WO2022231443A1

WO2022231443A1 - System and apparatus of low-maintenance air disinfection

Info

Publication number: WO2022231443A1
Application number: PCT/PH2022/050005
Authority: WO
Inventors: Drandreb Earl JUANICO
Original assignee: Juanico Drandreb Earl
Priority date: 2021-04-30
Filing date: 2022-04-30
Publication date: 2022-11-03

Abstract

The invention disclosed herein pertains to the passive disinfection of circulating air without filters by means of a synergistic combination of the contact germicidal effect of a metal surface, the radiative inactivating effect of germicidal electromagnetic wavelengths, and the enhancement by the radiation on the stability of the metal compounds responsible for contact inactivation. An apparatus is presented as an embodiment of implementing the system and validated through computer simulations and laboratory experiments. The apparatus can be retrofitted to existing ventilation systems and personal protective equipment without needing frequent maintenance.

Description

System and apparatus of low-maintenance air disinfection

Technical Field

The invention disclosed herein relates to the operation of a coupler that disinfects flowing air from airborne pathogens using a synergistic combination of three microbial inactivation mechanisms.

Background Art

Airborne or aerosol-transmissible pathogens thrive on the global interconnectedness of human society, resulting in pandemics. These kinds of pathogens also cause the infections afflicting enclosed poultry and livestock houses, e.g., avian or swine flu. According to the estimates by the International Labour Organization as of January 25, 2021 , the economic disruption due to the loss of productivity caused by the CoVID-19 pandemic reached an equivalent of US$ 3.4 trillion worldwide. This amount is roughly 4.4% of the 2019 GDP. The imposed lockdown measures and suspension of operations in most business sectors, especially tourism, precipitated such unprecedented economic slowdown not driven by any form of financial crisis.

Several methods to curtail the spread of infection are reactive and not immediately effective on rapid spreaders, such as the SARS-CoV2 and the African swine fever viruses. Wearing of face masks and shields, and social distancing practice confront low rates of compliance. Although vaccines have been known to offer some level of individual protection, a vaccine must be made every time a new or mutated infectious strain spreads across the human population. Many disease-causing viruses are known to mutate rapidly as they transfer from one victim to the next. Herd immunity through vaccination will also be difficult to achieve quickly on a massive scale. Hence, a

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SUBSTITUTE SHEETS (RULE 26) proactive and preventive disease-control strategy will be more effective than a reactive one like vaccination, quarantine, and other mobility-disrupting measures.

The disinfection of breathable air would offer a proactive means of controlling the spread of infection, particularly by disrupting the physical transmission of pathogens through air. The prior art presents all kinds of porous filters, such as high-efficiency particulate air (HEPA) filters, which directly impede the airflow to catch unwanted contamination carried by the air and allowing only the air to pass through. By impeding the airflow, porous filtering systems therefore require motors to force the air through the porous material, e.g., the air-purifier system disclosed in US Patent US10039852B2 or the self-contained air breathing device disclosed in Chinese utility model CN204337538U. The motors would consume substantial electrical power to maintain a continuous flow. Also, the pores of the filters eventually become clogged, hence, requiring replacement. While HEPA filters could trap microbial pathogens, these organisms may linger and lay dormant on the filter surfaces, remaining as infectious threats to anyone who will handle those filters during the time of replacement. There are several mechanisms of disinfection of aerosol transmissible pathogens that are known in the art; however, none have provided a means of air disinfection that employ a synergistic combination of two or more of such mechanisms. The Japanese patent JP4646210B2 exemplified a synergistic germicidal interaction between contact inactivation and UV irradiation in a material. The UV rays enhance the oxidation of copper (Badillo-Avila et al., 2019), whereas copper oxides are responsible for the germicidal action (Hans et al., 2013), in addition to the UV. However, this material is a paint product rather than an air disinfection device. The US Patent US8753575B2 disclosed a device that utilizes UV to disinfect air through the production of ozone.

