WO2023022868A1

WO2023022868A1 - Method and system for control of airborne transmissible pathogens in an indoor space

Info

Publication number: WO2023022868A1
Application number: PCT/US2022/038645
Authority: WO
Inventors: Cyril Tellis
Original assignee: Cyril Tellis
Priority date: 2021-08-17
Filing date: 2022-07-28
Publication date: 2023-02-23

Abstract

This disclosure relates to a method for controlling airborne transmissible pathogens in an indoor space having random human occupancy. The method involves acquiring information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and analyzing the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space. The method also involves generating real time information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; correlating the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

Description

METHOD AND SYSTEM FOR CONTROL OF AIRBORNE TRANSMISSIBLE PATHOGENS IN AN INDOOR SPACE

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

[0001] This disclosure relates to a method and system for controlling airborne transmissible pathogens in an indoor space.

2. Discussion of the Background Art

[0002] Pathogens are known to have harmful effects when introduced into inhabited areas, and represent a significant health hazard to humans that occupy such areas, due in part to acute and chronic illnesses caused by exposure to such pathogens. Such pathogens may be transmissible by air, including fine particulate matter in the air, e.g., dust. Certain indoor spaces, such as arenas, auditoriums, warehouses, industrial, business and educational complexes, and humans occupying those spaces and breathing the air therein, are susceptible to pathogens, or other biological contamination, especially when those indoor spaces have poor ventilation. Methods for remediating the air and protecting the occupants in indoor spaces from exposure to such pathogens and health hazards would therefore be beneficial.

[0003] In enclosed spaces, often such methods include passing the air via high efficiency particulate air (HEPA) filters. While this methodology may remove particulate matter, it has limited utility because the filters may become saturated and/or blocked even on short term use. Furthermore, some particles are too small to catch even with HEPA filters. The use of porous porcelain material in filtration systems to catch the too small particles has been used, but this leads to blockage of the pores and huge energy consumption (and frequent replacement of filter materials). [0004] For infectious disease-related bacteria or viruses, it is important to prevent them from entering into and growing in the indoor space. Removal of harmful microorganisms with such filtration technology is also problematic, because the microorganisms can be disassociated or displaced from the filter and released back into the air. Even more problematic, microorganisms may find solid media as ideal environment in for multiplication (growth) before circulating back to the air. The problem is not easily remediated by adding biocides to a filter system, because it can be inefficient in dry condition or the filter may become less absorbent if it is made wet. Furthermore, biocides in solid form may dissociate from the filter system and be released directly into the air, resulting in safety concerns.

[0005] Thus, there is a need for a generally applicable and practical method to remove airborne transmissible pathogens such as germs, bacteria and viruses from the air of enclosed air spaces, and to prevent or reduce exposure of these pathogens to individuals occupying those indoor spaces.

SUMMARY OF THE DISCLOSURE

[0006] This disclosure relates to a method and system for controlling airborne transmissible pathogens in an indoor space.

[0007] This disclosure also relates in part to a method for controlling airborne transmissible pathogens in an indoor space having random human occupancy. The method involves acquiring information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and analyzing the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space. The indoor space has at least one inlet for introducing an outdoor air stream into the indoor space, and at least one outlet for discharging an indoor air stream from the indoor space. The method also involves generating real time information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; correlating the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space; and controlling the airborne transmissible pathogens in the indoor space by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate.

[0008] This disclosure further relates in part to a system for controlling airborne transmissible pathogens in an indoor space having random human occupancy. The system includes: one or more databases comprising information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and one or more databases comprising real time information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space. The indoor space has at least one inlet for introducing an outdoor air stream into the indoor space, and at least one outlet for discharging an indoor air stream from the indoor space. The system also includes at least one processor configured to: analyze the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space; and correlate the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

[0009] It has been surprisingly found that, in accordance with this disclosure, airborne transmissible pathogens in an indoor space having random human occupancy can be controlled by monitoring one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space, determining a rate for introducing an outdoor air stream into the indoor space, and discharging an indoor air stream from the indoor space, based on real time information and a predictive model, and controlling the airborne transmissible pathogens in the indoor space, based on determined rate.

[0010] Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Fig. 1 shows illustrative information types used in the systems and the methods of the present disclosure.

[0012] Fig. 2 shows illustrative additional information types used in the systems and the methods of the present disclosure.

[0013] Fig. 3 shows illustrative pathogen clusters in mucin and deposition on airborne particulate matter.

[0014] Fig. 4 schematically shows a system for controlling airborne transmissible pathogens in an indoor space having random human occupancy, in accordance with exemplary embodiments of the present disclosure.

[0015] Fig. 5 is a block diagram illustrating a method for controlling airborne transmissible pathogens in an indoor space having random human occupancy, in accordance with exemplary embodiments of the present disclosure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] As used herein, the term “indoor space” refers to any enclosed space in which some control of the air quality is desired. This includes enclosed spaces in which environmental air quality can affect occupying individuals or objects. The indoor space can be of any size and shape.

[0017] Enclosed spaces include such spaces as industrial, business, educational and recreational buildings, rooms, compartments, chambers, dwellings and the like which have limited air exchange with the outdoor environment, but are otherwise suitable for occupancy or use by humans. Examples of such enclosed spaces include public buildings, such as schools, classrooms, auditoriums, arenas, indoor stadiums, and the like; offices and working areas including laboratories, medical facilities such as clinics and hospitals, art galleries, warehouses, outbuildings; hotels and other lodging accommodations; restaurants and other eating establishments; theaters, transportation stations, such as railway stations, bus or subway stations, and airport terminals.

[0018] As used herein, “random human occupancy” refers to any arbitrary gathering of humans in an indoor space, without regard to age, gender, race, ethnicity, income, or other demographics.

[0019] As used herein, “particulate matter” is microscopic solid or liquid matter suspended in atmosphere. Illustrative particulate matter includes, for example, solid particles and liquid droplets, such as dust, water droplets, and the like.

[0020] Particulate matter includes solid particles and liquid droplets, and mixtures thereof, found in the air. Some particles, such as dust, dirt, soot, or smoke, are large or dark enough to be seen with the naked eye. Others are so small they can only be detected using an electron microscope. Particulate matter is classified as PM₁₀ and PM_2.5. PM₁₀ includes inhalable particles, with diameters that are generally 10 micrometers and smaller. PM_2.5 includes fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.

[0021] As used herein, the terms “pathogens” refer to airborne microorganisms such as bacteria, fungal spores, and mites, viral particles including Coronavirus (COVID-19) and variants, germs, and the like.

[0022] As used herein, the term “Relative Humidity” is defined as follows:

Relative Humidity = (actual vapor density/saturation vapor density) x 100%

[0023] The most common units for vapor density are g/m³. For example, if the actual vapor density is 10 g/m³ at 20°C compared to the saturation vapor density at that temperature of 17.3 g/m³, then the relative humidity is:

R.H. = (10g/m³/17.3g/m³) x 100% = 57.8%

[0024] Referring to Figs. 1 and 2, the information and real time information utilized in this disclosure for controlling airborne transmissible pathogens in an indoor space having random human occupancy, is set forth. The information and real time information includes particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space. In accordance with the method and system of this disclosure, the information can be stored in one or more databases and can be retrieved (e.g., by a processor). Particulate Matter

[0025] In accordance with this disclosure, particulate mater size and concentration can be used as indicator of the presence of airborne transmissible pathogens in an indoor space. Fig. 3 shows illustrative pathogen clusters in mucin and deposition on airborne particulate matter.

[0026] Particulate mater is microscopic solid or liquid mater suspended in atmosphere. Larger particles are generally filtered in the nose and throat via cilia and mucus, but particulate mater smaller than about 10 micrometers can penetrate the deepest part of the lungs such as the bronchioles or alveoli, and setle in the bronchi and lungs. Finer particles with a diameter of 2.5 micrometers or less can penetrate deep into the lungs and blood streams. Very small particles (<100 nanometers) can pass through the lungs to affect other organs. Pathogens may be transmissible by these nanoparticles in the air, causing acute and chronic illnesses in humans from exposure to such pathogens. The effects of inhaling particulate matter, including pathogens (e.g., viruses and bacteria) transmissible by the particulate mater, on the health of humans include acute and chronic illnesses such as severe acute respiratory syndrome (SARS), tuberculosis (TB), Coronavirus (COVID-19), flu, influenza, other respiratory diseases, and the like.

