CA2023751A1 - Dust precipitation from air by negative ionization - Google Patents

Abstract

"DUST PRECIPITATION FROM AIR BY NEGATIVE IONIZATION"
ABSTRACT OF THE DISCLOSURE
A system of precipitating dust includes providing a screen arrangement either in the form of a ceiling with walls or in the form of a canopy with the screen being penetrable by air. Inside the screen and particularly adjacent edges of the screen or the canopy there are provided negative ion emitters positioned in rows so as to generate a curtain of ions precipitating the dust from the air onto the ground for collection. Within the screen can be defined either a clean zone or the screen can be used to confine a dust producing process so as to precipitate the dust immediately adjacent the process to prevent it spreading to other areas. Emitters are provided in the form of a carbon fiber yarn which projects outwardly through openings in a channel member with the yarn being doubled back upon itself in some cases to provide a highly directional emission.

Description

2 ~

., .
~ DUST PRECIPITATION FROM AIR BY NEGATIVE IONIZATION
'`'`BACKGROUND OF THE INVENTION
.~ .
This invention relates to a system for dust ' precipitation from air using negative ionization of the air.
~.~
~- The concept and prospective commeccialization of negative ionization techniques has been around foc decades with ;
very little progress due to the lack of credibility arising from inappropriate, largely unsuccessful applications and clouded by exaggerated unsubstantiated claims.
- At the same time the effectiveness of the technique suffered because the equipment to generate and distribute the required volumes of negative ions was initially bulky, expensive, requiring constant maintenance and was ,,; .
generally unreliable. These circumstances meant that the effectiveness of applications deteriorated rapidly and became totally suspect in operation.
` The increasing employment of the technology is ~; being brought about by some basic trends:
- the development of equipment utilizing `~ electronics and new materials which provide a safe, reliable, inexpensive, and non polluting source of negative ions and their distribution.
- an increasing need to improve the air quality ~ ,.
1 -; -:-: ~! 2 ~ .?, ~ 7 ~ ~
.
~, in enclosed environments which have been designed to minimizeenecgy costs for heating, ventilating and aic conditioning installations.
- higher standards of safety and health in the workplace in regard to the contcol of micconic and submicronic pollutants identified as a health hazacd.
- zero defect objectives in manufacturing operations requicing more effective means to contcol the migration of fine dust and pollutants.
- hard evidence of the effectiveness of industrial applications and increasing supportive scientific evidence as cegards propec electco climate conditions for human ` comfort and working efficiency.
Off-shore countries, particularly Iscael have maintained a fairly high level of reseacch and development effort into pucsuing the effectiveness of negative ionization techniques in a wide range of applications with considerable success.
Progre~s in North America in this respect, industrially at least, has been limited to the elimination of static electricity, but with strong indications of a recent revival of air treatment by modular, fan assisted negative ion dispersal units.

. 2~ ~7~ ~.

,. .

, Conventional systems to obtain super clean aic 1 with filtration efficiencies in the micronic and sub-micronic ranges are capital intensive and expensive to run in tecms of energy consumption and maintenance costs.
At the same time the systems while fully effective on the air circulated can have little influence to '5"~
prevent small particulants and pollutants originating in the working plennum producing problems, apart from the inherent ,~ dilution refreshening process allowed by the cycle of air changes supplied to the area. An investigation into further ; prior art suggests that while the use of negative ionization techniques to impcove air quality and contain dust pollution in a general way is gaining ground, there is little doubt that the level of technology available is relatively crude.
Ions are created in natuce by sunlight, cosmic and terrestrial radiation and the friction of moving air and water that causes electrons to leave hydrogen, nitrogen and other molecules and to attach themselves to oxygen molecules.
Molecules with extra electrons from negative ions and have a positive effect on the environment. They neutralize odoucs and contribute to the clear air and the fresh smell we ---find in non-industrial, sparsely populated areas and at the seaside or healthy holiday resorts. ~ -:~,'" ~"~' 2 ~} r~ ~ r~ ~1 , à

