GB2515842A

GB2515842A - Apparatus for purifying air

Info

Publication number: GB2515842A
Application number: GB1315115.4A
Authority: GB
Inventors: John R Davidson
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-05-24
Filing date: 2013-08-23
Publication date: 2015-01-07
Also published as: GB201309356D0; GB201315115D0

Abstract

An air treatment module 112 comprising a treatment chamber having an air inlet and an air outlet is described. The treatment chamber further having at least one UV radiation source 128 so that air is exposed to UV radiation. The treatment chamber also has a support structure 132 where, part of the surface of the support structure has a photo catalytic surface. The photocatalytic surface is located so that UV radiation irradiates the support structure in use. The support structure is also configured to deflect air as it passes through the treatment chamber. The photocatalyst used may be titanium dioxide and air treatment module(s) may be flitted into air purifying units.

Description

Apparatus for purifying air

Field of the Invention

The present invention relates to apparatus for purifying / sterilising air, and in particular to air purifiers that clean and sterilise air within an enclosed space (such as a room or hospital ward).

Background to the Invention

The objective of air purification is to achieve a significant reduction in both airborne particles and micro-organisms that predominate in indoor air in particular in the healthcare environment. The desired intention is to reduce both the particulate and micro-organism content to a level considered beneficial to healthcare patients and to reduce the risk of transmission of diseases within the healthcare environment. Air purification may also be expressed as Air Cleaning and Disinfection System (ACDS).

Air purifiers, for filtering air, that attempt to remove contaminants from the air, such as particles, volatile organic compounds (VOCs) and/or bioaerosols, are known. These include ceiling mounted air purifiers including a fan which draws air in through an inlet, via a filter and out of an outlet. However, air purifiers of the prior art have a number of drawbacks.

Summary of the Invention

According to a first aspect of the invention, there is provided an air treatment module comprising a treatment chamber having at least one air inlet, at least one air outlet, the treatment chamber further having at least one UV radiation source for exposing air in the treatment chamber to UV radiation, the treatment chamber further having at least one support structure, at least part of the surface of the or each at least one support structure comprising a photocatalytic surface, the or each at least one support structure being arranged such that UV radiation from said UV radiation source irradiates the or each at least one support structure in use, the or each at least one support structure being configured to deflect air as it passes through the treatment chamber.

In the present invention, the methods of achieving a reduction in airborne micro-organisms is to expose them to both a) direct UV light and b) hydroxyl radicals using the same UV light source to generate them via the catalytic effect of photocatalyst coated plates in the airstream. Particle reduction can be by optional filtration using a HEPA grade filter and in a manner that exposes the upstream side (i.e. dirty side) to the same UV light source with added benefit of destroying any remaining micro-organisms that may have escaped the previous stage and that become trapped on the filter side.

Air purifiers of the prior art that incorporated photocatalysts tended to have a photocatalyst treated mesh at or near the outlet to the device. The free radicals that are generated have a short half-life, therefore do not travel far from the photocatalyst treated surface. The preconception was that by having a photocatalyst treated mesh at or near the outlet, air would pass through and, in close proximity to the treated surface.

The inventor has realised that by providing a support structure which acts as both a support for photocatalyt and as a means to deflect the air through the treatment chamber, this allows a higher surface area of photocatalyst to be provided than in prior art purifiers that have a photocatalyst treated mesh at the outlet, without significantly increasing air flow resistance. In the prior art purifiers with a photocatalyst treated mesh that air must travel through to exit the device, a large prorportion of the mesh must be void (i.e. open), so as not to cause too much air resistance to the air which needs to exit the device. The inventor has discovered that by providing a support structure which has a photocatalytic surface and which is also configured to deflect the air, the photocatalytic support need not have as high a proportion of void space as the prior art, or indeed any void space. This increases the surface area available for photocatalyst. The support structures of the present invention can be arranged around the UV light source and therefore subject to its maximum intensity so as to maximise its effect on the photocatalyst. The air deflecting support structures increase the turbulence in the air, therefore improving exposure of airborne contaminants to both UV radiation and hydroxyl radicals. In the present invention, the depth of photocatalyst treated support structure relative to the upstream-downstream axis of the treatment chamber can be greater in the present invention than in prior art devices, since in the present invention a photocatalyst treated mesh does not fully block the outlet.

Therefore, the residence time of air in contact with hydroxyl radicals is greatly increased in the present invention because of the distance travelled through the air deflecting support structures compared with travelling through the mesh on prior art devices.

In the apparatus described herein, the UV light sources are germicidal, in that they emit UV light of a certain wavelength that kills germs / pathogens in air which circulates through the apparatus (also known as UV germicidal irradiation or UVGI). Preferably the wavelength of the UV light emitted by the UV lights will be in the range 240 to 280 nm, which is known to have germicidal effect, and will preferably be around 254 nm. Air irradiated with UV light having wavelength of around 185 nm produces ozone.

Preferably the apparatus will not generate ozone. References to UV herein refer to UVGI.

The photocatalytic surface of the or each support structure may comprise a photocatalyst coating.

Preferably the module further comprises at least one reflective surface for reflecting UV radiation from the or each at least one UV radiation source. Highly reflective surfaces on the inner surfaces of the enclosure ensure there is a minimum of shadowing and a strong, even intensity of UV radiation, which spreads both upwards to the fan chamber/air inlet, and downwards onto the surface of any filter, if present.

Preferably the treatment chamber further comprises an enclosure. The enclosure partially encloses the treatment chamber. Air to be treated passes, via the air inlet, into the treatment chamber enclosure and out of the air outlet Preferably the or each at least one UV radiation source, the or each at least one support structure, and the or each at least one reflective surface are housed within the enclosure when assembled, such that the air treatment module is a self-contained unit that can be removably installed in an air circulation apparatus.

According to a further aspect of the invention there is provided an air treatment module comprising a treatment chamber having an enclosure, at least one air inlet, at least one air outlet, the treatment chamber further having at least one UV radiation source for exposing air in the treatment chamber to UV radiation, the treatment chamber further having at least one support structure, at least pad of the surface of the at least one support structure comprising a photocatalytic surface, the or each at least one support structure being arranged such that UV radiation from said UV radiation source irradiates the or each at least one support structure in use, the module further having at least one reflective surface for reflecting UV radiation from the at least one UV radiation source, wherein the or each at least one UV radiation source, the or each at least one support structure, and the or each at least one reflective surface are housed within the enclosure when assembled, such that the air treatment module is a self-contained unit that can be removably installed in an air circulation apparatus. The construction of the self-contained unit in modular format allows it to be used in a number of ways within any air movement and air distribution system.

Preferably the or each support structure is configured to deflect air as it passes through the treatment chamber. Preferably the or each at least one support structure has at least first and second opposing surfaces and wherein the or each support structure is arranged in use such that radiation from said UV radiation source can fall on at least part of both the first and second surfaces of said support structure. Many prior art devices only irradiate the upstream side of any mesh photocatalyst coated support structure, which decreases the efficiency of the system. Alternatively, some prior art systems include a separate, second UV radiation source or second set of UV radiation sources to radiate the downstream side of a mesh photocatalyst coated support structure. The present invention can however irradiate both the first and second surfaces of the support structure using a single UV radiation source. The terms downstream' and upstream' in this context aie used with ieference to the diiection of the flow of air through the apparatus in use, from the at least one inlet to the at least one outlet. Au enters at an upstream end of the treatment chamber and exits at the downstream end of the treatment chamber.

Pi-eferably at least part of a surface of the or each at least one support structure is arranged obliquely to the direction of airflow from the air inlet in use. In other words, the or each at least one support structure is arranged obliquely to the upstream-downstream axis of the treatment chamber. Preferably, said pad of the surface of the or each at least one support stiuctule fornis an obtuse angle relative to the substantial direction of airflow from the air inlet in use.

Pieferably the or each at least one suppoit structuie has apertures therein such that a portion of the au flowing through the treatment chamber will pass thiough the apertuies.

The passing of air through the holes gives rise to additional air turbulence, in addition to that created by the deflection of air by the at least one support structure. The remaining air flowing thiough the treatment chamber that does not pass thiough the apertuies will be deflected by said at least one support structure. The support structure may, for example, be perforated metal or a woven wile mesh.

Preferably the module has a plurality of said support structures, at least part of the surface of each support structure comprising a photocatalytic surface. By pioviding a plurality of support structures which have a photocatlytic surface and which are also configured to deflect the au, the suppoit stiuctures piovide passages therebetween, which the air passes through, increasing the contact time of the air with the free radicals genelated.

Preferably the or each at least one support structure comprises a plate, the plate having a first slot such that at least part of said UV radiation souice is ieceived by the slot when assembled. The UV radiation source can easily be removed and replaced by simply detaching it from its power source and removing it via the open end of the slots in the plurality of support structure plates.

Preferably the or each at least one support structure comprises a plate having a first portion which is arranged obliquely to the direction of airflow from the air inlet. This provides a first change of direction for the air, creating turbulence. Preferably the or each at least one support structure comprises a plate having a second portion which is arranged obliquely to the direction of airflow from the air inlet, and at a different angle relative to the direction of airflow from the air inlet from that of the first portion. This provides a second change of direction for the air, increasing the turbulence. Preferably the second portion extends from the first portion in a direction which is a mirror image in a mirror plane passing between the first and second portions and which is orthogonal to the initial direction of airflow from the air inlet. Preferably the or each at least one support structure comprises a plate having a third portion which is arranged at an angle relative to the second portion. This provides a third change of direction for the air, increasing the turbulence. Preferably the third portion is a planar portion which is parallel with the initial direction of airflow from the air inlet.

