Biosafety Cabinet (BSC): Introduction, Types, Handling Procedure

Introduction of Biosafety Cabinet (BSC)

A Biosafety Cabinet (BSC) is an enclosed, ventilated laboratory workstation for safely working with materials contaminated with pathogens. A high-efficiency particulate air (HEPA) filter is used to remove particles like fungus, bacteria, viruses, etc. from the cabinet’s interior. It is also known as biological safety cabinet or microbiological safety cabinet.

Types of Biosafety Cabinet (BSC)

Biosafety Cabinet (BSC)

Biosafety Cabinet is categorized into the following classes

Biosafety Cabinet Class I
Biosafety Cabinet Class II
Biosafety Cabinet Class III

Note: Biosafety Cabinet Class II is further following subtypes-
Type A1-It is not safe to work with hazardous chemical substances.
Type A2-Since the chances of the release of hazardous chemicals into the environment, A2 type cabinets are also not extensively used.
Type B1- 40% of the air is recirculated in the cabinet, whereas the remaining 60% is exhausted out of the facility.
Type B2-This type B2 cabinet is expensive, and its use is limited to toxicology laboratories where protection against hazardous chemicals is imperative.
Type C1- It differs from the other subtypes since it doesn’t require a dedicated ducted exhaust system, can work for an extended duration to increase operator protection in the case of exhaust failure, and can even run without the exhaust at all.

General Criteria for the Use of Biosafety Cabinet ( type I and II)

Perform work involving biohazardous agents in laminar flow biosafety cabinet. Do not conduct work with potentially infectious materials on an open bench.
Perform the inoculation and necropsy of infected experimental animals to a primary barrier such as a Class I or Class II ventilated cabinet.
Annually test and certify all biosafety cabinets by the authorized company with its logo and staff signature for adequate airflow and/or containment using a qualified testing laboratory.
Do not apply volatile toxic compounds, flammable solvents, or radioisotopes in laminar flow safety cabinets, unless the appropriate exhaust and/or filter systems are installed.
Take adequate precautions, with consideration for both equipment and operating practices, to reduce the potential hazards of aerosol-generating processes such as using centrifugation, sonication, grinding, fractionation, etc. Operate smaller laboratory equipment that may generate aerosols, in the appropriate safety cabinet, as determined by risk.

Effectively Using Biosafety Cabinet

Use Biosafety Cabinets (BSCs) effectively by following these procedures:
Keep the laboratory meticulously clean and also minimize the storage of unnecessary materials such as boxes and supplies, particularly near the BSC.
Wash hands thoroughly before and after working in the BSC. Wearing a clean lab coat/ apron and gloves while working in a BSC increases personal safety and helps reduce contamination of research materials.
The effectiveness of a BSC is a function of directional airflow, inward and downward, through a HEPA filter. Anything that disrupts the airflow pattern reduces cabinet effectiveness. e.g. include rapidly moving one’s arms in and out of the BSC, allowing people to walk rapidly behind you, drafts from ventilation systems, and drafts from open laboratory doors.
Realize how the cabinet works. Plan your work. Protect yourself, your research, and your co-workers.

Recommended Protocol for the Operation of Biosafety Cabinet

Put on a clean lab coat or apron. Thoroughly wash your hands. Put on gloves, if appropriate ( depending on nature work may need to follow personal protective equipment).
Turn on the Biosafety Cabinet. Wipe the work surface with 70% ethanol generally but may need to do extra activities depending on the nature of the task. e.g. In the CoVID PCR lab for RNA extraction first treat with hypochlorite (0.5%), follow with 70% ethanol, and lastly with UV light. Allow the cabinet to run at least five minutes before beginning work.
Wipe off each item needed for the procedure and place it in the safety zone of the cabinet.
Do not put objects over the front air intake grille; do not block the rear exhaust grille. Perform work at least six inches back from the front air intake grille.
Segregate contaminated and clean items and then minimize movement of contaminated items over clean ones. Remember . . . “work from clean to dirty.”
Follow good microbiological techniques (GMT), such as holding open tubes and bottles as horizontally as possible.
Always use pipetting aids and never do a mouth pipetting
While working in a BSC, use horizontal pipette discard pans containing appropriate disinfectant. Do not use vertical pipette discard canisters on the floor outside the cabinet.
It is not allowed to use the flame items since the flame creates thermal turbulence in airflow that may compromise sterility and safety; excessive heat buildup may damage the filters.
If you need to take out or introduce items within the BSC, move your arms slowly in and out of the BSC to minimize disruption of the airflow.
If you use equipment that creates air turbulence in the BSC like a centrifuge, blender, sonicator, etc., place the equipment in the back 1/3 of the cabinet and stop other work while equipment is operating.
Protect all vacuum systems from biohazard contamination by using a liquid disinfectant trap and a HEPA cartridge filter between the vacuum trap and the vacuum source in the cabinet.
Clean all spills in the cabinet instantly. Wait 3-5 minutes before resuming work if procedures allow.
Remove all materials and wipe all interior surfaces with 70% alcohol generally but may need to do extra activities depending on the nature of the task. e.g. In the CoVID PCR lab for RNA extraction first treat with hypochlorite (0.5%), follow with 70% ethanol, and lastly with UV light when you are finished working. Examine the tray under the work surface, disinfecting and cleaning as necessary. Let the cabinet turn it off or adjust auto-off.
Discard waste materials appropriately (autoclave, etc.).

Keynotes on Biosafety Cabinet

Remove lab coat and wash hands thoroughly before leaving biohazardous materials area.
There are four types of Biosafety levels (BSL) laboratories and they are-

Biosafety levels- I (BSL) laboratories
Biosafety levels- II (BSL) laboratories
Biosafety levels- III (BSL) laboratories
Biosafety levels- IV (BSL) laboratories

Biosafety levels (BSL) laboratories are four in number while biosafety cabinet three in number since BSL- I laboratory does not require BSC.
A biosafety cabinet has three zones, the left side clean zone, the mid-side working zone while the right side dirty zone.
Depending on types of BSC or generally annual validation is mandatory.
The size of the HEPA filter is 0.3µm.

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