SPACES

FIELD OF THE INVENTION

This invention relates to apparatus and methods for decontaminating or sanitizing air within enclosed spaces, including sealed enclosures such as rooms, cabins, chambers and environmental spaces, as well as within personal protective equipment.

BACKGROUND OF THE INVENTION

Heating, ventilation, and/or air conditioning (HVAC) systems are commonly used to control the climate comfort levels and air quality within a building, enclosure, vehicle, aircraft or other structure. HVAC systems, including many forced air HVAC systems, typically include an air filtration apparatus to help remove dust, pollen, airborne pathogens and other pollutants from the air recirculated or fed to the enclosed space and to protect the conditioned space occupants and the HVAC system itself from build-up of such contaminants which may negatively impact system performance and contribute to reduction in air quality.

Global demand for systems that rapidly inactivate microbial contamination within enclosed environments has increased significantly with the growing threat from pandemic viral infection, such as from influenza, Ebola, respiratory syncytial virus (RSV), MERS and SARS, especially SARS-CoV-2 and its many variant forms. Droplet and airborne transmission of diseases including COVID-19 is well documented. The rapid spread of COVID-19 disease in early-2020, as well as the severe economic damage resulting from the subsequent lockdowns and the social distancing measures needed to control the infection, demonstrate that there is an increased need for improved air ventilation methods and apparatus that are both reliable and straightforward to deploy.

Currently, HVAC systems that are designed to remove airborne contaminants, such as pathogens, utilize filtration technology as the main mitigation method. Ultra-low particulate air (ULPA) filters, high efficiency particulate air filters (HEPA) and bag filters of differing grades are the current industry standards. HEPA filters are commonly considered to be the most popular when it comes to HVAC air filters. They are designed to trap airborne contaminants that are as small as 0.3 microns in diameter and are the first choice for many domestic, commercial and industrial contexts. Nevertheless, ULPA and HEPA filters must be used with other air cleaning methods as their use results in a significant pressure drop in the airflow through the system which consumes fan power. In addition, even the very highest specification HEPA filters are no more than 99.97% efficient at collecting the most penetrating particles around the 0.3 micron limit. This may be adequate for inert particulate contaminants such as dust, pollen or protein antigens, but for microbial pathogens and especially viruses, which are capable of reproduction or replication, allowing even a handful of particles through the filter can be hazardous to health.

Over time, the mechanical seals around ULPA and HEPA filters can degrade allowing air to bypass the filter cassette which risks delivery of untreated air into protected spaces and enclosures. Use of ULPA and HEPA filters is expensive and they need to be frequently changed in order to maintain system efficiency and safety performance.

Hence, there is an urgent need to innovate solutions to efficiently and cheaply address airborne transmission of diseases caused by airborne pathogens including bacteria, viruses such as influenza and coronavirus (COVID), and fungal spores. Thus, providing a healthy atmosphere and environment for users of public facilities such as healthcare workers, patients, residents and shoppers, is an important objective.

Tenzin et al. (PLoS One; 2019; 14(9)) describe the use of fogging technology to disinfect aerosolised bacteria from pig farm weaning rooms using a solution of electrochemically activated solution generated by electrolysis of dilute sodium chloride, also referred to commonly as anolyte. Like many atmospheric sterilisation technologies currently in use, Tenzin requires that the room or enclosure to be treated is evacuated for a period of time before operating the sterilisation protocol based upon saturation fogging of the atmosphere. Clearly this presents a problem in enclosures, spaces or other enclosed environments which are continuously occupied - e.g. hospitals, hotels, shopping centres and aircraft cabins - where it is impractical to operate phases of decontamination which require complete evacuation.

WO 03/045534 A1 provides a purifying module for a ventilation system that includes a grid filter for intake air and a purifying chamber, into which a gas, such as a halogen gas, ozone, a peroxide containing gas or other chlorine or chlorine and oxygen containing compound, or a fluid mist containing chlorine atoms, such as hypochlorite ions can be introduced through one or more inlets/spigots. The purifying chamber can also be irradiated by ultraviolet and microwave radiation to assist with the decontamination effect provided by the fluid, by ionizing the cleaning fluid and also by directly killing pathogens itself. The antimicrobial fluid is removed from the purifying chamber via a pump.

CN 109028287 A discloses a salt purifier that utilizes the electrolysis of brine to generate a disinfecting fluid. Intake air is first filtered and enters an electrolysis chamber, together with evaporated brine that evaporates from a brine tank through a humidifying filter. The filtered air and brine are electrolysed together in the electrolysis chamber, with the electrolysis of the brine generating hypochlorous acid to kill bacteria and viruses present in the filtered air. US 2008/0028771 A1 discloses an air conditioner comprising an air filtering unit. The air conditioner comprises a heat exchange system and a fan to direct air flow through the heat exchanger to the air filtering unit, which utilises electrolytically activated tap water contained within the air filtering unit to kill viruses and bacteria in the airflow. The air filtering unit is made of a gas-liquid contact member, which is permeable to the air flow yet is treated to increase its water retentivity so that contact between the electrolytically activated water and the air flow can be maintained for a long time.

