WO2013140165A1

WO2013140165A1 - Biosafety cabinet

Info

Publication number: WO2013140165A1
Application number: PCT/GB2013/050720
Authority: WO
Inventors: Michael Aitchison; Michael Mellor; Shane STEVENSON
Original assignee: Howorth Air Technology Limited
Priority date: 2012-03-22
Filing date: 2013-03-20
Publication date: 2013-09-26
Also published as: GB2500872A; GB201204992D0

Abstract

The invention provides a biosafety cabinet decontamination apparatus, which comprises air feed means for feeding air to a biosafety cabinet, hydrogen peroxide feed means for feeding a fixed amount of hydrogen peroxide to the biosafety cabinet, and means for creating hydrogen peroxide vapour from the air and hydrogen peroxide, and dispersing the vapour in the biosafety cabinet. The invention also provides methods for decontaminating biosafety cabinets.

Description

BIOSAFETY CABINET

The present invention relates to biosafety cabinets, and in particular to apparatuses which can be used to decontaminate biosafety cabinets. The invention extends to methods for decontaminating biosafety cabinets.

A biosafety cabinet, also known as a biological or microbiological safety cabinet, is a fully enclosed, ventilated laboratory workspace for safely working with materials that are contaminated (or potentially contaminated) with pathogens requiring a defined biosafety level. Several different types of biosafety cabinet exist (i.e. Class I, II or III), which are distinguished from each other by the degree of biocontainment that is required. The main purpose of the biosafety cabinet is to serve as the primary means for protecting the laboratory worker and surrounding environment from pathogens. All exhaust air leaving the cabinet is filtered with a high-efficiency particulate air filter or HEPA, thereby removing harmful bacteria and viruses.

However, whenever a biosafety cabinet is serviced or relocated, including

replacement of its HEPA filters, it must be thoroughly decontaminated. Gas decontamination involves filling the cabinet with a poisonous gas, most commonly formaldehyde gas. Accordingly, most biosafety cabinets are fitted with a

formaldehyde unit, which produces the formaldehyde gas and emits it into the cabinet during decontamination. However, a significant problem of using

formaldehyde is that it is known to be a human carcinogen, and so presents a major health risk to the laboratory workers carrying out the decontamination procedure. There is therefore a need to provide an improved and dedicated biosafety cabinet, and associated apparatus for use in decontaminating such cabinets.

In a first aspect, there is provided a biosafety cabinet decontamination apparatus, the apparatus comprising air feed means for feeding air to a biosafety cabinet, hydrogen peroxide feed means for feeding a fixed amount of hydrogen peroxide to the biosafety cabinet, and means for creating hydrogen peroxide vapour from the air and hydrogen peroxide, and dispersing the vapour in the biosafety cabinet.

For at least the past 20 years, biosafety cabinets have been decontaminated using formaldehyde, which is carcinogenic. Advantageously, the apparatus of the first aspect uses hydrogen peroxide as a sterilising agent, which is not carcinogenic, and which therefore avoids the risk laboratory workers developing cancer. Furthermore, by using a fixed volume of hydrogen peroxide to create the vapour, not only is there no waste or residue, but also the correct amount of the sterilising agent is used, which is important due to its aggressive nature. The apparatus may comprise control means, which is arranged, in use, to control the amount of hydrogen peroxide and/ or air that is fed to the cabinet, and preferably the vapour creating means. The control means may comprise a timer which controls the length of time during which the hydrogen peroxide and/or air is fed to the cabinet, and preferably the vapour creating means. The timer may be connected to at least one valve which controls the flow of air and/ or hydrogen peroxide to the cabinet.

Preferably, the apparatus comprise a first valve for controlling the air flow to the cabinet and a second valve for controlling the flow of hydrogen peroxide to the cabinet. The or each valve may comprise a solenoid valve. Advantageously, the control means, and preferably the timer, ensures that the fixed amount of hydrogen peroxide is delivered to the cabinet to produce a fixed amount of vapour. The volume of hydrogen peroxide which may be supplied to the cabinet, and preferably the vapour creation means, maybe between lml and 50ml, or between 2ml and 30ml, or between 3ml and 20ml, or between 4ml and 15ml. Thus, the fixed amount of hydrogen peroxide which the hydrogen peroxide feed means is configured to feed to the biosafety cabinet maybe lml and 50ml, or between 2ml and 30ml, or between 3ml and 20ml, or between 4ml and 15ml.