[0027] Pathogens can reach humans through various transmission mechanisms: ingestion, inhalation, inoculation, contact, iatrogenic transmission, and coupling. The most common route of transmission is the expulsion of pathogens through the respiratory system by infected subjects and the penetration into the receptive host by inhalation. The saliva droplets from the infected subject are usually large and, because of their weight, travel short distances before falling to the ground. In this case, the transmission is defined as transmission by close contact. This transmission is different from what occurs in the aerosol, which is a suspension of solid or liquid particles within a gas phase. The diameter of these particles is normally between 0.001 and 100 micrometers; thus, they are very small particles that sediment slowly and are easily conveyed by air currents. In this case, the transmission is called long distance transmission. As small bacterial and viral particles are suspended in the aerosol, they can be transported by particles, even at long distances from the outbreaks of origin.

[0028] There is an association between airborne infections and ventilation systems in buildings. In a city environment, people normally spend about 90% of their time indoors. A low ventilation rate, particularly in industrial, business and educational complexes, increases the probability of pathogen contraction. In a building, for example, the air circulates from one environment to another with turbulent flow that favors the establishment of microenvironments in which pathogens proliferate. Pathogens are transported by the aerosol at a certain distance that depends on the design of the buildings in which they circulate. The small pathogens (e.g., bacterial and viral particles) that are suspended in the aerosol can be transported by particles.

[0029] Particulate matter, as defined by the Environmental Protection Agency (EPA), is a term that indicates the set of particles dispersed in the air for enough time to be diffused and transported. There are many sources of these particles. Particulate matter is classified as PM₁₀ and PM_2.5 based on a diameter of less than 10 micrometers or 2.5 micrometers, respectively.

[0030] Air is a vehicle through which microbial agents can move around the environment. Pathogens, including bacteria, viruses, plants and cellular fragments, fungi, parasites, and spores, can be components of the bioaerosol. Atmospheric particulate matter functions as a carrier, or as a transport vector, for many viruses, bacteria and germs. Thus, particulate matter can increase the effectiveness of the pathogen spread in the aerosol as it creates a microenvironment suitable for its persistence. PM₁₀ and PM_2.5 can be inhaled and, in addition to polluting particles, the associated microorganisms are inhaled, too. The microbial community composition and concentration are affected by particle concentration and dimension. The particles can also act as carriers, which have complex adsorption and toxicity effects on pathogens. Certain particle components are also available as nutrition for pathogens. The particulate matter source can influence the presence of specific pathogen groups. Environmental factors and stresses can also shape the pathogen community.

[0031] Inhalation can transport the particulate matter deep into the lungs, especially those smaller than 2.5 microns, and this allows the pathogen to develop within the respiratory tract and to cause infections.

[0032] With regard to the effect of particulate matter pollution and the spread of pathogens in the population, the different areas of the world with a high and rapid increase in COVID-19’s contagion were correlated to a greater level of air pollution. There are three world areas where there has been a high number of people infected by COVID-19, namely China, where the pandemic started; Italy; and the USA, and the link between these countries is the very high level of air particulate matter pollutants.

[0033] In accordance with this disclosure, the concentration of particulate matter in the indoor space should be controlled to prevent or minimize the amount of airborne transmissible pathogens in the indoor space. Particulate matter can include both pathogenic material and non-pathogenic material. The concentration of particulate matter in the indoor space can be affected by several factors including, for example, the number of occupants in the indoor space, the outdoor air quality, the size and shape of the indoor space, and the like. An illustrative method for particulate matter characterization, quantification and detection in an indoor space, including virus-like and bacteria-like particles, is described in Prussin II, Aaron J. et al., Total Virus and Bacteria Concentrations in Indoor and Outdoor Air, 2015, Environ Sci Technol Lett.; 2(4): 84-88, which is incorporated herein by reference. In conjunction with the predictive model of this disclosure, a baseline can be established for particulate matter in the indoor space, and when that baseline is exceeded, the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, can be adjusted to control the airborne transmissible pathogens in the indoor space.

[0034] In accordance with this disclosure, a particulate matter sensor (e.g., PM_2.5 sensor) can be utilized in the indoor space for measuring particulate matter levels in the indoor space. The real time particulate matter levels can be correlated with a predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space can be controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate. Also, particulate matter information can be analyzed to generate the predictive model for determining the presence of airborne transmissible pathogens in the indoor space.

Relative Humidity

[0035] In accordance with this disclosure, relative humidity can be used as indicator of the presence of airborne transmissible pathogens in an indoor space.

[0036] A large number of infectious diseases are transmitted by fine liquid particulate matter, for example, droplets. Various physical principles govern the fate of fine liquid particulate matter (e.g., droplets) and any viruses and bacteria trapped inside them, including relative humidity. Low relative humidity, as encountered, for instance, indoors during winter and inside aircraft, facilitates evaporation and keeps even initially large droplets suspended in air as aerosol for extended periods of time. Relative humidity affects the stability of viruses and bacteria in aerosol through several physical mechanisms such as efflorescence and inactivation at the air-water interface. Relative humidity can be a factor in the droplet spread of disease, particularly in indoor environment.

[0037] One of the prevalent ways in which numerous viruses, bacteria, and fungi spread among plants, animals, and humans is by droplets of various sizes. Humans produce respiratory droplets during talking, coughing, sneezing, and other similar activities. These droplets, which can contain pathogens, then spread outside the human body in different ways, enabling the pathogens to find a new host. The droplets can be inhaled by humans in close proximity, which provides a direct path for infection. Some particularly small droplets can remain airborne for longer periods of time and travel considerable distances, providing a path for disease transmission.

[0038] Droplet spread is the main mode of transmission for respiratory viruses and bacteria such as influenza, common-cold viruses, and some SARS-associated coronaviruses, including SARS-CoV-2. A typical and very common feature of respiratory infections is seasonality, a periodic upsurge in infection incidence corresponding to seasons or other calendar periods. In temperate regions, respiratory pathogens can exhibit an annual increase in incidence each winter, with variations in the timing of onset and magnitude of the increase.

[0039] For example, what the outdoor temperature does indirectly influences the relative humidity inside buildings. Heating the buildings in winter dries the cold air coming in from the outside, causing relative humidity to drop. As a result, indoor relative humidity in temperate regions typically varies between 10 and 40% in the winter months, which is significantly lower compared with its range of 40 to 60% in the summer months.

[0040] Relative humidity can play a role in the spread of infections through a number of different mechanisms. For example, relative humidity directly impacts how and to what extent the exhaled human droplets can spread through the air. The stability of winter viruses and bacteria trapped in those droplets can be correlated with low relative humidity (20 to 50%), while the stability of summer or year-round viruses can be correlated with higher relative humidity (80%). Dry air dries out the mucous membrane in the nose, which eases the invasion of infectious viruses and bacteria into the respiratory tract.

[0041] There are physical mechanisms of droplet and airborne transmission of disease in which relative humidity plays a role. Differences in relative humidity, for example, between 30 and 50%, can influence the spread of respiratory disease. Droplet size and composition can be influenced by relative humidity and by both the presence of solutes as well as efflorescence effects. Relative humidity can impact the sedimentation of larger droplets, and the deposition of aerosol. Various factors can influence the survival of viruses and bacteria in these droplets with respect to changes in relative humidity.

[0042] The size of droplets expelled during various human activities in indoor spaces such as breathing, talking, singing, coughing, and sneezing is an important factor in determining their fate, whether they evaporate, sediment, or persist in the air. A distinction can be made between larger respiratory droplets, which do not spread far from their origin and quickly sediment onto neighboring surfaces, potentially contaminating them and thus facilitating transmission of droplet-borne disease, and smaller aerosol particles, which are small enough to persist in the air, are influenced by various kinds of airflow, and can potentially transmit disease over larger distances.

[0043] Airborne transmission, as used herein, includes disease transmission by small size particles that can remain suspended in air for prolonged periods of time (i.e., aerosol) and consequently travel over long distances. Also, the size of respiratory droplets can influence where in the respiratory tract they can deposit, and by that the severity and spread of a disease. As used herein, all particles produced by respiratory activity are referred to as droplets, regardless of their size (e.g., large enough to quickly sediment or small enough to be transmited as aerosol particles).

