GB2180054A - Air curtains for cleaning polluted air - Google Patents

Abstract

An arrangement for controlling tobacco smoke pollution especially in places such as bars and restaurants for example comprises a system in which air, pressurised by a fan 10, is fed to a horizontally disposed duct 14 and discharged through a slot 16 or aligned series of apertures in the duct to produce a curtain of air 18 directed towards an opposed collector hood 20. The air collected by the hood 20 is conveyed to a filter 28 and then back to the pressurising fan 10 for recirculation. Smoke polluted air becomes entrained in the air curtain 18 and is removed from the environment. The air curtain 18 may be oriented horizontally or vertically. When oriented vertically it can also be very effective as a smoke pollution barrier for partitioning off localised regions of an enclosed space from adjacent regions where the pollution originates. <IMAGE>

Description

SPECIFICATION Method and means for controlling air pollution such as pollution from tobacco smoke in enclosed spaces This invention relatesto the control of air pollution and is particularly concerned with a method and means for controlling and limiting the extentofair pollution caused by smoke orfumes, such as smoke orfumesproduced by burning tobacco,within an enclosed space.

More specifically, the invention is particularly dir ectedtotheproblem of controlling the pollution caused by persons smoking in enclosed spaces, especially in commercial establishments such as bars or restaurantsfor example or in other places where many smokers may be present.In such situations it is desirableto reducethe resultant air pollution and, in some cases, also to limit its spread so as, perhaps, to enable a particular region or regions to be kept sub- stantiallyfreeoftabaccosmokepollution. Not only can heavytoabcco smoke pollution be a nuisance and very unpleasant for people subjected to it, as well as being damaging to the environment, but also it is now generally recognised that it can presenta serious health hazard even to the people who are not smoking but who inhale the polluted air.Apart, therefore, from trying to reduce the general level of pollution, it can often also be desirablethatthe pollu tionandthesmokerscausing itshouldbelimitedtoa particular localised region or regions separate from anotherfrom region or regions which can be kept substantially smoke free. For exampie, in a public bar a considerably amount of tobacco smoke pollution is commonly generated and it would be very desirable at least for the bar staff behind the bar counter to be protected as far as possible from continuous exposure to this pollution during theirworking periods; also, itcould be desirable and beneficial forcertain regions of the customers' area of the bar to be kept substantially smoke free for the benefit of nonsmoking customers, and the same is true in restaurants and similarestablishments.This need may also arise in offices for example and, in some cases, even in domestic environments.

Hitherto, some attempts in commercial establish ments to reduce tobacco smoke pollution at least in a localised region or regions have been made by installing electrostatic precipitators and/or sophisticated air conditioning. However, normal aircondition ing systems are often not particularly effective orefficient in dealing with the problem and electrostatic precipitators are also frequently not as effective as may be desired as well as being costly to install and proneto operating troubles in use.

It is accordingly an object of the present invention to provide a method and means for dealing more at isfactorywith this problem of smoke orfume pollution, especially tobacco smoke pollution, in establishments ofthetype mentioned and in other enclosed space environments.

Broadly, the invention provides a method of controlling and reducing air pollution within an enclosed space caused by smoke orfumes generated within a region or regions of that space, said method comprising establishing in said enclosed space, adjacent said pollution generating region or regions, one or more air curtains incorporated within an aircollection and circulation system which also includes air filtration means, said aircurtain orcurtains being effectiveto set up a smoke orfume barrier or barriers and at the sametimeto cause airborne pollution, es pecially smoke particles, from the pollution generating region or regions to be removed by becoming entrained in the flow ofairthatestablishes said curtain orcurtains,which air is collected,filtered andrecirculated.

The invention also provides air pollution control apparatus or installations for carrying out the above method.

Such apparatus or installations will generally comprise an air circulation system including fan means for providing a supply of pressurised air, at least one elongate supply duct arranged to discharge the pressurised airthrough aperture means in a common planeso asto setuptheaircurtain or curtains opposed complementary collector means disposed in substantially the same plane and arranged to collect the airfrom the air curtain orcurtains, duct means for conveying the airfrom the collector means to airfiltration means, and duct means for returning the air from the air filtration means to the pressurising fan means for recirculation.