JP 2000257913 A also discloses the use of electrolyzed salt water to disinfect micro-organisms in the airflow contained in an air conditioning system. The electrolyzed water can be applied to the airflow by means of a spray or by means of a disinfection element, which can be wetted by dropping or spraying the electrolyzed water onto it. The air conditioning system also comprises a blower for circulating air, and cooling and heating coils for adjusting the temperature and humidity of the airflow.

CN 209131066 U discloses an air purification device that uses slightly acidic electrolyzed water as a disinfectant. The electrolyzed water is applied as a spray onto ceramic corrugated plates, which are disposed across a spray chamber.

KR 20190011889 A discloses a method of air purification that involves the filtration of intake air, inducing a discharge to the air, removal of active species introduced when inducing the discharge to the air and then discharging oxygen to the room, the oxygen being generated by electrolysis of water.

CN 207299216 U discloses an air conditioning unit with an independent air treatment device, which works to purify air through use of a tank of electrolyzed water in communication with a water treatment member. The water treatment member may be made from a moisturizing cotton, which enables the airflow to come into contact with the electrolyzed water to kill bacteria. The water treatment member may be driven by a rotating motor to come into contact with the electrolyzed water such that each area of the water treatment member is wetted by the water periodically to maintain its effectiveness.

EP 1832817 A2 discloses an air filtering apparatus that uses an electrolytic water mist to disinfect an airflow. The mist fills a chamber and air passing through that chamber is disinfected by coming into contact with the mist.

It is an object of this invention to provide a method and apparatus that allows for improved, reliable and safe decontamination of airflows within HVAC or other ventilation systems. These and other uses, features and advantages of the invention will be apparent to those skilled in the art from the teachings provided herein. SUMMARY OF THE INVENTION

The present inventors have identified advantageous configurations of apparatus for use in HVAC or air cleaning systems using a safe disinfectant, referred to as anolyte, which is a product of electrochemically activated water (EAW). The apparatus of the present invention can easily be integrated in or retro-fitted to existing HVAC systems, incorporated within new HVAC systems, or could be used in separate/standalone portable, wearable, autonomous or fixed air handling or cleaning units.

In a first aspect the present invention provides for an apparatus for microbial disinfection of an air supply, the apparatus comprising:

(a) an impeller for generating an air stream through the apparatus; and

(b) a disinfectant unit for inactivating airborne microbial contamination within the air stream, wherein the disinfectant unit comprises a reservoir comprising a supply of a liquid disinfectant, the liquid disinfectant comprising an electrochemically activated aqueous solution, and a distribution system configured to ensure the air stream is contacted with the liquid disinfectant so as to inactivate airborne microbial contaminants within the air, wherein the disinfectant distribution system comprises a wicking system comprising a wick, the wick being partially immersed in the reservoir of liquid disinfectant to ensure impregnation of the wick with the liquid disinfectant, and at least one rotating element configured to enable rotation of the wick such that the region of the wick that is immersed in the reservoir changes as the rotating element and the wick rotate.

In specific embodiments of the invention the liquid disinfectant solution comprises an electrochemically activated aqueous solution of sodium chloride, which may have a loading of between 0.5 and 1.0% w/v and may have a pH of between 6 and 7. Suitably, the wicking system may comprise a linear wick. Typically the linear wick is comprised of a continuous loop of wicking material and the at least one rotating element comprises at least two rollers, the linear wick being suspended between the at least two rollers. In another embodiment the wick comprises a rotary wick. The rotary wick may be comprised of a disc of wicking material and the at least one rotating element may comprise a spindle, wherein the spindle is aligned coaxially with the air stream and the disc is substantially perpendicular to the air stream. In an alternative embodiment disinfectant distribution system comprises a disinfectant fogging or spraying system. A second aspect of the invention provides a HVAC system comprising the apparatus described herein.

A third aspect of the invention provides an air cleaning unit (ACU) system comprising the apparatus described herein.

A fourth aspect of the invention provides for a wearable air cleaning unit (ACU) system comprising the apparatus described herein.

A fifth aspect of the invention provides a method for inactivating airborne microbial contamination within an airstream comprised within a HVAC system, the method comprising locating a disinfectant unit within the HVAC system such that the air stream is directed through the disinfectant unit, wherein the disinfectant unit comprises a reservoir comprising a supply of a liquid disinfectant, the liquid disinfectant comprising an electrochemically activated aqueous solution, and a distribution system configured to ensure the air stream is contacted with the liquid disinfectant so as to inactivate the airborne microbial contaminants in the air, wherein the disinfectant distribution system comprises a wicking system comprising a wick, the wick being partially immersed in the reservoir of liquid disinfectant to ensure impregnation of the wick with the liquid disinfectant, and at least one rotating element configured to enable rotation of the wick such that the region of the wick that is immersed in the reservoir changes as the rotating element and the wick rotate.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can take many forms and arrangement of the steps. One or more embodiments of the invention will now be described, by way of example only and not to be construed as limiting the invention, with reference to the accompanying drawings, in which Figure 1 is a schematic drawing of a linear wick disinfectant solution induction system integrated in HVAC air handling unit (AHU) as described in one embodiment of the present invention;

Figure 2 is a schematic drawing of one arrangement of apparatus of an embodiment of the invention, in which a linear wick disinfectant solution induction system is integrated into an in situ portable or wearable fixed air cleaning unit (ACU);

Figure 3 provides illustrations of alternative disinfectant solution induction mechanisms in the air stream according to embodiments of the invention;

Figure 4 depicts a wearable personalized carry over air cleaning unit (ACU) in use.

