GB2633060A

GB2633060A - Apparatus and method for air management

Info

Publication number: GB2633060A
Application number: GB2313206.1A
Authority: GB
Inventors: Mole Alan
Original assignee: Hydroxyl Tech Ltd
Current assignee: Hydroxyl Tech Ltd
Priority date: 2023-08-30
Filing date: 2023-08-30
Publication date: 2025-03-05
Also published as: GB202313206D0; WO2025045660A1

Abstract

An air decontamination apparatus 1 comprising: a housing (10, fig. 1); a hydroxyl generator 40; an ultraviolet emitting device 50; an ozone depletion catalysing device 60 comprising a catalytic surface 61, wherein the or each ultraviolet emitting device 50 is arranged such that ultraviolet light emitted from the ultraviolet emitting device 50 is incident on the catalytic surface 61; a hydrocarbon emitting device 70, the hydrocarbon emitting device 70 being arranged to emit a hydrocarbon in a variable amount; and an air stream generator 20. In one embodiment the apparatus 1 comprises an ozone measuring device 30 and a control unit arranged to control the hydrocarbon emitting device 70 to emit a hydrocarbon in an amount determined in dependence on an amount of ozone detected by the ozone measuring device 30. In another embodiment the air stream generator 20 is in the form of a fan, wherein the diameter of the housing (10, fig. 1) is gradually reduced in a direction parallel to a central axis of the fan i.e. is conical or pyramidal. There is also an ultrasonic diffuser which can be used as the hydrocarbon emitting device 70.

Description

Apparatus and method for air management The present invention relates to an air decontamination apparatus for the decontamination of air and management of the ambient ozone concentration, in particular within an indoor space, and to a method of air decontamination and management of ambient ozone concentration. In a further aspect, the present invention relates to an ultrasonic diffuser for use in an air decontamination apparatus.

Air purity and being able to consistently remove contaminants entrained in the air is extremely important, especially in supposedly sterile or hygienic environments, such as hospitals and kitchens. It is also beneficial having decontaminated air in doctors' surgeries, and workplace environments making it more difficult for germs and disease to spread.

In addition to microbiological contaminants, chemical gases or vapours can present a serious hazard, either as a by-product of industrial processing or as a malicious attack through terrorism or chemical warfare.

Various devices and methods are known for removing contaminants from indoor air space.

One particularly efficient method employs free radicals as the active component, in particular the hydroxyl radical (OH), a highly oxidative species, which has the advantage of having no significant toxicity to higher organisms. Hydroxyl radicals destroy all types of pathogens, allergens and odours plus most airborne irritants and pollutants. The hydroxyl radical is abundant in the troposphere, principally due to the natural presence of ozone and unsaturated hydrocarbons.

However, free radicals are missing or much reduced in indoor air, and known methods address this shortfall, resulting in similar concentrations of hydroxyl radical indoors as outdoors. Such methods comprise: a) directing an air stream to be decontaminated through a non-thermal plasma filter to generate free radicals, which neutralise contaminants in the air stream; b) breaking down ozone (a by-product of the free radical generation process) in the air stream output from the non-thermal plasma filter and increasing the concentration of said free radicals; and c) introducing a carbon-carbon double bond hydrocarbon into the air stream to preferentially react with any residual ozone, thereby breaking down the residual ozone and at the same time creating a hydroxyl radical cascade.

One such method is described in WO 2006/003382 Al.

The free radical generation process generated ozone as a by-product. Ozone is a powerful oxidant and under normal circumstances will continue to react in the air long after it has been generated. This creates a safety risk for an air decontamination apparatus operated by and in the general vicinity of people. Thus, for safety reasons, the level of free radicals generated by such methods and apparatus is typically limited to ensure that any ozone produced as a by-product of the free radical generation process does not exceed a target safe ambient concentration. As a result, the decontamination capacity of the apparatus is limited.

The present invention seeks to provide an improved air decontamination apparatus and method for decontaminating air.

According to a first aspect of the present invention, there is provided an air decontamination apparatus, the apparatus comprising: a housing having an air inlet, an air outlet, an air flow passage between the air inlet and air outlet; an ozone measuring device arranged to detect a concentration of ozone at or near the air inlet; a hydroxyl generator located downstream of the ozone measuring device; an ultraviolet emitting device located downstream of the hydroxyl generator; an ozone depletion catalysing device comprising a catalytic surface, wherein the or each ultraviolet emitting device is arranged such that ultraviolet light emitted from the ultraviolet emitting device is incident on the catalytic surface; a hydrocarbon emitting device downstream of the ozone depletion catalysing device, the hydrocarbon emitting device being arranged to emit a hydrocarbon in a variable amount; and an air stream generator arranged to generate and direct an air stream from the air inlet to the air outlet, through or across the hydroxyl generator, ultraviolet emitting device, ozone depletion catalysing device and hydrocarbon emitting device, wherein the apparatus further comprises a control unit arranged to control the hydrocarbon emitting device to emit a hydrocarbon in an amount determined in dependence on an amount of ozone detected by the ozone measuring device.

With the arrangement of the present invention, the hydrocarbon output of the air decontamination apparatus is dynamically linked to the ambient ozone concentration, said concentration arising from existing ambient ozone and ozone output by the apparatus itself. Accordingly, hydrocarbon can be emitted in an amount sufficient to break down ozone within the ambient air to safe levels. The concentration of hydroxyl radicals generated by the hydroxyl generator can therefore be maximised, irrespective of preexisting and varying ambient ozone concentrations. Excess ozone generated as a byproduct of the hydroxyl generation can be broken down by controlling the hydrocarbon emitting device to emit the required amount of hydrocarbon.

Additionally, the apparatus can be used to decrease or increase the ambient ozone concentration to any target concentration, irrespective of pre-existing, naturally varying ambient, and ozone concentrations consequential of the apparatus itself.

Further, earlier decontamination devices were hitherto unable to automatically adjust outputs downwards in small spaces, leading to a potentially poor qualitative user experience in such cases. This present invention also allows the apparatus to dynamically reduce outputs in small indoor spaces, maintaining a high-quality user experience and reducing indoor space constraints.

