GB2345005A

GB2345005A - Assembly of rotary air purifying units

Info

Publication number: GB2345005A
Application number: GB9828347A
Authority: GB
Inventors: Jeffrey Martyn Sass
Original assignee: VACMATIC INTERNATIONAL Ltd
Current assignee: VACMATIC INTERNATIONAL Ltd
Priority date: 1998-12-22
Filing date: 1998-12-22
Publication date: 2000-06-28
Also published as: GB9828347D0

Abstract

An air cleaner for a room comprises an assembly of rotary air purifying units. Two, three, six or eight units are mounted on a frame with their inlets facing in different directions. Each unit may comprise a rotary filter element 52, Fig 5, which rotates at high speed to draw in air axially (arrow 54) and discharge it laterally by centrifugal force (arrow 56) through stationary filter element 58 to filter the air. A skirt (50) separates inlet and outlet flows. The skirt and filter elements may be easily removed without the use of tools. Alternatively, Fig 8, the units may have common outlets 32, 34 with skirts 46, 48. The units may be mounted in banks (Fig 7) and controlled remotely by infra red or ultrasonic signals.

Description

TITLE :"Rotary Air Purifying Means" BACKGROUND This invention relates to rotary air purifying means, sometimes called rotary air cleaners. Air cleaners are well-known items of apparatus that suck air in and pass it through a filter system to take out impurities, also called pollution. There are also electrostatic air cleaners.

These types of air cleaner make excessive noise and/or pass air through too slowly. They require frequent changes of filters to maintain the efficiency, or in the case of the electrostatic type are difficult to clean with, usually, high maintenance costs.

If the amount of pollution, or the volume of air to be cleaned, is large, the air cleaner could be made larger or operated more rapidly, but there rapidly comes a point at which the noise of the air cleaner becomes so great that it is unacceptable. Very high-speed, heavy duty motors would be needed, and fan blades or impellers used to create suction, producing severe motor and air movement noise. A possible alternative that has been proposed is to use a plurality of air cleaners placed about the room.

This, too, has disadvantages. The separate air cleaners tend to conflict rather than co-operate, possibly due to the airflow patterns which they create in the room so that some volumes of air tend to be purified repeatedly while other volumes are relatively untouched, or simply due to a single pocket of air being urged in several directions at once, towards respective air cleaners. Again, such an arrangement is difficult to set up to work efficiently, and also difficult to control.

THE INVENTION According to one aspect of the invention, there are provided rotary air purifying means as claimed claim 1. Simply by putting a plurality of air purifying units into a single assembly, it is possible to overcome most, if not all, of the aforementioned disadvantages. Further improvements in the airflow patterns, air cleansing and noise level reduction can be obtained by utilising the features of claims 2 to 16.

Manufacturing advantages and substantial improvements in consistency of performance, e. g. due to reduction in vibration, as well as substantial noise reduction that is particularly needed with the use of a plurality of the air purifying units, are found in utilising the features of claims 17 to 19. Such features are obtainable if each unit is as disclosed in published patent specification GB1346762 in the name of Patent Protection Limited, entitled"A Power Driven Air Filter". Further improvements to the efficiency of such units can be obtained by utilising the features of claims 20 and 21; for example, the features of claim 20 provide means for depositing any particles and bacteria passed by the previous filtering stages, and incidentally killing such bacteria. Fumes, bacteria and so on are forced through the outer filter. This contains carbon granules in a woven material, to absorb cigarette smoke. The features of claims 22 and 23 greatly improve the usefulness of the arrangement by making it more user-friendly; especially in non-industrial applications, intermediate between domestic and industrial applications, as well as in both the latter cases, these features make the arrangement much easier to use, even though the features may involve some slight degree of increased costs and difficulty in the course of manufacture. The features of claims 24 to 27 allow improvements to manufacture and use of the arrangement; for example, the features of claim 27 may be utilised to give the exterior of the arrangement a similar appearance to its surroundings in the room. The features of claims 28 to 41 allow the operation and control of a plurality of such units to be made more automatic and secure, safer, easier and more user-friendly, with a wider variety of control.