Figure 5 shows a graph of air cleaning efficiency in inactivating an air supply contaminated with airborne E. coli according to an embodiment of the invention that utilises an anolyte linear wicking system within an ACU. Figure 6 shows photographs of agar plates exposed to a supply airstream inoculated with a E. coli aerosol and passed through an ACU of the type depicted in Figure 2; (a) shows the results when only using a HEPA filter, (b) shows the results when a wicking disinfectant solution induction system is integrated into the ACU. Figure 7 shows a photograph of a range of agar plates tested, similarly to those in

Figure 6; the top row of plates are control (with no HEPA or disinfectant unit), the second row show the results of HEPA filtration only, the third row EAW disinfectant unit only, the fourth row a combination of HEPA filtration and EAW disinfectant unit. Figure 8 shows a Scanning Electron Microscope (SEM) image at 40,000x magnification of the E. coli bacterial culture used in the examples with measurements of the cells shown; the scale bar at the bottom indicates a length of 4 microns.

Figure 9 shows agar plates seeded with E. coli by a six-stage cascade impactor after 30 seconds of exposure to three air cleaning methods used for the mitigation of airborne infections, namely a HEPA filter, an air cleaning unit (ACU) as according to an embodiment of the invention and an integrated system of a HEPA filter and an ACU as according to an embodiment of the invention together, as well as a control plate. Figure 10 shows a graph of the bacterial number against time for the agar plates shown in Figure 9, showing the air cleaning efficacy of the three devices at different cleaning periods. Figure 11 shows the effect of Newcastle Disease Virus (NDV) before (A) and after passing through three air purifying devices, namely a HEPA filter device (B), a device according to an embodiment of the invention with an integrated EAW disinfectant unit and HEPA filter (C) and a device with an EAW disinfectant unit (D).

Figure 12 shows the effect of treatment of SARS-CoV-2 virus with EAW.

Figure 13 shows a transmission electron micrograph (TEM) of SARS-CoV-2 before (a) and after (b) contact with EAW for approximately 30 minutes. The scale bar shows a length of 50 nm. Figure 14 shows the Cycle Threshold (CT) values of SARS-CoV-2 over five sequential days when treated with EAW (red) compared to the non-treated virus (blue).

Figure 15 shows the effect of EAW on Aspergillus niger and Aspergillus fumigatus over 4 minutes of direct contact.

DETAILED DESCRIPTION OF THE INVENTION

The air cleaning methodology utilizes a liquid disinfectant induction system that includes, but is not limited to, linear wicking systems and/or rotary wicking systems which may be supplemented with one or more fogging systems and spraying systems, to introduce the liquid disinfectant into the HVAC airstream. In specific embodiments of the invention the liquid disinfectant comprises electrochemically-activated water (also referred to as “anolyte”). Advantageously, embodiments of the invention enable configurations that reduce loss of pressure across airflow impellers - e.g. fans - in the Air Handling Units (AHU) or standalone units. This, in turn, reduces energy demand of the improved HVAC systems and AHUs.

Prior to setting forth the invention, a number of definitions are provided that will assist in the understanding of the invention. All references cited herein are incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

As used herein, the term “comprising” means any of the recited elements are necessarily included and other elements may optionally be included as well. “Consisting essentially of means any recited elements are necessarily included, elements that would materially affect the basic and novel characteristics of the listed elements are excluded, and other elements may optionally be included. ‘Consisting of means that all elements other than those listed are excluded. Embodiments defined by each of these terms are within the scope of this invention.

The term “enclosed space” is intended to refer to an enclosed volume of space that is defined by solid boundaries, such as walls, that are relatively impermeable to gas transfer. Suitably the enclosed space is defined within an enclosure, for example, such as a room, vessel, conduit, cupboard, tent, cabin or a chamber. The enclosed space will typically comprise an atmosphere as well as one or more windows, ports, doors or other access channels. The enclosed space may be in intermittent or continuous gaseous communication with a ventilation system such as a HVAC system.

According to one embodiment of the present invention the disinfectant solution comprises electrochemically-activated water, also called “anolyte”. Electrochemically-activated water is generated by at least partial electrolysis of pure water or a dilute aqueous solution of sodium chloride, around 0.5% to 1 .0% w/v in an electrolytic cell. The resulting anolyte solution is usually weakly acidic or around neutral pH (e.g. a pH of between 6 and 7) and comprises mixed oxidants, typically free chlorine and free oxygen and hydroxyl radicals, in solution including species such as hypochlorous acid (HOCI) and hypochlorite ions. In specific embodiments the anolyte solution has a pH of not less than 6, suitably not less 6.3; and not more than 6.6, suitably around 6.5. Depending upon the mode of manufacture anolyte solutions with significantly stronger redox potential and lower pH can also be produced. Suitably a free available chlorine (FAC) level of at least 25 ppm and at most 500 ppm is deemed effective for antimicrobial use according to context of proposed use. According to embodiments of the present invention the disinfectant solution can be manipulated to specific requirements and may comprise concentrations of at least 1%, 2%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 99% by weight or more of anolyte. Some anolyte solutions with concentrations as low as 1% are known to be effective in killing vegetative bacterial cells and as low as 5% for eradication of C. difficile spores (Robinson et al. (2010) App. Microbiol. 50(3): 289-294). Methods and apparatus for the production of biocidal anolyte type solutions are described in EP-1878704-A1.