[0044] Relative humidity can impact the behavior of droplets. After droplets are expelled from the mouth or nose into the air, they undergo various physical and chemical processes, evaporation being the most notable among them, that change their structural properties. In the air, these droplets (or droplet particles) are subject to gravity, Brownian motion, electrical forces, thermal gradients, electromagnetic radiation, turbulent diffusion, and the like.

[0045] Human respiratory droplets are composed mainly of water (~90 to 99%), with the remainder being mostly inorganic ions, sugars, proteins, lipids, DNA, and, potentially, microorganisms including pathogens. The exact droplet composition depends strongly on many factors. For example, the amount of water in a droplet can be dependent on relative humidity.

[0046] Relative humidity can affect the deposition of small aerosol particles. The effect on small aerosol particles can be weaker than the effect on the sedimentation of larger droplets. The size dependence of the lifetime of smaller aerosol particles can be weaker than for larger droplets.

[0047] With regard to the behavior of respiratory droplets, their aerosolization, and sedimentation, and the influence of relative humidity, the droplets can carry viruses, bacteria and other pathogens and are thus an important source of disease transmission. The amount of viable, infectious virus particles in an individual droplet is characterized by viral load, the amount of virus in a given volume of the droplet medium (e.g., sputum or saliva).

[0048] Relative humidity can be related to seasonal changes because of indoor heating, but its impact on pathogens is not universal. In particular, pathogen viability can decrease as relative humidity falls below 100%, since the droplet gets more and more dehydrated and the environment progressively deviates from physiological conditions. Pathogen viability can often recover as relative humidity is decreased below 50%. In the range of ambient conditions, relative humidity of 30 to 50%, decreasing the air humidity can increase the amount of pathogens that survive in the droplets. From the infection point of view, this effect acts together with the effect of weaker droplet deposition at low relative humidity in making drier air more effective for the spread of infections. The response of pathogen viability to changes in relative humidity can be affected in different ways and degrees by virus structure, the presence, composition, and concentration of solutes, pH gradients, and the available air-water interface, and the like.

[0049] Response of virus survival to changes in relative humidity can be linked to the presence or absence of a lipid envelope. Broadly speaking, enveloped viruses (such as influenza viruses, coronaviruses, and respiratory syncytial virus (RSV)) tend to survive longer at low relative humidity

while non-enveloped viruses (such as adenoviruses, rhinoviruses, and polioviruses) tend to survive longer at high relative humidity (70 to 90%), with relative humidity ~ 100% being in general favorable for virus survival regardless of the lipid envelope. The effects of relative humidity on survival can differ from virus to virus, or even between different strains of the same virus.

[0050] Evaporation of water from a droplet can induce various physico-chemical transformations in the droplet, such as changes in the concentration of solutes (e.g., ions and proteins) as well as changes in the pH. Not only can droplet composition influence the sedimentation behavior of respiratory droplets, but it also can affect the way an aerosolized virus survives or is inactivated. While the micro-environment in the droplet is close to physiological conditions at very high relative humidity (~100%) and becomes dry when relative humidity is low it is likely that virus viability at intermediate relative

humidity is governed mostly by the droplet composition. Droplet composition can play a role in the response of virus viability in droplets at different relative humidity. The main components of respiratory droplets (e.g., salt, lipids, and proteins) react to relative humidity, and affects virus viability.

[0051] Salt ions are a ubiquitous component in physiological fluids, and when their concentration changes, the viability of pathogens exhibits different responses. For example, salt ions can interact with lipid membranes of viruses and can cause structural and mechanical changes, potentially leading to inactivation of enveloped viruses. Ionic concentration for the assembly and stability of enveloped viruses can be related to the stability of lipid membranes and the interactions of various capsid proteins with the membranes.

[0052] The concentration of salt in the droplet residue depends on both droplet composition and relative humidity. Close to relative humidity of 100%, salt concentration in the droplet can stay at levels close to physiological conditions, and virus viability is thus well-preserved. Intermediate values of relative humidity (50% to

can involve concentrated and even supersaturated salt conditions that can be toxic to the virus, and viability consequently decreases with decreasing relative humidity. In a very dry environment salts can undergo efflorescence and crystallize out of the solution.

The concentration of the remaining dissolved ions in the droplet residue is low and consequently virus viability can improve.

[0053] Respiratory droplets can differ to great extent in the amount of various proteins, biopolymers, and lipids they contain. Different responses of virus viability to changes in relative humidity can be based on the origin and composition of droplets. The total composition of the droplet can determine how the droplet shrinks with time and whether or not it undergoes an efflorescence transition. [0054] Droplets can vary in their pH, which can change with relative humidity and with that affect, for example, the viability of aerosolized viruses by changing the electrostatic properties or conformation of viral proteins. The fate of aerosolized pathogens can depend not only on the physico-chemical environment in the droplet, but also on the location of the pathogen inside it, as droplets themselves can be internally heterogeneous.

[0055] Seasonal periodicity of respiratory infections in humans can be driven by complex mechanisms, including relative humidity in indoor spaces. Low indoor relative humidity, as experienced during winter months or in not well ventilated indoor spaces, can increase the transmission of respiratory diseases, and pathogens responsible therefor. As described herein, droplet and airborne transmission can be influenced by relative humidity.

[0056] Relative humidity can play a role the moment respiratory droplets are exhaled into the air. Dry air can accelerate droplet evaporation while at the same time can dehydrate them more, so that the size of droplet residues after evaporation has stopped is smaller than in more humid air. Both effects can cause the droplets to settle to the ground more slowly and remain in the air longer at low relative humidity, thereby leaving more potential pathogens suspended in the air. Relative humidity can govern the extent to which pathogens carried by the droplets survive. This can depend both on the droplet composition as well as on the structure of the pathogen. The viability of pathogens can improve when relative humidity is lowered (e.g., below 50). Efflorescence can occur at least to some extent in respiratory droplets. It can accentuate the effects of relative humidity by changing droplet size, and thereby can affect the nature of droplet composition.

[0057] Indoor relative humidity during winter in temperate climates is typically around 20% lower than during summer, and an important reason for this is heating of indoor spaces. Maintaining indoor relative humidity can aid in preventing the spread of infectious

diseases. Relative humidity can affect the behavior of droplets and any pathogens contained in them, and this can allow control indoor relative humidity in such a way as to minimize the spread of droplet- and aerosol-borne disease.

[0058] In accordance with this disclosure, the relative humidity in the indoor space should be controlled to prevent or minimize the amount of airborne transmissible pathogens in the indoor space. In an embodiment, the relative humidity in the indoor space should range from about 20 % to about 70 %, preferably from about 20 % to about 60 %, and more preferably from about 30 % to about 50 %. In conjunction with the predictive model of this disclosure, a baseline can be established for relative humidity in the indoor space, and when that baseline is exceeded, the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, can be adjusted to control the airborne transmissible pathogens in the indoor space.

[0059] In accordance with this disclosure, a relative humidity sensor can be utilized in the indoor space for measuring relative humidity levels in the indoor space. The real time relative humidity levels can be correlated with a predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space can be controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate. Also, relative humidity information can be analyzed to generate the predictive model for determining the presence of airborne transmissible pathogens in the indoor space.

Carbon Dioxide

[0060] In accordance with this disclosure, carbon dioxide concentration can be used as indicator of the presence of airborne transmissible pathogens in an indoor space. [0061] Carbon dioxide (CO₂) indirectly reflects the level of indoor oxygen level. Typically, the higher the indoor CO₂ level, the lower the indoor oxygen level. CO₂ is typically found in outside air at concentrations between 300 and 500 parts per million (ppm), and is exhaled by human beings at an approximate rate of 0.01 cubic feet per minute (cfm) per person for a person doing low impact work. Variations in the number of people in an enclosed space compared to the amount of outside air supplied into the enclosed space can easily increase indoor CO₂ levels to between 500 and 2500 ppm. As such, CO₂ can be used as an excellent indicator of proper ventilation on a per person basis sometimes referred to as the cfin of outside air per person, since the level of CO₂ in a space is directly related to the number of people in a space divided by the rise in CO₂ from outdoor levels. Human beings are typically unaffected by levels of CO₂ such as up to 5000 ppm, for limited periods of time, which would be extremely rare to find in any indoor space of ordinary construction.

[0062] In addition to CO₂ being used as an indicator of proper ventilation, CO₂ concentration in an indoor space can also be used as an indicator of the potential presence of pathogens in the indoor space. If ventilation is inadequate in an indoor space occupied by humans, the CO₂ levels will rise through human exhalation, along with other exhalation contaminants, including, for example, pathogens such as germs, bacteria, viruses, and the like.