In some embodiments of the invention, the appar atus or installation is arranged so asto setuptheair curtain or curtains in a vertical plane, and in this case the vertically oriented smoke orfume barrier or barriers so formed may in effect partition off said pollution generating region or regions from a second localised region or regions in the enclosed space thereby enabling said second localised region orregionsto be maintained in a relatively unpolluted condition.

Forth is purpose, the circulation system should usually be designed and operated, particularly in respect ofthe velocity and means of air circulated, so asto ensure that theairflowthroughoutthe air curtain or curtains is a laminarflowwithoutturbulence, and in practice the velocity of the airflow in the or each curtain can be sufficiently low as to avoid creating any unacceptable atmospheric disturbance whilst maintaining its effectiveness as a barrierto smoke laden air.

Also, the installation or apparatus may include both fan means for pressu rising the air at a point in the circulation system upstream of the air curtain or curtains as well asfan meansforproducing asuction or negative pressure downstream ofthe curtain or curtains so as to assist in extracting the airthrough the collector. Furthermore, the or each vertically oriented air curtain is preferably set up by an upwardly directed current or currents of air. Thus, pressurised airfor producing the or each air curtain may be discharged through an upwardly presented slot or row of maligned apertures in a horizontal pressurised discharge duct at the bottom, and the collector means may be in the form of an overhead elongate extraction hood or open duct aligned vertically with the discharge duct.

Preferably the filtration means will comprise a filter having a replaceable filter element, and the pres surising fan means and the suction fan means will be arranged either side of the filter and are designed to provide a balanced circulation system.

In other embodiments ofthe invention, the apparatus or installation may be arranged so asto setup the air curtain or curtain in an overhead horizontal plane at a convenient position below ceiling level, and may advantageously be designed in the form of a composite self-contained unit. With this type of arrangement, the unit may be of generally compact and possibly transportable form but will usually be designed to provide a somewhat higher cross flow rate of air in the air curtain or curtains than in the case of vertically oriented air curtain or curtains, i.e. sufficiently high to ensure that a high proportion of smoke laden or polluted air in the vicinity is induced into the horozontal curtain cross flow for collection and filtering.With such units being of relatively small dimensions, one or more units may be provided in a large room or enclosure at different locations so asto give the degree of pollution control required, without need for any extensive structural modifications, and the versatility of such units can give considerable scopeforplanning and arranging the apparatusor installation to the best advantage in different situations. Such units may in some cases even be scaled down sufficiently as to be mounted on a stand orsupporting base which may be placed on the floor or even on a table and means may also be provided for adjusting the height and/or orientation of the unit.

Byway of example, embodiments of the invention will be more particularly described with reference to the accompanying drawings.

In the drawings; Figure lisa schematic diagram illustrating the general principle of the air circulation system which may be employed in some embodiments ofthe invention; Figure2 is a diagram representing in plan view in typical bar provided with an air pollution control arrangement in accordance with a first embodiment ofthe present invention; Figure 3 is another diagram of the same bar shown in vertical section taken along line Ill-Ill of Figure 2; Figure 4 is a further schematic diagram of the air circulation system ofthe embodiment illustrated in Figures 2 and 3; Figure5isaviewsimilarto Figure 3 but illustrating the use of an air pollution control arrangement in ac cordance with a second embodiment of the invention; Figure 6is a diagram showing the apparatus of said second embodiment in plan view; and Figure 7illustrates diagrammatically a smaller transportable form ofthe apparatus.

The same reference numerals are used throughout the different figures ofthe drawings to indicate like parts.