With reference to Fig 1., an embodiment of the invention provides an HVAC system (10) that manages and distributes supply air (80) to an enclosed space such as a room, chamber or cabin. The air may be sourced from the external atmosphere (e.g. outside air) (20) or recirculated return air (21) from within the enclosed space, or mixed between the two types of air in the AHU mixer box. Excess or overflow air may be vented externally as exhaust air (22). Hence, external or recirculated air (20, 21) represent air flow inputs to the system (10) and supply or exhaust air (80, 22) represent outputs from the system. In embodiments of the invention the apparatus of the system (10) may be a substantially airtight sealed system that prevents inflow of non-treated air from other sources, e.g. where the supply air is for use in clean rooms or in clinical or food preparation areas.

Intake air (20,21) is drawn into a central duct (12) within the system (10). In the embodiment shown in Fig. 1 external air (20) may pass through a particulate filter (30) prior to entry into the central duct (12). Recirculated air (21) may or may not be passed through additional particulate filtration (30) dependent upon the context and requirements of the system. Movement of air through the system and out into the enclosed space is under the control of an impeller (70), suitably a fan or other form of air moving device, that is located within the duct (12) or proximate and in gaseous communication therewith. As air is drawn through the system is passes through a thermal control unit (40) that provides heating and/or cooling of the air flow. In a specific embodiment of the invention the heating is mediated via a heating coil (42) and cooling via a cooling coil (41). Thermally conditioned air passes along the central duct (12) to a disinfectant unit (50) that comprises a wicking structure (51) that is impregnated with a disinfectant solution - e.g. anolyte solution. Location of the disinfectant unit (50) downstream of the thermal control unit (40) may in some instances facilitate disinfection because the air stream is at its highest relative humidity at this point and the air stream may pass through the wicking without causing undue evaporation of disinfectant solution. The disinfectant unit (50) may further comprise a disinfectant fog or aerosol generator, which is mixed with the airstream to effect adequate sterilization from microbial contamination. Hence, in this way, supply air is drawn along the duct (12) and through the disinfectant unit (50) such that any airborne microorganisms comprised within the air are sufficiently exposed to the disinfectant solution and inactivated. Adequate airtight sealing around the edges of the disinfectant unit (50) is important to ensure airflow is substantially directed through the unit (50) and does not bypass exposure to disinfectant solution.

Following the disinfectant stage the thermally conditioned and disinfected/sanitized airstream is directed as supply air into the enclosed space. It is an option for the supply air to pass through one or more additional filters (60) located at any point along the central duct (12) depending upon need and context of the installation. For example, installation in air flow systems that provide ISO 146644-1 cleanroom standard class 7 or below may require several filters (60), such as sequential HEPA or ULPA filtration units. In specific embodiments of the invention, the disinfectant unit (50) may be integrated into the filter (60), or vice versa, as a single disinfection and particulate filtration unit.

It will be appreciated that an HVAC installation may comprise a plurality of systems as shown in Fig. 1 arranged in series or in parallel, or both. In addition, in certain embodiments the disinfectant unit (50) may be placed upstream of the thermal control unit (40) as desired or specified, for example, in order to reduce evaporation of anolyte in environments where heating of the airstream is more prevalent, such as in geographical latitudes closer to the poles. A further embodiment of the invention is set out in Fig. 2 in which a disinfectant unit is comprised within an in room, portable or wearable air cleaning/conditioning apparatus (100) or ACU. Contaminated or externally sourced air is drawn into the apparatus (100) via the contaminated air inlet (124). The contaminated are may be directed through one or more filters including a HEPA or ULPA filter (160) and/or an activated carbon filter (161). Additional microbial or airborne biosterilisation capability may be provided by locating an ultraviolet germicidal irradiator (UVGI) unit (190) within the apparatus (100). An impeller (170), such as a fan, provides air moving functionality and may be situated within or proximate to the system (100). Filtered air is drawn through the apparatus and passes through a disinfectant unit (150) that comprises a wicking structure (151) that is impregnated with a disinfectant solution - e.g. anolyte solution. Alternatively, the disinfectant unit (150) may comprise a disinfectant fog or aerosol generator. Disinfected and sanitized air is expelled from the apparatus (100) via a clean air outlet (180) as supply air.