[0063] CO₂ levels in buildings correlate with the airborne spread of pathogens and infection. CO₂ is generated by the exhaled air of people who stay indoors. Each person in a building will exhale approximately eight litres of air per minute, air that has been in close contact with the lung tissue. Alongside CO₂ at a concentration around 40,000 parts per million (ppm), the exhalation also contains tiny liquid droplets (aerosols) which, due to their size, can float in the air for a long time. These droplets can contain any pathogen particles present in the lungs. [0064] Since pathogens are spread through the air, higher CO₂ levels in a room likely mean there is a higher chance of transmission if an infected person is inside. For pathogen control, the more fresh, outside air inside an indoor space, the better. Bringing in this air dilutes any contaminant in an indoor space, whether a virus or other pathogen, and reduces the exposure of anyone inside.

[0065] In an embodiment, a target of 1 ,000 ppm CO₂ can be used for pathogens in indoor spaces. Pathogens are in the air, and can fill an indoor space. The amount of pathogen in the air can accumulate, and an increased exposure can result. With indoor human occupancy, in a poorly ventilated indoor space for a long period of time, the humans would be at risk even if distanced, because the air moves around in the indoor space.

[0066] Factors such as the number of infected people in an indoor space, and measures such as mask-wearing or air filtration may reduce presence of the airborne pathogens without reducing CO₂ levels. Certain activities increase pathogen emission far more than CO₂ levels, such as talking, singing and shouting. Both CO₂ and pathogens are diluted by ventilation with outdoor air. They are not, however removed by recirculating the air, for example through heat exchangers.

[0067] With several humans in an indoor space, the measurement of CO₂ concentration provides a measure of what percentage of the air is inhaled, which consists of air that has already been exhaled by other people. The mass balance shows that a measured CO₂ concentration of approximately 1200 ppm means that almost 2% of the air in the indoor space has already had lung contact at least once. At this level, every 50th breath that a person takes in this indoor space consists of air that has already been exhaled. CO₂ measurement can assist in classifying the risk from potentially infectious pathogen aerosols. [0068] In an embodiment, for a health assessment of CO₂ in indoor air and potential pathogen presence in the indoor space, a concentration of <1000 ppm can be considered hygienically harmless, a concentration between 1000 and 2000 ppm as questionable, and anything above it as unacceptable.

[0069] In accordance with this disclosure, the CO₂ concentration in the indoor space should be controlled to prevent or minimize the amount of airborne transmissible pathogens in the indoor space. In an embodiment, the CO₂ concentration in the indoor space should be less than about 1500 parts per million, preferably less than about 1000 parts per million, and more preferably less than about 800 parts per million. In conjunction with the predictive model of this disclosure, a baseline can be established for CO₂ in the indoor space, and when that baseline is exceeded, the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, can be adjusted to control the airborne transmissible pathogens in the indoor space.

[0070] In accordance with this disclosure, a CO₂ sensor can be utilized in the indoor space for measuring CO₂ levels in the indoor space. The real time CO₂ levels can be correlated with a predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space can be controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate. Also, CO₂ information can be analyzed to generate the predictive model for determining the presence of airborne transmissible pathogens in the indoor space.

Temperature

[0071] In accordance with this disclosure, temperature can be used as indicator of the presence of airborne transmissible pathogens in an indoor space. [0072] The transmission of infection via the airborne route relies on several factors, including the survival of the airborne pathogen in the environment as it travels between susceptible hosts. Temperature is an environmental factor that can affect the airborne survival of viruses, bacteria and other pathogens.

[0073] The various stages of the successful transmission of airborne infection depend on the production of an infectious agent from a source case and the arrival of sufficient numbers of viable organisms to cause infection or disease in a secondary host. Environmental exposure is a common hazard for all such organisms (whether viruses, bacteria or other pathogens) during this journey between hosts. Temperature can act to inactivate free- floating, airborne infectious organisms. Temperature can affect the various infectious organisms in different ways and degrees, and it is sometimes difficult to make generalizations.

[0074] Temperature in different parts of indoor spaces can differ. Typically, indoor space temperatures can range from as low as 20°C or lower up to 30°C or higher.

[0075] Temperature is a factor affecting virus survival, as it can affect the state of viral proteins (including enzymes) and the virus genome (RNA or DNA). Viruses containing DNA can generally be more stable than RNA viruses, but high temperatures also affect DNA integrity. Generally, as temperature rises, virus survival decreases. Maintaining temperatures above 60°C for more than 60 minutes can generally be sufficient to inactivate most viruses. Most airborne viruses will have been exhaled with a coating of saliva or mucus that will act as an organic barrier against environmental extremes. Higher temperatures for shorter times can be just as effective to inactivate viruses.

[0076] The survival of viruses, bacteria and other infectious agents can depend partially on temperature, and reducing virus viability may prevent direct transmission of viral infections, as well as the triggering of immune-mediated illnesses. Temperature can be directly correlated with relative humidity. As described herein, relative humidity describes the amount of water vapour held in the air at a specific temperature at any time, relative to the maximum amount of water vapour that air at that temperature could possibly hold. At higher temperatures, air can hold more water vapour, and the relationship is roughly exponential, air at high temperatures can hold much more water vapour than air at lower temperatures.

[0077] Like viruses, bacteria also have different types of outer coats (Gram-positive surrounded by a peptidoglycan outer coat and Gram-negative surrounded by a lipopolysaccharide outer coat), but in addition, some bacteria (anaerobic species) are highly sensitive and cannot grow in the presence of oxygen. Temperatures above about 24°C appear to universally decrease airborne bacterial survival.

[0078] The survival of airborne bacteria can be different than with viruses. Bacteria within the same structural classification (e.g. Gram-negative) can vary in how they respond to temperature.

[0079] Perhaps more than viruses or bacteria, airborne fungi and their spores have the potential to be blown into indoor spaces that use natural ventilation, and certain species of fungi, e.g. Aspergillus species (Aspergillus flavus and Aspergillus fumigatus), can potentially be life-threatening airborne contaminants. Even in otherwise healthy people in indoor environments, fungi and their spores may trigger hypersensitivity reactions such as rhinitis, sinusitis or asthma.

[0080] Seasonal variation of airborne fungal and spore concentrations can depend on seasonal changes in environmental factors, such as temperature. Generally, fungi and their spores are more resilient than viruses and bacteria, being able to withstand greater stresses owing to dehydration and rehydration. Fungal spore counts can be highest indoors in summer. Outdoor fungal spore levels are important in natural ventilation as they affect the resulting indoor levels of these particles. There is a positive correlation between spore levels and higher temperatures.

[0081] Although high temperatures (more than 30°C) may reduce the survival of certain airborne pathogens, the tolerance of people in indoor spaces in such conditions will also need to be considered.

[0082] In accordance with this disclosure, the temperature in the indoor space should be controlled to prevent or minimize the amount of airborne transmissible pathogens in the indoor space. In an embodiment, the temperature in the indoor space should range from about 20 °C to about 26 °C, preferably from about 20 °C to about 24 °C, and more preferably from about 20 °C to about 22 °C. In conjunction with the predictive model of this disclosure, a baseline can be established for temperature in the indoor space, and when that baseline is exceeded, the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, can be adjusted to control the airborne transmissible pathogens in the indoor space.

[0083] In accordance with this disclosure, a temperature sensor can be utilized in the indoor space for measuring temperature levels in the indoor space. The real time temperature levels can be correlated with a predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space can be controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate. Also, temperature information can be analyzed to generate the predictive model for determining the presence of airborne transmissible pathogens in the indoor space.

Random Human Occupancy

[0084] In accordance with this disclosure, random human occupancy can be used as an indicator of the presence of airborne transmissible pathogens in an indoor space. Every human occupant in an indoor space poses a risk as a carrier of pathogenic material. Accordingly, an increase in human occupancy in an indoor space can potentially increase pathogen levels in the indoor space, especially if one or more of the human occupants are infected.