Preferably, the ozone measuring device is located downstream of and adjacent to the air inlet, such that the ozone concentration of ambient air entering the apparatus through the air inlet is reliably measured.

The ozone measuring device is preferably capable of measuring low ambient ozone concentrations with high resolution. Preferably, the ozone measuring device has a resolution of 100 parts per billion (ppb) or less, more preferably 10 ppb or less, and most preferably 1 ppb or less. In particularly preferred embodiments, the ozone measuring device has a resolution of approximately 1 ppb. Preferably, the ozone measuring device is capable of detecting ozone at a concentration of 10 parts per million (ppm) or less, more preferably 5 ppm or less, and most preferably 1 ppm or less. In particularly preferred embodiments, the ozone measuring device has a detection range of 0 to 2 ppm.

The hydroxyl generator may be an ozone-producing non-thermal plasma cell.

Alternatively, the hydroxyl generator may be an ultraviolet light source arranged to emit ultraviolet light having a wavelength of less than 240 nm, preferably having a wavelength in the range 181 to 185 nm. Ultraviolet light at such wavelengths generates ozone by photolysis of oxygen, simultaneously generating hydroxyl radicals as a by-product.

However, any means suitable for generating hydroxyl radicals with the air stream may be used.

Preferably, the ultraviolet emitting device is arranged to emit ultraviolet light having a wavelength greater than 240 nm, more preferably having a wavelength of 254 nm.

Ultraviolet radiation of such wavelengths acts to break down ozone by photolysis.

Preferably, the ultraviolet emitting device comprises one or more charged-couple device (CCD) ultraviolet light sources. Such light sources do not require periodic replacement reduce energy costs and are more controllable than traditional ultraviolet light sources, which have been found to rapidly degrade with use in such apparatus and cannot be switched on and off to control ozone output, without causing failure. In contrast, it has been found that the use of CCD ultraviolet light sources permits periodic activation of the light source for controlling ozone output, without performance issues.

Where the hydroxyl generator comprises an ultraviolet light source (e.g. an ultraviolet light source of wavelength less than 240 nm, preferably 181 to 185 nm), the ultraviolet emitting device and the ultraviolet light source of the hydroxyl generator may be coincident with each other.

Preferably, the hydrocarbon emitting device comprises a replaceable and/or rechargeable hydrocarbon reservoir.

The catalytic surface of the ozone depletion catalysing device may be provided on an outer surface of the hydrocarbon reservoir. Accordingly, where the hydrocarbon reservoir is replaceable, replacement of the hydrocarbon reservoir allows simultaneous replacement of the catalytic surface. Such catalytic surfaces typically have a short (-12 month) life span and thus this arrangement allows for simple, low cost, periodic replacement of the catalytic surface at the same time as replacing the hydrocarbon reservoir.

In one embodiment, the catalytic surface is provided as a label or other covering of the hydrocarbon reservoir. For example, the catalytic surface may be provided as a background (e.g. a white background) of the label on the replaceable hydrocarbon reservoir.

Preferably, the ozone depletion catalysing device comprises a substantially cylindrical outer surface, where the catalytic surface defines at least a portion of the substantially cylindrical outer surface, and wherein the ultraviolet emitting device comprises an array of ultraviolet light sources arranged about the substantially cylindrical outer surface and spaced apart therefrom. In preferred embodiments, the ultraviolet emitting device comprises an array of at least four, more preferably eight, ultraviolet light sources. The array of ultraviolet light sources is preferably in an annular arrangement surrounding the outer surface of the ozone depletion catalysing device. Preferably, the catalytic surface is provided around the entire circumference of the ozone depletion catalysing device, to maximise the available area of the catalytic surface for the depletion of ozone.

Preferably, the air stream generator is in the form of a fan, and a diameter of the housing is gradually reduced in a direction parallel to a central axis of the fan. The central axis of the fan is to be understood as a rotational axis of the fan about which the fan blades rotate, in use. The housing may be symmetrical about the central axis of the fan. The central axis of the housing may be coincident with the central axis of the fan. In preferred embodiments the housing is conical or pyramidal, wherein the fan is located at the base of the housing (that is, the at the widest part of the conical or pyramidal housing). The air outlet of the air flow passage is preferably located at the position of smallest diameter of the housing (e.g. at the tip of the conical or pyramidal housing). The air outlet is preferably positioned on the central axis of the housing and/or central axis of the fan.

In such embodiments, the fan, being at 90 degrees to the airflow and of annular shape, creates a pattern of airflow with a waveform, the highest speed of each blade of the fan being a tip of the fan blade, which creates the highest airflow. Similarly, a base of each blade, joined to a boss of the fan, with the lowest speed creates the slowest airflow.

Accordingly, the pattern of airflow across the totality of the apparatus takes the form of a section of sine wave, wherein the highest air flow is generated at a location adjacent the housing and the slowest air flow is generated at the centre of the air flow path defined by the housing. Accordingly, the ozone depletion catalysing device (in particular, the catalytic surface thereof) and the ultraviolet emitting device may be located within a central region of the housing, in proximity to the central axis of the housing where the slowest air flow is generated. This creates the dwell time necessary for the most efficient photocatalytic oxidation to occur, with concomitant benefits in the creation of hydroxyl radicals by the creation and conversion of ozone in the presence of the catalytic surface.

The housing may comprise a plurality of apertures located downstream of the fan and upstream of the air outlet. The high-speed air movement at the tip of the fan blades pushing air through the apertures creates a dilution effect in a ring concentric to the central axis of the housing, wherein the concentration of ozone within the air stream is reduced by the action of the ultraviolet emitting device and ozone depletion catalysing device depleting ozone within the remaining air stream. Accordingly, the totality of ozone produced when measured at the outlet is below any internationally recognised safety guidelines.

Therefore, by increasing the airflow, it is possible to proportionally increase the mass of ozone produced by the air decontamination device, without emitting a totality of ozone at the outlet which would breach such guidelines. This allows an increased volume of airspace to be treated. The overall concentration of ozone within the ambient air is maintained at target levels by emitting an amount of hydrocarbon in response to the concentration of ozone detected by the ozone measuring device.

