Biological safety cabinets (BSC) are designed to provide three types of protection:
- Protection for personnel from material inside the cabinet
- Protection for the material inside of the cabinet from personnel and the environment
- Protection for the environment from the material inside of the cabinet
There are three types of BSCs, Class I, II, and III. Class I are designed to provide personnel and environmental protection only. The material (research experiment) inside the cabinet is not protected and thus subject to contamination. The use of Class I BSCs is not advised at Stanford; talk to biosafety if you feel you need to purchase one.
Class II cabinets meet requirements for the protection of personnel, product and the environment. There are four types of Class II cabinets (A, B1, B2, and B3), each differentiated according to the method by which air volumes are recirculated or exhausted.
Class II, type A: The Class II, type A biosafety cabinet does not have to be vented, which makes it suitable for use in laboratory rooms which cannot be ducted. This cabinet is acceptable for use of low to moderate risk agents in the absence of volatile toxic chemicals and volatile radionuclides.
Class II, type B1: The Class II, type B1 biosafety cabinet must be vented. 30% of the air is exhausted from the cabinet while 70% is recirculated back into the room. This cabinet may be used with etiologic agents treated with minute quantities of toxic chemicals and trace amounts of radionuclides required as an adjunct to microbiological studies if work is done in the directly exhausted portion of the cabinet, or if the chemicals or radionuclides will not interfere with the work when recirculated in the downflow air.
Class II, type B2: The Class II, type B2 biosafety cabinet must be totally exhausted. 100% of the air from the cabinet is exhausted through a dedicated duct. This cabinet may be used with etiologic agents treated with toxic chemicals and radionuclides required as an adjunct to microbiological studies.
Class II, type B3: The Class II, type B3 biosafety cabinet must be vented. 70% of the air is exhausted from the cabinet while 30% is recirculated. This cabinet may be used with etiologic agents treated with minute quantities of toxic chemicals and trace quantities of radionuclides that will not interfere with work if recirculated in the downflow air.
Class III cabinets are gas-tight, designed for use with high-risk (BSL-4) agents. There are no Class III cabinets at Stanford University.
