Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L9/00—Disinfection, sterilisation or deodorisation of air
  • A61L9/16—Disinfection, sterilisation or deodorisation of air using physical phenomena
  • A61L9/18—Radiation
  • A61L9/20—Ultraviolet radiation
  • A61L9/205—Ultraviolet radiation using a photocatalyst or photosensitiser
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61L—METHODS OR APPARATUS FOR STERILISING MATERIALS OR OBJECTS IN GENERAL; DISINFECTION, STERILISATION OR DEODORISATION OF AIR; CHEMICAL ASPECTS OF BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES; MATERIALS FOR BANDAGES, DRESSINGS, ABSORBENT PADS OR SURGICAL ARTICLES
  • A61L2/00—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor
  • A61L2/02—Methods or apparatus for disinfecting or sterilising materials or objects other than foodstuffs or contact lenses; Accessories therefor using physical phenomena
  • A61L2/08—Radiation
  • A61L2/10—Ultraviolet radiation
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F1/00—Room units for air-conditioning, e.g. separate or self-contained units or units receiving primary air from a central station
  • F24F1/0007—Indoor units, e.g. fan coil units
  • F24F1/0071—Indoor units, e.g. fan coil units with means for purifying supplied air
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
  • F24F8/00—Treatment, e.g. purification, of air supplied to human living or working spaces otherwise than by heating, cooling, humidifying or drying
  • F24F8/20—Treatment, e.g. purification, of air supplied to human living or working spaces otherwise than by heating, cooling, humidifying or drying by sterilisation
  • F24F8/22—Treatment, e.g. purification, of air supplied to human living or working spaces otherwise than by heating, cooling, humidifying or drying by sterilisation using UV light

Definitions

• the present invention generally relates to infection and microbial control methodologies and devices related thereto.
• ROS Reactive Oxidizing Species
• ROS is the term used to describe the highly activated air that results from exposure of ambient humid air to ultraviolet light.
• Light in the ultraviolet range emits photons at a frequency that when absorbed has sufficient energy to break chemical bonds.
• UV light at wavelengths of 250-255 nm is routinely used as a biocide.
• Light below about 181 nm, up to 182-187 nm is competitive with corona discharge in its ability to produce ozone.
• Ozonation and UV radiation are both being used for disinfection in community water systems.
• Ozone is currently being used to treat industrial wastewater and cooling towers.
• Hydrogen peroxide is generally known to have antimicrobial properties and has been used in aqueous solution for disinfection and microbial control.
• Vaporized aqueous solutions of hydrogen peroxide produce an aerosol of microdroplets composed of aqueous hydrogen peroxide solution.
• Various processes for "drying" vaporized hydrogen peroxide solutions produce, at best, a hydrated form of hydrogen peroxide. These hydrated hydrogen peroxide molecules are surrounded by water molecules bonded by electrostatic attraction and London Forces.
• electrostatic means the ability of the hydrogen peroxide molecules to directly interact with the environment by electrostatic means is greatly attenuated by the bonded molecular water, which effectively alters the fundamental electrostatic configuration of the encapsulated hydrogen peroxide molecule.
• the lowest concentration of vaporized hydrogen peroxide that can be achieved is generally well above the 1.0 ppm OSHA workplace safety limit, making these processes unsuitable for use in occupied areas.
• Photocatalysts that have been demonstrated for the destruction of organic pollutants in fluid include but are not limited to TiO 2 , ZnO, SnO 2 , WO 3 , CdS, ZrO 2 , SB 2 O 4 and Fe 2 O 3 .
• Titanium dioxide is chemically stable, has a suitable bandgap for UV/Visible photoactivation, and is relatively inexpensive. Therefore, photocatalytic chemistry of titanium dioxide has been extensively studied over the last thirty years for removal of organic and inorganic compounds from contaminated air and water.
• photocatalysts can generate hydroxyl radicals from adsorbed water when activated by ultraviolet light of sufficient energy, they show promise for use in the production of PHPG for release into the environment when applied in the gas phase.
• Existing applications of photocatalysis have focused on the generation of a plasma containing many different reactive chemical species.
• the majority of the chemical species in the photocatalytic plasma are reactive with hydrogen peroxide, and inhibit the production of hydrogen peroxide gas by means of reactions that destroy hydrogen peroxide.
• any organic gases that are introduced into the plasma inhibit hydrogen peroxide production both by direct reaction with hydrogen peroxide and by the reaction of their oxidized products with hydrogen peroxide.
• the photocatalytic plasma reactor itself also limits the production of PHPG for release into the environment. Because hydrogen peroxide (reduction potential 0.71 eV) has greater chemical potential than oxygen (reduction potential -0.13 eV) to be reduced as a sacrificial oxidant, it is preferentially reduced as it moves downstream in photocatalytic plasma reactors as rapidly as it is produced by the oxidation of water.