Preferably the or each at least one reflective surface is integral with or mounted to an inner surface of the enclosure. Preferably the or each at least one reflective surface is profiled to incorporate a plurality of formations. Preferably the or each at least one reflective surface has a plurality of convex protuberances extending into the treatment chamber. The plurality of shallow, convex protuberances scatter the UV radiation.

Preferably the enclosure comprises side walls. Each side wall is arranged substantially parallel with the initial direction of airflow from the air inlet when assembled. The enclosure may comprises four side walls. The enclosure is preferably rectangular in shape, having two short side walls and two long side walls. The enclosure may be sized such that the combined length of a short side wall and a long side wall of an enclosure matches the length of a standard recess in a suspended ceiling. The enclosure of said air treatment module may be sized such that four identical air treatment modules can be arranged in an air circulation apparatus, with a long side wall of a module adjacent a short side wall of a neighbouring air treatment module, around a central space. The central space provides space for an air inlet duct and/or a central fan.

Preferably the or each UV radiation source is mountable such that it is rigidly fixed relative to the enclosure when assembled. As such, the air treatment module comprises a modular, self-contained unit that can be removably installed as a single unit, including the UV radiation source Preferably the or each at least one support structure is mountable such that it is rigidly fixed relative to the enclosure when assembled. As such, the air treatment module comprises a modular, self-contained unit that can be removably installed as a single unit, including the support structures Preferably the module further comprises means for releasably connecting the or each at least one UV radiation source to a power source.

Air circulation apparatus may be provided incorporating at least one air treatment module as described above. Preferably an air circulation apparatus may be provided incorporating four air treatment modules as described above.

Preferably the air circulation apparatus is configured to be ceiling mounted.

Alternatively the air circulation apparatus may be installed in a wall-mounted or free-standing air circulation apparatus, for example focused to a specific location, such as a hospital bed.

Preferably the air circulation apparatus is configured to be installed in a recess in a suspended ceiling. The air circulation apparatus may have a housing that is approximately 600 mm x 600 mm if it is fit a recess in a standard European suspended ceiling grid. The air circulation apparatus may of course be provided in a different size to fit a standard suspended ceiling grid recess of a different size.

Preferably the apparatus further comprises fan means. The fan means can be any means to move air. The fan means moves air in through the at least one inlet and out of the at least one oulet. The fan means creates a turbulent air zone in the treatment chamber downstream of the fan means in use Preferably the apparatus further comprises at least one filter. The at least one UV radiation source, the at least one support structure, and the at least one filter may be located downstream of the fan means in the turbulent air zone in use Preferably the at least one UV radiation source is arranged such that at least a portion of radiation from the at least one UV radiation source irradiates the at least one filter in use.

According to a further aspect of the present invention there is provided apparatus for purifying air, the apparatus comprising a treatment chamber having at least one air inlet, at least one air outlet, at least one filter, and fan means for moving air in through the at least one inlet, through the at least one filter and out of the least one outlet, the treatment chamber further having at least one UV radiation source for exposing air in the treatment chamber to UV radiation, wherein the at least one UV radiation source is arranged such that at least a portion of radiation from the at least one UV radiation source irradiates the at least one filter in use, the treatment chamber further having at least one support structure coated with a photocatalyst, the at least one support structure being arranged such that UV radiation from said at least one UV radiation source irradiates the at least one support structure in use, wherein the fan means creates a turbulent air zone in the treatment chamber downstream of the fan means in use, and wherein the at least one UV radiation source, the at least one support structure, and the at least one filter are located downstream of the fan means in the turbulent air zone in use.

Air containing pathogens passes through the air treatment chamber housing the UV (ultraviolet) light source, the apparatus employing three different techniques to destroy or capture pathogens, all provided by means of the same UV radiation source: 1) irradiation of pathogens with UV radiation as they pass the UV radiation source in the air flow, 2) irradiation of the filter to kill pathogens trapped on the filter, 3) irradiation of the at least one photocatalyst coated support structure, the photocatalyst generating free radicals which de-activate or kill pathogens in the air. Thus the apparatus has a triple killing effect on pathogens, and by means of creation of a turbulent air zone in the treatment chamber, all three occur in a turbulent air flow zone that ensures uniformity of exposure and provides more efficient pathogen treatment. The UV radiation source may comprise a single UV lamp or more than one UV lamp. Where the UV radiation source comprises more than one UV lamp, each UV lamp is employed in three of the above pathogen treating techniques.

The UV radiation source kills pathogens such as bacteria, viruses, and spores in the air as it passes the UV radiation source in use. The killing potential will depend on the dose' (i.e. UV strength and exposure time). The same at least one UV radiation source is also arranged such that at least a portion of its UV radiation irradiates the at least one filter, this having the advantage that pathogens trapped on the filter will be subjected to irradiation by the UV radiation source, over a prolonged period of time and well in excess of the killing dose', killing the pathogens trapped on the filter. Although the air passing through the filter will already have been irradiated with UV light before passing through the filter, some pathogens in the air may not have been killed by the UV irradiation before becoming trapped in the filter; the UV irradiation of the filter kills further pathogens that are trapped on the filter. When the filter requires replacement, since the filter has been subjected to UV radiation, the level of pathogen contamination on the filter will have been considerably reduced, thus reducing the risk of a person replacing the filter from coming into contact with or being infected by pathogens from the filter. The same at least one UV radiation source also activates the photocatalyst coating of the at least one support structure, generating reactive free radicals, which de-activate or kill pathogens in the air.

Preferably the fan means is a centrifugal fan. By using a centrifugal fan (as opposed to an axial flow fan), the air downstream of the fan is highly turbulent (i.e. there is a highly turbulent zone downstream of the fan means). Consequently, the air in the highly turbulent zone, downstream of the fan means, remains in the housing for longer before exiting the housing than if an axial flow fan were used for example. The air in the chamber can be made turbulent by other means when it is not practical to use a centrifugal fan by, for example, fitting fixed guide vanes in the approximate position of the fan. In this case an axial flow fan may be employed instead of a centrifugal fan.

The UV radiation source is situated in the discharge zone of the fan means, and is thus situated in a highly turbulent zone. This increases the likelihood of pathogens being irradiated, as the turbulence in the turbulent zone increases the exposure of pathogens in the air to UV radiation from the UV source. The at least one support structure is downstream of the fan means in use. This means that the free radicals are generated in the highly turbulent discharge zone of the fan means, increasing the likelihood of pathogens coming into contact with the free radicals. Preferably, the at least one filter is downstream of the at least one UV light source. Preferably there is no filter upstream of the at least one UV light source as this would be contaminated by pathogens trapped in it, which would not have been subjected to the sterilising effect of UV light. A filter upstream of the UV light source would present a potential source of infection when replacing this filter. Advantageously, the device has no areas where pathogens remain untreated.

Preferably the filter has an upstream side and a downstream side, at least a portion of radiation from the at least one UV radiation source irradiating the upstream side of the at least one filter in use, such that filter contamination is reduced. More pathogens will be trapped at the upstream side of the filter than the downstream side, therefore irradiation of the upstream side of the filter reduces pathogen contamination on the filter. This reduces the risk of a person manually replacing the filter from coming into contact or being with infected by pathogens from the filter.

Preferably the at least one support structure is profiled to incorporate a plurality of forrriations. The forrriations may be shaped as corrugations, dimples, embossed areas, and/or upstanding elements such as ribs or the like. Advantageously, this increases the surface area of the support structure, increasing the amount of photocatalyst coating that can be provided on each support structure. Preferably the plurality of formations comprises a plurality of crests and/or troughs displaced from a notional centre plane of said support structure. Preferably the surface of the at least one support structure is corrugated, dimpled or embossed.

The at least one support structure may comprise at least part of an inner surface of the treatment chamber. The at least one support structure may comprise a solid plate.

Preferably the or each at least one support structure is mounted to one or more inner surfaces of the treatment chamber.

Preferably the photocatalytic surface /photocatalyst referred in any aspect of the invention above comprises titanium dioxide. When activated by UV light, titanium dioxide reacts with water vapour in the air, forming reactive hydroxyl radicals. The hydroxyl radicals oxidise pathogens in the air, de-activating or killing the pathogens.

The apparatus may ceiling mounted in use. When ceiling mounted, the apparatus can be used to fully circulate air around a whole room.

Preferably the at least one outlet has at least one adjustable guide means which is adjustable such that the direction and/or velocity of discharge of air from the outlet can be controlled. The adjustable guide means allow air to be circulated around a portion of a room, rather than around a whole room. Preferably the adjustable guide means comprises at least one pivotable guide vane. Preferably the air outlet faces laterally when the apparatus is ceiling mounted, and the pivotable guide vane is pivotally mounted at its top end, and pivotable from a vertical orientation, in the direction of the air flow, such that air can be directed laterally and downward.

Preferably the apparatus further comprises air flow sensing means and processing means, the processing means being operable to receive inputs from the air flow sensing means and to produce an output based on the inputs for controlling the speed of the fan means. The flow sensing means and processing means allow the fan speed to be adjusted to increase the fan speed as the filter becomes clogged.

Preferably the apparatus further comprises fan speed warning means adapted to issue a warning signal when the speed of the fan means is above a pre-determined level.

Preferably the fan speed warning means is adapted to issue a warning signal when the fan means is operating at its maximum speed. When the fan speed has reached a pre-determined level, close to its maximum preset speed, the warning means will emit a first warning signal. When the fan has reached its maximum preset speed, the warning means will emit second, different warning signal. The first and second warning signals will alert users when the filter needs replacing or when the apparatus is not functioning properly. The first warning signal will alert a user that the filter will require replacing shortly. The second warning signal will alert a user that the filter requires immediate replacement.

