WO2008004925A1

WO2008004925A1 - Air filter for clean rooms including inclined filter elements

Info

Publication number: WO2008004925A1
Application number: PCT/SE2006/050245
Authority: WO
Inventors: Cédric LANCIEUX
Original assignee: Camfil Ab
Priority date: 2006-07-06
Filing date: 2006-07-06
Publication date: 2008-01-10

Abstract

The present invention relates to a filter (1´) for cleaning the air in clean rooms in hospital environment, which filter is placed at the ceiling of a 5 clean room, has a frame supporting a plurality of filter elements, and contains a through-going opening (4´) for the passage of electric equipment, said opening being surrounded by filter elements (6,12,13), wherein the air-flow leaving a filter element is unidirectional. According to the invention filter element(s) (12) along a side of said opening (4´) in the 10 filter (1´) and filter element(s) (13) along the opposite side of said opening are inclined upwardly and all other filter elements (6) are extending horizontally. 15 20 25 Figure 2 for publication

Description

Air filter for clean rooms including inclined filter elements

TECHNICAL FIELD

The present invention relates to a filter for cleaning the air in clean rooms in hospital environment, which filter is placed at the ceiling of a clean room, has a frame supporting a plurality of filter elements, and contains a through-going opening for the passage of electric equipment, said opening being surrounded by filter elements, whereby the air-flow leaving a filter element is unidirectional.

BACKGROUND OF THE INVENTION

It is always a risk that a patient during an surgical intervention gets infected by air-borne bacteria or other disease carriers. In order to reduce this risk, the air in "clean rooms" in hospital environment is circulated through filters before and during surgical operations or interventions, for example. Examples of when the demands on the air cleaning are especially high are in neonatal units, aseptic operating theatre suites, burn units, rooms for immunodeficient patients, grafts, units for cancer chemotherapy, oncology and haematology-oncology and high security microbiology laboratories. In several of these examples filters placed in the ceiling of a room and having a through-going opening for electrical equipment such as light sources, are used. A problem with such filters is that a dead zone for the air-flow in the room is created under said opening in the filter. Such a dead zone has several drawbacks. Firstly, the initial cleaning of the air in the room containing the filter will take much longer time since particles within the dead zone will not be circulated until they have left the dead zone. Secondly, possible contagious particles entering the dead zone will stay a relatively long time therein before leaving the dead zone and being circulated to the exhaust filter. These dead zones are mostly located above the area in the room which is illuminated by said light source, which area often contains the most sensitive part of a patient. In a surgical operation, for example, the area to be illuminated is the operation area, i.e. the area in which the surgical intervention takes place.

An objective of the present invention is to eliminate or at least significantly reduce the magnitude of the dead zone under an opening in a filters of the aforesaid type.

SUMMARY OF THE INVENTION

This objective is accomplished by a filter for cleaning the air in clean rooms in hospital environment, which filter is placed at the ceiling of a clean room, has a frame supporting a plurality of filter elements, and contains a through-going opening for the passage of electric equipment, said opening being surrounded by filter elements, wherein the air- flow leaving a filter element is unidirectional, characterised in that filter element(s) along a side of said opening in the filter and filter element(s) along the opposite side of said opening are inclined upwardly and all other filter elements are extending horizontally.

In a preferred embodiment, the angle of inclination of the inclined filter elements is 5-15°, preferably 9°. Furthermore, the filter elements along the periphery of the filter are all extending horizontally. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the enclosed Figures, of which;

Fig. 1 schematically discloses an exploded perspective view of a conventional clean room filter,

Fig. 2 schematically discloses a partly sectional perspective view of a filter for a clean room according to a preferred embodiment of the invention, and

Fig. 3 and Fig 4 schematically disclose the air-flow in a room provided with a conventional filter and a filter according to the present invention, respectively.