• wavelengths of light used to activate photocatalysts are also energetic enough to photolyze the peroxide bond in a hydrogen peroxide molecule and are also an inhibitor in the production of PHPG for release into the environment. Further, the practice of using wavelengths of light that produce ozone introduces yet another species into the photocatalytic plasma that destroys hydrogen peroxide.
• a method of providing microbial control and/or disinfection/remediation of an environment generally comprises (a) providing a photocatalytic cell that preferentially produces hydrogen peroxide gas; (b) generating a Purified Hydrogen Peroxide Gas (PHPG) that is substantially free of, e.g., hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces), ozone, plasma species, and/or organic species; and (c) directing the gas comprising primarily PHPG into the environment such that the PHPG acts to provide microbial control and/or disinfection/remediation in the environment, preferably both on surfaces and in the air.
• PHPG Purified Hydrogen Peroxide Gas
• the method comprises (a) exposing a metal, or metal oxide, catalyst to ultraviolet light in the presence of humid, purified ambient air under conditions so as to form Purified Hydrogen Peroxide Gas (PHPG) that is substantially free of, e.g., hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces), ozone, plasma species, and/or organic species; and (b) directing the PHPG into the environment such that the hydrogen peroxide gas acts to provide infection control and/or disinfection/remediation in the environment, preferably both on surfaces and in the air.
• PHPG Purified Hydrogen Peroxide Gas
• Another aspect of the invention relates to a diffuser devic for producing PHPG that is substantially free of, e.g., hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces), ozone, plasma species, and/or organic species.
• the diffuser device generally comprises: (a) a source of ultraviolet light; (b) a metal oxide catalyst substrate structure; and (c) an air distribution mechanism.
• Another aspect of the invention relates to methods for the control of the production of PHPG.
• the production of PHPG is controlled via selection of wavelength in the photocataylic cell so as to improve PHPG yield, through balancing feed air between fresh air containing no PHPG and recirculated air that contains a desired level of PHPG, and combinations thereof.
• Another aspect of the invention relates to the oxidation/removal of VOCs from ambient air by PHPG once it is released into the environment.
• Another aspect of the invention relates to the removal of ozone from ambient air by PHPG once it is released into the environment.
• Figure 1 is a cross-section of a particular embodiment of a diffuser device of the invention
• Figure 2 is a cut away view of a particular embodiment of a diffuser device of the invention.
• Figure 3 is a cross-section of a 360 degree pedestal-mounted embodiment of the diffuser device.
• Figure 4 is a cross-section of an airfoil-shaped embodiment of the diffuser device, e.g., intended for use inside building air ducts.
• Figure 5 is a cross-section of an embodiment of the diffuser device that may be, e.g., retrofitted to overhead fluorescent lighting fixtures.
• Figure 6 is a cross-section of a humidified embodiment of the diffuser device.
• Figure 7 is a cross-section of an embodiment of the diffuser device including a humidity sensor.
• Figure 8 is a cross-section of an embodiment of the diffuser device, e.g., for use in small areas.
• Figure 9 is a cross-section of an on-board embodiment of the diffuser device, e.g., for use inside aircraft, ground vehicle, and mass transportation air supply systems.
• Figure 10 is a frontal view of a preferred embodiment of a diffuser device of the invention
• Figure 11 is a cut away view of a preferred embodiment of a diffuser device of the invention.
• Figure 12 is a side view of a preferred embodiment of the diffuser device of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• the present invention relates generally to microbial control and/or disinfection/remediation methods and devices related thereto.
• photocatalytic processes may be utilized in the methods and devices described herein.
• the fundamental nature of a photocatalytic process is to create active intermediates in a chemical reaction by absorption of light. This occurs when a photon of the appropriate wavelength strikes the photocatalyst. The energy of the photon is imparted to a valence band electron, promoting the electron to the conduction band, thus leaving a "hole" in the valence band. In the absence of an adsorbed chemical species, the promoted electron will decay and recombine with the valence band hole.
• Recombination is prevented when the valence band hole captures an electron from an oxidizable species - preferentially molecular water - adsorbed to an active surface site on the photocatalyst.
• a reducible species adsorbed on the catalyst surface - preferentially molecular oxygen - may capture a conduction band electron.
• the photocatalyst preferentially reduces hydrogen peroxide (reduction potential 0.71 eV) instead of molecular oxygen (reduction potential -0.13 eV), and the reaction shifts to the following equilibrium which takes place within the majority of the plasma reactor volume.