Preferably the apparatus further comprises UV warning means adapted to issue a warning signal when the at least one UV radiation source is approaching or is at the end of its effective life. This alerts users when the UV radiation source requires replacing. The purpose of this system is to advise that a routine maintenance/replacement is due and will need acting on in reasonable time to avoid/reduce the risk of one of the UV sources failing.

Preferably the apparatus further comprises UV monitoring means operable to determine whether the at least one UV radiation source is functioning and to stop the fan means from operating if said UV radiation source is not functioning. The UV monitoring means is operable to monitor whether the at least one UV radiation source is functioning, or if there is more than one UV radiation source, whether one or more of the UV radiation sources is functioning. If the or one of the UV radiation sources is not functioning, the fan means will be stopped from operating, such that air will not be circulated through the apparatus. Preferably the UV monitoring means is operable to issue a warning signal if the at least one UV light source is not functioning. The purpose of this waming system is to advise that the system needs immediate attention because one or more UV source has ceased functioning and thus cannot be relied on to sterilise the air in what might be a highly critical application.

Preferably the air inlet is adapted to reduce noise output. Preferably the air inlet has a sound absorbing lining. Preferably the air inlet comprises a tube, the tube having a sound absorbing lining.

Preferably the fan means is an electronically controlled fan. Suitably, the fan means has reduced noise characteristics and operates with lower energy requirements According to a further aspect of the invention, there is provided a kit for assembly into apparatus according to any aspect of the invention as described above, wherein the kit comprises the parts of the apparatus as described above.

Brief Description of the Drawings

Preferred embodiments of the present invention will now be more particularly described by way of example with reference to the accompanying drawings, wherein: Figure 1 shows a cross-sectional view of an air purifying apparatus of a first embodiment of the invention, taken through the line A-A of figure 2, the apparatus shown mounted onto a false ceiling; Figure 1A shows a cross-sectional view of the apparatus of figure 1 taken through the line B-B of figure 1, the apparatus shown with the housing removed and not mounted in a ceiling, looking into the treatment chamber showing the position of the UV lights, filters and coated walls; Figure lB shows a cross-sectional view of an air purifying apparatus of an alternative embodiment of the invention which is similar to the figure 1 embodiment but has an axial flow fan, the cross-sectional view taken through the line A-A of figure 2; Fig 1C shows a cross sectional view of the apparatus of figuie 1B, taken thiough line C-C of figure lB and showing the guide vanes, UV lights, filters and coated walls; Figure 2 shows a perspective view of an air purifying apparatus of figure 1 or figure 1B, as viewed from below; Figure 3 shows a perspective view of an air purifying apparatus of figure 2, with the face plate shown open; Figure 4 shows a cross-sectional schematic diagram of a further embodiment of the invention, showing an air purifying device for mounting onto a solid a ceiling; Figure 5 shows a schematic diagram of an air purifying device of figure 4, showing cilculation of air around a room; Figure 6 shows a schematic diagram of an air purifying unit of figure 5, showing cilculation of air around the room by means of adjustable guide vanes; Figure 1 shows a schematic, plan view of the experimental layout of the test chamber used in experiments on an embodiment of the invention; Figures 8 to 10 show results of the tests on an embodinient of the invention; Figure 8 is a graph showing the effect of the device on the concentration of airborne S. aureus (with the UV lamps off); Figure 9 is a graph showing the effect of the device on the concentration of airborne S. aureus (with the UV lamps on); Figure 10 is a graph showing particle concentrations in the test chamber; Figures 11 to 14 show a further embodiment; Figure 1 1A shows a side view of an air treatment module, the side wall nearest the viewer having been removed; Figure 11B shows a cross-sectional view of the module of Figure hA, taken through the line D-D of figure hA; Figure 12 shows a close-up view of the module of Figure 1 hA, showing air flow pattern through the unit; Figure 13 shows an air circulation apparatus incorporating four modules of Figure 11k the figure being a cross-sectional view taken through the line C-C of Figure 14A; Figure 14A shows a first cross-sectional view of the apparatus of Figure 13, taken through the line A-A of Figure 13; Figure 14B shows a first cross-sectional view of the apparatus of Figure 13, taken through the line B-B of Figure 13.

Description of the Preferred Embodiments

Referring to figure 1, which is a cross-section through AA on Figure 2, an air purifying unit 10 is shown comprising a housing 12 having an air inlet 14 and air outlets 16. The air inlet 14 comprises an inlet duct 34. The unit 10 is shown installed in a ceiling aperture 18. The housing 12 has an upper portion or treatment chamber 22 and a lower portion or outlet chamber 24, the treatment chamber 22 extending above the aperture 18 and the outlet chamber 24 extending below the aperture 18. The outlet chamber 24 of the housing projects laterally away from the treatment chamber 22, such that the outlet chamber 24 provides a flange which abuts against the underside of the ceiling in use. In figure 1, the outlet chamber 24 abuts against the underside of false ceiling tiles 27, the treatment chamber being disposed between false ceiling T' bars 29 on either side. Referring to Figure 2, the unit 10 has a face plate 15 mounted to the underside of the outlet chamber 24 and forms with housing 12 an elongated air outlet slot 16 on four sides. Referring to figure 3, the face plate 15 is pivotally connected to the housing by means of hinges 17, such that it can be opened after releasing fixing bolts 55 to access the internal cavity of the housing. When closed, the face plate 15 is secured by fixing bolts 55 and the face plate comes into contact with a gasket 37 to provide an airtight seal between the inlet duct 34 and the outlet chamber 24.

Referring to figure 1, the housing further includes a centrifugal fan 26 mounted to the centre of the top of the inside of the treatment chamber 22. There are four UV lights 28 in the treatment chamber 22, one arranged on each side of the housing 12. Referring to Figures 1, 1A and 3, there are four filter panels 30 in the treatment chamber 22, one located below each UV light 28.

The UV lights are germicidal, in that they emit UV light of a certain wavelength that kills germs! pathogens in air which circulates through the unit. Preferably the wavelength of the UV light emitted by the UV lights will be in the range 240 to 280 nm, which is known to have germicidal effect, and will preferably be around 254 nm. Air irradiated with UV light having wavelength of around 185 nm produces ozone. Preferably the device will not generate ozone. The UV lights are housed within the treatment chamber 22, in an area of very high turbulence, resulting in improved effectiveness of the germicidal UV light and ensuring uniformity of high doses of UV radiation to each passing micro-organism particle.

Referring to figure 1A, each UV light 28 has a longitudinal axis and the four UV lights 28 are arranged such that each has its axis parallel with the plane of the corresponding filter 30 that the particular UV light 28 is located above. By use of this arrangement, UV radiation from each UV light 28 is emitted directly onto each corresponding filter 30, such that pathogens trapped on the filter will be subjected to high doses of UV radiation, killing the pathogens trapped on the filter.

Referring to figure 1, the treatment chamber 22 of the housing includes one or more support structures such as plates or tiles 32a mounted to the inside of the top surface of the housing. The treatment chamber 22 further includes four plates or tiles 32b, one mounted on each side of the inside of the treatment chamber 22. The tiles 32a, 32b are solid tiles coated with a photocatalyst. Titanium dioxide is preferably used as the photocatalyst. When the titanium dioxide is irradiated with UV radiation, the titanium dioxide reacts with water vapour in the air, forming reactive hydroxyl radicals. The hydroxyl radicals oxidise pathogens in the air, de-activating or killing the pathogens. A significant proportion of pathogens in the air circulating through the unit will be killed by the action of reactive hydroxyl radicals before the pathogens reach the filters 30.

Over time, the photocatalyst coated tiles may become covered with particles from the air, and may need periodic cleaning. This can be done by wiping over the photocatalyst coated tile with a damp cloth, and can be done regularly whenever the UV lamps and/or filters are replaced.

Preferably the surfaces of the tiles are corrugated, dimpled or otherwise embossed.

Providing the surfaces of the tiles with raised areas and/or depressions increases the surface area of each tile, providing a greater surface area on each tile that can be coated with photocatalyst.

The support structures may be any structure that is capable of providing a support for a photocatalyst coating. Alternatively, instead of providing tiles mounted inside the treatment chamber, the inner surfaces of the treatment chamber could be directly coated with photocatalyst. Some existing air purifying units of the prior art include a mesh or honeycomb structure coated with photocatalyst, the mesh or honeycomb structure enveloping a UV light (see for example US 2003/0230477). This arrangement of the prior art has the disadvantage that it would restrict the amount of radiation that could reach the upstream side of filters (UV shadowing would occur with photocatalyst coated mesh structures interposed between the UV lights and the filters, thus reducing the reduction in contamination of the filters by the UV irradiation). An advantage of coating the inner surfaces of the treatment chamber with photocatalyst or coating tiles/plates mounted to the inner surfaces of the treatment chamber is that this does not restrict the amount of radiation that reaches the upstream side of filters 30.

Furthermore, with the photocatalytic coated mesh or honeycomb structures of the prior art, mounting of the mesh or honeycomb structures in the air flow pathway causes resistance to the flow of air. For mesh/honeycomb structures, the surface area that can be exposed to the UV source is thus lirriited to the maxirrium surface area allowed by the fan to overcome the air resistance. However, if the inner surfaces of the treatment chamber have photocatalyst coating, or plates/tiles coated with photocatalyst are affixed to the inner surface of the treatment chamber, this allows a greater surface area of photocatalyst to be exposed to the UV source. By using a photocatalyst coating on the inner surfaces of the chamber, the UV light can irradiate without obstruction all of the faces of the treatment chamber, without causing any disadvantage to the air flow properties. Another advantage of using photocatalyst coated tiles mounted to the inner surface of the chamber or coating the inner surface of the treatment chamber with photocatalyst coating rather than having rriesh/honeycorrib structures is that the tiles/inner surface of the treatment chamber will be easier to clean (by simply wiping over them with a damp cloth), whereas it would be more difficult to remove particles that are stuck on the surfaces of mesh/honeycomb structures.