Generally, the advantages of the embodiments are that they are cheaper to make, easier to handle, easier to manipulate, easier to set up, cheaper to install, they produce a concentrated (but quiet) high air flow rate at one point rather than spread out and inefficient, they are omni-directional, they provide a better air flow cleaning pattern (because they are not taking in cleaned air to re-filter it, so much as taking in maximally polluted air, and they provide more efficient purification. These advantages are in contrast to the prior proposal of a plurality of air purifying units spaced apart around a room, which tend to conflict rather than co-operate, and the result is inefficient purifying. Also, it is difficult, and therefore expensive, though not impossible, to control all of them by a single remote control unit.

Another feature of the embodiments is that no high speed motors are used and no fan blades or impellers are used to create suction, cutting down motor and air movement noise.

According to another aspect of the invention, there is provided an air purifying system comprising a plurality of air purifying units (e. g. spaced apart around a room), characterised in that they are adapted for all of them to be controllable by a single wireless (in the sense of not being connected thereto by wire) remote control unit.

This control unit might operate by coded infra-red or ultrasonic signals, and might be a unit comprising a plurality of (e. g. infra-red) transmitters pointing in different directions.

PARTICULAR DESCRIPTION RELATING TO THE DRAWINGS Reference will now be made by way of example to the accompanying drawings, in which: Figures 1 to 5 are plan views of different embodiments of the invention; Figures 6 is a front elevation of one of the air purifying units of such embodiments; Figure 7 is a side elevation of two banks, each of the Figure 4 embodiment; Figure 8 is a perspective view of a variation of the Figure 4 embodiment; Figure 9 is a schematic vertical cross-section of the Figure 8 embodiment; Figure 10 is an enlarged partly cut-away plan of the Figure 6 unit; and Figure 11 is a schematic partial perspective view of a room in a building embodying the invention Referring to the drawings, rotary air purifying means 10 comprise an assembly 12 of a plurality of air purifying units 14. Each said unit 14 has an inlet 16 and these inlets 16 point in respectively different directions 18,18. Said directions 18 (represented by arrows pointing in a sense opposite to the direction of airflow) are substantially radial from a notional common centre 20. As seen in Figure 4, said directions 18 comprise a spread of directions arranged substantially in a plane and spread around 360 degrees, and said plurality is preferably six. In the Figure 5 embodiment, said plurality is eight. Both of these embodiments are suitable for pedestal (or column) mounting or for suspension from a ceiling. In the Figure 3 embodiment, said directions 18 comprise a spread of directions arranged substantially in a plane and spread around 180 degrees for mounting to a wall, said plurality being three. In the Figure 2 embodiment, also for mounting to a wall, said plurality is two and the spread of centre directions 18 is substantially less than 180 degrees. In the Figure 1 embodiment, said directions 18 comprise a spread of directions arranged substantially in a plane and spread around 90 degrees for mounting into a wall corner, and said plurality is two. The preferred embodiments of those in which adjacent units 14 point in directions which are at 60 degrees to each other. In the embodiments of both of Figures 1 and 2, and to some extent with the embodiment of Figure 3, the spread of air intake does not quite reach the wall and this avoids interfering with a non-polluted layer of air that usually occurs by the wall. In a development of the embodiments of 1 to 5, the whole of the arrangement shown in the Figure constitutes a bank 22 of the units 14, and there is at least one more bank 22 above this, as indicated in Figure 7. The spacing 24 between the banks 22 is at least half a metre, preferably substantially 1 m. Each bank may be 31 in. in diameter, 16 in. in height (which includes two skirts 46,48 of 2 in. height).

Each unit 14 is shown with a series of slots 26 all around its circumference, which slots 26 together constitute its outlet 28. As seen in the Figure 8 embodiment, the units 14 have at least one common outlet 32; the units 14 apart from their inlets 16 are mounted inside a housing 30 so that their outlets 28 feed into the inside of housing 30 and hence feed common outlet 32. On the opposite (underneath) face of housing 30, there is another common outlet 34, and these two common outlets 32,34 face in opposite directions, i. e. up and down. As indicated in Figure 9, the arrangement comprises means 36 in the form of plates 36 to direct different parts 38, 40 of the outflow of a said unit 14 to two different outlets 32,34. As also seen in Figure 9, two neighbouring said units 14 are thereby arranged for neighbouring parts 42,44 of the outflow of the respective units 14 to be directed to different outlets 32, 34.

