GB2286986A

GB2286986A - Isolator and method of operating it

Info

Publication number: GB2286986A
Application number: GB9426415A
Authority: GB
Inventors: David Watling
Original assignee: MDH Ltd
Current assignee: MDH Ltd
Priority date: 1994-01-31
Filing date: 1994-12-30
Publication date: 1995-09-06
Also published as: GB9401821D0; GB9426415D0

Abstract

An isolator is provided having an inner wall 7 defining an inner chamber 6, outer wall 5 defining an outer chamber 4 which surrounds said inner chamber, and means for maintaining the outer chamber at a pressure which is less than both the pressure in the inner chamber and the pressure of the atmospheric air outside the outer chamber. Toxic materials may be processed in the inner chamber with much reduced risk of contaminating the environment outside the isolator. <IMAGE>

Description

ISOLATOR AND METHOD OF OPERATING IT This invention relates to isolators (namely enclosures in which operations can be carried out without contamination of the surroundings) and methods of working them.

In the past there have been two classes of isolators, the so-called positive and negative types. If one wishes to perform a sterile operation such as the preparation of drugs for injection it is conventional to maintain the isolator chamber in which the preparation is done at a pressure slightly higher than atmospheric so that any leakage at seals or joints is outwards. In negative operation, for example where toxic materials are being processed, the isolator is run at a pressure slightly lower than atmospheric so that any leakage is inwards.

There is now however a need to be able to process under sterile conditions some materials and particularly the cytotoxic class of pharmaceuticals which are toxic, some extremely so, and yet are being prepared for administration by injection and therefore have to be sterile. In this situation there is a conflict between the criteria of negative and positive pressure operation of an isolator.

According to the invention we provide a solution to that problem by an isolator which is suitable for performing sterile operations on toxic materials by virtue of the fact of having a double chamber, with an inner chamber being surrounded by an outer and means for maintaining the outer chamber at a pressure which is less than both that of the inner chamber and of the atmospheric air outside the outer chamber. The pressure of the inner chamber is preferably greater than atmospheric, but this is not mandatory.

The invention provides also a method of operating an isolator which consists in forming in an inner zone of the isolator an air circulation at a first pressure surrounded at an outer zone of the isolator by an air circulation of a second pressure, the second pressure being negative in relation to atmospheric and the first pressure positive in relation to atmospheric.

Relative flow rates in the different zones or chambers of the isolator can be assured by control of respective fans so that the required pressure characteristics are provided. Such control may be automated if preferred.

An embodiment of the invention is seen in the accompanying diagrammatic drawing.

An isolator 1 is freestanding on legs 2 in a room 3 which by way of further precaution may be a "clean room".

The isolator has an outer volume 4 defined by an enclosure 5 and an inner volume 6 defined by an enclosure 7.

The inner enclosure 7 includes a recirculating fan 8 which draws air from the outer chamber 4 within the outer enclosure 5. This air is passed under pressure via a plenum 10 through a high efficiency particle arrestor ("Hepa") filter 9 so as to form downward, preferably laminar, flow 11 to a perforated base 12 of the inner enclosure 7. Operations to be performed take place on or above the perforated base 12. An advantage of the air flow being downwardly directed is that gravity assists in the process of sweeping quickly through the inner volume any residual dust particles present in the air.

In one wall of the inner enclosure 7 is an aperture 13 through which a glove 14 for an operator, which is sealed at 15 to the outer enclosure 5, passes. A shutter 16 is slidable on the outer wall of the enclosure 7 in the region of the aperture 13. Such an arrangement enables an operator standing in the room 3 to arrange for automatic processing apparatus or the like within the volume 6 to be set up with appropriate charges and then to withdraw the glove 14 into the outer volume and shut the shutter 16 to complete the enclosure of the inner chamber.

If it is desired for an operator to operate continuously in the inner volume, the wall adjacent the aperture 13 would be brought outwardly to become closely adjacent to the wall 5 of the outer enclosure at the region of the seal 15, with the glove being sealed closely adjacently to both walls. Nevertheless, an otherwise continuous duct-like volume is to be maintained by the outer enclosure 5 around the inner enclosure 7.

Air circulation in the outer enclosure 5 is assured by an extraction fan 17 drawing air from that outer volume via a Hepa filter 18 through exhaust duct 19 and passing that extracted air to the atmosphere or to further purification.

Air for feeding both the inner and outer volumes 4 and 6 is brought from the ambient atmosphere by inlet fan 20 via Hepa filter 21 through inlet duct 22.