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SUBSTITUTE SHEETS (RULE 26) However, ozone is a health hazard, which when inhaled can lead to adverse health effects. The device also employs electrostatic precipitators and a humidification system that contribute to the payload, making the disinfection device bulky for retrofitting existing ventilation systems. In contrast, the US Patent US9999696B2 disclosed a compact irradiating tube for the UV disinfection of fluids. The exposure of the fluid is maximized using a specific geometry applied to the interior of the tube. However, if the fluid is air, the straightforward path provided by the tube will limit the flow speed of the air if exposure time must be maximized. Another US patent US10323851 B2 also described a channel in which a flowing fluid receives dosage of UV for disinfection. This channel likewise offers a short path length for airflow, abbreviating the exposure time of pathogens to the UV radiation. Longer channels will be needed to increase the air-disinfection efficiency. Thus, the state of the art on air- disinfection devices do not take advantage of a synergistic combination of various disinfection mechanisms to enhance disinfection efficiency, thereby ensuring the compactness of the device and efficacy of the pathogen inactivation.

A coupler is a plumbing component used to join two fluid-conveying segments (e.g., pipes or ducts) so that flow from one segment continues through the other segment. The present disclosure is directed to a coupler for airflow that maximizes the germicidal effects of exposure time with radiation, contact time with a metallic surface, and heat to rid the aerosol-laden air of potent microbial entities that could eventually cause a disease to, if inhaled, by a human, poultry, or livestock. Head gears, such as face masks or helmets, as illustrated by several patents and utility models, e.g., US8733356B1 , AU2020100228A4, KR1020170069674A, CN204337538U, could take advantage of a coupler that mediates the airflow through at least one of the tubes that supply breathable air or expel exhaled air back to the atmosphere. The coupler also

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SUBSTITUTE SHEETS (RULE 26) keeps the UV sources at a much safer distance away from the skin, unlike the UV- embedded face masks disclosed in Australian patent application AU2020100228A4 and US Patent US8733356B1. Leaked UV radiation is likely to cause skin harm, such as sunburn or skin cancer, from prolonged exposure.

Retrofitting a coupler to existing ventilation systems in public transport or buildings will provide for a pre-emptive control strategy against aerosolized pathogen transmission. Minimal disruption to economic activity will ensue as stringent quarantines need not be imposed to curtail the spread of infection across the human, poultry or livestock population.

Summary of Inventions

The invention can be implemented as retrofit component to existing- , or as an essential part in future, ventilation systems.

The coupler may be constructed from a hollow cylinder with an internal structure in the form of a static mixer. In the following description, reference to the cylinder is merely for illustration. Any other shape of the cross section of an airflow channel should be equally effective. A helical mixer is an example of a static mixer that modifies the flow path of air through the cylindrical tube. The mixer can be fabricated from copper plates. The construction begins with two flat copper plates embedding an insulating sheet, e.g., rubber or silicone, for electrical isolation. The resulting copper-insulator-copper (CIC) sandwich will be twisted. Multiple twisted CIC sandwich units will be attachable end to end at 90 degrees relative angle to form a helical structure. On each sandwich unit sits atop a pair of diametrically opposite LEDs. Helical mixing, as with many similar static mixing techniques, stretches the residence time of aerosols leading to higher contact

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SUBSTITUTE SHEETS (RULE 26) probability with the copper surface and longer exposure times to UV irradiation than in the absence of such mixing. The mixer has an integrated electrical connectivity to supply power to the LEDs, the connection of which would include a heat sink, e.g., aluminum, that supports the LED, straddling from one end of the sandwich unit to the other. The heat sink conducts the heat generated from the LED toward the copper plate. Without loss of generality, the mixer can be made entirely of copper plate without an insulator embedded in the middle. The entire mixer assembly can be seamlessly inserted into (and pulled out of) the hollow cylinder.

The hollow cylinder is preferably made from a material that has a high UV reflectivity. This material may preferably be a polytetrafluoroethylene (PTFE), which has at least 95% reflectivity of UV wavelengths. A US patent application US20190233308A1 takes advantage of this PTFE property for UV-based water treatment. This level of reflectivity should effectively confine most of the UV energy inside the PTFE tube. UV leakage is kept low. The confinement of the UV energy would imply that the power input needed to operate the LED is kept at a minimum.

