, as shown diagrammatically in FIG. 13C, the aerosol sampler can comprise a condensation-based separator 274 configured to introduce steam into the sampled airflow. The resulting condensation of causes aerosolized particles having an aerodynamic diameter of less than ten microns to drop out of the airflow.

Alternatively, as shown in diagrammatically FIG. 13D, the aerosol sampler can comprise an impactor 276 configured to capture aerosolized particles having an aerodynamic diameter of less than ten microns.

Alternatively, as shown diagrammatically in FIG. 13E, the aerosol sampler can comprise an electrostatic precipitator 278 configured to capture aerosolized particles having an aerodynamic diameter of less than ten microns.

The aerosol sampler is configured so that the thoracic and respirable fractions, upon being separated from the air stream, drop into, and become suspended in a liquid solution positioned beneath the aerosol sampler as shown in FIGS. 13A-13E (step 106 in FIG. HA). The sampled air from which the thoracic and respirable fractions have been separated is released back in the ambient environment to complete the bio sampling process. The liquid into which the virus particles are dropped acts as a base of a colloidal solution in which the particles are absorbed. The liquid can be any of deionized water, distilled water, isopropyl alcohol, disodium laureth sulfosuccinate (DLS) solution, and other types of liquids that become polarized upon the absorption of virus particles. Thus, the absorption of viral particles into the liquid changes the electrochemical properties of the liquid; and the presence of virus particles can be detected by measuring the change in electrical properties of the liquid. This in turn can facilitate the determination an airborne viral load in the space from which the particles were obtained.

The electrochemical properties of a liquid also are dependent on handling, i.e., shaking, which can result in vibrations that produce more electrostatic charge separation of the virus particles. The electrochemical properties of a liquid also are dependent on environmental factors such as the temperature of the liquid. Therefore, to eliminate ambiguous or erroneous results due to changes in temperature and other environmental factors, the virus detection system 12 uses a two-chamber analysis technique in which one liquid-fdled chamber is used as a reference, and the other liquid-filled chamber contains a colloidal solution of entrapped sampled particles. More specifically, the virus detection system 12 further comprises a reference chamber 230, and a sample chamber 232, as shown in FIG. 10.

As noted above, the thoracic and respirable fractions, upon being separated from the air sample in the aerosol sampler, are absorbed into a liquid solution. Upon completion of the predetermined sampling period, this solution is transferred to the sample chamber 232. The reference chamber 230 contains the same liquid composition, in the same volume, as the sample chamber 232, but the liquid composition in the reference chamber 230 does not include any absorbed particles. The liquid composition in the reference chamber 230 otherwise is substantially identical to the liquid composition in the sample chamber 232.

Also, the liquid composition in the reference chamber 230 is maintained at substantially the same environmental conditions, including temperature, as the liquid composition in the sample chamber 232. The relevant properties of the liquid composition in the reference chamber 230, therefore, can act as a baseline against which changes of the conductivity of the solution in the sample chamber 232 can be evaluated. As discussed below, this technique helps to maximize the signal to noise ratio in the signal that ultimately is used to indicate of the viral load in the sample chamber 232.

The virus detection system 12 further includes a two-probe/four-electrode system to measure the relevant characteristic of the solutions in the reference chamber 230 and the sample chamber 232. More specifically, the virus detection system 12 comprises a first conductivity probe 236 and an identical second conductivity probe 238, shown in FIGS. 10 and 14. The first conductivity probe 236 is suspended in the solution in the sample chamber 232. The second conductivity probe 238 is suspended in the solution in the reference chamber 230. The first conductivity probe 236 and the second conductivity probe 238 each include a positive electrode 239a and a negative electrode 239b.

The virus detection system 12 also comprises a first alternating frequency generator 240, a second frequency generator 241, and a differential frequency detector 242, also shown in FIGS. 11 and 14. The first frequency generator 240 is communicatively coupled to the first probe 236, and to the differential frequency detector 242. The second frequency generator 241 is communicatively coupled to the second probe 238, and to the differential frequency detector 242. The first and second frequency generators 240, 241 each generate a sinusoidally -varying voltage that produces an alternating electrical potential across the positive and negative electrodes 239a, 239b of the respective first and second conductivity probe 236, 38 (activities 108a, 108b in FIG. HA). The frequency of the voltage is characteristic of the RC (resistance/capacitance) of the alternating current (AC) circuit driving the alternating voltages.