• Purified Hydrogen Peroxide Gas may be produced using a photocatalytic process with a purpose-designed morphology that enables the removal of hydrogen peroxide from the PHPG reactor before it is forced to undergo subsequent reduction by the photocatalyst. Denied ready availability of adsorbed hydrogen peroxide gas, the photocatalyst is then forced to preferentially reduce oxygen, rather than hydrogen peroxide. Hydrogen peroxide gas may then generally be produced simultaneously by both the oxidation of water and the reduction of dioxygen in the photocatalytic process.
• the amount of hydrogen peroxide produced may be doubled, then removed from the system before the vast majority of it can be reduced - thereby resulting in an output of PHPG that is thousands of times greater than the incidental output of unpurified hydrogen peroxide from an equal number of active catalyst sites within a photocatalytic plasma reactor under the same conditions.
• This purpose-designed morphology also enables the production of PHPG at absolute humidities well below those at which a photocatalytic plasma reactor can effectively operate. For example, PHPG outputs greater than 0.2 ppm have been achieved at an absolute humidity of 2.5 milligrams per Liter. In the purpose-designed morphology the dominant reactions become:
• PHPG may be generated in any suitable manner known in the art, including but not limited to, any suitable process known in the art that simultaneously oxidizes water in gas form and reduces oxygen gas, including gas phase photo-catalysis, e.g., using a metal catalyst such as titanium dioxide, zirconium oxide, titanium dioxide doped with cocatalysts (such as copper, rhodium, silver, platinum, gold, etc.), or other suitable metal oxide photocatalysts.
• a metal catalyst such as titanium dioxide, zirconium oxide, titanium dioxide doped with cocatalysts (such as copper, rhodium, silver, platinum, gold, etc.), or other suitable metal oxide photocatalysts.
• PHPG may also be produced by electrolytic processes using anodes and cathodes made from any suitable metal, or constructed from metal oxide ceramics using morphology that permits immediate removal of hydrogen peroxide gas before it can be reduced.
• PHPG may be produced by high frequency excitation of gaseous water and oxygen molecules on a suitable supporting substrate using morphology that permits immediate removal of hydrogen peroxide gas before it can be reduced.
• the method generally comprises (a) generating a gas comprised of Purified Hydrogen Peroxide Gas (PHPG) that is substantially free of, e.g., hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces), ozone, plasma species, and/or organic species; and (b) directing the gas comprised of PHPG into the environment such that the PHPG acts to provide microbial control and/or disinfection/remediation in the environment, preferably both on surfaces and in the air.
• PHPG Purified Hydrogen Peroxide Gas
• Purified Hydrogen Peroixde Gas or PHPG generally means a gas form of hydrogen peroxide that is substantially free of at least hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces) and substantially free of ozone.
• the method comprises (a) exposing a metal, or metal oxide, catalyst to ultraviolet light in the presence of humid purified ambient air under conditions so as to form Purified Hydrogen Peroxide Gas (PHPG) that is substantially free of, e.g., hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces), ozone, plasma species, and/or organic species; and (b) directing the PHPG into the environment such that the PHPG acts to provide infection control and/or disinfection/remediation in the environment, preferably both on surfaces and in the air, removal of ozone from the ambient air, and removal of VOCs from the ambient air.
• PHPG Purified Hydrogen Peroxide Gas
• the ultraviolet light produces at least one wavelength in a range above about 181 nm, above about 185 nm, above about 187 run, between about 182 ran and about 254 nm, between about 187 nm and about 250 nm, between about 188 nm and about 249 nm, between about 255 nm and about 380 nm, etc.
• wavelengths between about 255 nm and 380 nm may be preferred to improve yields of PHPG.
• the diffuser device for producing Purified Hydrogen Peroxide Gas (PHPG) that is substantially free of, e.g., hydration (in the form of water in solution or water molecules bonded by covalence, van der Waals forces, or London forces), ozone, plasma species, and/or organic species.
• PHPG Purified Hydrogen Peroxide Gas
• the diffuser device generally comprises: (a) a source of ultraviolet light 4; (b) a metal or metal oxide catalyst substrate structure 3; and (c) an air distribution mechanism 5, 6, and/or 7.
• the air distribution mechanism may be a fan 5 or any other suitable mechanism for moving fluid, e.g., air, through the diffuser device.
• the selection, design, sizing, and operation of the air distribution mechanism should be such that the fluid, e.g. air, flow through the diffuser device is generally as rapid as is practical. Without intending to be limited by theory, it is believed that optimal levels of PHPG are generated for exiting the diffuser device under rapid fluid flow conditions.
• the ultraviolet light source 4 may generally produce at least one range of wavelengths sufficient to activate photocatalytic reactions of the humid ambient air, but without photolyzing oxygen so as to initiate the formation of ozone.