The flow path of air through the static mixer increases the likelihood of collisions between the aerosol and the mixer surface. These collisions would be inelastic, which would result in either the immediate adhesion of droplets or further sputtering into smaller droplets on the copper surface of the static mixer or the inner wall of the cylinder. As the droplets are trapped inside the coupler, the accelerated evaporation of the moisture component of the droplets, due to the heat radiated by the heat sink, would expose the germ load to the toxicity of copper ions generated by natural oxidation (Wang & Cho, 2009) and the photolytic effect of UV irradiation.

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SUBSTITUTE SHEETS (RULE 26) The synergistic combination of different modes of germicidal inactivation reduces the volume of the coupler for a given disinfection efficacy. The heat generated from the operation of the LEDs, which the heat sink conducts toward the copper plates, could accelerate the evaporation of aerosol droplets, which would expose the microorganism load to the UV. If the aerosol droplet collided with the static mixer surface, the germicidal activity of copper ions would add further blow to the exposed pathogens. The UV irradiation contribute to the corrosion of copper (Deng et al., 2020), enhancing the antimicrobial efficacy of the surface. The confinement of the UV energy inside the cylinder for an appreciable period further reduces the power input to the LEDs. The cooperative air-disinfecting interactions among UV, heat and copper pave the way for a compact product that would be suitable as an add-on part or retrofit in ventilation systems.

The low-maintenance air-disinfecting coupler is a proactive solution to the recurring widespread infection caused by aerosol transmissible microbial pathogens. It can be connected inline, like standard couplers, to the plumbing of most ventilation/ventilator systems, HVAC/air conditioning, room/building recirculation system, and even portable headgears or facial masks for outdoor applications. The combat against current and future airborne pathogens would necessitate a proactive solution. Predicting the future infective strains is as challenging as pre-empting how they would transmit across the population. While reactive measures, such as vaccination, may be successful to some extent, many casualties must initially pile up before the measures take effect, such as in the form of herd immunity.

Brief Description of Drawings

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SUBSTITUTE SHEETS (RULE 26) It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

FIGURE 1. Detailed view of a helical mixer element and its components. FIGURE 2. Internal view of the disinfecting coupler assembly showing the mixer elements and external view highlighting the enclosing tube.

FIGURE 3. Computed trajectory of the aerosol droplets inside the coupler.

FIGURE 4. Deposition of droplets on the inner walls of the coupler and residence time. FIGURE 5. Lateral view of a flow adapter system employing a plurality of disinfecting couplers that join an intake and an exhaust manifold.

FIGURE 6. Illustration of an embodiment for retrofitting the disinfecting couplers to the recirculation HVAC system in a public transport cabin (e.g., bus or train). The concept is like the HVAC system in airplane cabins (not shown). FIGURE 7. Illustration of an embodiment for utilizing the disinfecting coupler in a split case HVAC system of a car.

FIGURE 8. Illustration of an embodiment for linking the disinfecting coupler to the exhalation valve of full-mask, half-mask, and quarter face-piece. The concept of linking the coupler to the air supply tubes of self-contained wearable respirators should be similar (not shown).

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SUBSTITUTE SHEETS (RULE 26) FIGURE 9. Aerosol mass reduction results from experiments with prototype and oxide deposits scraped from baffle surface.

Description of Embodiments

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention.

The mixer element is the basic unit of a static mixer baffle. It consists of two flat copper plates 101a and 101b separated by a flat sheet of flexible insulator material 102. This flat multilayer composite object is then twisted to form a segment of a helical surface with both ends having the same orientation. The copper plates are conductive, representing an electric terminal on each side of the helical object. An ultraviolet light- emitting diode (or UV LED) 103 is placed facing the saddle point on each side of the helical object. The bottom side 103a includes conducting terminals to which electricity is supplied through heat and electricity conducting objects 104a and 104b, which may be made from aluminum or some other conductive material that offers substantial UV reflectivity. The conductor 104a connects (e.g., by soldering) only to copper plate 101a whereas the other conductor 104b connects only to plate 101b. These conductors may therefore derive external electricity by way of the copper plates, while dissipating heat generated by the LED 103a to the same plates, which offer larger surface area suited for the radiative heat transfer to the air. Thus, the objects 104a and 104b serve the dual purpose as electricity supplier and heat sink. The top side 103b includes the

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SUBSTITUTE SHEETS (RULE 26) radiating component. The supplier/sink objects 105a and 105b play the analogous roles for LED 103b as 104a and 104b do for LED 103a.