,~In the Pcairie regions of Canada, the phenomenon -~
best manifests itself by the invigoration experienced after a summer storm with lightning, which relieves the heavy }'`
`depressing conditions which gradually build up periodically in such areas during the summer.
;Positive ions are produced by car and factory exhausts, cigarette smoke, dust, soot, fumes from new processes and other domestic and industrial pollutants.
-: .
'r~lIn the wide open spaces these pollutants are ,............................................................................ .
attracted to the negative ground and are harmlessly discharged.
But in the enclosed environments of modern society - metals, cars, builings lined and furbished with synethetic materials, etc., these pollutions cannot be discharged to earth.
At the same time the enveloping car bodies and building structures that keep the positive ions in, also keep the beneficial negative ions out because their electrical charges are absorbed by steel and concrete, bricks and siding material.
A controlled output of negative ions can be produced by electronic means/corona discharge and this source is an approved alternative for the Polonium Ionizers withdrawn from the market by 3M in February 1988. The source generation of ozone is 90 low as to be almost immeasurable and well below ..

-~

r?
.''`Z
.~
~,.j ~ ' ' the FDA maximum of 0.05 ppm.
SUMMARY OF THE INVENTION
It is one object of the present invention to provide an improved method for cleaning air within a building using the negative ionization principles in a unique manner to obtain air which is cleaned to a high degree with low capital and maintenance costs.
According to a first aspect of the invention, therefore, there is provided a method of precipitating particles from air within a building comprising defining a zone within the building at least partly partitioned from a remaining part of the building, separating the zone from the .
building by a screen which is perforated to allow transmission therethrough of air and light, and mounting within the zone a ~ plurality of emitters of negatively charged air ions.~
... ~.. , . According to a second aspect of the invention, therefore, there is provided an emitter of negatively charged air ions for use in precipitating particles from air within a building comprising an elongate member defining a channel ~ therealong and having a closed front surface, a conductor ;-~
IR,~ ~ mounted in the channel member, means defining a plurality of ~,~
openings in front surface through which portions of the -,...
!~ conductor pcoject, and connector means on the channel member ~, ~;

~ ::
~,~ .:. -~

2 i~

::,b~ 6 ''.
for connecting a high voltage to the conductoc such that the exposed portions of the conductor generate ions in air exposed to the conductor focwardly of the fcont face.
The provision of the elongate multiple emittec enables a high very degree of flexibility to be used in the location and mounting of the emittecs foc the negative ionization tceatment so that the units can be installed very quickly and at low capital cost.
The use of the screen to separate the zone to be cleaned fcom the remaindec of the building enables a system ~o be used known as a "clean-zone" or as an altecnative a "reverse clean-zone" in which the major dust emitting pcocess is mounted within the zone and the negative ionization treatment used to extract the dust from the aic pcioc to its celease to the remainder of the building.
The screen is pceferably focmed of a matecial which is pecmeable to air and light ~qo that the zone can be mounted within the building without cegard to the location of the ventilation units and provision of lighting. In many cases, therefoce, the zone can be developed at an area leaving the ventilation systems and lighting systems outside of the zone so that there is no interference whatever with the ; ~-existing utilities within the building. The light and air ~,., ;

movement necessacy for ventilation can then take place through the screen with the screen and the negative ionization system cooperating to extract the dust and to prevent its penetration through the scceen.
The system as installed, constantly and efficiently will precipitate about 99% of the fine dust particles and pollutants in a work area defined and isolated by specially constructed barriec screens.
With the correctly calculated and distributed negative ion density within the zone, all further migration of the precipitation micronic and submicronic pacticles will be effectively and continuously prevented, as a result of the electro-climate created and maintained in the "Clean Zone" `
area.
The emitters are pceferably separated from any aic flow generating systems such as fans or aic duct outlets so that the ions are freely emitted into the are to be cleaned wihtout passage of the ions or any air stream carrying the ions through a filter. Thus the particles are separated from the air by a precipitation technique which causes the particles to fall to the floor for collection by conventional house cleaning techniques. -~
The enclosuce which acts as a cage to isolate and i 2 ~ ~ rl ~ ~