The air decontamination apparatus may further comprise an inner shield, located within an outer cover of the housing in which the apertures are formed, the inner shield being arranged to permit the passage of air from within the housing to the external environment via the apertures formed in the outer cover of the housing, and to shield the catalytic surface of the ozone depletion catalysing device and the ultraviolet emitting device from incoming radiation entering the housing through the apertures formed in its outer cover.

Preferably, the hydrocarbon emitting device is an ultrasonic diffuser. The ultrasonic diffuser may be arranged to activate at timed intervals so as to control the amount of hydrocarbon emitted by the hydrocarbon emitting device, and preferably the control unit is arranged to control the frequency and/or the duration of the timed intervals in dependence on the amount of ozone detected by the ozone measuring device, so as to control the amount of hydrocarbon emitted by the hydrocarbon emitting device.

The ultrasonic diffuser may comprise a reservoir for holding a hydrocarbon, an ultrasonic vibrating element, and a porous interface member arranged, in use, to be in fluid communication with liquid held within the reservoir, wherein the porous interface member is positioned in relation to the ultrasonic vibration element such that vibration of the ultrasonic vibration element causes diffusion of liquid contained within the porous interface member. With this arrangement, it has been found that the use of the porous interface member provides a particularly accurate and reliable dosing rate of the hydrocarbon by the ultrasonic mechanism, thus ensuring that hydrocarbon can be accurately and reliably emitted in a desired amount, in response to the ozone concentration of the ambient air entering the air flow passage, as detected by the ozone measuring device. The ultrasonic vibrating element is preferably an ultrasonic plate.

The porous interface member may be a sponge, foam pad, microfiber cloth, sintered porous plastic (e.g. sintered polypropylene), or similar porous member. The interface member may be formed of polyethylene foam, for example. The interface member preferably comprises a foam material having a pores per inch (PPI) value of 10 to PPI, more preferably 45 to 100 PPI, more preferably 60 to 100 PPI, more preferably 75 to 100 PPI, and most preferably 80 to 100 PPI. A smaller cell and tighter cell structure is preferred to ensure controlled transfer of liquid from the reservoir to the ultrasonic vibration element. It has been found that a PPI value of 80 to 100 PPI is particularly advantageous in this regard.

In some embodiments, the ultrasonic diffuser may comprise a wick arranged to extend into the hydrocarbon reservoir, so as to be immersed in liquid contained in the reservoir, in use, and the porous interface member is interposed between the wick and the ultrasonic vibration element.

The porous interface member acts as a shock absorber and interface to the between the liquid held within the reservoir and the ultrasonic vibrating element. Where a wick is provided, as is preferred, the porous interface member acts as an interface between the wick and the ultrasonic vibration element. The mechanical effect of ultrasonic vibration to a tip of the wick is reduced, allowing liquid to be successfully transferred to from the wick to the ultrasonic vibrating element (preferably an ultrasonic plate) with the necessary degree of accuracy to ensure hydrocarbon is emitted in the desired amount.

Preferably, the ultrasonic diffuser comprises a casing arranged to hold the ultrasonic vibrating element and porous interface member, the casing being arrange to releasably engage with the reservoir so as to engage the porous interface member with the wick, such that, in use, the porous interface member is in fluid communication with liquid held within the reservoir.

In a second aspect of the present invention there is provided a method of decontaminating air, the method comprising steps of a) detecting an ozone concentration in an air stream to be decontaminated; b) directing the air stream through a hydroxyl generator so that free radicals are produced by which contaminants in the air stream are neutralised; c) subjecting the air stream downstream of the hydroxyl generator to ultraviolet radiation in the presence of an ozone depletion catalyst, so as to break down ozone in the air stream; and d) introducing a hydrocarbon into the air stream to preferentially react with residual ozone in the air stream, wherein the hydrocarbon is introduced in an amount dependent on the detected ozone concentration in the air stream.

The method is preferably performed using a apparatus in accordance with the first aspect of the present invention.

In a third aspect of the present invention, there is provided an ultrasonic diffuser comprising a reservoir for holding a hydrocarbon, an ultrasonic vibrating element, and a porous interface member arranged, in use, to be in fluid communication with liquid held within the reservoir, wherein the porous interface member is positioned in relation to the ultrasonic vibration element such that vibration of the ultrasonic vibration element causes diffusion of liquid contained within the porous interface member. With this arrangement, it has been found that the use of the porous interface member provides a particularly accurate and reliable dosing rate of the hydrocarbon by the ultrasonic mechanism, thus ensuring that hydrocarbon can be accurately and reliably emitted in a desired amount.

The porous interface member may be a sponge, foam pad, microfiber cloth, sintered porous plastic (e.g. sintered polypropylene) or similar porous member. The interface member may be formed of polyethylene foam, for example. The interface member preferably comprises a foam material having a pores per inch (PPI) value of 10 to 100 PPI, more preferably 45 to 100 PPI, more preferably 60 to 100 PPI, more preferably 75 to 100 PPI, and most preferably 80 to 100 PPI. A smaller cell and tighter cell structure is preferred to ensure controlled transfer of liquid from the reservoir to the ultrasonic vibration element. It has been found that a PPI value of 80 to 100 PPI is particularly advantageous in this regard.

The ultrasonic diffuser may be arranged to activate at timed intervals so as to control the amount of hydrocarbon emitted by the ultrasonic diffuser. The ultrasonic diffuser may be arranged to control the frequency and duration of the timed intervals so as to control the amount of hydrocarbon emitted by the ultrasonic diffuser. Such fine control of hydrocarbon emission rates has hitherto been lacking and is achieved in the present invention by means of the provision of a porous interface member.

The ultrasonic diffuser may comprise a wick arranged to extend into the hydrocarbon reservoir, so as to be immersed in liquid contained in the reservoir, in use, and the porous interface member is interposed between the wick and the ultrasonic vibration element.