A coupler assembly 200 can be made from a hollow tube a sequence of mixer elements inserted into a hollow tube. The air may enter on either side of the assembly. For the sake of clarity, let us suppose the air enters from the side nearest to mixer element 201a, then through 201b, and exiting through the side nearest to 201c. Nevertheless, both sides are interchangeable. The UV LEDs 103 are fixed through the supplier/sink objects (not shown) that straddle across each mixer element. The LEDs 103 each face the saddle point of the mixer elements and may be aligned directly on top or slightly off the saddle point. The hollow tube 202 can be made from pure PTFE, which are widely available from commercial sources. Due to PTFE’s high UV reflectivity (at least 95%), the interior of the hollow tube 202 therefore acts almost like a “mirror” to ultraviolet, effectively confining the energy of this radiation produced by the LEDs 103 inside the tube and concentrated towards the surfaces of the mixer elements 201a, 201b, and 201c. Although some UV energy may leak out through the ends of the coupler assembly, most of the energy are confined and utilized in the photoreduction of the copper surfaces (Fleisch & Mains, 1982) and photoinactivation of any microbial entities trapped within the assembly (Heftling et al., 2020). As it is a coupler assembly, the ends of 200 will include screw threads or other form of adapter, as is apparent to those of ordinary skill in the art, to connect to standard piping or tubing. The coupler would ideally appear as any ordinary coupler externally. The two-phase fluid dynamics of aerosol-laden airflow through the coupler 200 enhance the collision probability between the aerosols and the internal structure comprising of the mixer baffle and interior surface of the tube. The baffle distorts a laminar or turbulent airflow into “twisting” trajectories, which effectively lengthen the

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SUBSTITUTE SHEETS (RULE 26) residence time of the air inside the tube. The resulting helical flow of air and inertia of the aerosol droplets drive the latter to collide with the interior walls of the coupler. The collision will be inelastic due to the adhesion of the water droplets. The droplet’s adherence may be immediate or the droplet will sputter into smaller droplets after colliding with a wall, depending on its velocity before collision. Although the smaller droplets may end up becoming stragglers, which stay afloat and evaporate at a lower rate, the twisted trajectory of the flowing air will likely push them toward the latter parts of the interior right before the exit. It Is possible that some droplets may coalesce in air, increasing the inertia of the droplet, thereby steering it in a collision course with the inside walls. Thus, the most probable plight of the droplet is that it ends up attached to an internal wall, either on the baffle surface or the interior of the tube, as fluid- dynamics simulations indicate.

Air passes through the coupler either in a laminar or turbulent flow. The average mass of the aerosol droplets is 7.64 x 10-9 kg with a peaked distribution around this value, while the particle diameter is around 5.0 x 10-7 m. The density of the aerosol is that of saliva at about 1300 kg/m3. With these parameters, the trajectory of the droplets inside the coupler is calculated using a computational fluid simulation software. The airflow through the tube is assumed to be generally turbulent so that the fluid flow is solved using a Menter shear stress transport (SST) turbulence model. The droplets may stick to a surface with a probability of 0.2, which is consistent with known properties of saliva. The droplet trajectories eventually end up with a collision to the baffle surface and inner wall of the tube as illustrated in Figure 3. Some droplets break up into smaller droplets after colliding and may stay afloat in the air inside the coupler for some time. However, the turbulent airflow drives these remaining droplets in swirling motions within the tube so that eventually they still find themselves colliding

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SUBSTITUTE SHEETS (RULE 26) to the inner wall of the coupler. Only a few droplets find their way near the outlet side of the tube, and even there, the swirling motion may still drive them to the inner walls.