define the area/volume required for the application, is considered to be a basic and essential feature of the "clean zone" concept. The design, constcuction and materials employed, all con~ribute to ensucing the effectiveness of the system.
Installation of the "Clean Zone" enclosure is simple and flexible and easily fitted ee~ro-actively with the minimum difficulty to accomodate existing equipment.
The light open nature of the enclosure gives little sense of restriction to employees inside the zone and it is generally unnecessary to upgrade lighting levels in the area after the installation of the zone.
The effectiveness of the system is readily measurable and can be demonstrated by the simple action of energizing and deenergizing the AC power input.
The results in regard ~o the control of fine dust, and reduction of inclusions are fully substantiated in practical cost effective terms by satisifed industrial end users in regard to~
- reduced level of rejections due to inclusions;
- increased productivity - improved working environment inside and outside the zone.

-- 2 ~s~

g Accocding to a ~hird aspect of the invention, thece is pcovided a method of cleaning particles fcom air within an area of a building comprising mounting emitters of negatively chacged ions in the acea of the building ~eparate from any aic flow acrangements foc causing aic flow within the acea, causing the ions to engage particle~ in the area and to precipitate the pacticles downwardly onto a flooc of the area and collecting the particles fcom the flooc.
Preferably the method includes a canopy which assists in dicecting the particles away from a source of the particle~ e.g. a dust pcoducing machine towacds sides of the machine for precipitation on the floor.
With the foregoing in view, and other advantages as will ~ecome apparent to those skilled in the art to which ~his i~v~ention relates as this specification proceeds, the inven~ion is herein describ~d by reference to the accompanying ~acawings focming a part hereof, which includes a descciption of the best mode known to the applicant and of the prefecred typical embodiment of the prin~ciples of the present invention, in vhich~
DESCRIPTIO~ OF THE DRAWINGS
. . .
Figure 1 i~ an isometric view showing a screen sy~tem defining a zon~ for ~eparatiQn f~om the remaindec of ,)J~ 3 1 ~ ~

building and including ionization generating elements mounted within the zone.
Figure 2 is a top plan view of the zone of Figuce 1 showing the location of the ion emitters.
Figuce 3 is a cross-sectional view showing a modified arrangement of screen assembly defining a zone within ~ ~
a building. ~ ~-Figure 4 is a cross-sectional view through an emitter element of a type shown schematically in Figures 1 and 2.
Figure 5 is an isometric view of the emitter element of Figure 4.
Figure 6 is a cross-sectional view through a second emitter element of the type illustrated schematically in .:
Figure 1.
Figure 7 is an isometric view of the emittec of Figure 6.
Figure 8 is a cros3 sectional view showing a modified arrangement of the screen assembly of Figure 3.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
In Figures 1 and 2 i9 illustrated a zone defined 2 ~

by a surrounding wall stcucture generally indicated at 10 within which i9 mounted a machine 11 which is illustcated ~ ;
schematically and is wholly enveloped by the surrounding wall structure defining the zone.
The wall structure compcises two side walls 12 and 13 togethec with end walls 14 and 15 each of which includes .
an opening 16 and a slidable closing dooc 17. Accoss the top - ~;
of the walls is pcovided a ceiling 19. The height of the walls is arcanged to be approximately equal to the minimum wocking height of the ocdec of eight feet and up to a maximum of the ocdec of ten feet so that the ceiling 19 is genefally positioned beneath the roof or ceiling stcucture of the building and is separate from the lighting, duct wock and othec utilities which ace often pcovided in stcuctural buildings of an industrial type.
This ccitical acea or zone is enclosed using a slotted metal ~tcuctuce as the main suppoctive fcamewock, housing panels coveced with perforated scceen matecial of a type which is permeable to aic and light but is cesistant to ;-teh pa sage of dust oc other fine pacticles. One example of material which can be used is known as TAK Barrier Screening.
The TAK Barcier Screening is a fine gauge fabcic, treated with a special tacky cesin. This Baccier screening is ,. ~'' : '' 2~3~