The disinfectant unit (50, 150) may comprise a linear wick or a rotary wick. A linear wick is characterized by administration of disinfectant solution to the periphery (e.g. one or more edges) of a wicking material that is supported so that the solution is drawn by capillarity through the wick material and thereby distributed across the wick surface. The linear wick may further comprise rollers located at opposing sides of a continuous loop of wicking material which extends between them. In this arrangement, which is depicted in Figure 3, continuous or intermittent rotation of the rollers enables the wicking material to be immersed in a bath of disinfectant solution during a cycle of rotation and the elevated to intersect with the airstream that then passes through the suspended loop of wicking material. Either or both of the rollers may be powered, and in alternative wicking arrangements more than two rollers may also be used. In contrast, a rotary wick is characterised by a wicking material formed into the shape of a disc that is partially immersed in a disinfectant source and which material is rotated about central spindle that is aligned with the axial direction of air flow. As the spindle rotates the wicking material is impregnated with disinfectant. The airstream is directed through the rotary wick. Fogging systems may be used in combination with a wick and provide a nebulised fine spray of disinfectant solution into the air stream. All embodiments of the disinfectant unit (50, 150) require a supply of disinfectant solution, such as anolyte, that may be provided from a reservoir tank, or may be generated in situ via an electrochemical water activation system comprised within the systems and apparatus of the invention.

Wicking material suitable for use within the disinfectant unit (50, 150) may suitably be comprised of polymeric materials (e.g. polyester), microfibre, woven or non-woven materials, glass fibre, carbon fibre, natural fibre (e.g. bamboo, wood fibre, cotton fibre, wool) or any material suitable for performing a wicking function. In an aspect of the invention the methods and apparatus are located within an enclosed space defined by a sealed enclosure such as a hospital ward, a laboratory, a pharmaceutical cleanroom, a food production hall, a fast food restaurant, a hotel room, a public transportation carriage, a compartment, a cabin, a pressurised tent, a spacecraft, or a shipping container etc to be supplied with sanitized clean air. The apparatus may be accompanied by devices to aid in the distribution of the clean supply air around the enclosure such as fans, diffusers or laminar air flow distribution systems. Whilst specific configurations of HVAC and ACU systems are described, it will be appreciated that liquid disinfectant induction - such as using anolyte solution treatment - may be contemplated at any location through an air supply network including within the treated enclosed space, air supply terminals and diffusers, air return terminals and diffusers, connecting ducts, return and recirculation ducts, fresh air supply intake(s), fresh air supply ducts, within heating units and exhaust ducts. In addition, the anti- microbial treatments may be used continuously or intermittently during operation. For example, it may be suitable to run an anti-microbial cycle of air supply treatment at specified times of day or only when needed - e.g. when sensor or other monitoring systems detect a risk of airborne microbial contamination. In a further embodiment of the invention the ACU system may be miniaturised and incorporated within a wearable unit as depicted in Figure 4. Hence, as an ACU the apparatus and methods of the invention may be comprised within self-contained breathing apparatus (SCBA) such as associated with hazmat or biohazard personal protective equipment. An embodiment of the invention provides for personal protective equipment comprising apparatus, such as an ACU, that utilises an integral disinfectant unit (50, 150) that uses an anolyte wicking or fogging/spray system as described herein. Personal protective equipment according to this embodiment may find utility in protecting frontline workers, such as emergency or healthcare workers, in cases such as pandemic disease, biohazard release or biological weapons attack. According to embodiments of the invention the apparatus may also be accompanied by environmental sensors to determine the efficacy of the decontamination/sterilization processes within the HVAC or air cleaning apparatus, such as biological indicators, chemical indicators, enzymatic indicators or any other indicator that measures the biocontamination. The apparatus may also comprise one or more sensors in order to measure the environmental conditions within the apparatus or within enclosed space, such as a humidity sensor, a barometric pressure sensor, a temperature sensor, a pH sensor or disinfectant concentration sensor. In the latter case, the disinfectant concentration sensor may determine if the disinfectant unit (50, 150) is adequately supplied with disinfectant solution and/or whether a wicking structure (51 , 151) is sufficiently impregnated with disinfectant solution.

The invention as described in the aforementioned embodiments and the accompanying claims provides improved utility in processes, controls and apparatus related to the technical problem of efficient microbial inactivation and decontamination of air supply to enclosed spaces. In particular embodiments, the simplicity of design of the disinfectant unit allows for significant reductions in the complexity of manufacture compared to prior art systems, improved reliability, simplified controls. In addition, in certain embodiments the removal of the need for additional HEPA and ULPA filtration and the concomitant drop in airflow allows for much reduced operational power draw, and in some cases improved efficiency of air supply distribution. All these benefits are significant contributors to the enhanced environmental credentials of the methods and apparatus described.

The systems and apparatus of the invention are suited to elimination of airborne microbial contamination including from bacterial pathogens including, E. coir, C. difficile, Salmonella spp., Legionella spp., Staphylococcus spp. (including MRSA), and Bacillus spp. (including B. anthracis)·, as well as viral pathogens including measles morbillivirus, chickenpox virus (Varicella); influenza virus, hanta virus, coronavirus (including SARS, MERS and SARS-CoV-2), adenovirus, enterovirus, norovirus, ebola virus, Newcastle disease virus and respiratory syncytial virus (RSV). Other airborne microbial contamination may include fungal spores, such as from moulds including Aspergillus spp. and Stachybotrys chartarum. The air cleaning efficiency of apparatus of an embodiment of the present invention is shown in Figure 5 (described in more detail below) where the prevalence of airborne E. coli contamination within the air of an enclosed room is measured over a time course where an ACU is deployed. The apparatus of the invention is surprisingly effective at reducing and maintaining a sanitized atmosphere within only minutes of deployment.