The fans 8, 17 and 20 are all of variable rate and are electronically controlled through lines 23, 24, 25 by control box 26 to which are fed flow data from inlet duct 22 via line 27 and pressure data from the inner and outer volumes 4 and 6 by lines 28 and 29 respectively.

The control 26 arranges that a sufficient flow is present in the inner volume 6 to sweep away toxic material which may escape from processing but that this volume maintains a positive pressure in relation to the pressure of the outer volume 4, while the fans 17 and 8 assure an air flow indicated generally at 30,31 from air exhausted through the base 12 around the inner chamber while maintaining the pressure in the outer enclosure below that of the atmosphere in the room 3.

The necessary pressures and hence flow rates are to some extent dictated by the relative flow resistance of the apertures in the perforated base tray 12. The design of these apertures can thus influence the design requirements of the control 26.

It is of course possible to arrange for manual control of the fans 8,17,20, in which case an operator would be responsible for maintaining the necessary pressures.

From the arrangement illustrated it can be seen that any toxic material escaping within the inner chamber is swept through the perforated base to be taken up by air flow 30,31 and either recirculated by fan 8 to be caught on Hepa filter 9, or to be caught on the Hepa filter 18 as it is drawn towards the exhaust fan 17, but due to the negative pressure obtained within the outer chamber 4 in relation to the atmosphere, there is no chance of the toxicity escaping. On the other hand, any leakage from the outside atmosphere drawn in by leaking to the outer volume 4 will not penetrate direct to the inner volume since the latter has higher pressure, and if circulated by fan 8 will be caught by filter 9.

In alternative preferred embodiments, the perforated base 12 is replaced by perforations in a lower portion of the side walls of the inner volume 7, the lowermost wall of the inner volume 7 preferably being substantially impermeable. In this case operations take place on a solid base inside the inner volume, and the pressures in the inner and outer volumes are selected with reference to the flow resistance through the perforated lower portion of the side walls.

Many modifications of the preferred embodiments described above are possible within the scope of the invention. For example, although the gas within the inner and outer volumes has been described as air, it is possible to employ any other gas the use of which is compatible with the operations to be performed in the inner volume.

Apparatus may be provided for supplying such gas to the isolator.

Claims

CLAIMS:

1. An isolator having inner wall defining an inner chamber intended for performing operations therein, an outer wall defining an outer chamber which surrounds said inner chamber, and means for maintaining the outer chamber at a pressure which is less than the pressure in the inner chamber and the pressure outside the outer chamber.

2. An isolator according to claim 1, in which an inner aperture is formed in said inner wall and an outer aperture is formed in said outer wall, the isolator further comprising a shutter for closing said inner aperture and a glove of which a sleeve is sealed around the periphery of the outer aperture, whereby with said shutter in an open condition a user may insert his hand into the glove and reach into the inner chamber through said inner aperture.

3. An isolator according to claim 1, in which an inner aperture is formed in the inner wall and an outer aperture is formed in the outer wall, the isolator further comprising a glove of which a sleeve is sealed or sealable around the respective peripheries of the inner and outer aperture.

4. An isolator according to claim 3, in which a portion of said inner wall surrounding said inner aperture and a portion of said outer wall surrounding said outer aperture are relatively repositionable to bring said inner and outer apertures into proximity.

5. An isolator according to any one of the preceding claims further comprising means for causing a downward, laminar flow of gas within said inner chamber.

6. An isolator according to claim 5 further comprising one or more high efficiency filters for filtering the gas within said inner and/or outer chambers.

7. An isolator according to any one of the preceding claims in which a lowermost portion of said inner wall is perforated.

8. An isolator according to any one of the preceding claims in which one or more lower portions of the sides of the inner wall are perforated.

9. An isolator according to any one of the preceding claims in which the pressure outside the outer chamber is atmospheric.

10. An isolator according to any preceding claim further comprising control means for regulating the pressure in said inner and outer chambers.

11. An method of operating an isolator comprising the step of circulating gas in an inner region of the isolator at a first pressure and in an outer region of the isolator outside said inner region at a second pressure, and maintaining said second pressure at a value lower than said first pressure and lower than a pressure outside the outer region, the inner region being intended for performing operations therein.

12. A method according to claim 11 in which the circulation in said inner region is laminar and downwardly directed.

13. A method for operating an isolator according to claim 11 or claim 12 including regulating respective pressures within said inner and outer regions using respective pressure sensors located therein.

14. An isolator substantially as described herein with reference to the accompanying drawing.

15. A method for operating an isolator substantially as described with reference to the accompanying drawing.