Biological Safety Cabinets Information
Biological safety cabinets protect both the specimen and the user from biological contamination. Particulate-free air is passed down from the top of the hood, across the work surface, and then captured before entering a worker's breathing zone. The air is then filtered before being exhausted, usually back into the laboratory.
Three kinds of biological safety cabinets, designated as Class I, II, and III have been developed to meet varying research and clinical needs.
The Class I biological safety cabinets provide personnel and environmental protection but no product protection. It is similar in air movement to a chemical fume hood, but has a HEPA (high-efficiency particulate air) filter in the exhaust system to protect the environment. All of the types of biological safety cabinets use HEPA filters in their exhaust and/or supply systems.
Class II biological safety cabinets are divided into four grades, A, B1, B2, and B3. All Class II biological safety cabinets provide personnel, environmental, and product protection. The Class II, Type A cabinet recirculates approximately 70% of the air through a supply filter, and exhausts approximately 30% of the air through an exhaust filter to the room. Type B1 cabinets meet the requirements of the National Cancer Institute (NCI) specification for a General Purpose Clean Air Biological Safety Cabinet. Class II Type B2 biological safety cabinets are widely used in toxicology laboratories and similar applications where chemical effluent is present and clean air is essential. Class II Type B3 cabinets recirculate approximately 70% of the air through a supply filter, and exhaust approximately 30% of the air through an exhaust filter. The exhaust is directed to the outside through a facility exhaust system.
Class III biological safety cabinets are designed for use with biosafety level 4 microbiological agents, and provide maximum protection to the environment and the worker. They are gas tight enclosures with a non-opening view window. Access for passage of materials into the cabinet is through a dunk tank or double-door pass-through box that can be decontaminated between uses.
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