electronically compatible with negative ion presence and wocks harmoniously to create a dust free enclosuce, trapping large pacticles, yet allowing the zone to bceathe without any increase in air speeds across the fabric.
The enclosure which acts as a cage to isolate and define the area/volume required for the application is considered to be a basic and essential feature of the "clean zone" concept. The design, construction and matecials employed, all contribute to ensuring the effectiveness of the system.
Installation is simple and flexible and easily fitted cetcoactively with the minimum difficulty to accommodate existing equipment.
The light open nature of the enclosure gives little sense of restriction to employees inside the zone and it i9 genecally unnecessary to upgrade lighting levels in the area after the installation of the screens.
Strategically located emittecs at ceiling level within the enclosure produces a bombardment of negative ions to precipitate particles inside the zone. At the same time a high density is created within the confines of the enclosure which will not allow particles to penetrate the screens, in either direct1on.

- - 2 ~

. ~...
- 13 - ~
" ~-All openings into the zone required for access ace pcotected by a curtain of ions which comprises a pecipheral distcibution of emitters to form an high density concentration of directed negative ions to precipitate any dust which might othecwise migrate into the area. Altogether a total scceened, "cage" effect is produced with a fully isolated Clean Zone separate and distinct from the general working area of the facility.
On completion of a Clean Zone, and activation of the ion generation system, an ultra Clean Zone will be established for process within 24 hours. This protection will be available as long as the system is in operation with the necessacy negative ions densities being maintained automatically at the pcoper levels.
The slotted steel frame wock is indicated at 20 and is of a conventional nature available for receiving wall panelq and for bug screens. A solid panel is indicated at 21 and the scceen material iR indicated at 22.
The ceiling is formed in the same structure employing wholly the screen material 22. The enclosure can thu~ be formed relatively ~imply by the assembly of the frame work following which the panels are simply flipped into place to define the completed zone. In Figures 1 and 2 there is ' . ~

2 ~
,.

provided a plurality of emitters of negative ions including two separate types of emitters indicated at 25 and 26 cespectively.
The details of the emitters 25 are shown in Figures 6 and 7 and the details of the emitters 26 are shown in Figures 4 and 5.
Turning thecefore to the emittecs 25 shown in Figures 6 and 7, this emitter comprises an elongate channel member 30 focmed in two halves 31 and 32 which are snap fit togethec along a joining line 33 to form an enclosed elongate tubular membec. End caps 34 are provided of a type shown in Figure 4 which comprise a press fit into the end of the tubular member thus focming a complete enclosure. The emitter 26 as shown in Figures 4 and 5 comprises the same basic housing stfuctufe. The length of the housing can be selected according to requirements as shown in Figures 4 and 5 the emitter is of a celatively short length whe~eas in Figure 6 and 7 the emitter 25 can be significantly longer.
Each of the housings includes a connector 36 of a type including a body 37 which has an outer screw thread 38 and an end cap 39. The body can thus be attached through an opening in the housing simply by clamping into place by one or more nuts 40 and 41. In the arrangement shown in Figure 6 there are two nuts provided each on a respective side of a wall of the housing so as to space the end cap 39 away from the 2'~ r?~
,.~

wall. In the arrangement shown in Figure 4, the end cap is clamped against the end face of the housing by the nut 40 on the opposed side of the wall of the housing. The housing includes a central bore which cacries a conductoc 42 and a volume of the sleeve which projects outwardly beyond the inner end of the body to connect to a conductor 43 provided within the housing. The tubular connector 42 is thus of a type which can receive simply a single pole connector by which high voltage fcom a generator 45 (Figuce 2) can be connected to the emitter with a plurality of emitters arranged in series by connection of a wire fcom each to the next.
The conductor 43 is formed of a yarn of a conductive fibre material for example carbon fibres which are cut into staple fibres and then spun and twisted to form a multi fold yarn. The housing i9 focmed of very suitable insulating plastics matecial so that the conductor yarn can simply be thceaded into the housing and can cest against the housing without forming a short circuit.
In Figures 4 and 5, a front face of the emitter which is defined by the upper face of the uppec part 31 has a plurality of openings 48 substantially equidistantly spaced along the front face in a single line across the centre of the front face. The yarn is then threaded simply in a stitch 2 $ ~ r3 - 16 ~