Referring to figure 1A, each UV light 28 has a longitudinal axis and the four UV lights 28 are arranged such that each has its axis parallel with the plane of the corresponding coated tiles 32a, 32b. By use of this arrangement, UV radiation from each UV light 28 is emitted directly onto each corresponding coated side tiles 32a, 32b, such that the generation of hydroxyl radicals will kill pathogens passing in the turbulant air zone of the treatment chamber.

By locating the photocatalyst and UV lights in the discharge zone of the fan, they are in an area of veiy high turbulence and this provides uniformity of exposure which results in improved effectiveness of the reaction between the hydroxyl radicals and airborne pathogens.

In the embodiment of figure 1 fan 26 is a centrifugal flow fan (rather an axial flow fan), although a mixed flow fan could be used in the unit of figure 1. With axial flow fans, the air blown by the fan flows in a single direction, parallel to the axis of the fan shaft (i.e. the blown au only has one component of velocity). Centrifugal fans blow air in a radial direction relative to the axis of the fan shaft (i.e. the blown air has two components of velocity). Mixed flow fans blow air in both axial and radial directions relative to the axis of the fan shaft. By using a centrifugal or mixed flow fan, the air exiting the fan is moie tuibulent than if an axial fan were used. Therefore, by using a centrifugal oi mixed flow fan, the microorganisms in the air are exposed to higher doses of UV light and hydroxyl radicals, as the turbulent air is present in the treatment chamber 22 longer than if an axial fan were used. The air puiifying unit 10 is airanged such that the axis of the air inlet 14 is parallel with the axis of the fan shaft around which the fan blades rotate and such that the UV lights 28 and photocatalyst coated paits of the unit (i.e. the photocatalyst coated tiles or photocatalyst coated inner surfaces of the treatment chamber) are arranged around the fan 26 in a plane that is perpendicular to the axis of the fan shaft. In this way, the UV lights 28 and photocatalyst coated parts of the unit are located in an area where the air is highly turbulent, such that the microorganisms are subjected to high doses of UV light and hydroxyl ladicals.

Referiing to figures lB and 1C, an alternative embodiment of the invention is shown.

The air purifying unit 100 of figures lB and 10 has all of the sanie features as the unit 10 of figure 1 (features common to both units 10 and 100 being labelled in the figures with the same refeience numelals) except that unit 100 of figuies lB and 1C has an axial flow fan 31. The axial flow fan 31 is utilised to cause air to flow through the treatment chamber 22. Turbulent conditions are created downstream of the axial flow fan 31 by means of a plurality of baffles or guide vanes 33 arranged around the central axis of the fan. Each guide vane 33 is a vertical panel, which curves in the horizontal plane such that air exiting the fan is directed in a radial direction relative to the axis of the fan shaft by each guide vane 33. In this way, air turbulence within the treatment chamber 22 is generated by alternative means other than a rotating centrifugal or mixed flow fan (as used in the figure 1 embodiment), namely by the introduction of fixed guide vanes in the figure lB and 1C embodiment. A centrifugal fan would generate a higher pressure than a similar sized axial ow fan, therefore a centrifugal fan would be preferred if using filters with a high resistance to air flow; however, centrifugal fans are generally more expensive and more noisy than axial flow fans. Where the filters provide less resistance to air flow, an axial flow fan can be used together with guide vanes to create turbulent conditions in the treatment chamber.

Referring to figures 1 or lB and 3, the air inlet 14 comprises an inlet duct 34 having a square cross-section. The face plate 15 has a circular opening 42 which overlies the square opening of the inlet duct 34 when the face plate 15 is closed. The contact surface between the inlet duct and the closed face plate 15 is lined with the gasket 37 to provide an airtight seal between the inlet duct 34 and the outlet chamber 24. There may be a grating (not shown in the figures) covering the circular opening 42 of the face plate 15 to prevent anything being inserted into the inlet 14. The circular opening 42 in the centre of the face plate 15 has radiused edges (i.e. curved, smooth edges rather than sharp edges). The radiused edges of the circular opening 42 smooth the airflow to reduce noise output of the unit and reduce friction losses. The axis of the inlet duct 34 runs vertically upwards, away from the face plate 15 when installed, leading to a circular opening 38 at the top end of the duct 34, the opening 38 located just below the fan 26.

The inlet duct 34 is lined with sound absorbing material 40, to reduce noise output of the unit 10. Foam, sponge or non-woven fibre materials that have special acoustic properties may be used as the sound absorbing lining.

Instead of using an inlet duct with a square cross-section, the inlet duct may have a circular or rectangular cross-section.

The fan 26, 31 is an electronically controlled fan, having low energy requirements and having a low noise output. Preferably the fan is a DC fan, but an AC fan or any electrically driven motor that is capable of moving air through the unit may also be used.

Referring to figures 1 or 1B, the outlet chamber 24 comprises four adjustable guide vanes 48a, 48b, one located at the mouth of each outlet 16. Each adjustable guide vane 48a, 48b is an elongate plate. Each vane 48a, 48b is pivotally mounted to the outlet chamber 24. Each of the units 10, 100 of figures 1 and lB show two possible arrangements for mounting guide vanes 48a, 48b. On the left hand side of the unit 10, is shown a top mounted guide vane 48a which is mounted along its top edge to the outlet chamber 24, such that the guide vane 48b is pivotable about its top edge. The guide vane 48a can be pivoted from a fully open configuration, in which the guide vane 48a is substantially parallel to the ceiling, to a partially open configuration, in which the guide vane 48a is oriented at an angle to the ceiling. The outlet chamber 24 includes a stop 50 which abuts the guide vane 48a when it has reached an angle of around 45° relative to the ceiling, preventing the guide vane 48a from closing the outlet any further.

When the guide vane 48a is oriented at an angle relative to the ceiling, rather than parallel with the ceiling, the air exiting the unit will be directed laterally and downward in the direction of arrow F1, such that air can be circulated around a specific zone of a room, below the unit.

On the right hand side of the unit 10,100 is shown a bottom mounted guide vane 48b which is mounted along its bottom edge to the outlet chamber 24, such that the guide vane 48b is pivotable about its bottom edge. The guide vane 48b can be pivoted from a fully open configuration in which the guide vane 48b is substantially parallel with the ceiling, to a partially open configuration, in which it is oriented at an angle to the ceiling.

The outlet chamber 24 includes a stop 50 which abuts the guide vane 48b when it has reached a certain angle (for example, the stop 50 on the right hand side of the unit of figure 1 is arranged to prevent the guide vane 48b from closing the outlet any further, once it has reached an angle of around 28° relative to its fully open configuration).

When the guide vane 48b is in its fully open configuration, it will direct air horizontally, in the direction of arrow F2. When the guide vane 48b is oriented at an angle relative to the ceiling, rather than parallel with the ceiling, the air exiting the unit will be directed laterally and upwardly, and at higher velocity.

If the stops 50 are removed, each vane 48a, 48b would be pivotable to a closed configuration, such that each vane 48a,48b fully obstructs each outlet. Preferably the unit 10, 100 will have guide vanes which are each mounted to the outlet chamber 24 in the same way (two different mounting systems for guide vanes are shown in each of figures 1, lB for the purposes of demonstrating different possible mounting systems).

By installing the unit in a ceiling of a room, with four top mounted the guide vanes 48a, each in the fully open configuration, the unit can be used to circulate air around the whole room. When the guide vanes 48a are each pivoted to a configuration between the open and closed configurations, the air exiting the unit is directed laterally and downward, such that air can be circulated around a specific zone of a room, below the unit.

Referring to figure 1 or 1B, at the top of the housing 12 is an electrical controls enclosure 52, for housing the electronics which control the unit 10, 100. Alternatively, the electrical controls could be wall mounted rather than mounted on top of the housing 12. The unit has an auto-speed control feature, to overcome the problem of the loss in airflow as the filters accumulate trapped particles. The unit 10, 100 has a flow sensing device (not shown in the figures) in the inlet airflow that monitors the airflow in the inlet duct 34. Airflow measurements from the flow sensing device are sent to a F'CB (not shown), which in response to the airflow measurements adjusts the speed of the fan.

The system has a filter change warning system whereby when the fan speed reaches a certain pre-determined speed, a warning signal will be emitted by the unit, to warn users that the filters will require replacing soon. When the Ian reaches its maximum pre-set speed (i.e. the speed that has been pre-set as a maximum speed which may be below the Ian's actual maximum speed), the unit will be shut off, so that the fan will not operate and air will not pass through the unit. A second, different warning signal may be emitted, to aleit users that the unit has been shut off and that the filters lequire changing. The warning signals may be emitted via means of visible lights that may be on a surface of the unit or wall mounted, or by means of sound. Such an auto-speed control safety system is advantageous in a health caie environment to alert staff to be aware and take action when the unit is not functioning properly due to blockage of the filter. Rathel than locating the flow sensing device in the inlet airflow, it could be located in the outlet airflow.

The unit also has a UV monitoring system, such that the system can automatically check whether the UV lights are reaching the end of their effective life or are not functioning. The UV monitoring system will monitor each UV light. If one oi more of the lights is reaching the end of its effective life, a warning signal will be issued to alert the user that a UV light will soon require replacing. This is done by means of an elapsed hour meter. A typical UV light will have will normally have a guaranteed life of 8000 houls (about 1 yeais normal use). Each time a new UV light is installed, an elapsed hour meter will monitor the elapsed time that the UV light is on for. Once the elapsed time reaches a pre-determined thieshold near the end of its guaranteed life, the warning signal will be issued.