• the ultraviolet light produces at least one wavelength in a range above about 181 run, above about 185 ran, above about 187 ran, between about 182 nm and about 254 nm, between about 187 ran and about 250 nm, between about 188 nm and about 249 nm, between about 255 nm and about 380 nm, etc.
• wavelengths between about 255 nm and 380 nm may be preferred to improve yields of PHPG including non-hydrated hydrogen peroxide in the substantial absence of ozone.
• the terms "substantial absence of ozone” “substantially free of ozone”, etc. generally mean amounts of ozone below about 0.015 ppm, down to levels below the LOD (level of detection) for ozone. Such levels are below the generally accepted limits for human health.
• the Food and Drug Administration (FDA) requires ozone output of indoor medical devices to be no more than 0.05 ppm of ozone.
• the Occupational Safety and Health Administration (OSHA) requires that workers not be exposed to an average concentration of more than 0.10 ppm of ozone for 8 hours.
• the National Institute of Occupational Safety and Health (NIOSH) recommends an upper limit of 0.10 ppm of ozone, not to be exceeded at any time.
• EPA's National Ambient Air Quality Standard for ozone is a maximum 8 hour average outdoor concentration of 0.08 ppm.
• the diffuser devices described herein have consistently demonstrated that they do not produce ozone at levels detectable by means of a Draeger Tube.
• PHPG may, however, be used for the removal of ozone from the ambient environment by means of the following reaction:
• PHPG may be used for the removal of VOCs from the ambient environment by means of direct oxidation of VOCs by the PHPG.
• PHPG may be used for microbial control, including but not limited to, as a biocide, for indoor air treatment, as a mold and/or fungus eliminator, as a bacteria eliminator, and/or as an eliminator of viruses.
• the PHPG method may produce hydrogen peroxide gas sufficient to carry out a desired microbial control and/or disinfection/remediation process. A sufficient amount is generally known by those skilled in the art and may vary depending on the solid, liquid, or gas to be purified and the nature of a particular disinfection/remediation.
• the amount of PHPG may vary from about 0.005 ppm to about 0.10 ppm, more particularly, from about 0.02 ppm to about 0.05 ppm, in the environment to be disinfected.
• Feline Calicivirus an EPA approved surrogate for Norovirus
• MRSA Methicillin Resistant Staphylococcus Aureus
• VRE Vancomyacin Resistant Enterococcus Faecalis
• C-Diff Clostridium Difficile
• Geobacillus Stearothermophilus and Aspergillus Niger.
• Such amounts of PHPG are safe to use in occupied areas (including, but not limited to, schools, hospitals, offices, homes, and other common areas), disinfect surface contaminating microbes, kill airborne pathogens, and provide microbial control, e.g., for preventing the spread of Pandemic Flu, controlling nosocomial infections, and reducing the transmission of common illnesses.
• the amount of PHPG may vary from about 0.005 ppm to about 0.40 ppm. PHPG levels of 0.2 ppm using a feed of untreated air containing absolute humidity as low as 3.5 mg/L can consistently be achieved.
• PHPG levels from about 0.09 ppm to about 0.13 ppm using humid recirculated air can be produced in the environment to be disinfected. Such amounts have been proven effective against, e.g., the HlNl virus. Such amounts of PHPG are also safe to use in occupied areas (including, but not limited to, schools, hospitals, offices, homes, and other common areas), disinfect surface contaminating microbes, kill airborne pathogens, and provide microbial control, e.g., for preventing the spread of Pandemic Flu, controlling nosocomial infections, and reducing the transmission of common illnesses.
• the humidity of the ambient air is preferably above about 1% relative humidity (RH), above about 5% RH, above about 10% RH, etc. In certain embodiments, the humidity of the ambient air may be between about 10% and about 99% RH. In one embodiment, the method of the invention includes regulating the humidity of the ambient air within the range of about 5% to about 99% RH, or about 10 to about 99% RH.
• the metal, or metal oxide, catalyst may be selected from titanium dioxide, copper, copper oxide, zinc, zinc oxide, iron, and iron oxide or mixtures thereof, and more preferably, the catalyst is titanium dioxide. More particularly, titanium dioxide is a semiconductor, absorbing light in the near ultraviolet portion of the electromagnetic spectrum. Titanium dioxide is synthesized in two forms - anatase and rutile - which are, in actuality, different planes of the same parent crystal structure. The form taken is a function of the preparation method and the starting material used. Anatase absorbs photons at wavelengths less than 380 nm, whereas rutile absorbs photons at wavelengths less than 405 nm.