The apparatus of the first aspect may be permanently securable to a biosafety cabinet, or it may be portable and moved between different cabinets requiring

decontamination. The apparatus may comprise a housing which maybe securable to a newly manufactured biosafety cabinet. Alternatively, the housing may be for use in retrofitting an existing cabinet, by replacing its formaldehyde unit. The housing may be connected to a supply of air. The air supply may be a cylinder of compressed air, or a compressor. The housing may comprise a hydrogen peroxide inlet through which an operator may supply hydrogen peroxide, preferably a fixed amount thereof. The housing may be coupled to the cabinet via the air feed means and hydrogen peroxide feed means. The air feed means may be arranged to feed air to the cabinet at a pressure of between about 1 and 10 bar, or between about 3 and 7 bar, preferably between about 4-6 bar, and more preferably about 5-5bar. The hydrogen peroxide feed means maybe arranged to feed hydrogen peroxide to the cabinet at a pressure of between about 5 and 20 psi, or between about 10 and 15 psi, preferably about 12 psi.

The means for creating and dispersing the hydrogen peroxide vapour may comprise a nozzle. The nozzle may be disposed either permanently or temporarily inside the cabinet. For example, in one embodiment, the nozzle may be supportable on a moveable stand. The nozzle may comprise an air inlet by which it is coupled to the air feed means. The nozzle may comprise a hydrogen peroxide inlet by which it is coupled to the hydrogen peroxide feed means.

The nozzle may be adapted to create the hydrogen peroxide vapour using ultrasonics. The nozzle may comprise a source of sonic energy which is capable of creating the vapour. The source of sonic energy may comprise a resonator chamber in which the air and hydrogen peroxide are aerosolised to create the vapour.

The vapour is preferably substantially dry. The humidity of the vapour may be about 80-95%·

The apparatus may comprise actuation means for initiating a decontamination cycle. The apparatus may be arranged, in use, to create vapour for approximately 5-40 seconds, preferably about 15-25 seconds. The apparatus may be arranged, in use, to clear the hydrogen peroxide feed means of hydrogen peroxide. This may take about 80-110 seconds, preferably about 90-105 seconds. The apparatus may comprise power indication means for indicating when the apparatus is switched on.

The apparatus may comprise cycle indication means for indicating when the apparatus is undertaking a decontamination cycle.

In a second aspect, there is provided a biosafety cabinet comprising the

decontamination apparatus of the first aspect.

The biosafety cabinet may be a Class I, II or III category cabinet. Preferably, the biosafety cabinet is a Class III category cabinet. In a third aspect, there is provided use of the decontamination apparatus of the first aspect for decontaminating a biosafety cabinet.

In a fourth aspect, there is provided a method for decontaminating a biosafety cabinet, the method comprising feeding air and a fixed amount of hydrogen peroxide to a biosafety cabinet, creating hydrogen peroxide vapour from the air and hydrogen peroxide, and dispersing the vapour in the cabinet.

The method may comprise the use of the apparatus of the first aspect.

All of the features described herein (including any accompanying claims, abstract and drawings), and/ or all of the steps of any method or process so disclosed, may be combined with any of the above aspects in any combination, except combinations where at least some of such features and/ or steps are mutually exclusive.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings, in which: - Figure ι is a perspective front view of one embodiment of a biosafety cabinet according to the invention. The cabinet includes a hydrogen peroxide sterilisation unit attached thereto;

Figure 2 is a perspective front view from above of one embodiment of the hydrogen peroxide sterilisation unit shown in Figure l;

Figure 3 is a perspective front view from below of the hydrogen peroxide sterilisation unit shown in Figure l; Figure 4 is a schematic side view of the hydrogen peroxide sterilisation unit shown in Figure 1;

Figure 5 is a schematic end view of the hydrogen peroxide sterilisation unit shown in Figure 1; and

Figure 6 is a schematic cross-sectional view of a nozzle assembly for producing hydrogen peroxide vapour. Examples

Referring to Figure l, there is shown one embodiment of a biosafety cabinet 2 in which a laboratory worker can work safely with biological materials, which may be contaminated with a pathogen (e.g. virus or bacteria). The cabinet 2 can be a Class I or Class II cabinet 2, but the embodiment shown in the Figure is a Class III cabinet 2, which is usually installed in a maximum containment laboratory and is specifically designed for work with BSL-4 pathogenic agents, providing maximum protection. The cabinet 2 includes a fully enclosed work area 4 provided on a support stand 6. The enclosure is gas-tight due to the presence of a sealed hood 8, and all materials enter and leave the work area 4 through a dunk tank or a double-door autoclave (not shown). Gloves 7 attached to the front prevent direct contact with any hazardous materials. All exhaust air leaving the cabinet 2 is filtered with a HEPA filter 9, thereby removing harmful bacteria and viruses.