EXAMPLES

Example 1.1 - Bacterial vegetative cell air cleaning assay Bacteria preparation:

Escherichia coli (E. coli ) strain ATCC® 25922 isolate is revived on nutrient agar (HiMedia Laboratories, India). Single colonies are suspended in 1% phosphate buffer saline (PBS) to achieve an inoculum equivalent to 0.5 McFarland standard of 2x10 ⁸ colony forming unit per milliliter (CFU/ml) as measured by Densi CHEK plus (Biomerieux, France).

Filter and EAW (anolyte) air cleaning efficacy:

EAW (anolyte) is selected as the liquid disinfectant due to its high microbial toxicity but relative level of safety when exposed to or inhaled in low concentrations by humans or animals. Anolyte solution with a pH of between 6.30 and 6.55 is utilised (Envirolyte Industries International Ltd., Talinn, Estonia). The anolyte solution typically comprises a target free available chlorine level of around 500 ppm at most and 25 ppm at least (representing a 19:1 dilution).

Briefly, 5 ml of 0.5 McFarland standard E. coli are seeded in a contained enclosed space using an automatic nebulizer (Omron) for 15 minutes. The efficacy of the HEPA filter, EAW and combined HEPA filter plus EAW unit are measured by the quantitative environmental sampling of bacteria into nutrient agar plates using Cascade Impactor Series 10-8XX (Tisch Environmental, Ohio, US) with airflow rate of 28.3 L/min and 15 minutes collecting time. Then the plates are incubated at 37 °C for 18-24 h. E. coli are counted using colony counter (Stuart Scientific, UK) and expressed as colony-forming units per cubic meter of air according to the following equation Total CFU/m ³ =N/Volume, Where N is the average of CFU of viable bacteria, Volume per cubic meter of air =28.3 litres /min X 15 min of sampling divided by 1000.

Results of an assay carried out according to this protocol are shown in Figure 5. The air was effectively decontaminated of airborne E. coli in less than one hour. In comparison to a HEPA filter alone, the combined HEPA filter plus EAW unit achieved far superior reduction in microbial contamination in less than 30 seconds operation as shown in Figures 6 (a) and (b) respectively. In Figure 7, results are shown of a series of the agar plates collected off the six stage cascade impactor. This figure demonstrates the number of E. coli colonies after 30 seconds of exposure to three air cleaning methods used for mitigation of airborne infections, namely, standalone HEPA- integrated UGVI filter, EAWwicking system and HEPA/EAW integrated system. The top agar plates demonstrate the control used in this experiment.

In Figure 8 a SEM image taken of the E Coli culture used to carry out this example. It is clear that the physical geometry of E Coli bacterium in terms of length and width varies from micron scale to nano scale. Hence, since industry standard HEPA filters can vary in specification in terms of particulate retention from lowest retention (E10) up to the highest (U17) it is apparent that as a standalone technology HEPA filters simply cannot solely impede bacteria. In most cases, viral particle geometry is even smaller than bacteria and on the basis of the present results would be expected to penetrate the HEPA even more extensively. The results indicate that the presently described approach provides a cost effective and elegant solution that will complement the current expensive HEPA filter arrangement and improve resistance to microbial contamination.

Example 1 .2 - Mitigation of bacteria (E. coli ) by applying the integrated ACU and HEPA filter

Briefly, 5 ml_ of 0.5 McFarland standard Escherichia coli (E. coli ) ATCC® 25922 were nebulized in a contained space with a volume of 1 34m ³ (L: 180cm x W: 60cm x H: 124cm), for 16 min (spray rate 0.312ml/min) using an automatic compressor nebulizer (NE-C28P, China). The efficacy of the HEPA filter (Beurer GmbH wellbeing, Germany), the air-cleaning unit (ACU), and the integrated ACU and HEPA filter was measured by the collection and counting of bacteria during the nebulization period, 16 minutes of continuous dispersion in presence of the above- mentioned devices respectively (Figure 10). Furthermore, in an additional experiment, the contained space was nebulized with a similar load of bacteria (5 ml_ of 0.5 McFarland standard), then cleaned for different times (0.5, 1, 2, 3, 4, 5, and 10 min) using the three devices separately. After completion of each cleaning period, bacteria were collected and quantified by sampling into nutrient agar plates using Cascade Impactor Series 10-8XX (Tisch Environmental, Ohio, US) with an airflow rate of 28.3 L/min (Figure 9). These plates were incubated at 37 °C for 18-24 h. The quantity of collected E. coli colonies was expressed as colony-forming units per cubic meter of air (CFU/m ³ ). As a control, the bacteria were dispersed, then collected and enumerated, without the application of any cleaning device. The efficacy of the three devices was compared while taking samples during dispersion and after the designated different cleaning intervals. Temperature and relative humidity were measured during the experiments with the Extech Instrument VPC300 Particle Counter (EXTECH Instrument VPC300, USA).