As shown in Figure 1, atypical air circulation system used in carrying outthe invention in some embodiments is basically an open circuit circulation system wherein air is pressurised by a fan 10 and fed through a supply duct 12 to a horizontally disposed elongate pressure duct 14 having a longitudinal slot 16 in its top surface through which the pressurised air is discharged in an upwards direction to produce a curtain 18 of upwardly moving airwhich is collected at the top by a vertically aligned overhead collec- tor or extraction duct or hood 20 from which a duct 22 leads to a suction fan 24.From the suction fan 24 the air is then passed through duct 26 to a filter 28 having a replaceable filter element, and from the filter 28 the filtered air is then passed backthrough duct 30 to the pressurising fan 10 for recirculation. If required, dampers D may be incorporated upstream and/or downstream of the pressurising fan in ducts 30 and 12 in order to facilitate further control and balancing of the circulatory flow.

In operation, as already indicated,the aircurtain 18 effectively forms a barrier to the spread of smoke laden air from one side to the other, and such polluted air reaching the curtain will also become entrained therein and passed round the circulatory system where the smoke pollution will be removed bythefilter28.

In a practical embodiment using the arrangement of Figure 1 for reducing the pollution in a typical bar and for enabling the bar staffto work in a relatively unpolluted smoke free atmosphere, as indicated in Figures 2 and 3theslotted discharge duct 14 maybe arranged along the length of the front of the bar counter40 so thatthe staff in the serving area 42 be- hind the bar counter 40 are screened from the custo mers' area 44 by the air curtain 18which extends up to substantially ceiling level. l n this embodiment, the duct 22 from the collector or extraction hood 20 is shown as extending back into a rearstockroom region 46 of the barwhich houses the fans 24 and 10 and filter 28.The particular arrangement of location of these components of the circulation system may however be varied as desired.

In practice, the fans 10 and 24 may conveniently be either of a bifurcated or centrifugal type.

Although the collector or extraction duct 20 is indicated as being in the form of a continuous elongate duct open along its underside, it may be desired be in the form of a hood or a series of short hoods connected to a common duct. Also, the pressurised discharge duct 14 is indicated as being in the form of a rectangular section slotted duct, but instead of having a continuous slot 16there may be a series of shorter slots or apertures. Also, the pressurised discharge duct 14 maybe designed so that its crosssectional area diminishes along its length in the direction away from the end to which the supply duct 12 is connected, thereby to reduce pressure differences along its length and maintain a more uniform airflow across the width ofthecurtain.

Operating details may of course be varied as required in accordance with the needs of the particular installation, but if for example the total volume ofthe enclosed bar area, that is, the customers' area 44 and the serving area 42 behind the counter of the bar which is illustrated in Figures 2 and 3, were to be 3600 cubicfeet (381 cubic metres) and if the mass of airto be circulated is calculated on the basis ofsixcom- plete air changes per hour (this could well be a typical figure) this would give a massflow of 360 cubiefeet per minute (38.1 cubic metres per minute).Atypical velocityforthe air in the pressurised duct could well be 2500 feet per minute (762 metres per minute), so that with for example the pressurised discharge duct 14 being of rectangular cross-section with dim ensionsof5inches by4inches (127mmx102mm), and with a 1/2 inch (12.7mm)wide discharge slot, this could result in a velocity of the air emerging from the slot 16 being of the order of 300 feet per minute (91.5 metres per minute).An air curtain in which the air currentvelocity is of this order of magnitude would be quite sufficient to provide an effective barrier to a smoke laden area and, also, to induce from the customers' area ofthe bar currents of polluted smoke laden airwhich would be entrained in the air curtain, as peviously mentioned, so asto be passed out through the extraction duct20forfilteringand recirculation.

Although in this particular example ofthe smoke pollution control arrangement being applied to a bar the pressurised discharge duct 14 has been shown as being mounted on the front of the bar counter 40 tow- ards the top thereof, the pressurised discharge duct could of course be positioned at floor level so that the air curtain would extend for practicallythefull height ofthe room, and this would usually be the arrangement employed where it is required to partition off a complete area of a room, such as in a restaurantfor example,forthe benefit of non-smokers.

In the second embodiment illustrated in Figures 5 and 6, an installation or apparatus is provided which is adapted to produce an overhead horizontally oriented aircurtain below ceiling level above a region or regions where it is expected that tobacco smoke pollution is most likely to be generated.