In fourth aspect of the present invention, there is provided an air decontamination apparatus comprising a housing having an air inlet, an air outlet, an air flow passage between the air inlet and air outlet; a hydroxyl generator located downstream of the air inlet; an ultraviolet emitting device located downstream of the hydroxyl generator; an ozone depletion catalysing device comprising a catalytic surface, wherein the or each ultraviolet emitting device is arranged such that ultraviolet light emitted from the ultraviolet emitting device is incident on the catalytic surface; an ultrasonic diffuser according to the third aspect of the present invention, the ultrasonic diffuser being located downstream of the ozone depletion catalysing device, the ultrasonic diffuser being arranged to emit a hydrocarbon in a variable amount; and an air stream generator arranged to generate and direct an air stream from the air inlet to the air outlet, through or across the hydroxyl generator, ultraviolet emitting device, ozone depletion catalysing device and ultrasonic diffuser, wherein the apparatus further comprises a control unit arranged to control an amount of hydrocarbon emitted by the ultrasonic diffuser.

In a fifth aspect of the present invention, there is provided an air decontamination apparatus, the apparatus comprising: a housing having an air inlet, an air outlet, an air flow passage between the air inlet and air outlet, a hydroxyl generator located downstream of the air inlet; an ultraviolet emitting device located downstream of the hydroxyl generator; an ozone depletion catalysing device comprising a catalytic surface, wherein the or each ultraviolet emitting device is arranged such that ultraviolet light emitted from the ultraviolet emitting device is incident on the catalytic surface; a hydrocarbon emitting device downstream of the ozone depletion catalysing device, the hydrocarbon emitting device being arranged to emit a hydrocarbon in a controlled, variable amount; and an air stream generator arranged to generate and direct an air stream from the air inlet to the air outlet, through or across the hydroxyl generator, ultraviolet emitting device, ozone depletion catalysing device and hydrocarbon emitting device, wherein the air stream generator is in the form of a fan, and a diameter of the housing is gradually reduced in a direction parallel to a central axis of the fan.

The central axis of the fan is to be understood as a rotational axis of the fan about which the fan blades rotate, in use. The housing may be symmetrical about the central axis of the fan. The central axis of the housing may be coincident with the central axis of the fan. In preferred embodiments the housing is conical or pyramidal, wherein the fan is located at the base of the housing (that is, the at the widest part of the conical or pyramidal housing). The air outlet of the air flow passage is preferably located at the position of smallest diameter of the housing (e.g. at the tip of the conical or pyramidal housing). The air outlet is preferably positioned on the central axis of the housing and/or central axis of the fan.

In a final aspect of the present invention, there is provided a replaceable hydrocarbon reservoir for use in an air decontamination apparatus, wherein the replaceable hydrocarbon reservoir comprises a covering on an outer surface, the covering comprising an ozone depletion catalyst. The ozone depletion catalyst may be any catalyst suitable for catalysing the depletion of ozone by ultraviolet radiation. The ozone depletion catalyst may be, for example, one or more of titanium, lead and manganese oxides.

The covering may be a label provided on the outer surface of the hydrocarbon reservoir. The ozone depletion catalyst may form a white background of a label of the hydrocarbon reservoir.

Non-limiting embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view of an air decontamination apparatus in accordance with the present invention; Figure 2 is a perspective view of the air decontamination apparatus of Figure 1, wherein a portion of an outer cover is cutaway to show the internal components of the apparatus; Figure 3 is an exploded view of the air decontamination apparatus of Figure 1; Figure 4 is a cross-sectional view of a hydrocarbon emitting device for use with the air decontamination apparatus of Figure 1; Figure 5 is an exploded view of the hydrocarbon emitting device of Figure 4; Figure 6 is a flow chart illustrating a method of decontaminating air in accordance with the present invention.

With reference to Figures 1 to 3, there is shown an air decontamination apparatus 1 in accordance with the present invention. The apparatus 1 provides a means for decontaminating air, particularly in an indoor space, as well as managing the ambient ozone concentration within said space.

The apparatus 1 comprises a housing 10 having an air flow passage 12, an air inlet 14 to the flow passage 12, an air outlet 16 exiting from the passage 12. As shown most clearly in Figure 3, the housing comprises an internal compartment 11 adjacent to the flow passage 12 for locating electrical components of the apparatus 1.

Located in the passage 12 are an air stream generator 20, an ozone measuring device 30, a hydroxyl generator 40, an ultraviolet light emitting device 50, an ozone depletion catalysing device 60 and a hydrocarbon emitting device 70.

The air stream generator 20 is provided adjacent the air inlet 14 of the passage 12.

The air stream generator 20, in this embodiment, is an electric fan 20 powered by mains electricity or battery packs (not shown) provided in the compartment 11. As a safety measure, a grill 13 is provided across the air inlet 14 to prevent accidental access to the fan 20 while in operation.

The ozone measuring device 30 is positioned immediately downstream of the fan 20. However, it will be appreciated that the ozone measuring device 30 may be located in any suitable location upstream of the hydroxyl generator 40, such that an ozone concentration within air entering the housing 10 can be measured prior to generation of hydroxyl radicals (and concurrent generation of ozone). The ozone measuring device 30 may be located immediately upstream or downstream of the air inlet 14.

The ozone measuring device 30 is a high sensitivity, low concentration ozone measuring device capable of detecting ozone at a concentration of 0 to 2 ppm at a resolution of 1ppb. An example ozone measuring device is the Ozone Gas Sensor model no. ZE25A-03, supplied by Zhengzhou \Mnsen Electronics Technology Co Ltd. The hydroxyl generator 40 is positioned immediately downstream of the ozone measuring device 30. Accordingly, the ozone concentration in the air stream is measured prior to the generation of hydroxyl radicals and is representative of the ambient ozone concentration.

The hydroxyl generator 40 may be any generator capable of generating hydroxyl free radicals within the air stream. In this embodiment, the hydroxyl generator 40 is a non-thermal plasma cell or filter. The non-thermal plasma cell comprises a cathode and an anode, between which is sandwiched a dielectric. The cathode and anode are powered by a power supply unit (not shown) housed in the compartment 11 of the housing.

The cathode and anode comprise reticulated (three dimensionally porous) conductive elements, in this case being aluminium and carbon composite. However, any rigid reticulated conductive or semi-conductive material could be used. The dielectric is activated alumina pellets, nominally 3 to 4 millimetres in diameter. However, again, the dielectric could be any suitable material to suit varying applications and specific requirements. The dielectric material may be coated with a catalytic material.