As illustrated by Figures 9 and 10, the three used air-cleaning devices reduced the number of bacteria in the air significantly while taking samples during dispersion and after the designated cleaning intervals compared to the control that comprises the collection of bacteria from the air before application of any device. Virtually all bactericidal effects occurred during the first 30 sec. of the cleaning period when using the ACU or the ACU/HEPA integrated system with the highest efficacy of cleaning. No single bacteria was collected when the air was cleaned using the ACU/HEPA integrated system and barely any when using the ACU alone, which showed a 99.3% reduction in the number of collected bacteria after 30 seconds of cleaning period. The results demonstrate the high efficacy of using the ACU as an air cleaner device against airborne bacteria.

Example 1.3 - EAW as a bactericidal surface disinfectant

A designated 10 cm x 10 cm of the laboratory bench’s working surface area was sprayed by 10Opl of 0.5 McFarland E. coli ATCC® 25922. Then, this area was covered by spluttering 500 pi EAW for a specific contact period (30 sec., 1 , 2, 3, 4, 5, and 10 minutes). After each period, the designated area was swabbed using a pre-wet swab in a zigzag pattern to cover the-studied area. Then the swab was placed in a tube with 1 ml PBS, shaken well, and rotated to ensure the release of bacteria if any in the liquid. Subsequently, a serial of 10-fold dilutions of this liquid was prepared. 20ImI of each serial dilution was streaked onto nutrient agar, incubated at 37°C for 16 to 18 hours, and then CFU/ml were counted. A comparable, controlled experiment was conducted as above however without the application of EAW. Each experiment was replicated 3 times and the average CFU/ml was calculated. E. coli spotted on a particular bench’s working surface area was sprayed with the EAW and left in contact for a time ranging from 30 s to 10 minutes. The growth of bacteria was entirely inhibited within 30 sec. of contact with EAW as no bacterial growth was detected on the plate with EAW free media, incubated at 37°C for 18-24 h.

Example 2.1 - Viral assay:

An attenuated 5 ml of Newcastle disease virus (NDV) is seeded in a contained enclosed space using an automatic nebulizer (Omron) for 15 minutes. The efficacy of the HEPA filter, EAW (anolyte) and combined HEPA filter plus EAW unit are measured by collecting the virus in a 25mm diameter cellulose ester filters using SKC Button Sampler (SKC Inc., Eighty Four, PA, USA). The filters are transferred into 1 ml Phosphate Buffered Saline (PBS), shaken for one minute. Then a haemagglutination test is performed, on this solution to measure the viral titre in order to determine the efficacy of air decontamination and comparing between the above- mentioned methods. Briefly, a serial of viral dilutions are added to a 96 well plate, and then 1% washed chicken Red Blood Cells (RBC) suspension is added to these wells, allowed to settle for 25 minutes. The last well in the dilution series showing no shield of settled Red blood cells is said to have haemagglutination. The titre of the virus can be calculated in terms of haemagglutination units per ml.

Example 2.2 - Mitigation of Newcastle disease virus (NDV) by applying the integrated ACU and HEPA filter

An attenuated 5 ml of NDV (Live vaccine, Nobilis® ND Clone 30, Holland) with viral load 3.934x10 ⁴ PFU/ml was nebulized in a contained microenvironment as mentioned above in bacteria assay. The efficacy of the three devices was compared, by the quantification of the collected virus after passing through these devices. Briefly, the sprayed virus was collected on 25mm gelatine filters (Satorius Stedium Biotech Gmbh, Gottingen, Germany) using Button Aerosol Sampler (SKC Inc., Georgia, USA) with an airflow rate of 4 liters/min. After viral collection, the gelatine filter was dissolved into 1300pl viral transportation media, serially diluted into a series of eight 10-fold dilutions. To determine the titer of the collected virus, 10Opl of each serial dilution was added, to monolayer Vero cells (kidney epithelial cells extracted from the African green monkey), grown into a 96 well plate at a density of 3x10 ⁴ cell/well. Following infection of the virus to Vero cells, the infected cells were incubated at 37°C and 5% CO2, monitored for 5 to 6 days to observe the cytopathic effect (CPE) on Vero cells. Finally, the viral titer was calculated by determining 50% tissue culture infective dose (TCID50)/ml, using a TCID50 calculator v.2.1. Our results showed that the titres of the NDV were decreased significantly after passing through the novel prototype device by more than 4 logs (3.16 TCID50/ml) compared to the titre of the NDV in the control (5.62x10 ⁴ TCID50/ml) collected without passing through any device. Moreover, NDV virus collected before passing through the prototype device showed significant CPE on Vero cells while no effect was depicted on the virus collected after passing through the prototype device (Figure 11). This figure depicts the significant CPE of NDV collected from the studied microenvironment before (A) and after passing through the HEPA filter device (B), novel integrated prototype, EAW+ filter (C) and the novel prototype with EAW (D).