pattern so that portions of the yarn are exposed on the outer side of the front face and portions of the yarn are maintained on the inner side of the fcont face that is within the housing as indicated at 49 and 50 respectively.
This form of emitter is substantially multidirectional so that when a high voltage of the ocder of 6000 volts is applied to the conductor 43 the exposed portions 49 of the yarn generate a corona effect causing the creation of ions in the area of the corona effect with those ions tending to escape from the exposed portion of the yarn 49 in all directions away from the front surface. The ions thus tend to spread away from the emitter in all directions and to attach to particles within the air. As the particles are heavier than air the particles tend towacd the ground surface and in view of the generally positive charge on the ground surface, the negatively chacged particles are attracted to the ground surface and fall to the ground surface for collection on the ground surface both in view of gravity and in view of the electrostatic attraction.
As shown in Figure 2, the emitters 26 are arranged in array around the centre of the zone. In the example shown there are four rows of the emitters arranged substantially equadistantly spaced across the width of the ~ 2 ~

zone. In this way the full area of the interior of the zone iB
bombarded with the ions which are spread equally thcoughout the centcal acea of the zone. As shown in Figure 1 the emitters 26 are mounted at the ceiling area on suitable supports (not shown). This places the height of the emitters generally at the height of the ceiling which would be in the ocdec of eight to ten feet from the gcound which has been found to be pacticularly effective since the ions are thus pcevented fcom dissipation to othec areas of the building before they can carry out their function of attachment to particles and transpocting those pacticles to the ground surface.
The emitter 25 shown in Figures 6 and 7 is modified celative to the emittec 26 in that the conductor 43 is confined into shoct poctions which project outwacdly from the front face of the channel membec 31. Thus the front face 31 includes foc each portion a paic of holes 55 and 56 which are closely positioned togethec with only a narrow sepacating poction 57. The conductoc i~ then threaded through the holes 55 and 56 and passes~thcough a collar membec 58 surcounding the holes and supporting the outerly projecting portion of the conductor 43 as indicated at 59. The collar membec 58 can be bonded to the front surface of the channel member oc can comprise a separately manufactured product which inserts from ~;, -,, , ,, -, ,, . , : . . . .

2~S~7~

: :

:

an undecside of the uppec sucface of the channel membec thcough a single hole in the wall 31 and pcovides by itself the pcopec suppoct foc the projecting portion 59.
The projecting portion 59 is confined to a short length of the front face of the channel member is caused to tucn back upon itself at a shacp angle. This tends to cause individual ones of the staple fibres 60 to pcoject outwacdly from the yarn at the point whece it is turned sharply thus forming a plucality of spikes which pcoject outwardly from the shacply turned poction of the conductoc 43. These spikes have been found to generate ions in a highly directional mannec in that the ions ace pceferentially genecated at the apex of the fibce ~pike and thus tend to be emitted in a direction generally at right angles to the front face.
The emitter 25 is therefore much more directional than the emittecs 26. In view of this propecty, the emittecs 25 ace thus arcanged to generate a curtain of ions lying in a plane longitudinal of the emitter 25 and at right angles to the fcont face.
Turning therefore to Figure 1 the emitters 25 are mounted around the opening 16 along the sides of the opening and along the top of the opening with the emitters facing inwardly to generate a curtain across the plane of the opening 2 ~ J , bg ~
.