As exemplified in Figures 2 and 8, said units 14 have inlets 16 and outlets 28, and there are skirt means 46,48 around the outlets 32,34 to direct outflow away from the inlets 16. As seen in the embodiments of Figures 1 to 5, said units 14 have skirt means 50 in the form of conical flares 50 around the inlets 16 to direct outflow away from the outlets 28. It will not normally been necessary to have both skirt means 46, 48 and skirt means 50 in the same embodiment.

Said units 14 operate without the aid of impellers and/or fan blades. More particularly, each unit 14 is of a centrifugal type that comprises a (primary) rotary filter element 52, Figure 5, and is adapted for this to rotate at a high speed to draw in air axially of the filter, in the direction 54, and discharge it laterally, in the direction 56, by centrifugal force to filter the air. Each unit 14 also comprises a (secondary) stationary filter element 58 arranged around the rotary element 52 to provide another stage of filtration of the air. The arrangement may further comprise an ionising trap or filter means 60, in the form of a wire 60 around each said stationary filter element 58, wire 60 being stiff and placed outside, and spaced from, the housing 62 of each unit 14, to act in known manner. Each unit 14 may further comprise a stationary filter element 64, in the form of a piece of silk 64, arranged to filter the air prior to the rotary element 52, e. g. to trap large polluting matter such as hairs and spiders'webs. The primary filters are washable and the secondary filters are changeable, to combat bacteria, toxic fumes, unpleasant fumes, germs, pollen dust, mites and dangerous particles.

As shown in more detail in Figure 10, the arrangement comprises means 66,68, 70 adapted to provide access to the filter elements 52,58, and/or to enable them to be removed and replaced, by hand without the use of tools. The adapting means could comprise a plastics core to each of rotary filter elements 52, the cores having a central hole which is a push fit onto rotary spindle 76; however, as shown by way of example in Figure 10, the adapting means 66,68,70 comprise clip means 66,68, means 66 being toggle clip means 66 whereby housing 62 can be readily attached to and removed from rear mounting 72, clip means 68 being in the form of a (spring) circlip 68 fitting into groove 69 on spindle 76 and having handles for finger release of it from groove 69 and holding a plate 74 in place against rotary filter element 52 to hold the same in position on rotary spindle 76, and male and female screw means 70 whereby flared skirt 50 can be attached to and removed from housing 62, all by hand and without the aid of tools ; alternatively, skirt 50 and housing 62 may be of plastics welded together.

In the embodiments of Figures 1 to 5, there is a frame 80 to which said units 14 are mounted, the frame 80 itself being mounted to wall, ceiling or pedestal. These embodiments may be used as shown, or the arrangement may comprise a housing 30 within which said units are mounted, e. g. as shown in Figure 8. The housing 30 may in fact replace frame 80, so that units 14 are mounted directly into housing 30. (The housing 30 then has inlet and outlet ports with guides and channels to enable the air to enter the system, pass through the filters freely at a speed that enables the filters to have full effect and be diverted to pass back the cleaned air into the area from which it came.) However, it is preferable to retain frame 80 so that said housing 30 can be removable, and in fact that is removable by hand without the use of tools. If appropriate, the housing 30 comprises a decorative facing 82 to surround each inlet 16. Each inlet 16 and outlet 28,32,34 is covered by bars 84 to protect against the insertion of fingers which might thereby be damaged, e. g. by parts rotating at high speed.

The arrangement comprises sensor means 86, Figure 10, adapted to be sensitive to pollution in the air to control operation of the air purifying means 10. The sensor means 86 comprise a smoke detector 86. For greatest efficiency, the sensor means 86 would, instead of being placed adjacent the purifying means 10, the located where the air is likely to be most polluted, e. g. above the bar 96 of a public house 94. The sensor means 86 may be made automatic by arranging for them to provide automatic control of the air purifying means 10, e. g. to engage boost in response to sensing a predetermined level of pollution.