[0085] Exposure to specific airborne pathogens indoors is linked to infectious and noninfectious adverse health outcomes. Elevated concentrations of indoor airborne pathogens can be attributable to human occupancy in the indoor spaces. Human occupancy in indoor spaces can increase the total aerosol mass and pathogen genome concentration in indoor air. Resuspended floor dust can be an important contributor to pathogen aerosol populations during human occupancy. Resuspension from the floor implies that direct human shedding may also impact the concentration of indoor airborne particles. Pathogens specific to the skin, nostrils, and hair of humans found in indoor air and in floor dust can indicate that floors are an important reservoir of human-associated pathogens, and that direct particle shedding of desquamated skin cells and their subsequent resuspension can influence the airborne pathogen population structure in a human-occupied indoor environment. Inhalation exposure to pathogens shed by current or previous human occupants may occur in communal indoor environments.

[0086] Airborne pathogens in the indoor environment are causative agents of several infectious diseases. These associations are important in industrialized countries and in cities of emerging nations where people spend at least 90% of their time indoors, in addition to particles suspended in outdoor air, material resuspended from surfaces as a result of human activities can be a source of indoor airborne particles. Other sources of indoor airborne pathogens may be human oral and respiratory fluid emitted via coughing, sneezing, talking, and breathing or the direct shedding of skin-associated microbiota. Resuspension of dust may also act as a human-associated source of airborne pathogens.

[0087] Through resuspension and direct shedding, human occupancy can influence the concentration and character of pathogens in indoor air. In indoor spaces, humans can be exposed to microorganisms originating from both the environment and other humans. Human occupancy is an important factor to consider in the design and operation of indoor spaces, so that the indoor spaces can be occupied with reduced human exposure to pathogens that can cause adverse health effects.

[0088] The more humans occupying a confined indoor space, the higher the probability of increased pathogen concentration in that indoor space. Human occupancy can produce a marked concentration increase of respirable particulate matter and pathogen genomes in an indoor space. Pathogens, including bacteria from human skin, contribute to indoor air pathogen populations.

[0089] With regard to indoor particle resuspension, the resuspension rate can be dependent on the size of abiotic particles. Human occupancy in indoor spaces can increase coarse-particle pathogen concentrations, and the association of pathogens with coarse particles emitted from desquamated human skin. The increases in airborne total particle mass concentrations during human occupancy, can be in diverse indoor environments. Such increases indicate that activity throughout indoor spaces during human occupancy can result in a greater concentration of particulate matter and pathogen aerosols in certain indoor spaces. [0090] An increase of airborne pathogens can be due to human occupancy and the resuspension of floor dust. During human occupancy of indoor spaces, resuspension and direct shedding of microorganisms from humans are potential sources of pathogen aerosol particles. The origin of many of the airborne pathogens is from human skin, hair, nostrils, and the oral cavity. Desquamated human skin cells are a contributor to particles in indoor air. Skin shedding may influence indoor air concentrations both through skin cells and their fragments directly becoming airborne, and also by deposition of cells onto floors and other surfaces followed by fragmentation and resuspension. The indoor air, ventilation supply duct air, HVAC filter dust, and floor dust include taxa of environmental origin. The presence of these environmental taxa in indoor air illustrates the potential importance of outdoor air particles conveyed through infiltration or ventilation and/or the tracked-in contribution of outdoor material to floor dust that is subsequently resuspended.

[0091] Human occupancy is a factor that contributes to the concentration of indoor airborne pathogen genomes. During human occupancy of indoor spaces, both resuspension and direct human shedding can contribute to elevate respirable particulate matter and pathogen concentrations above background concentrations. Through direct inhalation of resuspended or shed organisms, there is potential for cunent or previous occupants of an indoor space to contribute substantially to inhalation exposure to bioaerosols.

[0092] In accordance with this disclosure, the human occupancy in the indoor space can vary over a wide range. However, the human occupancy in the indoor space preferably should be controlled to prevent or minimize the amount of airborne transmissible pathogens in the indoor space. The number of humans occupying a particular volume of indoor space can be affected by several factors including, for example, the size and shape of the indoor space, temperature of the indoor space, relative humidity in the indoor space, and the like. In conjunction with the predictive model of this disclosure, a baseline can be established for the number of humans in the indoor space, and when that baseline is exceeded, the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, can be adjusted to control the airborne transmissible pathogens in the indoor space.

[0093] In accordance with this disclosure, conventional methods can be utilized for determining human occupancy in the indoor space. The real time human occupancy levels can be correlated with a predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space can be controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate. Also, human occupancy information can be analyzed to generate the predictive model for determining the presence of airborne transmissible pathogens in the indoor space.

Size and Shape of Indoor Spaces

[0094] In accordance with this disclosure, the size and shape of an indoor space can be used as indicator of the presence of airborne transmissible pathogens in the indoor space.

[0095] Indoor spaces (e.g., buildings) are complex ecosystems that house microorganisms interacting with each other, with humans and with their environment. There is a relationship between the community of microorganisms (e.g., pathogens) that, live indoors and the building design and human health. The phylogenetic diversity of airborne bacterial communities is typically lower indoors than outdoors, and mechanically ventilated indoor spaces typically contain less diverse microbial communities than do non-ventilated rooms. Bacterial communities in indoor environments can contain many taxa that are absent or rare outdoors, including taxa of potential human pathogens. Building attributes, specifically the source of ventilation air, airflow rates, relative humidity and temperature, can be correlated with the diversity and composition of indoor pathogen communities. The relative abundance of human pathogens can be higher indoors than outdoors, and higher in spaces with lower airflow rates. The relationship between building design and airborne bacterial diversity suggests that indoor environments can be managed, thereby altering through building design and operation the community of microbial species that potentially colonize the human microbiome in indoor spaces.

[0096] Humans spend up to 90% of their lives indoors. Consequently, the design and operation of the indoor environment has a profound impact on human health. Indoor spaces can be complex ecosystems that contain numerous organisms and microorganisms. The collection of microbial life that exists indoors includes human pathogens.

[0097] Today, ventilation remains a key design strategy to mitigate the spread of infectious disease indoors. Despite the growing body of data linking architecture and human health, we continue to live in an era where many buildings are associated with significant health risks. These risks include health risks resulting from exposure to indoor pathogens.

[0098] As for any indoor space, the composition of the indoor space microorganisms is determined by some combination of two simultaneous ecological processes: the dispersal of microbes from a pool of available species and selection of certain microbial types by the environment. The microbial species available for dispersal into most indoor spaces are likely to come primarily from outside air (introduced through ventilation), indoor surfaces and the bodies of humans and other micro- and macroorganisms residing and moving through indoor spaces. As described herein, temperature and relative humidity, as well as the source of ventilation air and occupant density, can influence the abundance and transmission of some pathogenic microbes indoors. [0099] The composition of airborne pathogens differ among outdoor air and indoor air. The relative abundance of potential pathogens can be higher in indoor air than in outdoor air. Indoor air can contain communities that are dominated by a few closely related pathogens that are related to known human pathogens. The abundance of potential pathogens in indoor spaces can be lower with higher rates of airflow through the indoor space.

[00100] Architectural design, in particular the ventilation air, can influence the diversity and composition of microorganisms in indoor spaces. Mechanically ventilated indoor spaces can contain an ecologically distinctive set of microbial taxa from those found in outdoor air. Humans can be important dispersal vectors for microbes that colonize the indoor spaces.

[00101] Indoor spaces are typically designed for human comfort by controlling factors such as humidity, temperature and airflow, and not as much attention has been directed as to how these factors influence the diversity and distribution of microorganisms indoors. There is a relationship between indoor environmental conditions, including relative humidity and temperature, and airborne pathogen community structure. This relationship can be due to a link between the growth or survival of certain taxa and environmental conditions in indoor spaces, or an increase in the dispersal of microbes from humans or material surfaces to the indoor spaces under these conditions. The indoor climate can influence human health through direct effects on microbial populations and communities.

[00102] Ventilation method and airflow can impact allergen, pollutant and pathogen load in the built environment. In accordance with this disclosure, increased airflow rates can decrease the potential pathogen load, and thereby being beneficial to human health. Many of the potentially pathogens in indoor spaces can be emitted from humans or material surfaces indoors, and the increased airflow can dilute the concentration of these pathogens relative to the non-human-associated pathogens that are more common in outdoor air.