' ' . "

of a high concentration of ions. This curtain acts to "attack"
any dust pacticles attempting to pass through the opening so that those particles are acted upon quickly and tend quickly to fall to the ground at the area of the opening. As a back up for the emittecs 25 at the opening, one or more rows of furthec emitters 25 can be positioned inwardly of the opening. Thus in Figure 2 there are two further .ows of emitters one positioned just inside the opening and the next behind the first thus forming three curtains of ions acting specifically on the dust tending to move thsough the opening carried by persons or equipment passing through that opening or by air movement through the opening.
The curtain of ions thus act at the openings in the zone and in addition the general level of ions within the zone acts in cooperation with the permeable tacky screen to cause dust and other particles to be collected at the screen rathec than to pass through the screen. It has been noted that :: ~
the ions have a tendancy to act upon the dust just outside of the screen so that large quantities of particles fall to be collected on ground or other horizontal surfaces just outside the screen thus preventing the dust from passing through the screen.
As shown in Figure 3 there is provided a modified ' ' .. , ., , I

;'5 arrangement including a floor surface 70, a machine 71, a screen 72, an uppec ceiling 73 of the building and utilities including duct wock 74 and lighting 75.
In this case the scceen is modified in that it comprises simply a canopy supported from the ceiling oc roof on support wires 76. The canopy includes a ceiling 77 focmed in panels similac to the ceiling 19 togethec with fouc side wall portions 78 which hang down from the side edges of the ceiling.
The details of the construction ace not shown but are similar to that shown in Figuce l. This of course leaves the side walls of the zone open foc passage of persons or equipment but generates enough of a separation of the zone from the building to enable the cleaning of dust from around the machine 71.
Figuce 3 also illu~trates the arcangement in which the zone is sepacated from the ventilation systems including the duct work 74 and fcom the lighting systems which ace maintained without modification in the building. The light into the zone is thus provided by the conventional lighting of the building. The ventilation or aic movement within the zone is provided by the conventional building ventilation systems including the duct work 74 and a nozzle 80 which projects aic to move downwardly -~
through the screen and into the zone. ~ ;
In the arrangement of Figure 3, the dust is .. . ~

', . ,:. , ' , : ~ ' ~ ~ :

; Y . ' i : ~ ' ' ' . ' 2 ~ , ~ 7 ~ 1 pcevented fcom passing into the interior of the zone through the open side walls by the generation of a curtain of ions similar to that at the opening 16. Thus the emitters 25 are positioned so as to generate a curtain projecting downwardly at the open side walls and this can be backed up by one or more further rows of emitters 25 positioned inwardly of the side -walls. Also similac to the construction shown in Figures 1 and 2, interior emitters can be of the type illustrated at 26 to generate a moce even spread of ions throughout the zone. -~
In Figures 1 and 2 the machine 11 illustrated schematically comprises a machine for carrying out an industrial process of a type which requires very clean air fof example a paint spraying machine or part molding machine so that this machine is maintained within a clean zone in which the dust in the remainder of the building is kept outside of the zone and is prevented from entering the zone and from remaining within the zone once it has entered. The clean zone must of course be backed up with good housingkeeping practices ;~
which will not be explained in detail here. -In the arrangement shown in Figure 3, the zone is effectively a "reverse clean zone" in which the machine 71 is of a type which generates high levels of dust, for example a paper cutting machine or a textile spinning machine. In this ,,,,,, ,~

2 ~ J, ~ ~

case the machine itself is surrounded by a zone which protects the cemainder of the building from receiving the high quantities of dust generated by the machine itself. In this way instead of maintaining the whole of the building cleaned, it is only necessary to clean the acea surcounding the machine concerned so that the dust from that machine is prevented from escaping to the remaindec of the building and is also contained within that area by the action of the negative ions on the dust particles and the tendency to precipitate and thus to collect on the gfound surfaces from which they can be readily removed by normal housekeeping systems.
The emitters are entirely fcee from any forced air effect so that neither the ions noc any pacticle laden air passes through a filter. Thus the negatively charged ions collect onto the particles causing them to conglomerate and to precipitate onto the floor. The floor thus acts as a collector for the particles and this can be readily cleaned by conventional housekeeping practices. In addition, the tendancy of the particles at the area above the machine is to rise 80 that the bombardment of the particles in the air space of the canopy with the ions causes the particles to tend to flow outwards of the machine and to precipitate out onto the floor at the sides of the machine.

~.5i,' ."~

~3.