DESCRIPTION OF EMBODIMENTS

In Figure 1, a conventional filter 1 for clean room application is shown in an exploded perspective view. This filter comprises a leak-tight plenum 2 having lateral air inlets 3. In the middle of the upper wall of the plenum an opening for electrical equipment, such as for example cables, is made. This opening is isolated from the rest of the plenum by a wall 4 surrounding said opening an extending vertically downward. A frame 5 for supporting several filter panels 6, for example HEPA MEGALAM filter panels commercially available from Camfil Fair is affixed to the lower peripheral edge of the plenum 2. Preferably, the frame 5 allows these filter panels to be attached to the frame from below in order to enable swift exchanges of used filter units. Finally, a sub frame 7 containing a mask, grill or the like for obtaining an unidirectional air-flow from the filter is attached to the frame 5 or the peripheral edge of the plenum 2.

Extending downward from the opening in the upper wall of the plenum 2 is a tube 8 or the like, in which electric cables can be contained and which can support a lamp or lamps for lightening the area below the filter, which area in an operation theatre would be the surgical site on a patient placed on an operation table. A plate or plug 9 provides a seal between the space inside the wall 4 surrounding said opening and tube 8, and said tube 8. When mounted in a ceiling, the plenum 2 of the filter 1 will be located above the ceiling.

Filter 1 can have a length of 2-4 m and a width of 2-4 m.

In Figure 3, the air- flow in a theatre for surgical operations is schematically shown. The air-flow is indicated by small arrows. The filter 1 of Figure 1 is located in the ceiling of the theatre above an operation table 9. Two surgeons 10 are schematically disclosed standing beside the operation table. The air enters the theatre from the filter 1, the outlet of which provides an unidirectional air-flow. No air is leaving the filter in the area limited by wall 4. The air leaves the theatre through air outlets 11 disposed in the walls of the theatre near the corners thereof and near the floor of the theatre. The air drawn out of the theatre is re-circulated thereto possible with the addition of fresh air. The inlets of plenum 2 of the filter 1 are connected to the outlet side of a fan (not shown) and the outlets 11 in the theatre are connected to the inlet side thereof. The arrows in Figure 3 schematically illustrate the air-flow in the theatre. As can be seen in Figure 3, there is a dead zone DZ under the through- going opening in filter 1, i.e. in a volume extending under the middle thereof, in which the circulation of air is very slow. When the air circulation system is turned on before an operation it will therefore take some time before all air in the theatre has passed the filter and been cleaned. Furthermore, when a surgeon or nurse lean forward over a patient on the operation table 9 at least their heads will be present in zone DZ. There is nothing in this zone to prevent a bacteria- carrying particle leaving one of the surgeons 10 from falling down onto the operation wound of a patient lying on the operation table 9.

The filter 1 can be operated to change the air in a theatre of 45 m² 60-70 times per hour.

In Figure 2, a filter 1 ' according to a preferred embodiment of the present invention is schematically disclosed. Filter 1 ' is principally build in the same way as filter 1 shown in Figure 1 and components in filter 1 ' similar to components in filter 1 are given the same reference number as in Figure

1 with the addition of a prime sign. However, filter 1 ' is principally different from filter 1 in that all filter elements therein do not extend in a horizontal plane but two filter elements 12,13 located on opposite sides of wall 4' surrounding an opening in the upper wall of the plenum T, are inclined upwardly for reducing the dead zone, four filter elements can be inclined. The angle of inclination to the horizontal is α. By filter element is meant an element comprising a filter panel, for example a HEPA MEGALAM filter panel, and means, such as a grill, for providing a unidirectional air flow from the filter element and for protecting the filter media in the filter panel. Such a filter element should also be attachable to a frame which in turn is affixed to or a part of the plenum T.