The UV monitoring system will also monitoi each UV light to check whethel it is functioning. If one or more of the lights is not functioning, the unit will be automatically shut off, so that the fan will not operate and air will not pass through the unit. A second warning signal riiay be emitted, to alert users that the unit has been shut off and that one or more of the UV lights require changing. The UV monitoling system measures the current being drawn by the UV lights; when the current drawn falls by the equivalent of one UV light, a warning signal will be issued.

The warning signals may be emitted via means of visible lights which may be on a surface of the unit or wall mounted, or by means of sound. The system may also have means for indicating which light is not functioning or is reaching the end of its effective life. Such UV monitoring system is advantageous in a health care environment to alert staff to be aware and take action when the unit is not functioning properly due to non-functioning of one or more UV lamps.

At the top of the housing 12 are support points 54 for fitting tie rods to the main building structure.

In operation of the unit 10, 100, the fan 26, 31 is switched on, drawing air into the unit via the inlet 14, up the inlet duct 34 to the fan 26, 31. The air in the fan discharge zone is highly turbulent, and passes the UV lights 28, the photocatalyst coated plates or tiles 32a, 32b, and then passes through the filters 30. Once through the filters 30, the filtered air is directed out of the outlets 16. The unit 10, 100 is typically able to treat air from 5 to 20 times and hour, allowing it to achieve high decontamination levels as well as enabling the setting up of an airflow regime that will maintain high levels of sterility and cleanliness throughout the defined zone. The system does not just discharge sterile cleaned air, but creates a flow pattern in the defined zone, thus creating an integrated system for systematically and constantly treating the air in the whole of the defined space. The airflow rate and hence recycling ratio can be changed according to the level of activity occurring in the room. For example in a hospital ward when there is a bed change, the system can be adjusted to a high level of recycling or at night when the ward is quiet it can be turned down to a much lower level conserving power and reducing noise. These changes can be made manually or automatically using sensors (AIR devices or particle counters).

Figure 4 to 6 show a further alternative embodiment of the invention. The housing 12' of the air purifier lOis to be mounted to the underside of a ceiling. The unit has a central treatment chamber 22' with a fan 26' connected by a rotating shaft to an electric motor 52' and mounted on the underside of the roof of the treatment chamber. Unlike the embodiments of figures 1 and 1B, the filters 30' are arranged at the side of treatment chamber 22', there being a filter 30' laterally adjacent each UV light 28 (rather than underneath each UV light as in the arrangement of the units 10, 100 of figures 1 and 1 B). Interposed between the filters 30' and the fan 26' are a plurality of UV lamps 28'.

Similar to the embodiments of figures 1 and 1B, in operation, the fan 26' draws air into the unit via the inlet 14', to the fan 26'. The air in the fan discharge zone 22' is highly turbulent and passes the UV lights 28', then through the filters 30'. Once through the filters the air is directed out through outlets 16' and discharges via perforations or grill (not shown) on all four side walls of purifier 10' into the room in substantially horizontal directions. The unit 10' has photocatalyst coated plates or tile 32a' mounted to the inside of the top surface of the treatment chamber 22' and further photocatalyst coated plates or tiles 32c' mounted to the inside of the bottom surface of the treatment chamber 22', the photocatalyst coating generating hydroxyl radicals when irradiated with UV, to kill pathogens/microorganisms.

Figure 5 shows a schematic diagram of an air purifier unit of figure 4, the air purifier being mounted on a ceiling, the unit have no guide vanes and the unit being used to circulate air around the whole room. Figure 6 shows an air purifier unit mounted on a ceiling, the unit having a plurality of guide vanes or louvres 48', each being top mounted and adjusted partway between open and closed configurations, such that air is deflected laterally and downwardly, such that it recirculates around a specific part of the room, such as around a source of contamination. The guide vanes 48' may be adjusted and to any angle between the open and closed configurations, such that the size of the circulation zone can be controlled. The occupant(s) within the circulation zone will be protected from possible external contamination and conversely those outside the circulation zone will be protected from contamination arising from within the contamination zone. Alternatively, the guide vanes 48' may be non-adjustable, but fixed at a particular angle relative to the ceiling.

The units shown in figures 1 to 6 are for installing in or mounting to a ceiling, however the device may be adapted to be mounted/positioned elsewhere in a room.

Preferably, in the air purifying units of figures ito 6, filters are only located after air has passed UV light. Thele aie no pie-filters that filter air befoie the au has been irradiated with UV light; the device only has post-filters. Any pre-filtrations will trap at least some micro-olganisms, which will not be sterilised. Thus, this system has no areas where pathogens can remain untreated.

Pieferably, the unit is adapted such that no UV light will exit the housing 12, 12' as this could be harmful to people in the vicinity of the unit. In the units of figure 1 to 6, UV light is prevented from being dilected outside the unit by the filter panels 30, 30'.

Embodiment of Figures 11 to 14 A further embodiment will now be described with reference to Figures 11 to 14. This embodiment is similar to the previous embodiments except that this embodiment incorpolates self-contained, removably installable air tieatment modules and/or photocatalytic coated air deflector plates suliounding a soulce of UV ladiation. Each air treatment module optionally has reflector plates surrounding and facing towards the treatment zone. These features are further described below.

Referring to Figure 14A, an air purifying unit 110 is shown comprising a housing 112 having an air inlet 114 and air outlets 116. The air inlet 114 comprises an inlet duct 134. The unit 110 is shown installed in a ceiling aperture 118. The niounting of the unit in the ceiling aperture 118 is the same as that for the embodiment of Figures 1 and lB. The tieatment chambei-is disposed between false ceiling T' bais 129 on either side of the ceiling aperture. The unit 110 has a face plate 115 mounted to the underside of the unit 110 incorporating an outlet slot. The lace plate is pivotally connected to the housing by nieans of hinges 117, such that it can be opened to access the internal cavity of the housing. When closed, the face plate 115 can be secuied by suitable securing means. The unit 110 has guide vanes 148, similar to the guide vanes 48a, 48b of the Figure 1 1 B embodiments. The unit 110 may also have similar controls and monitoring systems as described above in relation to previous embodiments.

Referring to figure 14A, the housing further includes a fan 126 mounted centrally in the upper portion of the housing. The housing comprises four removable air treatment modules 122, which will now be described.

Each air treatment module 122 has a filter panel 130 located at its downstream end.

Each module 122 has an enclosure 139 providing a side boundary to the module 122, but leaving an open upstream end and an open downstream end to the enclosure 139, to allow air to pass through the enclosure 139. Referring to Figure 13, the enclosure 139 comprises two long side walls 139a and two short side walls 139b, forming a rectangular enclosure.

Each treatment module includes four UV lights 128 (although of course any number of UV lights can be included in each treatment module). Referring to figure 1 1A, each UV light 128 has a longitudinal axis and is arranged such that each has its axis parallel with the plane of the corresponding filter 130. By use of this arrangement, UV radiation from each UV light 128 is emitted directly onto a corresponding filter 130, such that pathogens trapped on the filter will be subjected to high doses of UV radiation, killing the pathogens trapped on the filter. Each UV light is mounted in a lamp holder 156, which in turn is mounted onto a lamp holder mounting bracket 157, the bracket being mounted to the inside of the enclosure 139. Other suitable means for fixing each UV light to the enclosure 139 could be used. Each bracket 157 includes an enclosure for housing a starter for the corresponding UV light. The enclosure also provides space for cabling to couple the lamp holder 156, and therefore the UV light, to a power source.

Connector means are provided such that the lamp holders 156 can be connected and disconnected to a power source. Each lamp holder 156 may have its own separate connector, or alternatively a single electrical connector may be provided for each module 122, which once connected, allows connection of each UV light to the power source.

Each treatment module 122 includes a plurality of support structures 132. Unlike the support structures of the previous embodiments, which are mounted to the insides of the treatment chamber, the support structures 132 of this embodiment are mounted within the open space of the treatment chamber. The support stiuctuies 132 aie each fixed to a mounting rod 158 (shown in Figures hA and 12, but not shown in the other Figuies for the sake of simplicity), which is in turn mounted to the inside of the enclosure 139. In this embodiment the mounting rod 158 is mounted to the lamp holder mounting bracket 157, however the mounting rod 158 may of course be mounted directly to the enclosure 139. The plulality of suppoit stiuctures 132 are evenly spaced out along the mounting rod 158, with spacer tubes 135 on the mounting rod 158, between each suppoit structure 132 to assist in pioviding even spacing.

Referring to Figure 1 1A, in this embodiment, the suppoit stiuctures 132 aie bent plates, which deflect air as it passes through the air treatment module. Referring to Figure 11B, each support structure 132 has first and second slots 132c, each for receiving a UV light 128. The suppoit stiuctuies 132 theiefoie suriound the UV lights, when assembled, but allow the UV lights to be easily removed via the slots. The bent support structures 132 are folded diagonally one way to the air stream and then diagonally the other way, providing zig-zag shaped plates, so as to cause three changes of air flow direction and thereby creating a series of voitices to increase the turbulence and improve the exposure of airborne contaminants to both UV radiation and hydroxyl ladicals. Figure 12 shows the changes in airflow dilection.

The support structures may be any structure that is capable of providing a support for the photocatalyst coating. The suppoit structures 132 are pieferably made of metal and are coated, preferably on all outer surfaces, with a photocatalyst, preferably titanium dioxide. The suppoit stiuctuies 132 provides a laige surface aiea for photocatalyst coating. The support structures 132 are in close proximity to the UV lights, when assembled, and will genelate hydioxyl radicals and hence add to the destiuctive effect on micro-organisms in suspension in the turbulent air flow.