At least one said unit 14 is adapted to be operable at at least two speeds, namely, a low speed for low duty or background purification and a high speed for heavy duty or boosted purification, by operation of switch means 88, Figure 5. These speeds are not critical and suitable speeds are known in the art. The switch means 88 of the various units 14 are interconnected so that the latter shall be operable with all of them at low speed, with all of them at high speed, and with at least one of them at high speed and at least one of them at low speed. The assembly 12 may be operable so that there are at least as many steps in total power as the number of units 14, e. g. with six units 14, it may be made possible to select 0,1,2,3,4,5 or 6 of them to be on 1/2 power or full power (7 selections). Preferably, though, the various switch means 88 are so interconnected that the various units 14 are operable in only three modes, namely, with all of them at high speed, with all of them at low speed, and with only one of them at high speed and the other (or all the others, depending upon which embodiment is being considered) at low speed.

The switching means 88 are adapted to switch at least one said unit operating at high speed (boost) back to low speed automatically after a predetermined time, e. g. after 10 to 300 minutes, this being pre-settable. The same switching means 88 may be further adapted to switch off said air purifying means 10 automatically after a predetermined time, and/or control either or both of said predetermined times. The switching means 88 may further be programmable to control functions of the air purifying means 10, e. g. times or periods to start, stop, boost and/or engage automatic sensor means, e. g. sensor means 86 when arranged to provide automatic control of air purifying means 10.

For example, in the Figure 4 embodiment, with boost increasing the flow rate from, say, 1/2 to 1, it is possible to boost the arrangement using the three steps of flow rate: 6x1/2 ; 1x1 + 5x1/2 ; 6x1 (where the first figure in each expression is the number of units 14 having the level of flow rate of the second figure). The last of these cases, which is maximum boost, gives the same dB level (relative to the threshold of hearing), 60 dB, as ordinary talking (see table below).

For control of the air purifying means 10, the latter comprises coded control means 90, Figure 11, so arranged that the same can only be controlled by a user possessing the necessary code (built into a remote control device 92). Control means 90 comprises control signal receiver means 90 adapted to receive control signals from remote control device 92 through a wireless (in the sense of absence of wire) connection. To select the 7 steps in total power, mentioned above, the device 92 may have 7 separate buttons, as well as buttons for other control features. If the arrangement is in a public house 94 or hospital 94, for example, remote control device 92 may be located at the bar 96 or nurses'station 96, respectively. Said wireless connection will usually be an infra-red connection, but, e. g. if there is a requirement for a control device 92 to operate simultaneously receivers that are spread well apart, it may be an ultrasonic connection. In order to prevent unauthorised use of remote control device 92, the same can be a hand-held device 92 instead of being fixed in place at the bar 96. The air purifying means 10 may comprise the remote control device 92, though this will then not be part of the aforesaid assembly 12. For further control of the air purifying means 10, when this comprises automatic sensor means 86, the air purifying means 10 is adapted for said remote control device 92 to override such sensor means 86.

In use of the arrangement, a building 94, e. g. a hospital 94, or other structure, e. g. a ship or aeroplane, has a room 98 in which is arranged said air purifying means 10.

The building 94 may comprise a leisure place, public house, cinema, restaurant or factory. If it comprises a hospital 94, said room 98 may be a recovery room 98 for patients recovering from anaesthetic, the arrangement being used for taking out (absorbing) anaesthetic fumes breathed out by a patient. Generally, the arrangement sucks in polluted air, filters it, and returns it to the inside working environment instead of it going outside. Said air purifying means 10 is adapted to filter substantially all the air in the room 98 at least once every ten minutes. Alternatively, the said air purifying means 10 can be arranged in an upper part of said room 98 and be adapted to filter substantially all of the air in the upper one-third of the room at least once every ten minutes.

The building 94 or other structure will then contain air purified by said air purifying means 10, the air being more or less purified according to how long and at what speed the purifying means 10 has been operating. Use of the air purifying means 10 provides a method of purifying air.

Each unit 14 contains 2 to 8 rotary filters, and takes out gases, smells and cigarette smoke. The filters do not need tools to access them (which greatly eases maintenance) but then the unit 14 needs a proper air-seal which is more difficult to produce.