The electrical potential across the positive and negative electrodes 239a, 239b causes an alternating current to flow between the positive and negative electrodes 239a, 239b, via the solution in which the first and second electrodes 239a, 239b are immersed. The frequency of the alternating current is related to the electrical conductivity of the solution. As noted above, the liquid solution in the sample chamber 232 becomes polarized upon the absorption of virus particles, such a COVID- 19 virus particles, that have spike proteins, since the presence of the spike proteins results in an electrostatic charge. Thus, the electrical conductivity of the solution is related to the presence or absence of virus particles in the sample chamber 232. The first and second frequency generators sources 240, 241 each produce a sinusoidal output signal having a frequency approximately equal to the frequency of the alternating current flowing through the respective first and second probes 236, 238. The output signals are transmitted to the differential frequency detector 242. The differential frequency detector 242 determines the frequency difference between the signals using a homodyne detection technique (step 110 in FIG. 11A). The differential frequency detector 242 can determine the frequency difference using a heterodyne detection technique, in alternative embodiments. The differential frequency detector 242 generates an output representative of the frequency difference, and sends the output to the controller 223. The differential frequency detector 242, the first and second frequency generators 240, 241, and the first and second probes 236, 238 thus constitute a homodyne frequency detection circuit. As discussed below, the frequency difference is processed to estimate the amount of virus particles in the solution within the sample chamber 232.

As noted above, the frequency of the alternating current flowing between the first and second probes 236, 238 and the respective first and second alternating frequency generators 240, 241 is related to the conductivity of the liquid solution which the first or second probe 236, 238 is immersed; and the conductivity of the solution is related to the presence or absence of virus particles in the solution. The frequency of the output signal generated by the first alternating frequency generator 240, therefore, is related to the amount of virus particles in the solution within the sample chamber 232.

The solution in the reference chamber 230 is substantially free of virus particles, and is maintained at substantially the same environmental conditions as the solution in the sample chamber 232. The frequency of the output signal generated by the second frequency generator 241, therefore, represents a baseline reference against which the effects of the any virus particles in the sample chamber 232 can be evaluated. By generating a signal representing the frequency difference between the respective outputs the first and second probes 236, 238, and using the difference to determine the presence or absence of virus particles in the sample chamber 232, small changes in the frequency of the current through the first probe 236, in effect, are amplified, as can be seen in FIG. 5. This amplification, in turn, improves the signal to noise ratio in the signal that ultimately is used to determine the presence and magnitude of the viral load in the sample chamber 232.

The output signal generated by the differential frequency detector 242 is transmitted to the controller 223. The output signal is processed to determine the presence, and amount of viral load in the solution within the sample chamber 232. In particular, the frequency difference between the respective current through the first and second probes 236, 238, as determined by the differential frequency detector 242, is correlated with a predetermined relationship between the viral load and the frequency difference (step 112 in FIG. HA). The predetermined relationship is generated by a calibration process in which the frequency difference is evaluated in the presence of varying amounts of virus particles in the sample chamber 232.

The viral load in the sample chamber 232 is correlated with the amount of thoracic and respirable particles in the airspace from with the sampled particles were obtained, to provide a determination of the presence, and magnitude of the viral load in the airspace (step 114). The presence, and greater amount of viral particles in the sample chamber 232, in relation to the reference chamber 230, i.e., the baseline condition without virus particles, generates a polarization of the liquid in the sample chamber 232 that is proportional to the number of virus particles absorbed in the liquid in the sample chamber 232. Thus, the characteristic frequency of the liquid in the sample chamber 232 changes monotonically with the virus load in the air from which the particles in the sample chamber 232 have been sampled.

The calculation of the viral load in the sample chamber 232, and the determination of the presence and magnitude of the viral load in the sampled airspace, can be performed by the edge-cloud server 246 of the alarm hub 13. Alternatively, the calculation of the viral load in the sample chamber 232, and the determination of the presence and magnitude of the viral load in the sampled airspace can be performed by other types of computing devices including, without limitation, the controller 223 itself.