~' ' The details of the electrical equipment generating the high voltage are not shown as these are well known to one skilled in the art. In addition the wiring connection3 and the necessary conduit are not shown.
As an alternative arrangement for use in some building structures, the emitte~ 25 can be used at the exit nozzle of the ventilation duct work so that the ions are directed into the air stream which passes through the nozzle as the aic emerges from the nozzle and is communicated into the building. The use of the emitters in the elongate or strip focm enables the emitters to be tailored to the specific nozzles concerned by simply cutting to length or selection from a number of available lengths and attachment at the nozzle.
Turning now to Figure 8, there is shown a canopy arrangement similar to that of Figure 3 including the source 71 mounted upon the floor sucface 70 and including a canopy ~ . .
generally indicated at 82. The canopy is again formed including a ceiling portion 83 and depending side walls 84 ~;
acfanged around the periphery of the ceiling and depending therefrom to a position at a height from the floor sufficient to allow persons and machinery to pass under without obstruction. -In this case the canopy is modified by the ;~

'' I

addition of two elements.
Firstly the ion emittecs of the type generally described above are pcovided in six rows indicated at 85, 86, 87, 88, 89 and 90. The two central rows 87 and 88 positioned above the source 71 are acranged instead of the previously described negative ion emitters to pcovide emission of positive ions. The construction of the device is substantially identical to that previously described but the electrical controls provide a positive voltage foc emission of the positive ions from the fibcous conductors.
Outside of the vertical area above the source 71 are provided the rows 85, 86 and 89, 90 positioned closely adjacent the sides of the rectangulac canopy. These emitters ace of the negative ion type previously desccibed.
In addition two further rows of emitters 91 and 92 ace provided located at a position approximately halfway down the ~ide walls 84 from a ceiling to the flooc. In a practical example, the canopy can have a ceiling height of twenty feet in which case the rows 91 and 92 will be positioned at a distance of approximately ten feet from the ground. The lowermost edge of the side walls is then positioned appcoximately six and one half feet from the g~ound to allow ceady cleacance. The emitters 91 and 92 ace arranged to emit ~ , negative ions.
This acrangement of the emitters tends to generate a flow of the particles indicated by the acrows 93 in which the particles rise from the source 71, move outwacdly undec the canopy and then precipitate downwardly toward the floor adjacent the sides of the canopy. This tendancy is enhanced by the positive ion emittecs at the central area and in addition the tendancy of the air to rise ovec the source in view of the fact that the source tends to generate heat and aic flow due to vacious moving pacts. The shape of the canopy and the location of the negative ion emittecs then tends to turn , ~
the pacticles to move outwacdly and downwardly foc :

pcecipitation downwardly towacd the floor 70. ~ -: ::
To provide an additional collection of the particles, there is pcovided a paic of collection sucfaces 94 and 95 each arcanged along a respective longitudinal side edge of the canopy. Each collection surface comprises a simple shelf type element extending outwardly and connected from the lowec most edge and inclined upwardly thecefrom and inwardly of the canopy to define between the wall 84 and the shelf element a V-shaped area in which the particles tend to collect. The negative ion emitters 91, 92 positioned just above the shelf element also assist in the collection of the particles in that '. ' '~, .

2 ~3 ~

area.
Automatic extcaction devices may be pcovided in the V-shaped area foc continual removal of the particles collecting in that acea. Foc example vacuum acrangements may pcovide along the length of the collection zone foc extcaction of the pacticles as they pcecipitate into the V-shaped area.
In a further modification of the emitters (not shown), each emitter is formed as a module in which the electrical supply unit for the module is connected to the end of the channel section forming the emitter. In this case the channel section forming in the emitter fcom which the electcodes protrude can have a length of the ocder of the eight feet and be dicectly connected to its own electrical supply and contcol unit. The modules can then be suspended from the ceiling of the canopy with a numbec and acrangement of the modules being selected according to design cequicements. This accangement has the advantage that the wiring necessary for insulation can now be provided by the conventional electrical supply system at conventional voltages within the building and is no longec necessary to pcovide high voltage wiring which requires different safety constructions.
Since various modifications can be made in my invention as hereinabove described, and many apparently widely diffecent embodiments of same made within the spirit and scope of the claims without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limieing sense.

