are a containment device equipped with High-Efficiency Particulate Arresting (HEPA) filters
, designed to provide worker or both worker and product protection from biohazardous materials. It is mainly used for working safely with infectious microorganisms or materials contaminated with pathogens. For this reason, Biosafety Cabinets are also known as microbiological safety cabinets. All exhaust air is HEPA-filtered as it exits the biosafety cabinet, removing harmful bacteria and viruses. This is in contrast to a laminar flow clean bench, which blows unfiltered exhaust air towards the worker and is not safe for work with pathogenic agents. Likewise, a fume hood fails to provide the environmental protection that HEPA filtration in a biosafety cabinet would provide.
Kinds of biosafety cabinets, designated as Class II
have been developed to meet varying research and clinical needs. These classes and the types of biosafety cabinets within them are distinguished in two ways: the level of worker and environmental protection provided and the level of product protection provided.
Class II, Type A Biological Safety Cabinets
The Class II, Type A Biosafety Cabinet provides protection to the worker, the experimental material and the environment. The Class II biological safety cabinet is the type most commonly used in biomedical and microbiological laboratories. Air flow is drawn from the room around the operator into the front grille of the cabinet, which provides worker protection. In addition, the downward laminar flow of HEPA-filtered air provides protection for experimental material inside the cabinet. Because cabinet air has passed through the exhaust HEPA filter, it is contaminant-free, providing environmental protection. The cabinet air is generally recirculated back into the laboratory in Type A. Consequently, Type A is not safe for work with hazardous chemicals except when ducted, usually with a thimble or canopy hood to avoid disturbing internal air flow.
Class II, Type B Biological Safety Cabinets
The Class II, Type B Biosafety Cabinet also provides protection to the worker, the experimental material and the environment. Type B biosafety cabinets works in exactly the same way as Type A biosafety cabinets. The main difference is that Type B biosafety cabinets are hard-ducted to an exhaust system. Hence, the cabinet air is released out of the building instead of being recirculated back into the room like in most Type A biosafety cabinets.