The non-thermal plasma cell utilises the characteristics of a non-thermal plasma to 'plasmalise' the constituent parts of the air within the dielectric core. In general terms, the outer ring electrons in the atomic structure of the elements comprising air (principally oxygen and nitrogen) are 'excited' by the intense electronic field generated by the non-thermal plasma, typically being 10Kv at 20KHz. The energised electrons release energy through collisions. However, little or no heat is emitted due to the insubstantial mass of the electrons and the consequent lack of ionisation that occurs. The released energy is sufficient to generated free radicals within the air stream, such as 0-and -OH. The free radicals are powerful oxidants, and will oxidise hydrocarbons, organic gases, and particles typically 2.5 microns and below, such as bacteria, viruses, spores, yeast moulds and odours. Only the most inert elements or compounds will generally resist oxidation.

It will be appreciated that alternative hydroxyl generators may alternatively or additionally be used. For example, the apparatus 1 may alternatively or additionally comprise an ultraviolet ozone -generating light source arranged to emit ultraviolet radiation at a wavelength of 240 nm or less, and preferably in the range 181 to 185 nm. Ultraviolet radiation at a wavelength less than 240 nm, particularly in the range 181 to 185 nm, generates ozone via pyrolysis of oxygen. Hydroxyl free radicals are generated as a by-product.

The UV radiation emitting device 50 includes one or more ultraviolet light sources 51 typically emitting at 254nm. In the illustrated embodiment, eight UV light sources 51 are arranged in an annular array surrounding and spaced apart from a catalytic surface 61 of the ozone depletion catalysing device 60. The UV light sources 51 are disposed in the flow passage 12, downstream of the hydroxyl generator 40. The UV light sources 51 are arranged such that the UV light emissions are incident on the catalytic surface 61 of the replaceable ozone catalysing device 60.

Alternatively, some types of UV light sources can be powered by including means of placing them within microwaves of a certain wavelength, such as a magnetron, thus removing the need for a separate hard wired power supply for the UV radiation emitting device 50. Where the hydroxyl generator comprises a UV ozone-generating light source, such a light source may similarly be powered by the same means.

The ozone depletion catalysing device 60 is located adjacent the UV radiation emitting device 50 located in the flow passage 12. That is, the ozone depletion catalysing device 60 and the UV radiation emitting device 50 are located within the flow passage such that radiation emitted by the UV radiation emitting device 50 is incident upon the catalytic surface 61 of the ozone depletion catalysing device 60. Accordingly, the breakdown of ozone effected by the UV radiation emitting device 50 is catalysed by the catalytic surface 61. The catalytic surface includes a coating of ozone-catalysing material, such as one or more of titanium, lead and manganese oxides.

At least the catalytic surface 61 of the ozone depletion catalysing device 60 is replaceable. This may be achieved by any appropriate means, such as a replaceable cartridge comprising the catalytic surface 61.

In the illustrated embodiment, the ozone depletion catalysing device 60 is provided on the surface of a reservoir 71 of the hydrocarbon emitting device 70. In preferred embodiments, the ozone depletion catalysing device 60 is in the form of a label or other covering of the hydrocarbon reservoir 71. The catalytic surface 61 can therefore be replaced periodically at the same time as the hydrocarbon reservoir 71, ensuring that the performance of the depletion of ozone within the flow passage 12 is maintained at an optimum level. At the same time, the apparatus 1 only comprises one replaceable component, improving ease of use. Any other suitable means of providing a replaceable surface coated with ozone catalysing material can be used.

With the arrangement of the present embodiment, the ozone depletion catalysing device 60 comprises a substantially cylindrical outer surface, being the cylindrical outer surface of the hydrocarbon reservoir 71. The catalytic surface 61 defines at least a part of the cylindrical outer surface the ozone depletion catalysing device 60 / hydrocarbon reservoir 71. Preferably, the catalytic surface 61 is provided around the entire circumference of the cylindrical outer surface the ozone depletion catalysing device 60 / hydrocarbon reservoir 71.

The ultraviolet emitting device 50 comprises eight UV light sources 51 are arranged in an annular array surrounding and spaced apart from a catalytic surface 61 of the ozone depletion catalysing device 60. This arrangement maximises the available area of the catalytic surface 61 available for ozone depletion, whilst also providing a convenient arrangement allowing easy removal and replacement of the ozone depletion catalysing device 60 as a component of the replaceable hydrocarbon reservoir 71.

The hydrocarbon emitting device 70 is located in passage 12 downstream from the ozone depletion catalysing device 60. The hydrocarbon emitting device 70 of the present embodiment will now be described with reference to Figures 4 and 5.

In the present embodiment, as discussed above, the hydrocarbon emitting device 70 includes a replaceable hydrocarbon reservoir 71 located adjacent to the UV radiation emitting device 50. However, it will be appreciated that in alternative embodiments, the hydrocarbon reservoir 71 may be a rechargeable hydrocarbon reservoir fixed within the housing 10 adjacent to the UV radiation emitting device 50, arranged to be refilled with hydrocarbon when required.

The hydrocarbon emitting device 70 is an ultrasonic diffuser for diffusing the liquid hydrocarbon held in the reservoir 71. The hydrocarbon emitting device 70 provides intermittent metered hydrocarbon releases at timed intervals, and by varying those intervals and the duration thereof the emissions can be increased or decreased.

The reservoir 71 contains a liquid hydrocarbon, for example an olefin such as a terpene and, more specifically, but not restricted to, linalool.

An outlet 72 of the hydrocarbon emitting device 70 is located at or in the vicinity of the centre of the passage 12 and downstream of the ozone catalysing device 60 and ultraviolet emitting device 50. The outlet 72 of the hydrocarbon emitting device 70 is adjacent the flow passage outlet 16 and is arranged to direct hydrocarbon emissions out of the passage 12 into the surrounding atmosphere.