~ ~' ~'' ;"'.

_ .. ~ ., ,, , .. . , .. , , , , I :

Claims

- 28 - (1) A method of precipating particles from air within a building comprising defining a zone surrounding a source of the particles, providing a canopy over a floor of the zone, the canopy including a ceiling having a peripheral edge and wall means depending from the peripheral edge substantially wholly around the peripheral edge to a position spaced from the ground by a height suitable to allow the passage under a lowermost edge of the wall means by a person, and providing a plurality of ion emitters within the canopy such that the ions emitted therefrom cause precipitation of the particles downwardly from the canopy toward the floor.
(2) A method according to Claim 1 including providing a plurality of negative ion emitters arranged adjacent sides of the canopy.
(3) The method according to Claim 1 wherein the negative ion emitters are arranged adjacent the ceiling.
(4) The method according to Claim 1 including providing collector surfaces defined at the lowermost edge of the wall means.
(5) The method according to Claim 4 including providing ion emittor means at a position within the canopy just above the collective surfaces.

(6) The method according to Claim 4 wherein the collector surfaces include a surface inclined from the horizontal so as to be inclined downwardly toward the lowermost edge from a position inwardly of the canopy and upwardly of the lowermost edge.
(7) The method according to Claim 1 including providing a plurality of emitter means of positive ions arranged above the source and a plurality of emitter means of negative arranged to sides of the source so as to cause precipitation of the particles from the source preferentially to the sides of the source.
(8) The method according to Claim 1 wherein the canopy is formed from a perforated mesh material.
(9) A method of precipating particles from air within a building comprising defining a zone including a floor and a space above the floor in which is located a source of the particles such that the zone extends above and around the source, providing a plurality of ion emitters in the zone, locating over the source emitters of positive ions locating to sides of the source and above the floor emitters of negative ions so as to cause particles from the source to precipitate preferentially to the sides of the source.
(10) The method according to Claim 9 including locating the emitters in rows in substantially the same horizontal plane.
(11) The method according to Claim 9 wherein the emitters of negative ions are arranged to the sides of an area vertically above the source.
(12) The method according to Claim 9 including providing collecting surfaces at a height above the floor at sides of the zone.
(13) A method of precipitating particles from air within a building comprising defining a zone within the building at least partly partitioned from a remaining part of the building, separating the zone from the building by a screen which is perforated to allow transmission therethrough of air and light, and mounting within the zone a plurality of emitters of negatively charged air ions.
(14) The invention according to Claim 13 wherein the emitters are mounted in an array within the zone, at least some of the emitters being separated from any air movement devices.
(15) The invention according to Claim 13 wherein the building includes ventilation systems for introduction of air into the building, the ventilation system being separate from the emitters.

(16) The invention according to Claim 15 wherein the ventilation system is positioned outside of the zone so that air movement within the zone is obtained by passage of air through the screen.
(17) The invention according to Claim 13 wherein the zone is arranged to surround an industrial process which constitutes a source of particles which is higher than that in the remainder of the building.
(18) A method of precipitating particles from air within an area of a building comprising mounting emitters of negatively charged ions in the area of the building separate from any air flow arrangements for causing air flow within the area, causing the ions to engage particles in the area and to precipitate the particles downwardly onto a floor of the area and collecting the particles from the floor.
(19) A method according to Claim 18 including forming a canopy over the area having a ceiling portion and depending wall sections at edges of the ceiling portion with lower edges of the wall sections having spaced from the floor, positioning the emitters adjacent the wall sections and at the ceiling portion so as to emit ions into the air space defined within the canopy, locating a source of particles to be cleaned underneath the canopy so that the particles tend to rise into the canopy and causing the ions to precipitate the particles to sides of the source for collection on the floor adjacent the source.
(20) A method according to Claim 19 including mounting emitters on the lower edge of the wall sections and directing the ions directionally downwardly therefrom.