The results of a simulation, shown in Figure 4, indicate that for a mean inflowing air speed of 80 cm/s it would only take about 0.5 s for about 32% and 28% of the incident aerosols to deposit on the baffle surfaces 401 and inner tube walls 402, respectively. Only a very small percentage of the incident droplets 403 get through the tube. The smaller droplets could remain floating within the coupler for a residence time 404 of about 2.5s until they dissipate. Within this residence time 404, the exposed microbial load on the tube walls and baffle surfaces would have received an average UV dose of about 25 J/m2 and 2.5 J/m2, respectively. These UV doses would have been more than sufficient to photolyse 98% of the microbes on the tube walls and about 30% on the baffle surfaces at a 50% relative humidity (RH), as published studies have quantified (McDevitt et al., 2012). However, on the baffle surfaces, the exposed microbes would also confront the germicidal toxicity of the UV-enhanced copper corrosion.

The irradiation of UV onto the inner walls of the coupler indicates that most of the radiation energy is confined within the coupler. A higher flux of radiation impinges on the surface of the static mixer baffle, whereas the inner wall of the hollow cylinder reflects the radiation efficiently. The UV irradiation of copper can supplement the natural oxidation of the metallic surface. Typically, the copper metal surface would oxidize rapidly at room temperatures and even faster at high relative humidity. The outermost oxide layer is a thin cupric oxide, CuO, film on top of another oxide layer, i.e., the cuprous oxide or Cu20. However, CuO offers less germicidal toxicity than Cu20. The reason for this outward layering is that Cu20 forms first on Cu metal due to its lower enthalpy of formation than of CuO. At high RH, the Cu20 oxidizes to CuO,

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SUBSTITUTE SHEETS (RULE 26) which forms the outermost layer most exposed to air and the UV radiation. The CuO may then undergo photoreduction with prolonged exposure to the UV. The byproduct of this photoreduction is Cu metal in amorphous form. This amorphous copper would then oxidize naturally back to Cu20. This process leads to a higher concentration of Cu20 on the baffle surface, which maintains an efficient contact germicidal toxicity to the infectious microbes.

A droplet stuck on the wall may eventually dry up due to evaporation. The evaporation process may be accelerated by the heat generated by the LEDs 103 and conducted to the plates 101 through the heat sinks 104 and 105. The evaporation of a droplet exposes any microbial load to the inactivation agents found within the coupler, namely, heat, radiation, and corrosion (Scully, 2020). From those droplets that adhered to the copper surfaces and evaporated, the exposed microbial load become open to the toxicity of copper ions (Warnes et al., 2015; Warnes & Keevil, 2013; Warnes et al., 2012; Warnes & Keevil, 2011). The copper ions may be products of natural oxidation or UV-assisted corrosion (Badillo-Avila et al., 2019). From those droplets that found their way elsewhere within the coupler 200, the exposed microbial load become open to the UV radiation.

The coupler 200 can be integrated as a component of a flow adapter system 500. In situations that require higher flow volumes, the size of coupler 200 need not be scaled up accordingly. Instead, multiple couplers may be integrated by dividing the flow through inlet pipe 501 into multiple smaller flows through an intake manifold 502. Every coupler 200 connects each outgoing pipe of the intake manifold 502 to the incoming pipe of the exhaust manifold 503 that eventually lead to the outlet pipe 504. This flow adapter system more or less preserves the flow volume flowing in through 501 and flowing out through 504.

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SUBSTITUTE SHEETS (RULE 26) Alternative embodiments of the mixer element may infuse the copper surfaces 101a and 101b with infused nanoparticles or with reflective coating such as PTFE. Also, other forms of static mixers (e.g., non-helical or complex geometry) may achieve an optimal performance in terms of disinfection without deviating substantially from the concept herein disclosed.

The reflective coating may include other types of insulating or even conductive materials, e.g., aluminum or combinations thereof, without substantially deviating from the functionality as disclosed herein.

In some variations, the heat sink may take the form of graphite or graphene-based materials due to their higher thermal conductivity.

The static mixer surface may also be coated with photocatalyst material to speed up the material and radiation interactions. The coating might also apply to the inner surface of the enclosing cylinder. Some variations may interchange the surface properties of the static mixer baffle and hollow cylinder inner surface. In other variations, the inner-cylinder and mixer-baffle surfaces both contain copper to enhance the contact inactivation rate further. Any further improvements or permutations intended to optimize the effect disclosed herein should be apparent to those of ordinary skill in the art.