In the present embodiment, the reservoir 71 holds a wick 73 topped with a porous interface member 74 in the form of a sponge or similar absorbent pad interposed between the wick 73 and a vibrating element (plate) 75 of the ultrasonic diffuser. Suitable ultrasonic vibrating elements are widely available and will be known to the skilled person. With the present invention, it has been found that the use of the porous interface member 74 provides a particularly accurate and reliable dosing rate of the hydrocarbon by the ultrasonic mechanism, thus ensuring that hydrocarbon can be accurately and reliably emitted in a desired amount, in response to the ozone concentration of the ambient air entering the air flow passage 12, as detected by the ozone measuring device 30.

The wick 73 is formed of a high density fibre and the porous interface member 74 is formed of a different, porous material, preferably a foam pad or sponge.

Whilst the above arrangement has been found to be particularly effective, other suitable means for accurately supplying volatilised hydrocarbon to the outlet 72 of the hydrocarbon emitting device 70 may be used.

A cap 76 engages with a neck of the reservoir 71 by means of a screw-thread mechanism, with a seal 78 interposed between the cap 76 and the neck of the reservoir 71 so as to ensure an airtight fit. The cap 76 holds the wick 73 such that the wick 73 extends into the reservoir 71, preferably to the bottom of the reservoir 71. The ultrasonic vibrating element 75 is held by a casing 77 comprising an outer part 77a and an inner part 77b, the inner part 77b being arranged to engage with the cap 76 so as to locate the vibrating element 75 on the reservoir. The porous interface member 74 is also held within the casing 77. The hydrocarbon emitting device 70 is arranged such that, when the casing 77 is located on the reservoir 71, the porous interface member 74 engages with the wick 73 so as to be in fluid communication with liquid held within the reservoir 71. Vibration of the vibrating element 75 thus causes diffusion of liquid held within the reservoir 71 through the outlet 72 and into the air flow path 12 of the housing 10.

Each of the ozone measuring device 30, the hydroxyl generator 40, the UV radiation emitting device 50, the ozone catalysing device 60 and the hydrocarbon emitting device 70 can be powered by power supply units (not shown) provided in compartment 11.

The air decontamination apparatus 1 can be solely powered by mains electricity, solely powered by battery packs, which may be rechargeable, or may selectively utilise both power sources. The compartment 11 also houses a control unit (e.g. in the form of a PCB), arranged to receive a signal signals from the ozone measuring device 30 and to control the operation of at least the hydrocarbon emitting device 70 in response to the ambient ozone concentration detected by the ozone measuring device 30, so as to emit a desired amount of hydrocarbon in dependence on the ambient ozone concentration. The control unit therefore dynamically links the ozone measuring device 30 to the hydrocarbon emitting device 70 such that the hydrocarbon emitting device 70 is controlled continuously to emit the necessary amount of hydrocarbon so as to maintain ambient ozone at a target concentration.

To optimise air decontamination performance in the context of a particular application or circumstance, the air that enters the apparatus may be split into various internal sub channels, which may in turn be re-combined, so as to control the proportions of the input air that pass by any combination of the hydroxyl generator, UV radiation emitting device and the ozone catalysing device.

Operation of the air decontamination apparatus 1 according to the present invention will now be described, with further reference to Figure 6, which illustrates an embodiment of a method of decontaminating air in accordance with an aspect of the present invention. The air decontamination apparatus 1 is intended to decontaminate air and manage ozone concentration within a building, room, chamber, enclosure, trunking, pipe, channel or other enclosed or substantially enclosed space. In use, the air decontamination apparatus 1 is positioned within the space to be decontaminated.

The apparatus is energised, and the fan 20 generates a stream of ambient air along the air flow passage 12 defined by the housing 10.

The input ozone concentration in the input air is measured by the ozone measuring device 30.

The air stream passes initially past the hydroxyl generator 40 (which may be a non-thermal plasma cell and / or a UV light source arranged to emit ultraviolet radiation at a wavelength of 240 nm or less, and preferably 181 to 185 nm). The hydroxyl generator 40 generates hydroxyl radicals within the air stream in the presence of humidity and/or residual hydrocarbon. Ozone is generated as a by-product. The hydroxyl free radicals are powerful oxidants, and will oxidise hydrocarbons, organic gases, and particles typically 2.5 picometres and below, such as bacteria, viruses, spores, yeast moulds and odours. Only the most inert elements or compounds will generally resist oxidation.

The hydroxyl generator 40 produces ozone as one of the by-products. This is entrained in the airstream downstream of the hydroxyl generator 40. The half-life of ozone is dependent on atmospheric conditions and, itself being a powerful oxidant, under normal circumstances will continue to react in the air long after it has exited the air decontamination apparatus 1. This is unacceptable for an apparatus operated by and in the general vicinity of people.

The airstream therefore passes to the ultraviolet radiation omitting device 50 and ozone depletion catalysing device 60, which are downstream of the hydroxyl generator 40. Ultraviolet radiation omitted by the ultraviolet radiation omitting device 50 (typically at 253.4 nm wavelength) acts to break down ozone entrained in the airstream. The catalytic service 61 of the ozone depletion catalysing device 60 acts to catalyse this breakdown.

The photo-oxidative depletion of ozone increases the free radical level, and particularly the level of hydroxyl radicals within the airstream. These free radicals also vigorously oxide contaminants remaining within the airstream.

It is not possible to destroy all of the ozone entrained in the airstream using the UV radiation emitting device 50 and ozone depletion catalysing device 60. Accordingly, the hydrocarbon emitting device 70 emits a hydrocarbon into the airstream in order to reduce the remaining residual ozone to acceptable levels. Ozone reacts preferentially with the hydrocarbon vapourised into the air stream.

The hydrocarbon may be any hydrocarbon suitable for depleting ozone by preferential reaction therewith, and is preferably an olefin (a hydrocarbon containing a carbon-carbon double bond in its molecular structure), such as a terpene and, more specifically, but not restricted to, linalool. Linalool is preferred, since it is naturally occurring, has no known toxicity at the concentration used, and is commonly used to 'extend' perfumes and fragrances.

The concentration of ozone at the air inlet 14, as measured, is used to continuously adjust the amount of hydrocarbon to be emitted to achieve a target ambient concentration of ozone.