Titanium Dioxide is available commeicially in a watei based suspension form. To get an even coating of Ti02 on to the metal surface it is important to pre-treat the metal with a hydrophilic coating. This reduces the effect of the Ti02 water based solution from forming beads and ensures an even spread of the active ingredient. Usually a minimum of three coats of Ti02 suspension is required to provide sufficient concentration for the Ti02 to act as a catalyst in forming hydroxyl radicals in the presence of UVGI light.

In this embodiment, the support structures 132 are rriade of perforated metal.

Therefore, as the support structures 132 cause changes in airflow direction, some air will spill through the holes in the support structures 132 and give rise to even more air turbulence. Alternatively, the support structures 132 may be solid plates or woven wire mesh. It will be understood that the bent support structures may of course be incorporated into an air purifying unit like that of the previous embodiment, that does not have removable, modular treatment zones.

Each of the walls of the enclosure has a reflective inner surface 41. The reflective surface 41 may be provided on plates that are mounted to the inner surface of the enclosure walls 139a,139b or the inner surfaces of the enclosure 139 can be directly treated such that they are reflective. The reflective surfaces 41 are dimpled highly reflective plates that reflect and scatter the UVGI light so as to prevent shadowing effects and give uniform UVGI light strength to the airborne contaminates passing through the treatment module. Preferably the dimpled reflective surface has protuberances that extend away convexly from the surface. In the previously described embodiments the inner walls of the treatment chamber were coated with photocatalytic coating, which meant that the inner walls could not be used as reflectors. However, since photocatalytic coating is provided on the support structures 132, which surround the UV lights 128, reflective coatings can be provided on the inner walls, ensuring maximum and uniform intensity of UVGI light in the treatment zone. The reflective surfaces 41 may have surface profiles other than being dimpled, for example they could be flat, planar surfaces.

The reflection and scattering effect ensures a high proportion of the UV radiation extends upstream and downstream of the treatment zone. This increase the time particles and micro-organisms are in contact with UV radiation by at least a factor of two. It also ensures the face of the filter 130 is subjected to a high and even concentration of UV radiation such that any particles and micro-organisms trapped on the surface are subject to a continuous exposure to UV radiation. This makes the filter element safer to handle and dispose of when its routine replacement is necessary. The position of the filter as the last stage in the treatment zone is preferred as a final opportunity to capture and destroy micro-organisms.

The air treatment modules 122 provide self-contained units that can be removably installed, singly or in multiples, in an air purifying unit 110, such as that of the Figure 1 1A embodiment, or for example, in any ducted airflow system of which the air moving device can be remote. The air treatment modules 122 can be installed in any configuration to fit into air conditioning ducting of any sort. The construction in modular format allows the modules to be used in a number of ways within any air movement and distribution system. The size of the modules can be adjusted to suit economical criteria provided the UV radiation wattage and number and shape of deflector plates and filter size are in the same ratio to the airflow cross-sectional area.

Referring to figure 13, the air purifying unit 110 of Figures 11-14 has four air treatment modules 122 installed within its housing 112. The air treatment modules 122 are arranged with a long side wall 139a of a module adjacent a short side wall 139b of a neighbouring air treatment module, around a central fan 126. Each air treatment module 122 is releasably mounted in the air purifying unit 110 using suitable mounting means.

The UV lights 128 and support structures 132 can be mounted in the enclosure 139 of the air treatment module 122 before installation of the air treatment module 122 in the air purifying unit 110. Therefore, the UV lights 128 and support structures 132 can easily be installed in the air purifying unit 110, simply by installing a pre-assembled air treatment module 122. The construction of the apparatus allows periodic maintenance on an air treatment module 122 to be easily performed whilst the air treatment module 122 is installed in the air purifying unit 110. Firstly, the filter 130 can be removed in order to replace it or to reveal access to the UV lights 128, such that the UV lights 128 in each air treatment module 122 can be replaced as and when needed. Replacement of a UV light is carried out by disconnecting the UV light from its lamp holder and removing the light from the corresponding slot 132c in the surrounding support structure 132. If it is desired to gain closer access the support structures 132 or reflective surfaces 41, then the entire air treatment module 122 can be removed from the air purifying unit 110 by disconnecting the bulb holders from the power source (as explained above, there may be separate connectors for disconnecting each bulb holder from the power source, or preferably a single electrical connector is provided for each module which, once connected, allows connection of each UV light to the power source) and then dismounting the module 122 from the air purifying unit 110.

Where situations arise that may not require the same level of particulate removal or there is insufficient upstream fan performance, then the filters 130 may be omitted or a lower grade filled. Preferably there are no pre-filters that filter air before the air has been irradiated with UV radiation; preferably, the device only has post-filters, or no filters. Thus, this system has no areas where pathogens can remain untreated.

In all of the embodiments described herein, the filter panels may comprise HEPA filters (high-efficiency particulate air filters). HEPA filters are well-known in the prior art.

It will be understood that photocatalysts other than titanium dioxide may be used for the embodiments described herein, such as gold oxides, or a combination of several photocatalysts. The support structures can be made of glass, ceramics or metal, the material being chosen to provide the best substrate for the chosen photocatalyst.

Experimental Experiments were carried to evaluate the performance of an air purifying device as described above in terms of its ability to reduce the concentration of airborne Staphylococcus aureus in the test chamber, to determine the effect of the UV lamps on the level of performance, and to evaluate the effect of the UV lamps on the level of contamination in the filters.

The Device The device was fitted onto the centre of a test chamber ceiling using the mountings in situ. The device was fitted with four identical filters and four UV lamps. The device used in these experiments did not include any photocatalyst coated plates. During the initial experiment the UV lamps remained switched off to determine the disinfection capacity of the filters. During the second experiment the UV lamps were switched on to determine the additional disinfection capacity if any of the UV lamps.

The Test Microorganism The device was tested using aerosols of Staphylococcus aureus an important nosocomial pathogen. S. aureus is a gram-positive cocci which is an opportunistic pathogen which causes infection at sites of lowered host resistance, such as damaged skin or mucous membranes. In recent years, drug resistant strains of S. aureus, including methicillin resistant S. aureus (MRSA) have become endemic in many hospitals. MRSA causes a range of infections including surgical site infections, pneumonia and septicemia, especially in patients with vascular access devices and is associated with significant morbidity and mortality. Although infection with MRSA is generally associated with person to person contact, airborne transmission of S. aureus, including MRSA, has occurred in a variety of settings, including operating theatres, intensive care, burns and orthopedic units.

Experimental Methodology Evaluation of the øerformance of the device Two identical experiments were performed according to the following protocol. During the initial experiment the test device was operated with the UV lamp switched off and in the second experiment the UV lamps were switched on. Comparison of the two results will determine whether the UV lamps had any effect upon the disinfection capabilities of the device. The experiments were carried out in an aerobiological test chamber at (see figure 7), which comprised a 32.25m3 hermetically sealed negatively pressurised room in which the air flow rate, temperature and relative humidity could be constantly controlled and monitored. The experiments were carried out with the ventilation system set at 3 AC/hr at ambient temperature (approx 20°C) and relative humidity (approximately 50%). Figure 7 shows a plan view of the experimental layout of the test chamber having a low level air inlet (a), a high level air outlet (b), a high level sampling point (c), a nebulizer for introducing bacterial/fungal aerosol (d), the device (e) and a particle counter (f).

During the experiments the bacterial aerosols were generated using a 6-jet Collison nebuliser operating at a flow rate of 12 1/mm and at a pressure of 138 N/m2 (20 psi).

This was connected to the room via a 25 mm diameter pipe which terminated in a plastic sphere containing twenty four 3mm diameter holes through which the aerosol was dispersed even into the chamber. Air samples were collected through a plastic pipe located close to the room air outlet grille. This pipe was connected to a six stage Andersen sampler loaded with sterile nutrient agar plates. During the sampling process air passed through the sampler and the bacteria were deposited onto the agar plates.

Each stage of the sampler represents a particular size range and this allows the size distribution of the aerosol to be determined. All the experiments were performed using stages 5 and 6 (the smallest two stages) since previous experiments have shown that the majority of the aerosol is captured in these two stages. The sampling time was varied depending upon the concentration of the bacterial culture with the aim of collecting between 200 and 300 colony forming units on the agar plates.

The test room was set up as shown in Figure 7 prior to the start of each experimental run and the chamber door closed and locked and both the sampling pod (c) and the nebuliser pod (d) sealed. The air fans were then switched on and operated at maximum speed for 30 minutes in order to ensure that the air in the chamber was sterile (filtered outside air). During this purging period the test device remained switched off. The temperature and relative humidity inside the chamber were controlled at approximately 2000 and 50% respectively throughout the experiments. During the initial sterilisation period the pre-sterilised nebuliser was prepared and filled with lOOrril of bacterial suspension at a concentration of approximately 105 organisms/mI of sterile distilled water. The nebuliser was then connected to the inlet tube ready for the start of the expeiiment.

After the initial purging period the ventilation rate was reduced to 3 AC/hr and nebulisation of the bacterial cultuie then began and the concentration in the test chamber was allowed to stabilize for 30 minutes. A total of ten samples were then taken at 3 minute intervals duiing which time the device iemained switched off. Once all ten samples had been taken the device was switched on remotely and the bacterial concentration in the test chambei was allowed to stabilize for 30 minutes. A further ten samples were then taken at 3 minute intervals. The agar plates were incubated at 37°C for 24 hours after which the number of colonies on each plate was counted. All the counts were subjected to standard positive-ho/c correction in order to account for multiple impaction (Macher 1989). The collected counts for each set of plates (stages 5 and 6) were added together to give a total count and niultiplied to give a count per m3 of test chamber air. Each set of samples represents ten replicates taken during steady state, the first ten being the concentration without the device and the second with the device. The mean was taken of the ten replicate samples to give a mean concentration with and without the device. This allowed the mean reduction in concentiation to be calculated used to give an indication as to the efficacy of the device In older to deterniine the statistical significance of the results a t-test was carried out on the two data sets (before and after the device was switched on). The purpose of the test is to determine whether the means of the two data sets are statistically diffeient from each other. The test yields a p-value and the smaller the p-value the less likely the diffeience between the two data sets is the result of chance. During the whole experimental period the concentration of particles within the test chamber was also measured using a portable particle counter set to sample every minute.