[00103] In construction today, indoor spaces are designed within an envelope of temperature, humidity, airflow and light availability that is physically comfortable for humans. In accordance with this disclosure, an understanding of the ecology of microorganisms in indoor spaces can allow this model to be expanded to design indoor spaces that maximize human health and well-being by linking architectural and environmental conditions to the ecology of indoor microbes. Reducing direct contact with the outdoor environment may not always be an optimal design strategy for pathogen management. Just as natural ecosystems are managed to promote the growth of certain species and inhibit the growth of others, with regard to the environment of microorganisms in indoor spaces, the building of indoor spaces can be managed, altering through building design, size and operation the pool of microorganisms that potentially colonize indoor spaces occupied by humans.

[00104] In accordance with this disclosure, the size and shape of the indoor space can vary over a wide range. The size and shape of the indoor space preferably should be designed to prevent or minimize the amount of airborne transmissible pathogens in the indoor space. The size and shape of the indoor space can be affected by several factors including, for example, the intended purpose of the structure or building, location, climate, and the like.

[00105] In accordance with this disclosure, conventional methods can be utilized for determining the size and shape of the indoor space. The real time size and shape of the indoor space can be correlated with a predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space can be controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate. Also, size and shape of indoor space information can be analyzed to generate the predictive model for determining the presence of airborne transmissible pathogens in the indoor space.

[00106] Algorithms can be employed to determine formulaic descriptions of the integration of the information for particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and optionally information for size and shape of the indoor space, random human occupancy of the indoor space, and temperature of the indoor space, using any of a variety of known mathematical techniques. These formulas, in turn, can be used to derive or generate one or more analyses and updates for identifying associations between the information for particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, information for size and shape of the indoor space, random human occupancy of the indoor space, and temperature of the indoor space, and generating one or more predictive models for determining the presence of airborne transmissible pathogens in the indoor space, using any of a variety of available trend analysis algorithms.

[00107] For example, these formulas can be used to create one or more datasets to store information, and that information can be used to generate predictive models for determining the presence of airborne transmissible pathogens in indoor spaces, and associations between the information for particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and optionally information for size and shape of the indoor space, random human occupancy of the indoor space, and temperature of the indoor space, for various indoor spaces and human occupancy thereof.

[00108] In an embodiment, logic is developed for creating one or more groupings of information for particulate matter size and concentration in the indoor space, one or more groupings of carbon dioxide concentration in the indoor space, one or more groupings of relative humidity in the indoor space, and optionally one or more groupings of information for size and shape of the indoor space, one or more groupings of information for random human occupancy of the indoor space, and one or more groupings of information for temperature of the indoor space,. The logic is applied to create associations between the information for particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and optionally information for size and shape of the indoor space, random human occupancy of the indoor space, and temperature of the indoor space, and generating one or more predictive models for determining the presence of airborne transmissible pathogens in the indoor space.

[00109] In accordance with the method of this disclosure, information can be stored in one or more databases and can be retrieved (e.g., by one or more processors). The information can contain, for example, information for particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space. Other information can include, for example, size and shape of the indoor space, random human occupancy of the indoor space, and temperature of the indoor space.

[00110] In an embodiment, all information stored in each database can be retrieved. In another embodiment, only a single entry in each of the one or more databases can be retrieved. The retrieval of information can be performed a single time, or can be performed multiple times. In an exemplary embodiment, only information pertaining to a specific indoor space is retrieved from each of the databases.

[00111] In accordance with this disclosure, a high level process flow involves, for each indoor space; acquiring information (e.g., from one or more databases) including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space; analyzing the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space; wherein the indoor space has at least one inlet for introducing an outdoor air stream into the indoor space, and at least one outlet for discharging an indoor air stream from the indoor space; generating real time information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space; correlating the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space; and controlling the airborne transmissible pathogens in the indoor space by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate.

[00112] In accordance with the method of this disclosure, one or more predictive models are generated based at least in part on the information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space. Predictive models can be generated based on the information obtained and stored in the one or more databases. The information for generation of the predictive models can be different in every instance for every indoor space. In one embodiment, all information stored in each database can be used for generating predictive models. In an alternative embodiment, only a portion of the information is used. The generation of predictive models can be based on specific criteria for each indoor space and random human occupancy.

[00113] Predictive models are generated from the information obtained from each database. The information is analyzed, extracted and correlated for various indoor spaces and can include information relating to one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space.

[00114] In accordance with this disclosure, real time information is generated including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space. The real time information is correlated with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. The airborne transmissible pathogens are controlled in the indoor space by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate.

[00115] There is the potential for numerous predictive models including, for example, various indoor spaces of different sizes and shapes, different particulate matter sizes and concentrations in the indoor spaces, different carbon dioxide concentrations in the indoor spaces, different relative humidities in the indoor spaces; different random human occupancies of the indoor spaces, and different temperatures in the indoor spaces.

[00116] Predictive models can be updated or refreshed at a specified time (e.g., on a regular or periodic basis). Updating predictive models can include updating any of the information including information of one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space, used for generating the predictive models. The process for updating predictive models can depend on the circumstances for particular indoor spaces, and the need for the updated information itself.

[00117] Information for generating predictive models can also be combined or matched with other sources of data. For example, other information can be based on environmental, geographical or demographical data. Environmental and geographical information can include, for example, outdoor air quality, outdoor temperature, outdoor relative humidity, outdoor carbon dioxide concentration, outdoor air particle concentration, and the like. Demographic information can include, for example, information about humans occupying the indoor spaces such as age, health, and the like.

[00118] One or more processors or controllers oversee the system for controlling airborne transmissible pathogens in an indoor space having random human occupancy of this disclosure. The one or more processors or controllers typically have at least one input, configured to receive the input data signals, and at least one output, configured to transmit output data signals. The output data signals include instructions for varying or maintaining the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. Airborne transmissible pathogens in the indoor space are controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate.

[00119] In one exemplary embodiment, the input data signals include one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and temperature in the indoor space. In one exemplary embodiment, the output data signals include instructions for varying or maintaining the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. The indoor space can include at least one input air blower having a motor for introducing the outdoor air stream into the indoor space, and at least one output air blower having a motor for discharging the indoor air stream from the indoor space. The speed or torque of the motor of the at least one input air blower can be varied by the output data signals from the processor, to control the rate of outdoor air introduced into the indoor space. Likewise, the speed or torque of the motor of the at least one output air blower can be varied by the output data signals from the processor, to control the rate of indoor air discharged from the indoor space.

[00120] In another exemplary embodiment, the one or more processors or controllers include a plurality of inputs and outputs, allowing for additional input or output data signals to be sent or generated. In one particular embodiment, the processor or controller is a process logic control (PLC). In another exemplary embodiment, the one or more processors or controllers may also include one or more computers having associated software, wherein the one or more computers provide the user or operator the ability to make changes to the designated programming, thus introducing more flexibility into the system. Moreover, the one or more computers can be accessed remotely through a network which allows monitoring and control of the circulation system from various locations.

[00121] The at least one processor is configured to: analyze the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space; and correlate the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. [00122] The at least one processor is also configured to control the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. The at least one processor can have at least one input, configured to receive input data signals, and at least one output, configured to transmit output data signals. The output data signals include instructions for varying or maintaining the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

[00123] Further, the data input signals into the at least one processor can be generated from one or more sensors. The one or more sensors can measure the various property characteristics of the indoor space and communicate this information to the processor.

[00124] In an embodiment, the parameters for particulate matter size and concentration in the indoor space, the carbon dioxide concentration in the indoor space, the relative humidity in the indoor space, and the temperature of the indoor space, can all be set within a predetermined range. When outside of the predetermined range, the at least one processor is configured to vary the rate for introducing an outdoor air stream into the indoor space, and discharging an indoor air stream from the indoor space, so as to restore the parameters to within the predetermined range.

[00125] Embodiments of the present disclosure have been described with reference to the accompanying drawings, in which some, but not all, embodiments of the disclosure are shown. Indeed, the present disclosure can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure can satisfy applicable legal requirements. Like numbers refer to like elements throughout. [00126] As used herein, the one or more databases configured to store the information or from which the information is retrieved, the one or more databases configured to store the real time information or from which the real time information is retrieved, can be the same or different databases.

[00127] The steps and/or actions of a method described in connection with the embodiments disclosed herein can be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium can be coupled to the processor, such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral to the processor. Further, in some embodiments, the processor and the storage medium can reside in an Application Specific Integrated Circuit (ASIC). In the alternative, the processor and the storage medium can reside as discrete components in a computing device. Additionally, in some embodiments, the events and/or actions of a method can reside as one or any combination or set of codes and/or instructions on a machine-readable medium and/or computer-readable medium, which can be incorporated into a computer program product.