The air stream is finally directed from the apparatus to the atmosphere via the air outlet 16. The hydrocarbon and ozone emitted from the apparatus rapidly spread throughout the indoor space by molecular diffusion. As the hydrocarbon and ozone preferentially react, a 'free radical cascade' is triggered. More than forty interrelated reactions occur, many of which produce a series of short half-life oxidants such as hydro peroxides, super oxides, hydro-oxy peroxides, and hydroxy peroxides. Each of these oxidants breaks down releasing yet further free radicals, which in turn promulgate the production of these oxidative species within the atmosphere of the enclosed space.

The products of these preferential reactions have zero vapour pressure, and hence condense on any remaining particles in the air stream or adjacent surfaces. As a result, decontamination of contaminants occurs throughout the indoor space.

As the air decontamination apparatus recirculates air within the space to be decontaminated, in use, it draws in ozone, hydrocarbon and free radicals with the ambient air. As such, the apparatus is largely self-cleaning.

Referring again to Figures 1 to 3, the housing 10 of the present embodiment will now be described in more detail. It will be appreciated that other arrangements of the housing 10 may be used.

The housing 10 comprises an outer cover 80 having a cap 81 defining the outlet 16 of the air flow passage 12. The cap 81 is removable from the outer cover 80, providing an opening 82 in the outer cover 80 for insertion and removal of the replaceable hydrogen reservoir 71 / ozone depletion catalysing device 60. The cap 81 comprises a plurality of apertures 83 to allow the air stream to exit the air flow passage 12 into the external atmosphere. The outer cover 80 further comprises a plurality of orifices 84 in side walls of the outer cover 80, said orifices 84 providing a flow path from the air flow passage 12 within the housing to the external atmosphere.

The outer cover 80 is generally pyramidal in form and has a diameter D that is gradually reduced in a direction parallel to a central axis Al of the fan 20, corresponding to a general direction from the air inlet 14 to the air outlet 16. The outer cover 80 is symmetrical about the central axis Al of the fan 20. The outer cover 80 may take other forms in which the diameter is gradually reduced, in particular a conical form may be used in some embodiments. The outer cover 80, having a pyramidal, conical or other symmetrical form, has a central axis A2 that is coincident with the central axis Al of the fan 20.

The fan 20, being at 90 degrees to the airflow and of annular shape, creates a pattern of airflow with a waveform, the highest speed of each blade 21 of the fan 20 being a tip 22 of the fan blade 21, which creates the highest airflow. Similarly, a base 23 of each blade 21, joined to a boss 24 of the fan, with the lowest speed creates the slowest airflow.

Accordingly, the pattern of airflow across the totality of the apparatus takes the form of a section of sine wave, wherein the highest air flow is generated at a location adjacent the outer cover 80 of the housing 10 and the slowest air flow is generated at the centre of the housing 10.

The catalytic surface 61 of the ozone depletion catalysing device 60 and the ultraviolet emitting device 50 are located towards the centre of the housing 10, and are thus positioned in a region of slowest air flow. This creates the dwell time necessary for the most efficient photocatalytic oxidation to occur, with concomitant benefits in the creation of hydroxyl radicals by the creation and conversion of ozone in the presence of the catalytic surface 61.

Simultaneously the high-speed air movement at the tip of the blades pushing air through the multiple orifices 84 in the outer cover 80 creates a dilution effect in a ring concentric to the central axis A2 of the housing 10, wherein the concentration of ozone within the air stream is reduced by the action of the ultraviolet emitting device 50 and ozone depletion catalysing device 60 depleting ozone within the remaining air stream. Accordingly, the totality of ozone produced when measured at the outlet 16 is below any internationally recognised safety guidelines. Therefore, by increasing the airflow, it is possible to proportionally increase the mass of ozone produced by the air decontamination apparatus, without emitting a totality of ozone at the outlet 16 which would breach such guidelines. This allows an increased volume of airspace to be treated. The overall concentration of ozone within the ambient air is maintained at target levels by emitting an amount of hydrocarbon in response to the concentration of ozone detected by the ozone measuring device 30.

The housing 10 further comprises an inner shield 85 located within the outer cover 80, having a shape that generally conforms to the shape of the outer cover 80. As shown most clearly in Figure 1, the inner shield 85 comprises a plurality of louvres (slats) 86. Adjacent louvres 86 overlap in a direction of the central axis A2 of the housing 10 (which coincides with the central axis Al of the fan 20) and are spaced apart in a direction perpendicular to the central axis A2 of the housing 10. Accordingly, the inner shield 85 defines a plurality of pathways for the flow of air from the airflow path 20 defined within the housing 10 to the external environment via the orifices 84 of the outer cover 80. At the same time, the inner shield 85 provides a barrier to ambient light entering the housing 10 via the orifices 84.

With reference to Figure 3, in particular, the housing 10 comprises a base 90 having an inner base 91 and an outer base 92. A gap between the inner base 91 and outer base 92 defines the compartment 11 for housing electrical components of the air decontamination apparatus 1.

The fan 20 is located within the base 90, upon which the outer cover 80 is mounted. The air inlet 14 is located within the base, such that an air stream generated by the fan 20, when activated, is drawn through the air inlet 14 and directed into the airflow passage 12 defined by the housing 10. A non-return valve (not shown) is provided within the air inlet 14, the non-return valve being arranged to permit air flow into the air flow passage 12 and to prevent air flow from the air flow passage 12 into the external environment through the air inlet 14.

The invention has been described above with reference to specific embodiments, given by way of example only. It will be appreciated that different arrangements of the system are possible, which fall within the scope of the appended claims.