The results of the air-sample analysis, i.e., viral load in the sampled airspace, are subjected to a validation process, discussed below (step 116 in FIG. HA). If the results are deemed valid, the results of the air-sample analysis, and other environmental data, can be transmitted to, and displayed and/or stored on one or more display or storage devices (step 118). For example, the alarm hub 13 can include the visual display 251 which is communicatively coupled to the edge cloud server 246 by a wired or wireless means. The viral load determined by the virus detection system 12 can be displayed on the display 251. The dynamic social distance, calculated by the edge-cloud server 246 as discussed above based on the viral load and other environmental factors, also can be displayed on the visual display 251. The above noted information also can be displayed on the mobile device 79 and/or a desktop computer 256 of the alarm hub 13.

Environmental data such as the ambient CO ₂ level, PM concentration, air temperature, and relative humidity also can be displayed on the visual display 251. Other information, such as a plot of the airborne viral load over time, also can be displayed. If the viral load is above a safe level, a warning message, such as “High Viral Load Detected. Please Use Proper Safety Precautions and Air Purification” also can be displayed.

The virus detection system 12 also can include a wireless gateway 252b. The wireless gateway 252b is communicatively coupled to the controller 223, and facilitates communication between the controller 223, the edge-cloud server 246 of the alarm hub 13, and other devices on which the air-sampling results, environmental data, and warnings can be displayed, processed, and/or stored. Also, data can be further processed and/or stored on the edge-cloud server 246 or other computing device. Communication between the wireless gateway 252b and the above-noted devices can be facilitated by any suitable means, such as the internet, a cellular network, Wi-Fi, a local area network, a wide area network, BLUETOOTH, etc.

The controller 223 can be further configured so that, upon the detection of a high viral load, the controller 223 immediately generates warnings and notifications cautioning recipients to take adequate precautions, such as leaving the area, to reduce the potential for viral exposure and possible infection (step 120 of FIG. 11 A). For example, the controller 223 can be configured to send such warnings and notifications to pre-designated recipients by way of e-mail or text messaging, via the alarm hub 13. In one possible application, and without limitation, the pre -de signaled recipients can include the normal occupants of a particular floor of an office building on which the virus detection system 12 is used to monitor air quality. The controller 223 also is configured so that, upon the detection of an unacceptable viral load, the controller 223 generates a command that, upon being received by the air purification device 11 via the alarm hub 13, causes the air purification device 10 activate and begin purifying the ambient air in the manner discussed above (step 122). Also, the controller 223 generates an output that, when received by the alarm hub 13, causes the alarm hub 13 to activate audible and visual warnings as discussed below, to alert the individuals near the system 10 that the local airborne viral load is at a dangerous or otherwise unhealthy level.

An embodiment of the virus detection system 12 was tested with different polar and non-polar dopants with distilled water. The frequency of the respective AC currents passing through the probes immersed in the sample and reference solutions was recorded with every viral dosage. The virus selected for the testing was a live attenuated MMR (measles, mumps and rubella) vaccine, at a concentration of 140 viral particles per 10 pL. As can be seen in Fig. 15A, the frequency of the output of the sample probe increased linearly as the viral load was increased. As can be seen in FIG. 15B, the difference between the output frequencies of the sample probe and the reference probe likewise increased linearly as the viral load was increased. The testing also was conducted using polio and rotavirus live attenuated vaccines; and similar frequency responses were found using these viruses. Depending on coronal spike structure of the different virus particles, and their timing in the air and the manner in which the particles interface with water droplets, each type of virus particle will generate different level of Zeta potential and Debye radius. Therefore, the virus detection system 12 relies on an advanced adaptive signal processing technique of comparing the response of the sample probe with a time series of baseline data to predict whether there is a burst of viral activities in the monitored airspace.