Domestic air purifiers may be considered to pass < 200 cubic feet per minute, and industrial air purifiers to pass > 450 cubic feet per minute.

TEST RESULTS The system, e. g. as illustrated in Figure 4, will run at half speed when in standby mode and only at full speed when required, saving electricity and noise at half speed, when the noise level with six motors running is between faint and very quiet, and only up to moderate to normal conversation level when at full speed.

The sound tests were carried out in a room 10 ft by 14 ft by 8 ft (1120 cubic feet) The instruments used were: (1) digital sound survey meter, made by Dawe, model D-1405E; (2) a standard air flow instrument made by Airflow Developments Limited, model AV2, with a 100 mm head.

Units of noise level measure in the following table are dB: Number Air Flow (cubic feet per minute) Noise Level in dB of units Half Speed Full Speed Half Speed Full Speed Horizontal VerticalHorizontal Vertical 1 120 240 33.4 33.6 49.08 50.3 2 240 480 35.1 35.7 52.3 52.8 3 360 720 36.7 36.9 54.4 54.8 4 480 960 37.7 37.8 56.0 55.8 5 600 1200 38.4 38.8 57.2 56.1 6 720 1440 39.6 40.5 58.6 57.9 8 960 1920 40.8 42.2 60.0 59.7 NOTE : 30 dB = faint (rustle of paper); 40 dB = town at night; 50 dB = moderate (quiet office) ; 60 dB = normal conversation; 70 dB = large department store.

The measurements were made with the sound survey meter head at 1 m from each assembly, which was 0.75 m (31 in.) in diameter, on the spindle axis line, though it was found that moving the head circumferentially around the assembly did not give appreciable variation in noise level. Also, the Air Flow figures are averaged, e. g. 240 in the table was averaged from readings from 235 to 253, but these variations did not give any appreciable variation in the noise level."Vertical"refers to the axis of the assembly 10 in the orientation illustrated, with the spindles 76 horizontal. The assemblies 10 were also tested on their side,"Horizontal".

Frequency of air changes were as follows, calculated using a room volume measuring 26 ft by 20 ft by 9 ft as an example, for which the cubic capacity (volume) was 4680 cubic feet or 132 cubic metres, with a consumption of 90 watts for each motor (in a unit 14 as from a domestic purifier). For one motor, at half speed 1.44 changes per hour (one change every 42 minutes), at full speed 2.88 changes per hour (one change every 21 minutes), and pro rata for more motors. For a purifier for industrial application, using a 270 watt motor, for one motor, at half speed 4.17 changes per hour (one change every 14.4 minutes), at full speed 8.34 changes per hour (one change every 7.2 minutes), and pro rata for more motors.

A prior art heavy duty extractor fan for 1200 cubic feet per minute gives a noise level of 72 dB, without filters, the addition of which would require a larger motor and produce even higher noise levels. For an extractor for 1800 cubic feet per minute, the noise level is 75 dB, again without filters. These figures are to be compared with the figures in the table for an embodiment of the invention.

The motor 100, Figure 10, of a unit 14 is in a chamber in the cap-shaped rear mounting 72, and this can be provided with acoustic muffling 102, further to deaden any motor noise.

It will be apparent to one skilled in the art, that features of the different embodiments disclosed herein may be omitted, selected, combined or exchanged and the invention is considered to extend to any new and inventive combination thus formed.

Claims

1. Rotary air purifying means, characterised in that it comprises an assembly of a plurality of air purifying units.

2. Means as claimed in claim 1, characterised in that each said unit has an inlet and these inlets point in respectively different directions.

3. Means as claimed in claim 2, characterised in that said directions are substantially radial from a notional common centre.

4. Means as claimed in claim 2 or 3, characterised in that said directions comprise a spread of directions arranged substantially in a plane and spread around 360 degrees.

5. Means as claimed in claim 4, characterised in that said plurality is six.

6. Means as claimed in claim 2 or 3, characterised in that said directions comprise a spread of directions arranged substantially in a plane and spread around 180 degrees for mounting to a wall.