The coupler may find utility for the disinfection of circulating air in the passenger cabins of buses, trains, or airplanes. In an exemplary embodiment, the cross section of a train or bus in Figure 6 shows the typical components of the HVAC system. The air handling unit (AHU) 600 consists of either a cooling or heating unit 601 from which the temperature conditioned air 606 is delivered through the vents and flowing 605 to the cabin 607. The couplers

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SUBSTITUTE SHEETS (RULE 26) 200 may be applied to the pathway of the conditioned air 606 toward the vents 605, effectively disinfecting the air. The coupler may also be used in a similar manner on other channels or ducts through which air would flow. For example, the supplementary fans 602 help recirculate the air from inside the cabin and back. Couplers may disinfect the air that traverses through the looping path 604 driven by the supplementary fan 602. An essential part of the cabin HVAC system is the recirculation of air through 603 that leads back to the AHU where it can be mixed with outside air and reconditioned through the cooling/heating unit 601 . The recirculated air 603 may contain the aerosol droplets coming from the passengers’ breathing, sneezing or coughing. The couplers will trap and disinfect any pathogen load carried by the droplets before it flows into the mixing compartment or exhausted to the atmosphere. A similar approach applied to the passenger cabins of airplanes should be apparent to those of ordinary skill in the art.

Another exemplary embodiment of utilization of the couplers can be applied to the car HVAC system, particularly a split case system with integral blower shown in Figure 7. Other car HVAC systems are similar. The HVAC consists of adjustable doors to feed the air from the inside 700 or outside 703 the car. The recirculating air door 701 can be switched close or open, the latter case allowing the inside air 700 to be driven by the motor and blower assembly 704 towards the evaporator 705. The outside air door 702 does a similar function to the outside air 703. The inside air recirculation is essential to keep the temperature inside the car cooler or warmer than outside. Through recirculation the HVAC reduces the work that it needs to do to stabilize the temperature and humidity inside the car. However, any aerosol droplets floating in the inside air will also get recirculated and distributed inside the car. If these droplets carry pathogenic microbial loads, then the circulation will expose everyone inside the car. A

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SUBSTITUTE SHEETS (RULE 26) coupler integrated before or after the recirculating air door 701. The exact placement of the coupler should be apparent to those of ordinary skill in the art. Human exhalation is the source of the aerosols that could spread an infection. Face masks have been considered as an essential for epidemic control because it minimizes the droplets from the mouth of a person that could transmit pathogenic microbes. Commercially available face masks come in three major varieties: the full, half, and quarter mask. The full mask includes a face shield that also protects the wearer’s eyes in addition to the nose and mouth. The half mask does not have the face shield, while inhaled air 802 goes in through two filtered inlets 803 on both sides of the head. The quarter face-piece only has one filtered inlet 803, much like the full mask but without the face shield. The common feature among these types of masks is the exhaust valve 800. The coupler 800 can be integrated downstream far away from the face to eliminate the exposure of the face to any UV radiation.

Experiments of the prototype 903 confirm the synergy among the tube material, baffle material and the UV irradiation. The PTFE material combined with copper helical baffle and UV caused the highest reduction of aerosol mass. The aerosol mass was estimated from multiple measurements of the relative humidity (RH) at the inlet and outlet. The RH value can be converted to aerosol mass using the technique provided by Kuang et al. (2018). The result 901 with an estimate of 79.6% aerosol reduction corroborates the simulation results 401 and 402 in combination with vaporization losses from the radiative heat transfer. The use of a non-PTFE tube dramatically reduces the effect, as shown in result 902. The presence of the helical baffle also consistently resulted to higher aerosol reductions regardless of the UV. The UV interaction with the copper surface produced a mixture of oxides on the surface with a characteristic dark red color indicative of a mixture of CU2O and CuO, which is

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SUBSTITUTE SHEETS (RULE 26) dominated by the former. The dominance of C112O can be associated with the UV and provides higher germicidal efficacy to the copper surface. From the above description of preferred embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.

References Patent Literature

WO 1992020974A1 (1992). Disinfectant system.

US 7226542B2 (2007). Fluid treatment apparatus.

JP 4646210B2 (2011). Inactivating agent of the phage virus [Translation from Japanese]. US 8069853B2 (2011). Breath responsive powered air-purifying respirator.