Claims

Claims 1. An air decontamination apparatus, the apparatus comprising: a housing having an air inlet, an air outlet, an air flow passage between the air inlet and air outlet; an ozone measuring device arranged to detect a concentration of ozone at or near the air inlet; a hydroxyl generator located downstream of the ozone measuring device; an ultraviolet emitting device located downstream of the hydroxyl generator; an ozone depletion catalysing device comprising a catalytic surface, wherein the or each ultraviolet emitting device is arranged such that ultraviolet light emitted from the ultraviolet emitting device is incident on the catalytic surface; a hydrocarbon emitting device downstream of the ozone depletion catalysing device, the hydrocarbon emitting device being arranged to emit a hydrocarbon in a variable amount; and an air stream generator arranged to generate and direct an air stream from the air inlet to the air outlet, through or across the hydroxyl generator, ultraviolet emitting device, ozone depletion catalysing device and hydrocarbon emitting device, wherein the apparatus further comprises a control unit arranged to control the hydrocarbon emitting device to emit a hydrocarbon in an amount determined in dependence on an amount of ozone detected by the ozone measuring device.
2. An apparatus as claimed in claim 1, wherein the ozone measuring device is located downstream of and adjacent to the air inlet.
3. An apparatus as claimed in claim 1 or 2, wherein the hydroxyl generator is an ozone-producing non-thermal plasma cell, or wherein the hydroxyl generator is an ultraviolet light source arranged to emit ultraviolet light having a wavelength of less than 240 nm, preferably having a wavelength in the range 181 to 185 nm.
4. An apparatus as claimed in any preceding claim, wherein the ultraviolet emitting device is arranged to emit ultraviolet light having a wavelength greater than 240 nm, preferably having a wavelength of 254 nm.
5. An apparatus as claimed in any preceding claim, wherein the hydrocarbon emitting device comprises a replaceable and/or rechargeable hydrocarbon reservoir.
6. An apparatus as claimed in any preceding claim, wherein the catalytic surface of the ozone depletion catalysing device is provided on an outer surface of the hydrocarbon reservoir.
7. An apparatus as claimed in any preceding claim, wherein the ozone depletion catalysing device comprises a substantially cylindrical outer surface, where the catalytic surface defines at least a portion of the substantially cylindrical outer surface, and wherein the ultraviolet emitting device comprises an array of ultraviolet light sources arranged about the substantially cylindrical outer surface and spaced apart therefrom.
8. An apparatus as claimed in any preceding claim, wherein the air stream generator is in the form of a fan, and a diameter of the housing is gradually reduced in a direction parallel to a central axis of the fan.
9. An apparatus as claimed in claim 8, wherein the housing is symmetrical about the central axis of the fan and wherein a central axis of the housing is coincident with the central axis of the fan.
10. An apparatus as claimed in claim 9, wherein the housing is conical or pyramidal.
11. An apparatus as claimed in any one of claims 8 to 10, wherein the air outlet of the housing is positioned on the central axis of the fan.
12. An apparatus as claimed in any one of claims 8 to 11, wherein the housing comprises a plurality of apertures located downstream of the fan and upstream of the air outlet.
13. An apparatus as claimed in any preceding claim, wherein the hydrocarbon emitting device is an ultrasonic diffuser.
14. An apparatus as claimed in claim 13, wherein the ultrasonic diffuser is arranged to activate at timed intervals so as to control the amount of hydrocarbon emitted by the hydrocarbon emitting device, and preferably wherein the control unit is arranged to control the frequency and/or the duration of the timed intervals in dependence on the amount of ozone detected by the ozone measuring device, so as to control the amount of hydrocarbon emitted by the hydrocarbon emitting device.
15. An ultrasonic diffuser for use as a hydrocarbon emitting device of an air decontamination apparatus as claimed in any one of claims 1 to 14, wherein the ultrasonic diffuser comprises a reservoir for holding a hydrocarbon, an ultrasonic vibrating element, and a porous interface member arranged, in use, to be in fluid communication with liquid held within the reservoir, wherein the porous interface member is positioned in relation to the ultrasonic vibration element such that vibration of the ultrasonic vibration element causes diffusion of liquid contained within the porous interface member.
16. An ultrasonic diffuser as claimed in claim 15, further comprising a wick arranged to extend into the hydrocarbon reservoir, wherein the porous interface member is interposed between the wick and the ultrasonic vibration element.
17. An ultrasonic diffuser as claimed in claim 16, further comprising a casing arranged to hold the ultrasonic vibrating element and porous interface member, the casing being arranged to releasably engage with the reservoir so as to engage the porous interface member with the wick.
18. An ultrasonic diffuser as claimed in any one of claims 15 to 17, wherein the interface member is a foam pad, preferably formed of polyethylene or polypropylene.
19. An apparatus as claimed in any one of claims 1 to 14, wherein the hydrocarbon emitter is an ultrasonic diffuser as claimed in any one of claims 15 to 18.
20. A method of decontaminating air, the method comprising steps of: a) detecting an ozone concentration in an air stream to be decontaminated; b) directing the air stream through a hydroxyl generator so that free radicals are produced by which contaminants in the air stream are neutralised; c) subjecting the air stream downstream of the hydroxyl generator to ultraviolet radiation in the presence of an ozone depletion catalyst, so as to break down ozone in the air stream; and d) introducing a hydrocarbon into the air stream to preferentially react with residual ozone in the air stream, wherein the hydrocarbon is introduced in an amount dependent on the detected ozone concentration in the air stream.
21. A method as claimed in claim 20, wherein the method is performed using the apparatus of any one of claims 1 to 14 or 19.
22. An air decontamination apparatus, the apparatus comprising: a housing having an air inlet, an air outlet, an air flow passage between the air inlet and air outlet, a hydroxyl generator located downstream of the air inlet; an ultraviolet emitting device located downstream of the hydroxyl generator; an ozone depletion catalysing device comprising a catalytic surface, wherein the or each ultraviolet emitting device is arranged such that ultraviolet light emitted from the ultraviolet emitting device is incident on the catalytic surface; a hydrocarbon emitting device downstream of the ozone depletion catalysing device, the hydrocarbon emitting device being arranged to emit a hydrocarbon in a controlled, variable amount; and an air stream generator arranged to generate and direct an air stream from the air inlet to the air outlet, through or across the hydroxyl generator, ultraviolet emitting device, ozone depletion catalysing device and hydrocarbon emitting device, wherein the air stream generator is in the form of a fan, and a diameter of the housing is gradually reduced in a direction parallel to a central axis of the fan.
23. An apparatus as claimed in claim 22, wherein the housing is symmetrical about the central axis of the fan and a central axis of the housing is coincident with the central axis of the fan.
24. An apparatus as claimed in claim 23, wherein the housing is substantially conical or pyramidal.
25. An apparatus as claimed in any one of claims 22 to 24, wherein the housing comprises a plurality of apertures located downstream of the fan and upstream of the air outlet.