[00128] In one or more embodiments, the functions described can be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions can be stored or transmitted as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage medium can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures, and that can be accessed by a computer. Also, any connection can be termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. "Disk" and "disc", as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs usually reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[00129] Computer program code for carrying out operations of embodiments of the present disclosure can be written in an object oriented, scripted or unscripted programming language such as Java, Perl, Smalltalk, C++, or the like. However, the computer program code for carrying out operations of embodiments of the present disclosure can also be written in conventional procedural programming languages, such as the "C" programming language or similar programming languages.

[00130] Embodiments of the present disclosure are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products. It can be understood that each block of the flowchart illustrations and/or block diagrams, and/or combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create mechanisms for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks.

[00131] These computer program instructions can also be stored in a computer- readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function/act specified in the flowchart and/or block diagram block(s).

[00132] The computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer- implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions/acts specified in the flowchart and/or block diagram block(s). Alternatively, computer program implemented steps or acts can be combined with operator or human implemented steps or acts in order to carry out an embodiment of this disclosure.

[00133] Thus, apparatus, systems, methods and computer program products are herein disclosed to generate predictive models, to determine the rate for introducing the outdoor air stream into the indoor space, to determine the rate for discharging the indoor air stream from the indoor space, to determine associations between the information for particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and optionally information for size and shape of the indoor space, random human occupancy of the indoor space, and temperature of the indoor space, and to determine the presence of airborne transmissible pathogens in the indoor space. [00134] Referring to Fig. 4, an illustrative building 400 shown that includes a roof 402, a ceiling 404, and an indoor space 406. Installed between the ceiling 404 and the roof 402 is a ventilation system 408 for introducing an outdoor air stream 410 into the indoor space 406, and discharging an indoor air stream 412 from the indoor space 406 to the outdoor space 414, for the purpose of controlling airborne transmissible pathogens in the indoor space. Ventilation system 408 includes multiple sensors including a particulate matter sensor 416 for measuring particulate matter level in the indoor space 406, a CO₂ sensor 418 for measuring CO₂ level in the indoor space 406, and a relative humidity sensor 420 for measuring relative humidity level in the indoor space 406. The particulate matter sensor 416 may be operated using an optical method, in a manner similar to, for example, a standard laser air quality monitor. In an embodiment, the particulate matter sensor 416 is a commercially available laser based air quality sensor. The carbon dioxide sensor 418 may be any suitable commercially available sensor. The relative humidity sensor 420 may be any suitable commercially available sensor.

[00135] Referring again to Fig. 4, a first motor 422 drives a first air blower 424 for introducing an outdoor air stream 410 into the indoor space 406. Air stream 410 may be used for diluting and/or displacing indoor particulate matter, CO₂ and relative humidity. Ventilation system 408 through air stream 410 keeps interior air circulating, and prevents stagnation of the interior air. Similarly, a second motor 426 drives a second air blower 428 for discharging an indoor air stream 412 into the outdoor space 414. Air stream 412 may be used for removing and/or discharging indoor particulate matter, CO₂ and relative humidity from indoor space 406. Ventilation system 408 through air stream 412 keeps interior air circulating, and prevents stagnation of the interior air.

[00136] In various embodiments, both motors 422 and 426 are commercially available, and can be electronic commutation (EC) motors, AKA brushless DC electric motor (BLDC motors, BL motors). The EC motors utilize an electronic circuit board to control the functionality of the motor. The motor may operate off of 115V or 220V AC single phase power, which is converted to DC power within the motor's circuitry. A control lead may be prewired from the motor which accepts a 0-10V DC signal. The control circuit can slow down or speed up the electric motors to meet changing indoor parameters for particulate matter, CO₂ and relative humidity. Varying the speed of the fans and associated electric motors can improve process control to meet changing speed or torque demands on a motor-driven system, and can reduce energy consumption as measured in kilowatt-hours (kWh) of electricity.

[00137] A control circuit for motors 422 and 426 is configured to receive operating instructions from the processor (not shown). The processor is configured to control the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, based on one or more parameters of particulate matter size and concentration, CO₂ concentration, and relative humidity.

[00138] The indoor space 406 can include ultraviolet germicidal irradiation (UVGI) for irradiating air in the indoor space. UVGI is the use of ultraviolet (UV) energy to kill viral, bacterial, and fungal organisms. UVGI fixtures produce UV-C energy, which has shorter wavelengths than more penetrating UV-A and UV-B rays and pose less risk to human health. Fixtures 434 and 436 are installed in the indoor space 406. The ultraviolet germicidal irradiation (UVGI) can use wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to confine the radiation to the upper-space area above people's heads, and to minimize exposure to human occupants in the lower-space area.

[00139] The ventilation system 408 may further include one or more filters 430 for reducing particle level in the outdoor air stream 410 that is to be introduced into the indoor space 406. For example, illustrative filters 430 may include an initial-efficiency filter, an intermediate-efficiency filter, and a high-efficiency filter arranged consecutively from upstream to downstream along flow direction of the outdoor air stream 410 that is to be introduced into the indoor space.

[00140] One or more filters 432 may be employed for reducing particulate matter level in indoor air stream 412 that is to be discharged into the environment, i.e. outdoor 414. For example, filters 432 may include an initial-efficiency filter, an intermediate- efficiency filter, and a high-efficiency filter arranged consecutively from upstream to downstream along flow direction of indoor air stream 412 that is to be discharged into outdoor 414, for reducing particulate matter level in the indoor air stream 412.

[00141] In an embodiment, the system of this disclosure can further include ultraviolet germicidal irradiation (UVGI) for irradiating air in the indoor space. The ultraviolet germicidal irradiation (UVGI) can use wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to confine the radiation to the upper-space area above people's heads, and to minimize exposure to human occupants in the lower-space area. Upper-room UVGI refers to a disinfection zone of UV energy that is located above people in the rooms they occupy. This kills airborne pathogens in the room where they are released. Fixtures are installed to prevent direct UV exposures to people in the room.

[00142] In another embodiment, the system of this disclosure can utilize one or more high efficiency particulate air (HEPA) filters in the indoor space. The one or more high efficiency particulate air (HEPA) filters can be positioned at the at least one inlet for introducing an outdoor air stream into the indoor space, and/or the at the least one outlet for discharging an indoor air stream from the indoor space.

[00143] With UVGI, air passes through a disinfection zone from air flow through, for example, fans, and/or open windows. The airborne pathogens are killed once they receive an appropriate amount of UV energy. The particles remain in the air, but they are no longer infectious. For airborne viral and bacterial particles, upper-room UVGI systems provide air changes per hour that are similar to the introduction of clean air into the indoor space. According to the CDC, UV research on SARS-CoV-2 indicates that the virus that causes COVID-19 is very similar to other coronaviruses (for example, SARS and MERS) regarding the UV dose necessary to inactivate it. Upper-room UVGI systems can be used to control SARS-CoV-2 as a useful ventilation tool to consider in reducing the spread of infectious pathogens.

[00144] The ultraviolet germicidal irradiation (UVGI) can use wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to target the radiation to the outdoor air stream being introduced through the one or more HEPA filters into the indoor space at the at least one inlet, and/or to the indoor air stream being discharged through the one or more HEPA filters from the indoor space at the at least one outlet.

[00145] Referring to Fig. 5, a system and method are disclosed for controlling airborne transmissible pathogens in an indoor space having random human occupancy. At 502, information is acquired including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space. The information is analyzed at 504 to generate one or more predictive models for determining the presence of airborne transmissible pathogens in the indoor space. At 506, real time information is acquired including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; and optionally size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space. At 508, the real time information is correlated with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space. At 510, the airborne transmissible pathogens in the indoor space are controlled by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate.

[00146] Where methods described above indicate certain events occurring in certain orders, the ordering of certain events can be modified. Moreover, while a process depicted as a flowchart, block diagram, or the like can describe the operations of the system in a sequential manner, it should be understood that many of the system's operations can occur concurrently or in a different order.

[00147] The terms "comprises" or "comprising" are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components or groups thereof.

[00148] Where possible, any terms expressed in the singular form herein are meant to also include the plural form and vice versa, unless explicitly stated otherwise. Also, as used herein, the term "a" and/or "an" shall mean "one or more" even though the phrase "one or more" is also used herein. Furthermore, when it is said herein that something is "based on" something else, it can be based on one or more other things as well. In other words, unless expressly indicated otherwise, as used herein "based on" means "based at least in part on" or "based at least partially on."