• a layer of titanium dioxide approximately 4 ⁇ m thick will absorb 100% of incident low wavelength light. Titanium dioxide is known to have approximately 9-14 x 10 14 active surface sites per square centimeter. An active surface site is a coordinatively unsaturated site on the surface which is capable of bonding with hydroxyl ions or other basic species. Its photocatalytic activity is influenced by its structure (anatase or rutile), surface area, size distribution, porosity, and the density of hydroxyl groups on its surface. Anatase is generally considered to a more active photocatalyst than rutile. It is known to adsorb dioxygen more strongly than rutile and remains photoconductive longer after flash irradiation than rutile. Anatase and rutile have band gap energies of 3.2 and 3.0 electron volts (eV), respectively.
• eV electron volts
• agents have been shown to have an influence on photocatalysis. Such agents may be added to the reaction environment to influence the photocatalysis process. As recognized by those skilled in the art, some agents enhance the process, while others degrade it. Still others act to enhance one reaction while inhibiting another.
• additive agents involve radical species in side reactions or in the formation of less reactive radicals incapable of performing the desired reaction. Yet others physically alter the photocatalyst, changing its performance.
• additive agents may be selected to optimize the formation of PHPG (optionally while minimizing or eliminating the formation of ozone, plasma species, or organic species).
• additive agents may include co-catalysts.
• Co- catalysts may be metals or coatings deposited on the surface of a catalyst to improve the efficiency of selected PHPG reactions.
• Cocatalysts may alter the physical characteristics of catalyst in two ways. First, they may provide new energy levels for conduction band electrons to occupy.
• co-catalysts may possess different absorption characteristics than the supporting photocatalyst. This may cause the order in which competing reactions take place on the co-catalyst to be different from that on the catalyst itself.
• Cocatalysts are generally most effective at surface coverages of less than five percent.
• Typical co-catalysts may be selected from platinum, silver, nickel, palladium, and many other metal compounds. Phthalocyanine has also demonstrated cocatalytic capabilities.
• a diffuser device in accordance with the invention may be of any suitable shape or size, including spherical, hemispherical, cubic, three dimensional rectangular, etc.
• the diffuser device may be configured as a sail shape, a 360 degree pedestal-mount, an airfoil-shape (e.g., intended for use inside building air ducts); an design that may be retrofitted to overhead fluorescent lighting fixtures, an design specifically configured for use in small areas (e.g., for use on-board aircraft, ground vehicles, and mass transportation air supply systems).
• Diffusers may also be configured in any number of fanciful shapes such as teddy bears, piggy banks, mock radio's, etc.
• the core of the diffuser device may be comprised of an ultraviolet light source.
• the ultraviolet light source 4 may be positioned at the center, or interior, of the diffuser device, may be of varied intensity depending on the size of the device and the application for which it is intended.
• the diffuser device may be of a general elongated wedge-shape.
• the ultraviolet source 4 e.g., may be tubular in shape may be contained within the elongated wedge-shaped, or tube shaped diffuser shell 2.
• a reflector 1 may serve to focus light in a specific direction within the interior of a device as required by its specific shape.
• the shell 2 of the diffuser device may be formed from any suitable substrate material, including ceramic, porcelain, polymer, etc.
• the polymer may be a porous or vented polymer that is both hydrophobic and resistant to degradation by ultraviolet light in the 380 nm to 182 nm range.
• a diffuser shell may be molded into any desired size and shape, and formed as any color desired.
• a phosphorescent material may be incorporated into the shell material so as to emit visible light upon absorption of UV light.
• the diffuser device also generally includes a fluid distribution mechanism.
• the fluid distribution mechanism generally serves to move fluid, such as air through the diffuser device. More particularly, the air distribution mechanism will generally direct fluid into the diffuser device, which will then diffuse out through the diffuser substrate.
• the fluid distribution mechanism will direct fluid through an intake vent 7 to a small fan (not shown) framed within an opening 5 in the diffuser device.
• the fan may also have a replaceable hydrophobic gas and/or dust filter 6 on the upstream side to prevent organic gases and/or dust from entering the diffuser device, thus ensuring that the PHPG remains substantially free of organic species.
• FIG. 3 a cross-section of a 360 degree pedestal-mounted embodiment of the diffuser device is illustrated.
• This is a variation of a diffuser device similar to that of Figures 1 and 2, e.g., that can be placed in the center of a large area.
• FIG. 4 a cross-section of an airfoil- shaped embodiment of the diffuser device, e.g., intended for use inside building air ducts is illustrated.
• the device is configured so as to provide a perpendicular vented surface to oncoming airflow at its leading edge, forcing air to flow into the device.
• the bank of light-emitting diodes and the photocatalytic sail are arrayed parallel to the trailing edge of the airfoil shape, taking advantage of the lower air pressure created by the trailing edge of the airfoil to draw PHPG from the device as it is produced.
• the diffuser device of Figure 4 may optionally be equipped with a supplementary internal fan (not shown)to facilitate greater airflow, an airflow sensor (not shown) to turn the device off when no air is flowing through the air duct, then on again when air flow resumes, or both.