US 8733356B1 (2014). Germicidal protective mask with ultraviolet light emitting diodes.

US 8753575B2 (2014). Method and apparatus for sterilizing and disinfecting air and surfaces and protecting a zone from external microbial contamination. US 8997515B2 (2015). Auxiliary device intended for adding to an air conditioning device.

CN 204337538U (2015). Personal wearable air purifier [Translation from Mandarin] US 9376333B2 (2016). Inline UV LED water disinfection and heating.

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SUBSTITUTE SHEETS (RULE 26) KR 1020170069674A (2017). Wearable air purifier [Translation from Korean] US 9999696B2 (2018). Compact system with high homogeneity of the radiation field. US 10039852B2 (2018). Air purifier using ultraviolet rays.

US 10294124B2 (2019). Method and apparatus for liquid disinfection by light emitted from light emitting diodes.

US 10520251 B2 (2019). UV light curing systems, and methods of designing and operating the same.

US 10323851 B2 (2019). UV tube for killing microorganisms and air conditioning system comprising the tube.

US 20190233308A1 (2019). UV reactor with PTFE diffuser.

AU 2020100228A4 (2020). Filter Mask with UVC LED. Non-Patent Literature

Fleisch, T.H. & Mains, G.J (1982). Reduction of copper oxides by UV radiation.... Applications of Surface Science 10, 51-62.

Wang, J. & Cho, W.D. (2009). Oxidation behavior of pure copper in oxygen.... ISIJ International 49, 1926-1931. Warnes, S.L. & Keevil, C.W. (2011 ). Mechanism of copper surface toxicity.... Applied and Environmental Microbiology 77, 6049-6059.

Warnes, S.L., Caves, V. & Keevil, C.W. (2012). Mechanism of copper surface toxicity in Escherichia coli 0157:H7 and Salmonella.... Environmental Microbiology 14, 1730-

1743.

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SUBSTITUTE SHEETS (RULE 26) McDevitt, J.J., et al. (2012). Aerosol susceptibility of influenza virus to UV-C light. Applied Environmental Microbiology, 78(6), 1666-1669.

Lin, H. & Frankel, G.S. (2013). Atmospheric corrosion of Cu by UV, ozone and NaCI. Corrosion Engineering, Science and Technology 48, 461-468.

Hans, M. et al. (2013). Role of copper oxides in contact killing of bacteria. Langmuir 29, 16160-16166.

Warnes, S.L. & Keevil, C.W. (2013). Inactivation of norovirus on dry copper alloy surfaces. PLOS One 9, e98333.

Warnes, S.L., Summersgill, E.N. & Keevil, C.W. (2015). Inactivation of murine norovirus on a range of copper alloy surfaces is accompanied by loss of capsid integrity. Applied and Environmental Microbiology 81, 1085-1091.

Hang, Xet al. (2015). Antiviral activity of cuprous oxide nanoparticles against Hepatitis C Virus in vitro. Journal of Virological Methods 222, 150-157.

Badillo-Avila et al. (2019). Fast rate oxidation to Cu20, at room temperature, of metallic copper films produced by argon-plasma bombardment of CuO films. Materials Chemistry and Physics 236, 121759.

Scully, J.R. (2020) Can antimicrobial copper-based alloys help suppress infectious transmission of viruses originating from human contact with high-touch surfaces? Corrosion 76, 523-527.

Zheng, C., Cao, J., Zhang, Y. & Zhao, H. (2020). Insight into the oxidation mechanism of Cu-based oxygen carrier (Cu-> Cu20 -> CuO) in chemical looping combustion. Energy Fuels 34, 8718-8725.

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SUBSTITUTE SHEETS (RULE 26) Deng, S., Lu, H. & Li, D.Y. (2020). Influence of UV light irradiation on the corrosion behavior of electrodeposited Ni and Cu nanocrystalline foils. Scientific Reports 10, 3049. Heftling, M. et al. (2020). Ultraviolet irradiation doses for coronavirus inactivation — review and analysis of coronavirus photoinactivation studies. GMS Hygiene and Infection Control 15, Doc08.

Kuang, Y. et al. (2018). A novel method for calculating ambient aerosol liquid water content based on measurements of a humidified nephelometer system. Atmospheric Measurement Techniques, 11, 2967-2982.