In this example, the apparatus is intheform of a composite self-contained unit48ofwhichtheel- ements comprise a fan 10', a horizontally disposed elongate pressure duct 14' having a longitudinal slot or series of aligned apertures (not shown) in a side face through which pressured air is discharged ion a horizontal direction to produce a curtain 18' of hori zontallymovingairwhich is collected byawidersiot- ted collection or extraction duct 20' spaced apart in the same horizontal plane. From the collection duct 20' the air is passed to a filter 28' and then back through duct 30' to the fan 10', so that again there is an open circuit circulation system but with a horizontal air curtain therein.

For structural convenience, the ducts 14' and 20' are provided by opposite side limbs of a single Ushaped duct of which the base section 50 is blanked off by internal cross-walls 52. Also, the filter 28' may comprise both a pre-filter, e.g. of gauze or the like,to remove larger particulate matter in the air and a main replaceable filter element, such as an activated carbon filter element for example, for removing the tobacco smoke, small dust particles and odour producing vapour, etc.

The unit48 may be of quite modest dimensions and in a typical example it may have an overall length of 12.75 ft (3.9 metres) and an overall width of 4.25 ft (1.3 metres) with the duct sections 14' and 20' each having a length of about 5ft (1.5 metres), and a dia meter of 6 inches (152 mm), spaced apart ata dis tance of 2.25ft (686mm). The dischargeslot inthe duct 14' may have a width of 1/2 inch (12.7 mm), and with these dimensions, providing a collection area of 11.25sq.ft(2.51 sq. metres),the collection capacity could be say 491 cubicfeet per minute (52 cubic metres per minute), and a typical value forthe velocity of the air emerging from the 1/2 inch dis charge slot may be ofthe order of 2350 feet per minute (716.3 metres per minute).This would gener allybesufficienttoensurethata high proportion of smoke laden polluted air in the vicinity ofthe in stalled unitwould be induced into this high velocity cross flow air in the curtain 18'.

Itwill be appreciated that air curtain arrangements, in accordange with the invention, by virtue ofthe combined respective "blow" and "suck" discharge and collector characteristics, are generally particularly well-adapted for the entrainment and removal of polluted surrounding air.

In Figure 5, the unit 48 is shown installed sothatthe duct portions providing the air curtain 18' and collection area are situated close to ceiling level above the customers' area in front of the bar and at right angles to the length of the latter. It will, however, be under stood that the positioning ofthe unit may be varied as desired, and in the example of Figure 5 it may in fact be more efficient and effective to position the overhead unit extending adjacent and parallel to the front of the bar with the pressure duct located nearest to the bar. Also, if desired, a number of such units may be installed in different positions and, moreover, such units may be installed with different orientations.Furthermore, in one particularfurtherdev- elopment,the size ofthe aircurtain andaircircula- tion unit 48 may even be scaled down sufficiently for itto be mounted on a stand orothersupporting base adapted to be placed on the floor or even on a table with, preferably, facilities for adjustment of the height and orientation of the air curtain circulation unit, an example ofthis being illustrated diagrammatically in Figure 7.Thus, in Figure 7 there is shown at 48' a scaled down version ofthe unit 48 previously described which in this instance is orientated vertically and mounted through an adjustable hinged connector60 on a stand 62 comprising a base 64 and an upstanding telescopically-adjustable column 66.

The latter allowsthe height ofthe unit 48' to beadju- sted and by means ofthe adjustable hinged connector 60 the orientation of the unit 42' can be adjusted if required between a vertical orientation and a hori zontal orientation.

Such stand mounted units can be completely transportable and may be made in a range of sizes to suit rooms of different sizes. They may be especially useful for use in an office or domestic environment or, for example, in hotel rooms for giving at least some measure of air pollution control.

It will of course be further understood that many other variations and modificatins can also be made, within the scope of the invention, in respect ofthe particulardetailswhich have been mentioned orillustrated herein merely by way of example.