• a supplementary internal fan (not shown)to facilitate greater airflow
• an airflow sensor (not shown) to turn the device off when no air is flowing through the air duct, then on again when air flow resumes, or both.
• FIG. 5 a cross-section of an embodiment of the diffuser device that can be retrofitted to overhead fluorescent lighting fixtures is illustrated. As shown, the fluorescent bulbs of the original fixture are removed, the fixture is provided with an airtight seal and wiring to power fans. Bulbs appropriate for PHPG production are then installed and the bottom of the fixture is fitted with an assembly containing intake fans and filters, a, e.g., rectangular photocatalytic sail, and a, e.g., rectangular vented diffuser.
• FIG. 6 a cross-section of a humidified embodiment of the diffuser device is illustrated. As shown, a wick is located downstream of the filter with its lower section immersed in a water tray. The tray can be refilled manually, or by automatic feed regulated by a water level sensor (not shown).
• FIG. 7 a cross-section of an embodiment of the diffuser device containing a humidity sensor is illustrated.
• the humidity sensor may be used, e.g., to turn off the device if an operating humidity above a predetermined operating parameter (e.g., 95%, 98%, 99%, etc.) is detected.
• a predetermined operating parameter e.g. 95%, 98%, 99%, etc.
• FIG. 8 a cross-section of an embodiment of the diffuser device for small areas is illustrated. This small device is designed to plug directly into a power outlet in a small room. The intake fan and filter on the edge of the device provide air to a small photocatalytic sail activated by a small array of light emitting diodes to produce PHPG.
• FIG. 9 a cross-section of an on-board embodiment of the diffuser device, e.g., for use inside aircraft, ground vehicle, mass transportation air supply systems, etc., is illustrated.
• the on-board device may be placed directly in the supply air flow and may be configured with an internal fan to offset the pressure drop that occurs as air passes through the device.
• the device may be configured so that it has the same external cross section as the internal cross section of the air flow duct for each particular application of the embodiment.
• FIG. 10 the frontal view of a preferred embodiment of a diffuser device is illustrated. This device is symmetrical in all three dimensions, and can be set into a pedestal-shaped bottom sleeve to stand upright as shown or mounted horizontally from a wall or ceiling by means of a bracket.
• FIG. 11 a cross-section of a preferred embodiment of a diffuser device is illustrated.
• This device employs an arc-shaped dust and VOC filter to provide improved filtration and to supply the intake plenum with filtered air.
• the arced filter more evenly distributes the air flow through a larger surface area, reducing pressure losses through the filter.
• the intake plenum supplies a bank of three fans that direct air perpendicularly through the arced photocatalytic sail positioned just inside the output vent. In this embodiment air flows in a direct line from the back to the front of the device. Two ultraviolet bulbs are offset out of the airflow to provide even illumination of the photocatalytic sail.
• This embodiment provides better performance, improving filtration by a factor of 7.66, improving airflow by a factor of 7.5, and doubling photon flux.
• This supplies humid air to the photocatalytic sail at a greatly improved rate (increasing PHPG production), and greatly reduces the dwell time of PHPG on the photocatalytic surface once produced, insuring that more PHPG survives to exit the system.
• Figure 12 Depicted in Figure 12 is the side view of the embodiment of the diffuser device of Figure 11.
• the interior surface of the diffuser shell may generally be used as the substrate by coating it with photocatalyst, which may include titanium dioxide doped with one or more other metals in certain embodiments.
• photocatalyst may be applied to the interior of the diffuser substrate as a paint.
• the application should generally be applied so as to prevent clogging of the pores within the diffuser substrate.
• air may be applied to the substrate, and forced through the pores of the substrate after application of the photocatalyst paint, both causing the coating to dry and keeping the pores clear by means of forced air. It may be preferred for the combination of photocatalytic coating and diffuser substrate to be opaque enough to prevent UV light from escaping the assembled diffuser device.
• the diffuser shell and the catalyst substrate are separate components, with the substrate layer situated just inside, and very close to, the interior surface of the diffuser shell.
• the diffuser device may be designed to operate over a pre-determined range of wavelengths so as to specifically improve PHPG yield, as described herein.
• the diffuser device may be humidified (see, e.g., Figure 6), or may be designed to operate at the specific humidity of operation, and operation parameters may be adjusted accordingly.
• the diffuser device may include a humidity sensor (see, e.g., Figure 7).
• the diffuser device may optionally include a control system to optimize PHPG yield based on the humidity of the operating environment, and/or to cease operation if humidity conditions are unfavorable.