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SUBSTITUTE SHEETS (RULE 26)

Claims

System and apparatus of low-maintenance air disinfection Claims

1. A system of passively eliminating pathogen loads from aerosols flowing in circulating air comprising at least one of a retrofit coupler or standalone module with a tube or duct, a baffle, a confined superposition of germicidal electromagnetic radiation, and a synergistic combination of contact and irradiative germicidal effect.

2. The system of claim 1 , wherein pathogen loads in aerosols are in the form of bacterium or virion and populations thereof, released to the atmosphere from the respiratory tract of an infected individual by sneezing, coughing, talking, shouting, exhalation, and similar actions involving the output of air through the mouth or nose.

3. The system of claim 1 , wherein the circulating air is the atmosphere in a confined or open space that moves due to passive, e.g., natural breeze, or by active ventilation, e.g., fan or air conditioning unit.

4. The system of claim 1 , wherein the tube or duct is made of material with high ultraviolet (UV) reflectivity that may or may not have a provision for attachment to external piping or tubing or to a system of high-efficiency particulate air (HEPA) filters.

5. The system of claim 1 , wherein the baffle is made of a germicidal metallic material, taking on a shape that fits across the interior cross section of the tube or duct and cutting the flow of air through the tube or duct but not significantly impeding the flow velocity, consequently establishing an axial flow pattern that increases the collision rate of the aerosols with the baffle surface.

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SUBSTITUTE SHEETS (RULE 26)

6. The system of claim 1, wherein the confined superposition of germicidal electromagnetic radiation is the standing wave and/or interference due to the multiple reflection of electromagnetic radiation across the inner walls of the tube or duct, retaining most of the radiative energy inside the tube or duct and may or may not dissipate such energy through radiative heat transfer leading to the vaporization of the moisture content of the aerosols, and photochemical reactions on the baffle surface.

7. The system of claim 1 , wherein the synergistic combination of contact and irradiative germicidal effect comprises the preferential formation of germicidal metallic compounds on the baffle surface by photoreduction with the exposure to the germicidal electromagnetic radiation, the contact germicidal effect on the pathogen upon encounter of those metallic compounds on the baffle surface, and the germicidal photolysis of the pathogens by direct irradiation.

8. An apparatus of passively eliminating pathogen loads from aerosols flowing in circulating air comprising at least one of a retrofit coupler or standalone module with a tube or duct, a baffle, a confined superposition of germicidal electromagnetic radiation, and a synergistic combination of contact and irradiative germicidal effect.

9. The apparatus of claim 8, wherein the germicidal electromagnetic radiation is UV of wavelength between 250 and 280 nm originating from a plurality of light- emitting diodes.

10. The apparatus wherein the tube or duct is made of polytetrafluoroethylene (PTFE) with at least 95% reflectivity of UV with wavelengths between 250 and

280 nm.

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SUBSTITUTE SHEETS (RULE 26)

11. The apparatus wherein the baffle is made of copper plates twisted to form a helical assembly with edges touching the inner wall of the tube or duct by a union or joint, and extending across a part or the entire length of the tube or duct.

12. The apparatus of claim 8, wherein the confined superposition of germicidal electromagnetic radiation is the standing wave and/or interference due to the multiple reflection of the UV across the inner walls of the tube or duct, retaining most of the radiative energy inside the tube or duct and may or may not dissipate such energy through radiative heat transfer leading to the vaporization of the moisture content of the aerosols, and photochemical reactions on the baffle surface.

13. The apparatus of claim 8, wherein the synergistic combination of contact and irradiative germicidal effect comprises the preferential formation of germicidal metallic compounds on the baffle surface by photoreduction with the exposure to the germicidal electromagnetic radiation, the contact germicidal effect on the pathogen upon encounter of those metallic compounds on the baffle surface, and the germicidal photolysis of the pathogens by direct irradiation.

14. The apparatus of claim 13, wherein the metallic compounds on the baffle surface are copper oxides with chemical symbol CU2O and CuO the mixture of both on the baffle surface is dominated by the former and have a characteristic dark reddish brown color.

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SUBSTITUTE SHEETS (RULE 26)