Results Disinfection capacity of the device with filtration only Figure 8 shows the concentration of airborne S. aureus during the trial with the device set up with no additional UV disinfection. It can be seen that there is a dramatic drop in the concentration of airborne S. aureus when the device was switched on. The concentration during the control period ranged from 2241 to 5346 cfu/m3 with an average concentration of 2784 cfu/m3. When the device was in operation the concentration ranged from 500 to 985 cfu!m3 with an average concentration of 702 cfu/m3 which represents a reduction in S. aureus from the air stream of 74.8%. A t-test carried out on the control and test data sets showed the difference between the two data sets to be highly significant (pc 0.01).

Disinfection capacity of the device with UV and filtration It can be seen in Figure 9 that the device operated with the UV lamps switched on had a dramatic effect upon the concentration of airborne S. aureus in the test chamber.

During the initial control period the concentration ranged from 3785 to 5023 cfulm3 compared to 198 to 517 cfu/ni3 when the device was switched on. The mean concentrations with and without the device were 4239 and 364 cfu/m3 respectively which represents a kill of 91.4%. The t-test shows that the difference between the two data sets is again highly significant (p<0.Ol).

Particle concentrations durinci the test chamber experiments Figure 10 shows the particle counts in the test chamber during the whole of the test period (Test 2 starts at approximately 150 minutes). It can be seen that the greatest concentration of particles is in the 0.3pm range and that the larger the particle size the smaller the concentration in the test chamber. All the particle size ranges follow the same broad pattern over the experimental period. The concentration of particles increases rapidly after the onset of nebulisation at approximately 15 and 150 minutes for tests 1 and 2 respectively. The peak concentration of particles in each size range is approximately the same in both tests. When the device is switched on in both tests there is a dramatic fall in the particle concentration (75 and 210 minutes) and it can be seen that the concentration reached during Test 2 is marginally lower than that in Test 1.

Discussion The results of the two tests carried out in the test chamber have shown that regardless of the presence of the UV lamps the device is extremely effective at reducing the concentration of airborne S. aureus within this chamber. An important aspect in the design of the system was to reduce the level of contamination in the filters for safe handling. The presence of the UV lamps significantly also improves the performance of the device in terms of its air treatment capacity from 74.8% with no UV to 91.4% with the UV lamps switched on.

The reduction in particle concentrations mirrors what is happening to the level of airborne bacteria in the test chamber with significant reductions in all size ranges but particularly the 0.3pm range. This shows that the device removes a whole range of particles from the air, whether or not they are pathogens. This helps to maintain clean air, and reduces the concentration of particles that may give rise to allergic reactions for example. There is also a slightly larger drop in particle concentration in Test 2 than in Test 1 which also ties in with the bioaerosol results.

In terms of filter contamination the presence of the UV lamps appeared to have a significant effect with the level of contamination with the UV lamps almost 50% less than that with no UV lamps. This result together with the fact that the performance of the device in terms of its air cleaning properties is also improved would suggest that the UV lamps are an important component of the device.

Conclusions

The overall conclusions from the experiments carried out can be summarized as follows: The device is capable of significantly reducing the concentration of airborne S. aureus within the test chamber regardless of whether the UV lamps are on or off.

The device is capable of significantly reducing the concentration of particles in the air within the test chamber regardless of whether the UV lamps are on or off.

The performance of the device in terms of its ability to reduce the concentration of airborne S. aureus within the test chamber is significantly improved when the UV lamps are switched on.

The presence of the UV lamps dramatically reduces the level of contamination of the filters compared to having no UV lamps.

The system of the present invention has a number of advantageous features, including: * the treatment chamber houses a UV light source that does three things by means of the same UV light source: 1) it irradiates particles as they pass by in the air flow 2) it irradiates any filters present 3) it irradiates the coated surfaces of the treatment chamber to generate hydroxyl radicals, and thus has a triple killing effect on pathogens, all of the pathogen treating effects occurring in a turbulent air flow zone that ensures uniformity of exposure and hence is a more efficiently pathogen killing machine. In addition the unit is designed to re-circulate air around a room to more effectively remove airborne pathogens.

The system is a device for cleaning and sterilising the air within an enclosed space (e.g. room or ward). The device is normally mounted centrally on the ceiling. Room air is drawn into a specially designed enclosure, typically using a fan, and then discharged via any one or a combination of UV lights, a photocatalyst and filters. These devices are housed within the treatment chamber in an area of very high turbulence, which results in improved effectiveness of the germicidal UV light and ensures the highest doses of radiation to each passing mico-organism particle. A further increase in the killing potential is provided by the creation of hydroxyl radicals by the photocatalyst.

* The treated air is discharged via either slots, louvers of guide vanes or combination thereof so as to create an airflow pattern within the room or section of room which will become a sterile and particle free zone. Thus occupant(s) within the zone will be protected from possible external contamination or conversely it may be used to protect those outside the zone from contamination arising from within the zone.

* The air is preferably treated from 5 to 20 times an hour; this is an important factor in achieving high decontamination levels as well as enabling the setting up of an airflow regime that will maintain high levels of sterility and cleanliness throughout the defined zone. This system is thus unique in that the design does not just discharge sterile cleaned air but creates a flow pattern in the defined zone to make it into an integrated system for systematically and constantly treating the air in the whole of the defined space. The number of circulations that the air makes through the system per hour may be lowered, for instance at night when there is low activity and when reduced noise is required.

* The system provides for the opportunity to apply a range of alternative techniques that will either de-activate or capture micro-organisms or other undesirable particles. Thus a choice of technique can be made to provide the most effective treatment for a particular micro-organism or group of organisms, particles and VOC5.

* The UV lights are situated in a turbulent zone. Where a fan is used, air discharging from the rotating fan is very turbulent and will more likely give maximum doses of UV radiation to micro-organisms in the air.

* When a photocatalyst surface coating on the inside of the chamber is used, the LJV lights activate the creation of hydroxyl radicals in the turbulent zone and of air discharging from the fan, and the hydroxyl radicals will thus be more effective as a result. Photocatalyst coatings applied to honey comb or mesh like structures may cause UV light shadowing, however this does not occur when using a photocatalyst surface coating on the inside of the chamber. Similarly, when a photocatalyst surface coating on support structures which act as air deflectors, UV lights activate the creation of hydroxyl radicals in the turbulent zone created by the deflectors, and the hydroxyl radicals will thus be more effective as a result.

* The face of the filter, if used: is exposed to UV light. Hence any micro-organisms trapped thereon will be subject to very large doses of UV radiation.

The face of the filter may be constantly exposed to germicidal UV light, thus exposing captured micro-organisms on the surface to many times the required dose of radiation needed to deactivate the micro-organism and hence render the filter safe' to handle when being replaced for maintenance purposes.

* Ceiling mounting generates an air circulation regime around the whole room, or around a specific part of the room when using the adjustable guide vanes. This makes the device a permanent feature, as opposed to a mobile facility.

* All devices that include filters will suffer a loss in airflow as they accumulate trapped particles. To overcome this there is a flow sensing device in the inlet airflow that via electronic devices with bespoke software will translate the signal and adjust the speed of the fan. When at pre-set near maximum and maximum, it will issue two levels of warning, attention' and stopped'. This is important in a health care environment to alert staff to take action and be aware the unit is not functional.

* The system will include an automatic check that a) all UV lights are functioning -if not, the system is stopped and displays a warning message and b) first warn' then stop' when the effective life of the lamps is approaching or reached. This is important in a health care environment to alert staff to take action and be aware the unit is not functional.

* Noise reduction is an important criterion, particularly in the health care industry.

The inlet duct is lined with sound absorbing materials.

* The device can utilise a DC electronically controlled fan with lower energy requirements and with lower noise output.

* The inlet and outlet of the housing can be arranged such that air can be constantly re-circulated within a room. The arrangement includes facility to adjust the angle and velocity of the air stream discharging from the housing.

* Within the box like treatment chamber there are mounted UV lights and arranged such that UV light will fall directly and unimpeded onto all its internal surfaces.

* Micro-organisms are destroyed (or inactivated) by direct exposure to UV light.

Air containing micro organisms in its passage through the treatment chamber will be subject to exposure to UV light.

* On the lower surface of the box like treatment chamber are mounted filters through which the air will pass before being discharged into the room. Air containing a variety of particles that will include micro organisms will be trapped on their surface and thus be subject exposure to UV light over prolonged periods.

* The four sides and top of the box like treatment chamber can be coated with a photocatalytic substance (directly on the walls or on tiles/plates attached to the walls) that will activate hydroxyl radicals when exposed to UV light and are known to destroy micro-organisms. Hence air containing micro organisms will be subject to exposure to the hydroxyl radicals and so render them harmless.

* The destructive effect on the micro-organism depends on the strength and time of exposure to UV light or in contact with hydroxyl radicals. As air passes through the chamber normally the particles suspended therein will be at different distances from the UV light source or the source of hydroxyl radicals and hence subject to different doses -some too much and some not enough. To overcome this disadvantage the air entering the treatment chamber is caused to become very turbulent with the result that all particles will have equal doses of UV and hydroxyl radical exposure. Thus by controlling the residence time within the treatment chamber by either adjusting the airflow rate delivered by the fan or adjusting the size of the chamber itself it becomes a more reliable and efficient means of destroying the micro-organisms.