[00149] It should be understood that the present disclosure includes various alternatives, combinations and modifications which could be devised by those skilled in the art. For example, steps associated with the processes described herein can be performed in any order, unless otherwise specified or dictated by the steps themselves. The present disclosure is intended to embrace all such alternatives, modifications and variances that fall within the scope of the appended claims.

[00150] The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A method for controlling airborne transmissible pathogens in an indoor space having random human occupancy, said method comprising: acquiring information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; analyzing the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space; wherein the indoor space has at least one inlet for introducing an outdoor air stream into the indoor space, and at least one outlet for discharging an indoor air stream from the indoor space; generating real time information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; correlating the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space; and controlling the airborne transmissible pathogens in the indoor space by introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, at the determined rate.

2. The method of claim 1 further comprising utilizing ultraviolet germicidal irradiation (UVGI) for irradiating air in the indoor space.

3. The method of claim 2 wherein the ultraviolet germicidal irradiation (UVGI) uses wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to confine the radiation to the upper-space area above people's heads, and to minimize exposure to human occupants in the lower-space area.

4. The method of claim 1 further comprising utilizing one or more high efficiency particulate air (HEPA) filters in the indoor space.

5. The method of claim 4 wherein the one or more high efficiency particulate air (HEPA) filters are positioned at the at least one inlet for introducing an outdoor air stream into the indoor space, and/or the at the least one outlet for discharging an indoor air stream from the indoor space.

6. The method of claim 5 wherein the ultraviolet germicidal irradiation (UVGI) uses wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to target the radiation to the outdoor air stream being introduced through the one or more HEPA filters into the indoor space at the at least one inlet, and/or to the indoor air stream being discharged through the one or more HEPA filters from the indoor space at the at least one outlet.

7. The method of claim 1, wherein the information further includes size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space.

8. The method of claim 1, wherein the real time information further includes size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space.

9. The method of claim 1 , wherein the information includes two or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space.

10. The method of claim 1, wherein the airborne transmissible pathogens comprise viruses and bacteria.

11. The method of claim 1 , wherein the particulate matter size in the indoor space is from about 0.01 microns to about 20 microns.

12. The method of claim 1, wherein the carbon dioxide concentration in the indoor space is maintained from about 400 parts per million to about 1200 parts per million.

13. The method of claim 1, wherein the relative humidity in the indoor space is maintained from about 20 percent to about 70 percent.

14. The method of claim 1, wherein the analyzing and correlating are performed algorithmically.

15. The method of claim 1 , further comprising utilizing at least one processor.

16. The method of claim 15, wherein the processor is a process logic controller.

17. The method of claim 15 further comprising utilizing at least one processor for controlling the rate of introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

18. The method of claim 15, wherein the at least one processor has an input that receives at least one input data signal, and an output that transmits at least one output data signal.

19. The method of claim 18, wherein the at least one input data signal includes one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and temperature in the indoor space.

20. The method of claim 18, wherein the at least one output data signal includes instructions for varying or maintaining the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

21. The method of claim 18, wherein the parameters for particulate matter size and concentration in the indoor space, the carbon dioxide concentration in the indoor space, the relative humidity in the indoor space, and the temperature of the indoor space, are set within a predetermined range, and when outside of the predetermined range, the at least one processor is configured to vary the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, so as to restore the parameters to within the predetermined range.

22. The method of claim 15, wherein the indoor space further comprises at least one input air blower having a variable speed motor for introducing the outdoor air stream into the indoor space, and at least one output air blower having a variable speed motor for discharging the indoor air stream from the indoor space.

23. The method of claim 22, wherein speed or torque of the variable speed motor of the at least one input air blower is varied by the output data signals from the processor, to control the rate of outdoor air introduced into the indoor space.

24. The method of claim 22, wherein speed or torque of the variable speed motor of the at least one output air blower is varied by the output data signals from the processor, to control the rate of indoor air discharged from the indoor space.

25. The method of claim 15, further comprising utilizing at least one sensor and/or measurement equipment in the indoor space.

26. The method of claim 25, wherein the at least one sensor and/or measurement equipment is for measuring one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, temperature in the indoor space, and size of the indoor space.

27. A system for controlling airborne transmissible pathogens in an indoor space having random human occupancy, the system comprising: one or more databases comprising information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; one or more databases comprising real time information including one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space; wherein the indoor space has at least one inlet for introducing an outdoor air stream into the indoor space, and at least one outlet for discharging an indoor air stream from the indoor space; at least one processor configured to: analyze the information to generate a predictive model for determining the presence of airborne transmissible pathogens in the indoor space; and correlate the real time information with the predictive model to determine a rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

28. The system of claim 27 further comprising ultraviolet germicidal irradiation (UVGI) for irradiating air in the indoor space.

29. The system of claim 28 wherein the ultraviolet germicidal irradiation (UVGI) uses wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to confine the radiation to the upper-space area above people's heads, and to minimize exposure to human occupants in the lower-space area.

30. The system of claim 27 further comprising one or more high efficiency particulate air (HEPA) filters in the indoor space.

31. The system of claim 30 wherein the one or more high efficiency particulate air (HEPA) filters are positioned at the at least one inlet for introducing an outdoor air stream into the indoor space, and/or the at the least one outlet for discharging an indoor air stream from the indoor space.

32. The system of claim 29 wherein the ultraviolet germicidal irradiation (UVGI) uses wall-mounted or ceiling-suspended, louvered/shielded UVGI fixtures to target the radiation to the outdoor air stream being introduced through the one or more HEPA filters into the indoor space at the at least one inlet, and/or to the indoor air stream being discharged through the one or more HEPA filters from the indoor space at the at least one outlet.

33. The system of claim 27, wherein the information further includes size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space.

34. The system of claim 27, wherein the real time information further includes size and shape of the indoor space, random human occupancy of the indoor space, and temperature in the indoor space.

35. The system of claim 27, wherein the information includes two or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, and relative humidity in the indoor space.

36. The system of claim 27, wherein the airborne transmissible pathogens comprise viruses and bacteria.

37. The system of claim 27, wherein the particulate matter size in the indoor space is from about 0.01 microns to about 20 microns.

38. The system of claim 27, wherein the carbon dioxide concentration in the indoor space is maintained from about 400 parts per million to about 1200 parts per million.

39. The system of claim 27, wherein the relative humidity in the indoor space is maintained from about 20 percent to about 70 percent.

40. The system of claim 27, wherein the analyzing and correlating are performed algorithmically.

41. The system of claim 27, wherein the processor is a process logic controller.

42. The system of claim 27 further comprising utilizing at least one processor for controlling the rate of introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

43. The system of claim 27, wherein the at least one processor has an input that receives at least one input data signal, and an output that transmits at least one output data signal.

44. The system of claim 43, wherein the at least one input data signal includes one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, and temperature in the indoor space.

45. The system of claim 43, wherein the at least one output data signal includes instructions for varying or maintaining the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space.

46. The system of claim 43, wherein the parameters for particulate matter size and concentration in the indoor space, the carbon dioxide concentration in the indoor space, the relative humidity in the indoor space, and the temperature of the indoor space, are set within a predetermined range, and when outside of the predetermined range, the at least one processor is configured to vary the rate for introducing the outdoor air stream into the indoor space, and discharging the indoor air stream from the indoor space, so as to restore the parameters to within the predetermined range.

47. The system of claim 27, wherein the indoor space further comprises at least one input air blower having a variable speed motor for introducing the outdoor air stream into the indoor space, and at least one output air blower having a variable speed motor for discharging the indoor air stream from the indoor space.

48. The system of claim 47, wherein speed or torque of the variable speed motor of the at least one input air blower is varied by the output data signals from the processor, to control the rate of outdoor air introduced into the indoor space.

49. The system of claim 47, wherein speed or torque of the variable speed motor of the at least one output air blower is varied by the output data signals from the processor, to control the rate of indoor air discharged from the indoor space.

50. The system of claim 27, further comprising utilizing at least one sensor and/or measurement equipment in the indoor space.

51. The system of claim 50, wherein the at least one sensor and/or measurement equipment is for measuring one or more of particulate matter size and concentration in the indoor space, carbon dioxide concentration in the indoor space, relative humidity in the indoor space, temperature in the indoor space, and size of the indoor space.