The validation process can be performed using a validation algorithm stored on, and executed by the edge-cloud server 246. The validation algorithm can be stored on and executed by a different computing device, such as the controller 223, in alternative embodiments. The validation process is based on inputs such as the carbon dioxide (CO2) level in the space from which the sample was obtained; the particulate matter (PM) concentration and distribution within the space; and the presence or absence of people in the space. The carbon dioxide concentration and the particulate matter concentration can be obtained from a respective carbon dioxide sensor 262 and particulate matter sensor 264. The presence and/or number of persons in the space can be evaluated based on inputs from one or more proximity sensors or motion detectors 286.

The CO2 level, PM concentration, and the presence or absence of people are factors that can indicate the likelihood that an airborne virus is present in a particular space. For example, a relatively low level of carbon dioxide, e.g., about 400 ppm or less, and/or a relatively low particulate level, e.g., about ten ug/m ³ (micro grams per cubic meter) or less, in the presence of one or more people in the space is an indication that the space has effective ventilation, which in turn is interpreted an indication that the likelihood of a significant viral load in the space is low. The absence of any people in the space likewise is interpreted an indication that the likelihood of a significant viral load in the space is low. Thus, if the virus detection system 12 generates an output indicating an unacceptably high viral load under such circumstances, the output is interpreted as a false positive, i.e., the result is considered invalid. The suspect result can be ignored, and if desired, the user can initiate another sampling cycle.

Conversely, a relatively high level of carbon dioxide, e.g., about 420 to about 450 ppm or greater, and/or a relatively high particulate level, e.g., about 50 ug/m ³ to about 100 ug/m ³ or greater, in the presence of one or more people in the space is an indication that the space has poor ventilation, which in turn is interpreted an indication that the likelihood of a significant viral load in the space is high. Thus, if the virus detection system 12 generates an output indicating an acceptably low viral load under such circumstances, the output is interpreted as a false negative, i.e., the result is considered invalid. The suspect result can be ignored, and if desired, the user can initiate another sampling cycle.

Alarm Hub

The alarm hub 16 is depicted in FIG. 16. The alarm hub 13 includes the edge cloud server 246, the display device 252, and the desktop computer 256. The alarm hub 16 also can include a wireless gateway 252c communicatively coupled to the edge-cloud server 246. The gateway 252c facilitates wireless communication with the air purification device 11, the virus detection system 12, and other devices on which the air-sampling results, environmental data, and warnings can be displayed, processed, and/or stored. Communication between the wireless gateway 252c and the above-noted devices can be facilitated by any suitable means, such as the internet, a cellular network, Wi-Fi, a local area network, a wide area network, BLUETOOTH, etc.

The alarm hub 13 further can include a visual alerting device in the form of one or more LED displays 258. The LED displays 258 are communicatively coupled to the edge-cloud server 246, and can be placed in locations where they can be seen easily by occupants within the space being monitored by the air sensing and purification system 10. Upon receiving an input from the air purification device 11 that the dynamic social distance has been violated, and/or upon receiving an input from the virus detection system 12 that the actual airborne viral load exceeds the predetermined threshold, the edge-cloud server 246 generates an output that, when received by the LED displays 258, causes the LED displays 258 to illuminate, thereby providing a visual indication to those in the vicinity of the LED displays 258 that the viral load in the local space is at, or is approaching an unsafe level (step 124 of FIG. 1 IB). Also, the edge-cloud server 246 can generate another output that, when received by the mobile device 97, causes the mobile device 97 to display a visual indication that the system 10 is in an alarm condition.

The alarm hub 13 further can include an audible alerting device in the form of one or more buzzers 260, depicted in FIG. 16. The buzzers 260 are communicatively coupled to the edge-cloud server 246, and can be placed in locations where they can be heard easily by occupants within the space being monitored by the air sensing and purification system 10. Upon receiving an input from the air purification device 11 that the dynamic social distance has been violated, and/or upon receiving an input from the virus detection system 12 that the actual airborne viral load exceeds the predetermined threshold, the edge-cloud server 246 generates an output that, when received by the buzzers 260, causes the buzzers 260 emit an audible sound such as a pulsing buzzing noise, thereby providing an audible indication to those in the vicinity of the buzzers 260 that the viral load in the local space is at, or is approaching an unsafe level (step 126 of FIG. 1 IB).