Claims (18)

1. A method of controlling and reducing air pollution within an enclosed space caused by smoke or fumes generated within a region or regions of that space, said method comprising establishing in said enclosed space, adjacent said pollution generating region or regions, one or more air curtains incorporated within an aircollection and circulation system which also includesairfiltration means, said aircurtain or curtains being effective to set up a smoke or fume barrier or barriers and at the same time to cause airborne pollution, especially smoke particles, from the pollution generating region or regions to be removed by becoming entrained in the flow or airthat establishes said curtain or curtains, which air is col lected,filtered and recirculated.

2. A method as claimed in Claim 1 wherein the or each air curtain is setup by discharging from an elongate apertured duct pressurised air in a plane con taining said duct, opposed complementary collector means disposed in substantially the same plane being provided to collect said air which is then conveyed from the collector means to said airfiltraiton means and, from said air filtration means, to pressurins fan meansfor recirculation.

3. A method as claimed in Claim 2wherein a suction effect at the collector means is promoted by suction fan means disposed intermediate said collector means and the air filtration means.

4. A method as claimed in any of the preceding claims wherein the air curtain or at least one ofthe air curtains is oriented in a substantially vertical plane.

5. A method as claimed in Claim 4wherein the vertically oriented air curtain or curtains provide a separating smoke orfume barrier or barriers between different adjacent regions of said enclosed space.

6. A method as claimed in Claim 4 wherein the vertically oriented air curtain or curtains provide a smoke orfume barrier or barriers arranged in effect to partition off said pollution generating region or regions from a second localised region or regions in said enclosed space thereby enabling said second localised region or regions to be maintained in a relatively unpolluted condition.

7. Amethodasclaimed in anyofClaims4to6 wherein the or each vertically oriented air curtain or curtains is set up by an upwardly directed current or currents of air.

8. A method as claimed in any ofthe preceding claims wherein the airflowthroughoutthe air curtain orcurtains isarranged to be a substantialiylaminar flowwithoutturbulence.

9. A method of controlling and reducing air pollution within an enclosed space caused by smoke or fumes generated within a region or regions of that space, said method comprising establishing in said enclosed space, adjacent said pollution generating region or regions, one or more air curtains substantially as herein described and illustrated with referenceto Figures 1 to4, Figures 5to 6, and/or Figure7 ofthe accompanying drawings.

10. An air poilution control apparatusorinstalla- tion for carrying out the method claimed in Claim 1, comprising an air circulation system including fan means for providing a supply of pressurised air, at least one elongate supply duct arranged to discharge the pressurised airthrough aperture means in a common plane so asto set up the aircurtain orcurtains opposed complementary collector means disposed in substantially the same plane and arranged to collect the airfrom the air curtain or curtains, duct means for conveying the air from the collector means toairfiltraiton means, and duct means for returning the airfrom the airfiltraiton means to the pressuris- ingfan meansforrecirculation.

11. An apparatus or installation as claimed in Claim 10 comprising in addition suction fan means disposed intermediate the collector means and the air filtration means in said air circulation system for producing a suction or negative pressure downstream ofthe or each air curtain.

12. An apparatus or installation as claimed in Claim 10 or 11, arranged so asto setupthe aircurtain or curtains in a vertical plane.

13. An apparatus or installation as claimed in Claim 12, wherein the or each elongate supply duct extends horizontally and has a discharge aperture or apertures arranged to provide an upwardly directed current or currents of airfor establishing said air cur- tain or curtains.

14. An apparatus or installation as claimed in Claim 13, wherein the discharge aperture orapertures is or are provided by an upwardly presented slot or row aligned apertures in the or each said supply duct.

15. An apparatus or installation as claimed in any of claims 10 to 1 4which is assembled or fitted in the form of a composite self-contained unitary structure.

16. An apparatus or installaiton as claimed in any of claims 10 to 14, designed as a transportable unit with the air circulation system assembled as a selfcontained unitary structure mounted on a stand or supporting base.

17. An apparatus or installation as claimed in Claim 16 in which adjustment means are provided for adjusting the orientation and/or height of the air circulation system on said stand or supporting base.

18. An air pollution control apparatus or installation substantially as herein described and illustrated with reference to Figures 1 to 4, Figures 5to 6, and/or Figure 7 ofthe accompanying drawings.