7. Means as claimed in claim 6, characterised in that said plurality is three.

8. Means as claimed in claim 2 or 3, characterised in that said directions comprise a spread of directions arranged substantially in a plane and spread around 90 degrees for mounting into a wall corner.

9. Means as claimed in claim 8, characterised in that said plurality is two.

10. Means as claimed in any one of claims 1 to 9, characterised in that said units are arranged in banks, one above another.

11. Means as claimed in any one of claims 1 to 10, characterised in that a plurality of the units have at least one common outlet.

12. Means as claimed in claim 11, characterised in that two of said common outlets face in opposite directions.

13. Means as claimed in any one of claims 1 to 12, characterised in that it comprises means to direct different parts of the outflow of a said unit to two different outlets.

14. Means as claimed in any one of claims 1 to 13, characterised in that two neighbouring said units are arranged for neighbouring parts of the outflow of the respective units to be directed to different outlets.

15. Means as claimed in any one of claims 1 to 14, characterised in that said units have inlets and outlets, and skirt means around the outlets to direct outflow away from the inlets.

16. Means as claimed in any one of claims 1 to 15, characterised in that said units have inlets and outlets, and skirt means around the inlets to direct outflow away from the outlets.

17. Means as claimed in any one of claims 1 to 16, characterised in that said units operate without the aid of impellers and/or fan blades.

18. Means as claimed in any one of claims 1 to 17, characterised in that each unit is of a centrifugal type that comprises a rotary filter element and is adapted for this to rotate at a high speed to draw in air axially of the filter and discharge it laterally by centrifugal force to filter the air.

19. Means as claimed in claim 18, characterised in that each unit comprises a stationary filter element arranged around the rotary element to provide another stage of filtration of the air.

20. Means as claimed in claim 19, characterised in that it comprises ionising trap or filter means around said stationary filter element.

21. Means as claimed in any one of claims 18 to 20, characterised in that each unit comprises a stationary filter element arranged to filter the air prior to the rotary element.

22. Means as claimed in any one of claims 18 to 21, characterised in that it comprises means adapted to provide access to the filter elements, and/or to enable them to be removed and replaced, by hand without the use of tools.

23. Means as claimed in claim 22, characterised in that the adapting means comprise clip means and/or toggle means.

24. Means as claimed in any one of claims 1 to 23, characterised in that it comprises a frame to which said units are mounted.

25. Means as claimed in any one of claims 1 to 24, characterised in that it comprises a housing within which said units are mounted.

26. Means as claimed in claim 25, characterised in that said housing is removable by hand without the use of tools.

27. Means as claimed in claim 25 or 26, characterised in that each said unit has an inlet and the housing comprises a decorative facing to surround each inlet.

28. Means as claimed in any one of claims 1 to 27, characterised in that it comprises sensor means adapted to be sensitive to pollution in the air to control operation of the air purifying means.

29. Means as claimed in claim 28, characterised in that the sensor means comprise a smoke detector.

30. Means as claimed in any one of claims 1 to 29, characterised in that at least one said unit is adapted to be operable at at least two speeds, namely, a low speed for low duty or background purification and a high speed for heavy duty or boosted purification.

31. Means as claimed in claim 30, characterised in that it is adapted for said units to be operable with all of them at low speed, with all of them at high speed, and with at least one of them at high speed and at least one of them at low speed.

32. Means as claimed in claim 31, characterised in that it is adapted for said the units to be operable in only three modes, namely, with all of them at high speed, with all of them at low speed, and with only one of them at high speed and the other/s at low speed.

33. Means as claimed in any one of claims 30 to 32, characterised in that it comprises switching means adapted to switch at least one said unit operating at high speed back to low speed automatically after a predetermined time.

34. Means as claimed in any one of claims 1 to 33, characterised in that it comprises switching means adapted to switch said air purifying means off automatically after a predetermined time.

35. Means as claimed in claim 33 or 34, characterised in that said switching means comprise means to control said predetermined time.

36. Means as claimed in any one of claims 1 to 35, characterised in that it is programmable to control functions thereof, e. g. times or periods to start, stop, boost and/or engage automatic sensor means.