* The air entering/passing through the treatment chamber is made turbulent by 1) In the case when centrifugal type fans are used mounting them in such a way that air discharging from their rotating periphery goes directly into the treatment chamber (figs. 1 & 1A), or, 2)11 using axial flow fans the air enters the chamber via guide vanes that impart a high speed tangential motion, similar to that of centrifugal fan, resulting in turbulent conditions. (Figs. lB & 10), or, 3) the zig-zag plates (figs 11-14).

* This device combines the destructive effects of both UV and hydroxyl radical exposure on micro organisms in combination with the entrapment and further opportunity of exposure to those destructive effects. This is a powerful combination for the purpose of inactivating the micro organisms.

* The UV sources are positioned so as expose all internal surface of the treatment chamber to direct and unimpeded radiation. This enables all three mechanisms to function using just one source of UV.

* The generation of turbulent air conditions within the treatment chamber ensures uniform exposure to the destructive mechanism. This introduces a level of control over the exposure which would otherwise be of a random nature and therefore less predictable.

The elements of the various embodiments may be incorporated into each of the other species to obtain the benefits of those elements in combination with such other species, and the various beneficial features may be employed in embodiments alone or in combination with each other. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims.

Claims

Claims 1. An air treatment module comprising a treatment chamber having at least one air inlet, at least one air outlet, the treatrrient chamber further having at least one UV radiation source for exposing air in the treatment chamber to UV radiation, the treatment chamber further having at least one support structure, at least part of the surface of the or each at least one support structure comprising a photocatalytic surface, the or each at least one support structure being arranged such that UV radiation from said UV radiation source irradiates the or each at least one support structure in use, the or each at least one support structure being configured to deflect air as it passes through the treatment chamber.
2. An air treatment module according to any claim 1, wherein the module further comprises at least one reflective surface for reflecting UV radiation from the or each at least one UV radiation source.
3. An air treatment module according to claim 1 or 2, wherein the treatment chamber further comprises an enclosure.
4. An air treatment module according to claim 3, wherein the or each at least one UV radiation source, the or each at least one support structure, and the or each at least one reflective surface are housed within the enclosure when assembled, such that the air treatment module is a self-contained unit that can be removably installed in an air circulation apparatus.
5. An air treatment module comprising a treatment chamber having an enclosure, at least one air inlet, at least one air outlet, the treatment chamber further having at least one UV radiation source for exposing air in the treatment chamber to UV radiation, the treatment chamber further having at least one support structure, at least part of the surface of the at least one support structure comprising a photocatalytic surface, the or each at least one support structure being arranged such that UV radiation from said UV radiation source irradiates the or each at least one support structure in use, the module further having at least one reflective surface for reflecting UV radiation from the at least one UV radiation source, wherein the or each at least one UV radiation source, the or each at least one support structure, and the or each at least one reflective surface are housed within the enclosure when assembled, such that the air treatment module is a self-contained unit that can be removably installed in an air circulation apparatus.
6. An air treatment module according to claim 5, wherein the or each support structure is configured to deflect air as it passes through the treatment chamber.
7. An air treatment module according to any preceding claim, wherein the or each at least one support structure has at least first and second opposing surfaces and wherein the or each support structure is arranged in use such that radiation from said UV radiation source can fall on at least pad of both the first and second surfaces of said support structure.
8. An air treatment module according to preceding claim, wherein at least part of a surface of the or each at least one support structure is arranged obliquely to the direction of airflow from the air inlet in use.
9. An air treatment module according to any preceding claim, wherein the or each at least one support structure has apertures therein such that a portion of the air flowing through the treatment chamber will pass through the apertures.
10. An air treatment module according to any preceding claim, wherein the module has a plurality of said support structures, at least part of the surface of each support structure comprising a photocatalytic surface.
11. An air treatment module according to any preceding claim, wherein the or each at least one support structure comprises a plate, the plate having a first slot such that at least part of said UV radiation source is received by the slot when assembled.
12. An air treatment module according to any preceding claim, whelein the or each at least one support structure comprises a plate having a first portion which is arranged obliquely to the direction of airflow from the air inlet.
13. An air treatment module according to claim 12, wherein the or each at least one suppoit structuie comprises a plate having a second portion which is arianged obliquely to the direction of airflow from the air inlet, and at a different angle relative to the direction of airflow from the air inlet from that of the first poition.
14. An au treatment module according to claim 13, whelein the or each at least one support structure comprises a plate having a third portion which is arranged at an angle relative to the second portion.
15. An au tieatnient module according to any of claims 2 to 14, wherein the or each at least one reflective surface is integral with or mounted to an inner surface of the enclosure.
16. An air treatment module according to any of claims 2 to 15, wherein the or each at least one reflective surface is piofiled to incorporate a plurality of formations.
17. An air treatment module according to claim 16, wherein the or each at least one i-eflective surface has a plurality of convex protubelances extending into the treatment chamber.
18. An air treatnient module according to any of claims 3 to 17, wherein the enclosure comprises side walls.
19. An air treatment module according to any of claims 3 to 18, wherein the or each UV radiation source is mountable such that it is rigidly fixed relative to the enclosule when assembled.
20. An air treatment module according to any of claims 3 to 19, wherein the or each at least one support structure is mountable such that it is rigidly fixed relative to the enclosure when assembled.
21. An air treatment module according to any of claims 3 to 20, wherein the module further comprises means for releasably connecting the or each at least one UV radiation source to a power source.
22. Air circulation apparatus, the air circulation apparatus incorporating at least one air treatment module according to any of claims 1 to 21.
23. Air circulation apparatus according to claim 22, wherein the air circulation apparatus is configured to be ceiling mounted.
24. Air circulation apparatus according to claim 22 or 23, wherein the air circulation apparatus is configured to be installed in a recess in a suspended ceiling.
25. An air treatment module or air circulation apparatus according to any preceding claim, further comprising fan means.
26. An air treatment module or air circulation apparatus according to any preceding claim, further comprising at least one filter.
27. An air treatment module or air circulation apparatus according to any preceding claim, wherein the at least one UV radiation source is arranged such that at least a portion of radiation from the at least one UV radiation source irradiates the at least one filter in use.
28. Apparatus for purifying air, the apparatus comprising a treatment chamber having at least one air inlet, at least one air outlet, at least one filter, and fan means for moving air in through the at least one inlet, through the at least one filter and out of the least one outlet, the treatment chamber further having at least one UV radiation source for exposing air in the treatment chamber to UV radiation, wherein the at least one UV radiation source is arranged such that at least a portion of radiation from the at least one UV radiation source irradiates the at least one filter in use, the treatment chamber further having at least one support structure coated with a photocatalyst, the at least one support structure being arranged such that UV radiation from said at least one UV radiation source irradiates the at least one support structure in use, wherein the fan means creates a turbulent air zone in the treatment chamber downstream of the fan means in use, and wherein the at least one UV radiation source, the at least one support structure, and the at least one filter are located downstream of the fan means in the turbulent air zone in use.
29. Apparatus according to any of claims 26 to 28, wherein the at least one filter is downstream of the at least one UV light source.
30. Apparatus according to any of claims 26 to 29, wherein the filter has an upstream side and a downstream side, at least a portion of radiation from the at least one UV radiation source irradiating the upstream side of the at least one filter in use, such that filter contamination is reduced.
31. A module or apparatus according to any preceding claim, wherein the or each at least one support structure is profiled to incorporate a plurality of formations.
32. A module or apparatus according to any preceding claim, wherein the surface of the or each at least one support structure is corrugated, dimpled or embossed.
33. A module or apparatus according to any preceding claim, wherein the photocatalytic surface comprises titanium dioxide.
34. A module or apparatus according to any preceding claim, wherein the at least one outlet has at least one adjustable guide means which is adjustable such that the direction and/or velocity of discharge of air from the outlet can be controlled.
35. A module or apparatus according to claim 34, wherein the adjustable guide means comprises at least one pivotable guide vane.
36. A module or apparatus according to any preceding claim, wherein the apparatus further comprises air flow sensing means and processing means, the processing means being operable to receive inputs from the air flow sensing means and to produce an output based on the inputs for controlling the speed of the fan means.
37. A module or apparatus according to any preceding claim, wherein the apparatus further comprises fan speed warning means adapted to issue a warning signal when the speed of the fan means is above a pre-determined level.
38. A module or apparatus according to claim 37, wherein the fan speed warning means is adapted to issue a warning signal when the fan means is operating at its maximum speed.
39. A module or apparatus according to any preceding claim, wherein the apparatus further comprises UV warning means adapted to issue a warning signal when the at least one UV radiation source is approaching or is at the end of its effective life.
40. A module or apparatus according to any preceding claim, wherein the apparatus further comprises UV monitoring means operable to determine whether the at least one UV radiation source is functioning and to stop the fan means from operating if said UV radiation source is not functioning.
41. A module or apparatus according to claim 38, wherein the UV monitoring means is operable to issue a warning signal if the at least one UV light source is not functioning.
42. A module or apparatus according to any preceding claim, wherein the air inlet has a sound absorbing lining.
43. A module or apparatus according to any preceding claim, wherein the air inlet comprises a tube, the tube having a sound absorbing lining.
44. A kit for assembly into a module or apparatus according to any preceding claim, wherein the kit comprises the parts of the apparatus according to any preceding claim.
45. A module or apparatus substantially as hereinbefore described with reference to any suitable combination of the accompanying drawings.