In Figure 4, the air-flow in a theatre for surgical operations is schematically shown. The air- flow is indicated by small arrows. The theatre in Figure 4 is identical to the theatre in Figure 3. The filter 1 ' of Figure 2 is located in the ceiling of the theatre above the operation table 9. Two surgeons 10 are schematically disclosed standing beside the operation table. The air enters the theatre from the filter 1 ', the outlet of which provides an unidirectional vertical air-flow from all filter elements except filter elements 12,13 which are inclined relative the horizontal by an angle 9°. The air leaving these elements 12,13 is inclined an angle 9° to the vertical. No air is leaving the filter in the area limited by wall 4'. As explained in relation to Figure 3, the air leaves the theatre through air outlets 11 and the air drawn out of the theatre is re-circulated. The inlets of plenum 2' of the filter 1 ' are connected to the outlet side of a fan and the outlets 11 in the theatre are connected to the inlet side thereof. The arrows in Figure 4 schematically illustrate the air-flow in the theatre. As can be seen in Figure 4, there is a dead zone DZl under the through- going opening in filter 1 ', i.e. in a volume extending under the middle thereof, in which the circulation of air is very slow. However, as is evident from Figure 4, the dead zone DZl is very small compared to the dead zone DZ in Figure 3. This is due to the inclined flows of air out of elements 12,13. These flows of air fairly soon encounter each other which makes zone DZl very small. Furthermore, a zone DZ2 in which air circulation is very slow is also present above the middle of the operation table 9. Also zone DZ2 is very small. When the air circulation system is turned on before an operation it will therefore only take a few seconds before all air in the theatre has passed the filter and been cleaned. Furthermore, when a surgeon or nurse lean forward from the upright positions shown in Figure

4, possible particles leaving their upper body parts will be carried away by the air-flow in the theatre in the direction towards the air outlets in the theatre, i.e. in a direction away from a patient lying on the operation table 9. The risk for the surgeon or nurse contaminating a patient is thereby greatly reduced in relation to the risk occurring in an air-flow in accordance with Figure 3. Moreover, since the air-flow in zone DZ2 is very small, the risk for contaminated particles leaving the surgical site is also very small.

From the foregoing it is evident that a very favourable air-flow in an operating theatre can thus be obtained by inclining the filter elements 12,13 of a conventional filter 1 along opposite edges of a through-going opening limited by the wall 4' by 9° relative the horizontal.

In the embodiment of Figure 2, the filter elements in the row containing the inclined elements 12,13, have smaller size than the other filter elements. The reason for this size difference is that it is preferred that all filter elements along the periphery of the filter should have a horizontal extension, i.e. should not be inclined relative the horizontal. Thereby all air leaving the peripheral area of the filter is flowing vertically, thereby creating sort of an air curtain preventing air in the upper part of the theatre from sidewise entering the volume under the filter. No air can thus be recirculated to the surgeons 10 in Figure 4 without having passed through filter 1 '. Although elements 12,13 is shown as elements separate from filter elements outside thereof in a peripheral direction, they can be integral with these elements if this is favourable for example for manufacturing reasons.

The angle of inclination is dependent of the size of the opening defined by wall 4' and also of a lot of other parameters, such as the height and other dimensions of the room containing the filter 1 '. According to the present invention the angle of inclination is 5-15°, preferably 7-11°, and most preferably 9°. The embodiment described can of course be modified in several ways without leaving the scope of invention. For example, the opening for electrical equipment in the upper wall of the plenum need not be disposed in the middle thereof but can be located anywhere. Several inclined filter elements can be arranged along opposite sides of the through-going opening in the filter but it is preferred that only one filter element is extended along each of these two opposite sides of the through- going opening as in the preferred embodiment. The present invention shall therefore only be limited by the content of the enclosed patent claims.

Claims

1. A filter (1 ') for cleaning the air in clean rooms in hospital environment, which filter is placed at the ceiling of a clean room, has a frame supporting a plurality of filter elements, and contains a through-going opening (4') for the passage of electric equipment, said opening being surrounded by filter elements (6,12,13), wherein the air- flow leaving a filter element is unidirectional, characterised in that filter element(s) (12) along a side of said opening (4') in the filter (T) and filter element(s) (13) along the opposite side of said opening are inclined upwardly and all other filter elements (6) are extending horizontally.

2. A filter according to claim 1, wherein the angle (α) of inclination of the inclined filter elements (12,13) is 5-15°.

3. A filter according to claim 2, wherein the angle (α) of inclination of the inclined filter elements (12,13) is 9°.

4. A filter according to claim 1,2 or 3, wherein the filter elements (6) along the periphery of the filter (1 ') are all extending horizontally.