As can be seen in Figure 1, attached to one side of the cabinet 2, there is provided a hydrogen peroxide sterilisation/decontamination unit 10, which is used to sterilise or decontaminate the cabinet 2 after it has been serviced or relocated. The unit 10 is shown in more detail from various different views in Figures 2-6. The unit 10 is generally cubic in shape having six sides. Air is supplied from an air compressor or cylinder (not shown) and fed into the base 24 of the unit 10 via an air inlet 18. Prior to the unit 10 being used to decontaminate the cabinet 2, an operator manually injects the correct quantity of liquid hydrogen peroxide into the top 22 of the unit 10 via hydrogen peroxide inlet 26. The air and the liquid hydrogen peroxide are kept separate inside the unit 10, and cannot mix. In use, however, the air exits the unit 10 via air outlet 32, and the liquid hydrogen peroxide exits the unit 10 via outlet 20. As shown in Figure 1, the air is fed along an air line 14 from the unit 10 to the side of the cabinet 2 at a pressure of about 5.5 bar. Similarly, the liquid hydrogen peroxide is fed from the unit 10 along a peroxide line 12 to the cabinet 2 at a pressure of about 12 psi. The air line 14 and peroxide line 12 extends through the side of the cabinet 2 and into the work area 4, where they are connected to a nozzle 34. The nozzle 34 produces hydrogen peroxide vapour 40 for decontaminating the work area 4. The nozzle 34 can be either fixed to the inside of the cabinet 2, or provided on a stand and moved between different cabinets 2, as required. Referring to Figures 2-5, the sterilisation unit 10 includes two LEDs, 28, 30. One of the LEDs 28 acts as a power indicator, and the other LED 30 acts as a

decontamination cycle indicator. The unit 10 also includes a button or switch 16, which is depressed by an operator to initiate a sterilisation cycle. Use of the sterilisation unit 10 will now be described in detail.

An operator first injects about 3-ioml of liquid hydrogen peroxide into the unit 10, the volume of peroxide depending on the amount of vapour 40 that would be required to fully decontaminate the work area 4 of the cabinet 2, which will depend on its size. A source of compressed air is then attached to the unit 10. Once the unit 10 has been set up in this way, the operator then starts a 2-minute decontamination cycle by depressing the switch 16, which is connected to a timer and solenoid valve (not shown), which is powered by a 240 volt electrical supply. Upon activation of the switch 16, the timer is initiated and the solenoid valve is opened, thereby allowing air and hydrogen peroxide to be fed from the unit 10 along feed lines 12, 14 and into the nozzle 34 disposed inside the cabinet 2. The nozzle 34 is shown in detail in Figure 6. Inside the nozzle 34, the air 14 and peroxide 12 are fed to a sonic air core 36 where they are allowed to mix. The mixture of liquid 12 and gas 14 is then blown into a resonating chamber 38, and this action generates a high pitch sound that breaks the spray down to create a vapour 40 which comprises very fine hydrogen peroxide droplets which have a consistent size (under 1 micron in diameter).

The vapour 40 ensures an even dispersion of the hydrogen peroxide solution throughout the target work area 4. The small droplet size results in no condensation or surface wetting inside the cabinet 2, and the vapour 40 is able to penetrate into areas normally inaccessible when using more conventional disinfection methods. The production of vapour 40 lasts for approximately 20 seconds, and the remainder of the decontamination cycle (i.e. about 1 minute, 40 seconds), involves blowing the residual hydrogen peroxide clear of the peroxide line 14, in order to avoid any harm coming to laboratory workers subsequently using the cabinet 2. After completion of the 2-minute cycle, the unit 10 is then switched off.