Example 2.3 - Antiviral effect of EAW against SARS-CoV-2

Vero Cells were seeded in 24 wells plate at a density of 3x10 ⁵ in Dulbecco's Modified Eagle Medium (DMEM), Sigma- Aldrich, Germany with 10% fetal bovine serum (FBS) 1% penicillin- streptomycin, and then incubated for 24h at 37 °C and 5% CO2. On the next day for cell infection, four different panels including negative control, EAW, positive control, (SARS-CoV-2), and treated virus (EAW- SARS-CoV-2) were prepared in sixtuplicate. The negative control contained one-third of Dulbecco's phosphate-buffered saline (DPBS), and two-thirds infection media (IM), which is DMEM with 1% penicillin-streptomycin and missing FBS. EAW panel included one-third DPBS, one-third EAW, and one-third IM. Positive control comprised of one- third DPBS, one-third virus (500 TCID50/well), and one third of IM. Finally, the treated virus panel had one third EAW, one-third of virus, and one-third IM. On infection the media was removed from the plate, cells washed twice with DPBS and then a 100 pi of each panel was inoculated onto each well, the plate was kept inside the CO2 incubator for 1 h and rotated every 5 minutes to prevent dryness and spread the inoculum. After one hour the inoculum was removed, cells washed once with DPBS and 500 pi of fresh IM was added to each well. The cells were observed daily for CPE and 50 pi of the media were collected every day from each panel and stored at -80 °C for further reverse transcriptase quantitative PCR (RT-qPCR) analysis. In addition to RT-qPCR, SARS-CoV-2 titer was calculated by deterring the 50% tissue culture infective dose (TCID50)/ml before and after treatment for one minute with EAW (as described above for NDV).

SARS-CoV-2 RNA was extracted from the above-stored media using the NucleoSpin RNA virus kit (Macherey-Nagel, Diiren, Germany) following the manufacturer’s instructions. Extracted RNA was subjected to RT-qPCR using NEB Luna Universal Probe One-Step RT-qPCR that target the viral RNA sequences using hydrolysis probes. The RT-qPCR reaction was performed in a total volume 12.5pl, containing 8.5pl of master mix (New England Biolabs, United Kingdom) 4pl of RNA sample. The reaction mixture was amplified using MicPCR, Bio molecular system cycler, Australia), under the following conditions: initial cycle of 55°C for 10 min, followed by 95°C for 1 min, and then 40 cycles of 95°C for 15 S, and 60°C for 60 S, as instructed by the kit supplier. Positive control was obtained from EVAg (https://www.european-virus-archive.com/). Samples were considered positive when the RT-qPCR Cycle Threshold Values (CT) were <35.

Vero cells were observed daily for CPE, expectedly no CPE nor adverse effect on the cells was observed in the negative control and EAW wells. On day 3 the positive control wells started to display CPE and on Day 5 the effect was significant where the cells lost their shape, membrane integrity, and adhesion of the cell walls (Fig. 12). SARS-CoV-19/EAW wells did not show CPE, however, under the microscope they appeared to show marginally higher cell morbidity compared to negative control and EAW wells. In addition to this, when visualizing SARS-CoV-2 treated with EAW under the transmission electron microscope, we observed the denaturing of the structure of the proteins on the surface of the virus and the disruption of the virus's lipid membrane (Figure 13).

As shown by Figure 14 the Cycle Threshold (CT) values of the SARS-CoV-2 treated with EAW remain constant over 5 consecutive days while the non-treated virus showed a continuous drop of CT values indicating replication of the untreated virus.

Example 3 - Antifungal effect of EAW against Aspergillus niger (A. niger) and A. fumigatus

The antifungal effect of EAW on Aspergillus spp. was assessed according to (3, 4) with slight modification. Briefly, 0.5 McFarland standard of inoculum suspension was prepared from the fresh mature 5-day-old culture of Aspergillus sp., grown on potato dextrose agar (Biochem Chemopharma, France), by gently scraping off the fungus using a sterile cotton swab and then the spores were transferred to 5ml PBS. Equal volumes of EAW were added to the spore suspensions and left for different periods (30S, 1 , 2, 3, 4, 5, 10, and 30 min). After completion of the specific contact period, the mixtures were centrifuged at 10,000 RPM for I min, and the supernatant was discarded. The pellets were re-suspended in 500pl PBS and then added to 5ml RPMI 1640 media supplemented with 2% glucose, incubated at 37°C in a shaking incubator for 48 h and turbidity was compared visually between all tubes. For quality control, an aliquot of the sterilized medium was prepared for sterility check. In addition, Growth control without EAW was prepared.

Figure 15 shows the effect of EAW of Aspergillus niger at different time points ranging from 30 seconds to 5 minutes. Tube A is a positive control (appears cloudy) and Tube B is a negative control (appears clear). Our results showed that EAW inhibits the growth of A. niger and A. fumigatus after 4 minutes of direct contact. In addition to the observed growth during the first 4 minutes was decreased compared to the positive untreated control. Hence the results show that the systems and methods of the invention show high efficacy against a image of microbial pathogens from bacteria, to virus such as Newcastle disease nand SARS-CoV-2 through to fungal spores.

The aforementioned embodiments are not intended to be limiting with respect to the scope of the appended claims, which follow. The choice of decontaminant, its rate of vaporisation, the specific design of the vaporiser unit and the quantity of carrier gas is believed to be a routine matter for the person of skill in the art with knowledge of the presently described embodiments. It is contemplated by the inventors that various substitutions, alterations, and modifications may be made to the invention without departing from the spirit and scope of the invention as defined by the claims.