• the diffuser design optimizes PHPG production by spreading the air permeable photocatalytic PHPG reactor surface thinly over a large area that is perpendicular to air flow (e.g., in certain embodiments, over a sail-like area), rather than by compacting it into a volume-optimizing morphology designed to maximize residence time within the plasma reactor.
• the exit path length for hydrogen peroxide molecules produced on the catalyst becomes diminishingly short, and their residence time within the PHPG reactor structure is reduced to a fraction of a second, preventing the vast majority of hydrogen peroxide molecules from being subsequently adsorbed onto the catalyst and reduced back into water.
• the catalyst substrate just inside the interior surface of the diffuser shell, not only is PHPG reactor surface area maximized, but the PHPG produced also passes out of the diffuser almost immediately and thus avoids photolysis from prolonged exposure to the UV light source.
• PHPG output concentrations as high as 0.40 ppm have been achieved.
• PHPG concentrations may be self-regulating due to the electrostatic attraction between PHPG molecules, which degrade to water and oxygen upon reacting with each other.
• PHPG self-regulation occurs whenever the concentration of PHPG results in intermolecular spacing that is closer in distance than the electrostatic attraction range of the PHPG molecules.
• PHPG molecules are attracted to, and degrade each other until Ae concentration drops sufficiently that the intermolecular spacing is greater than the electrostatic attraction range of the PHPG molecules.
• PHPG concentrations are maintained at levels well below the OSHA workplace safety limit of 1.0 parts per million.
• production of PHPG can be regulated by the PHPG reactor itself.
• PHPG production levels can be set at any level from 0.01 ppm up to 0.40 ppm by recirculating a small regulated fraction of treated air containing PHPG back through the PHPG reactor. When this is done, the PHPG output levels are governed by the following set of reactions.
• PHPG is preferentially reduced over oxygen and it takes only a small amount of recirculated PHPG to lower net production levels.
• a PHPG reactor that is otherwise designed for highest output can be set to a lower level simply by redirecting some of the air it has already treated back through the PHPG reactor.
• PHPG may be produced in the substantial absence of ozone, plasma species, and/or organic species, e.g., by the photocatalytic oxidation of adsorbed water molecules when activated with UV light in the ranges described herein.
• the diffuser substrate coated with photocatalyst on its interior (or diffuser shell lined on the interior with a thin sail-like air-permeable photocatalyst structure), may be placed over and around the ultraviolet lamp.
• An opening in the diffuser may serve as a frame into which the UV light's power source and structural support will fit.
• the diffuser device When assembled, the diffuser device may function as follows: (a) the fluid distribution mechanism directs air into the diffuser through an organic vapor and dust filter, creating an overpressure; (b) air moves out of the diffuser through the pores or vents in the substrate and/or diffuser shell; (c) moisture contained in the air adsorbs onto the photocatalyst; (d) when illuminated, the UV light produced by the lamp activates the photocatalyst, causing it to oxidize adsorbed water and reduce adsorbed oxygen, producing PHPG; and (e) the PHPG produced in the interior of the diffuser device then moves rapidly out of the diffuser through its pores or vents into the surrounding environment.
• PHPG may be generated by a Medium Pressure Mercury Arc (MPMA) Lamp.
• MPMA lamps emit not only ultraviolet light, but also visible light, and wavelengths in the infrared spectrum. It is important that when selecting a lamp, output in the ultraviolet spectrum should be closely examined. The ultraviolet spectral output is sometimes expressed graphically, showing the proportional output at the important ultraviolet wavelengths. The broad spectrum of the MPMA lamp is selected for its functionality.
• PHPG may be generated by Ultraviolet Light Emitting Diodes (UV LED's). UV LED's are more compact and banks of UV LED's can be arrayed in a variety of sizes and ways, enabling the production of smaller, more rugged systems.
• UV LED's Ultraviolet Light Emitting Diodes
• PHPG output may be regulated by control systems managing devices singly, or in groups.
• control systems may regulate operation by: (a) turning devices on and off; (b) regulating light intensity and/or fan speed; (c) monitoring ambient PHPG levels directly by means of automated colorimetric devices, by automated Draeger indicators, by means of flash vaporization of PHPG accumulated in an aqueous trap, by measuring the change in conductivity of a substrate sensitive to hydrogen peroxide accumulation, or by thermal means, measuring the heat evolved by the exothermic reaction between PHPG and a stable reactant to which it is electrostatically attracted; and (d) monitoring ambient PHPG levels indirectly through relative humidity.