Advantages of the sterilisation unit 10 residue in the fact that hydrogen peroxide is not carcinogenic, whereas formaldehyde, which is currently used to decontaminate biosafety cabinets 2, is. The unit can be permanently secured to the side of the cabinet 2, with a rigidly fixed nozzle 34 which produces the hydrogen peroxide vapour 40. Alternatively, the unit 10 and nozzle 34 may be portable and moved between different cabinets 2 requiring decontamination. The unit 10 can secured to newly manufactured cabinets 2, or, because it has the same dimensions and fixing points as existing formaldehyde sterilisation units that have been fitted to cabinets 2 for the past 20 years, it can easily be used to retrofit existing cabinets 2.

Claims

1. A biosafety cabinet decontamination apparatus, the apparatus comprising air feed means for feeding air to a biosafety cabinet, hydrogen peroxide feed means for feeding a fixed amount of hydrogen peroxide to the biosafety cabinet, and means for creating hydrogen peroxide vapour from the air and hydrogen peroxide, and dispersing the vapour in the biosafety cabinet.

2. An apparatus according to claim l, wherein the apparatus comprises control means, which is arranged, in use, to control the amount of hydrogen peroxide and/or air that is fed to the cabinet.

3. An apparatus according to claim 2, wherein the control means comprises a timer which controls the length of time during which the hydrogen peroxide and/or air is fed to the cabinet.

4. An apparatus according to claim 3, wherein the timer is connected to at least one valve which controls the flow of air and/or hydrogen peroxide to the cabinet.

5. An apparatus according to any preceding claim, wherein the apparatus comprises a first valve for controlling the air flow to the cabinet and a second valve for controlling the flow of hydrogen peroxide to the cabinet.

6. An apparatus according to any preceding claim, wherein the volume of hydrogen peroxide which is supplied to the cabinet is between lml and 50ml, or between 2ml and 30ml, or between 3ml and 20ml, or between 4ml and 15ml.

7. An apparatus according to any preceding claim, wherein the comprises a housing which is securable to a newly manufactured biosafety cabinet.

8. An apparatus according to any one of claims 1-6, wherein the apparatus is for use in retrofitting an existing cabinet, by replacing its formaldehyde unit.

9. An apparatus according to either claim 7 or 8, wherein the housing is connected to a supply of air, for example a cylinder of compressed air, or a compressor.

10. An apparatus according to any one of claims 7-9, wherein the housing comprises a hydrogen peroxide inlet through which an operator can supply hydrogen peroxide.

11. An apparatus according to any one of claims 7-10, wherein the housing is coupled to the cabinet via the air feed means and hydrogen peroxide feed means.

12. An apparatus according to any preceding claim, wherein the air feed means is arranged to feed air to the cabinet at a pressure of between about 1 and 10 bar.

13. An apparatus according to any preceding claim, wherein the hydrogen peroxide feed means is arranged to feed hydrogen peroxide to the cabinet at a pressure of between about 5 and 20 psi.

14. An apparatus according to any preceding claim, wherein the means for creating and dispersing the hydrogen peroxide vapour comprises a nozzle.

15. An apparatus according to claim 14, wherein the nozzle comprises an air inlet by which it is coupled to the air feed means.

16. An apparatus according to either claim 14 or 15, wherein the nozzle comprises a hydrogen peroxide inlet by which it is coupled to the hydrogen peroxide feed means.

17. An apparatus according to any one of claims 14-16, wherein the nozzle is adapted to create the hydrogen peroxide vapour using ultrasonics.

18. An apparatus according to any one of claims 14-17, wherein the nozzle comprises a source of sonic energy which is capable of creating the vapour.

19. An apparatus according to claim 18, wherein the source of sonic energy comprises a resonator chamber in which the air and hydrogen peroxide are aerosolised to create the vapour.

20. An apparatus according to any preceding claim, wherein the apparatus comprises actuation means for initiating a decontamination cycle.

21. An apparatus according to any preceding claim, wherein the apparatus comprises cycle indication means for indicating when the apparatus is undertaking a decontamination cycle.

22. A biosafety cabinet comprising the decontamination apparatus according to any one of claims 1-21.

23. A cabinet according to claim 22, wherein the biosafety cabinet is a Class III category cabinet.

24. Use of the decontamination apparatus according to any one of claims 1-21 for decontaminating a biosafety cabinet.

25. A method for decontaminating a biosafety cabinet, the method comprising feeding air and a fixed amount of hydrogen peroxide to a biosafety cabinet, creating hydrogen peroxide vapour from the air and hydrogen peroxide, and dispersing the vapour in the cabinet.