37. Means as claimed in any one of claims 1 to 36, characterised in that, for control thereof, it comprises coded control means so arranged that the same can only be controlled by a user possessing the necessary code.

38. Means as claimed in any one of claims 1 to 37, characterised in that, for control thereof, it comprises control signal receiver means adapted to receive control signals from a remote control device through a wireless (in the sense of absence of wire) connection.

39. Means as claimed in claim 38, characterised in that said wireless connection is an infra-red connection.

40. Means as claimed in claim 38 or 39, characterised in that it comprises said remote control device, and the same is a hand-held device.

41. Means as claimed in claim 40, characterised in that, for control thereof, it comprises automatic sensor means, and is adapted for said remote control device to override such sensor means.

42. Air purifying means substantially according to any example hereinbefore described.

43. Air purifying means substantially according to any example hereinbefore described with reference to and illustrated in the accompanying drawings.

44. A building or other structure, characterised in that it has a room in which is arranged air purifying means as claimed in any one of claims 1 to 43.

45. A structure as claimed in claim 44, characterised in that it comprises a hospital and said room is a recovery room for patients recovering from anaesthetic.

46. A structure as claimed in claim 44 or 45, characterised in that said air purifying means is adapted to filter substantially all the air in the room at least once every ten minutes.

47. A structure as claimed in claim 44 or 45, characterised in that said air purifying means is arranged in an upper part of said room and is adapted to filter substantially all of the air in the upper one-third of the room at least once every ten minutes.

48. A building or other structure, characterised in that it contains air purified by air purifying means as claimed in any one of claims 1 to 43.

49. A building or other structure substantially according to any example hereinbefore described.

50. A building or other structure substantially according to any example hereinbefore described with reference to and illustrated in the accompanying drawings.

51. Air, characterised in that it has been purified by air purifying means as claimed in any one of claims 1 to 43.

52. A method of purifying air, characterised in that it comprises use of air purifying means as claimed in any one of claims 1 to 43.

53. A method of purifying air substantially according to any example hereinbefore described.

54. A method of purifying air substantially according to any example hereinbefore described with reference to and illustrated in the accompanying drawings.

Amendments to the claims have been filed as follows

5. Means as claimed in claim 4, characterised in that said plurality is six.

7. Means as claimed in claim 6, characterised in that said plurality is three.

9. Means as claimed in claim 8, characterised in that said plurality is two.

-25. Means as claimed in any one of claims 1 to 24, characterised in that it comprises a housing within which said units are mounted.

30. Means as daimd in any onc of claims 1 to 29, characterised in that at least one said unit is adapted to be operable at at least two speeds, namely, a low speed for low duty or background purification and a high speed for heavy duty or boosted purification.

36. Means as claimed in any one of claims 1 to 35, characterised in that it is programmable to control functions thereof, e. g. times or periods to start, stop, boost 2ndZ0r engage automatic sensor means.

41. Means as claimed in claim 40, characterised in that, for contro : t' : recz, it comprises automatic sensor means, and is adapted for said remote control device to override such sensor means.

52. A method of purifying air, characterised in that it comprises use of air purifying means as claimed in any one of claims I to 43.

55. Rotary air purifying means, characterised in that it is adapted to take in air axially and put out processed air laterally and comprises air-flow control means adapted to help ensure that the outgoing air is not entrained in the ingoing air.

56. Means as cla ; med in claim 55, characterised in that said air-flow control means comprise skirt means.

57. Means as claimed in claim 55 or 56, characterised in that it has the further features of any one or more of claims 1 to 41.

58. Rotary air purifying means, characterised in that it comprises a plurality of rotary-filter air purifiers mounted to a single locatable mounting to operate in parallel.

59. Means as claimed in claim 58, characterised in that it has the further features of any one or more of claims 1 to 41 and/or 55 to 57.

60. Means or a structure having the features recited in any one or more of claims 13, 15,16,20,21,22,28, 33, 34, 36, 37, 38,41 and/or 45 apart from any reference in such claim or claims to any other claims.

61. Means or a structure as claimed in claim 60, having the further features recited in any one or more of said other claimjs.