• one embodiment of the invention was constructed as follows: (a) the device was constructed in the shape of a quarter-cylinder 20 inches in length, and with a radius of 8.5 inches; (b) the quarter cylinder was designed to fit into the 90 degree angle formed where a wall meets a ceiling, with the quarter-cylinder's straight sides fitting flush against the wall and ceiling, and the curved face of the cylinder facing out and down into the room; (c) as viewed from below, the right end of the quarter-cylinder supported a variable speed fan with a maximum output of 240 cubic feet per minute, and a high efficiency, hydrophobic, activated charcoal intake filter; (d) the left end of the quarter cylinder supported the power connection for the fan, and a fourteen inch Medium Pressure Mercury Arc (MPMA) lamp, positioned so that the lamp was centered within, and parallel to, the length of the quarter-cylinder; (e) a vented metal reflector was placed behind the MPMA lamp to reflect light toward the interior surface of the curved
• MPMA Medium Pressure Mercury Arc
• a curved sail-like photocatalyst structure was placed just inside, and parallel to, the interior surface of the curved face of the quarter-cylinder; (a) the catalyst substrate was eighteen inches long, eleven inches high, framed, and had a curvature from top to bottom with a radius of 8.25 inches; (b) was formed of fiberglass, and was coated with crystalline titanium dioxide powder; and (c) the titanium dioxide was applied to the fiberglass in five coats to ensure complete coverage of all fibers, then sintered in an oven to cause the photocatalyst crystals to bond both to each other and to the fiberglass.
• both the fan and the MPMA lamp were turned on: (a) intake air was drawn into the device through the high efficiency, hydrophobic, activated charcoal intake filter which removed by adsorption Volatile Organic hydroCarbons (VOCs), without removing moisture from the intake air; (b) the intake air was supplied to the back of the device, where the vented metal reflector redirected it evenly toward the photocatalyst structure, and the interior of the vented face of the quarter-cylinder; (c) moisture and oxygen from the intake air adsorbed onto the photocatalyst, which was activated by 255 nm to 380 nm light from the MPMA lamp; (d) the activated photocatalyst oxidized water to hydroxyl radicals, which then combined to form hydrogen peroxide, while dioxygen was simultaneously reduced on the photocatalyst to hydrogen peroxide; and (e) the Purified Hydrogen Peroxide Gas (PHPG) generated was immediately carried by the air flow off of the photocataly
• the Purified Hydrogen Peroxide Gas (PHPG) thus produced was: (a) substantially free of bonded water because it was produced by catalytic means rather than by the vaporization of aqueous solution; (b) the PHPG was substantially free of ozone because the MPMA lamp did not use any wavelengths capable of photolyzing dioxygen; (c) the PHPG was substantially free of plasma species because the morphology of the photocatalyst permitted the rapid removal of hydrogen peroxide from its surface before it could subsequently be reduced photocatalytically; (d) the PHPG was protected from Ultraviolet (UV) photolysis because it passed out through the light-impermeable, vented face of the quarter-cylinder immediately upon exiting the photocatalyst surface; and (e) the PHPG was substantially free of organic species because VOCs were adsorbed by the high efficiency, hydrophobic, activated charcoal intake filter.
• UV Ultraviolet
• the device was subjected to tests designed and implemented by two accredited laboratories to: (a) measure the output of Purified Hydrogen Peroxide Gas (PHPG); (b) confirm that the output was substantially free of ozone; (c) confirm that the output was substantially free of VOC 's; (d) measure the efficacy of PHPG against the Feline Calicivirus (an EPA-approved substitute for noroviruses), Methicillin Resistant Staphylococcus Aureous (MRSA), Vancomyacin Resistant Enterococcus Faecalis (VRE), Clostridium Difficile (C- Diff), Geobacillus Stearothermophilus, (a stable bacteria used by the insurance industry to verify successful microbial remediation), and Aspergillus Niger (a common fungus); and (e) test at a variety of ambient relative humidities including 35% to 40 % at 70 to 72 degrees Fahrenheit, 56% to 59% at 81 to 85 degrees Fahrenheit, and 98% at 78 degrees Fahr
• the PHPG measurement data also remained constant over time and indicated an upper equilibrium limit of approximately 0.08 ppm. This is also predictable due to the electrostatic attraction of PHPG molecules to each other whenever their intermolecular spacing becomes less than their mutual electrostatic attraction ranges. Under this condition excess PHPG reacts with itself to produce oxygen and water molecules. This upper limit of 0.08 ppm is also well below the OSHA workplace safety limit of 1.0 ppm and thus safe to breathe, indicating that PHPG systems can be safely and continuously used in occupied areas. [0094] All testing also indicated a complete absence of ozone in the device's output. [0095] In VOC testing, an approximate ambient concentration of 7 ppm of 2-propanol was established 2500 cubic foot room. The device was found to rapidly reduce VOC levels throughout the room.
• a comparison test indicated that the PHPG test device produces a PHPG equilibrium concentration thousands of times greater than the incidental output of unpurified hydrogen peroxide from an equal number of active catalyst sites within a photocatalytic plasma reactor under the same conditions.

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