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Types (Classes) of Biological Safety Cabinets

Nonvolatile chemicals can be used in all classes of biological safety cabinets. For volatile chemical use see table below. In certain cases, a charcoal filter may be added to prevent release of toxic chemicals into the atmosphere.

A front panel with armholes can be added to both Class I & II cabinets. Arm-length gloves can be attached to the panel with air drawn through an auxiliary air supply opening (which may contain a filter) and/or around a loose-fitting front panel. Access to the interior of these cabinets is through a double-door air lock on the side of the cabinet.

Class I
Class I cabinets provide worker and environmental protection, but no product protection. Air drawn accross the interior work surface is not HEPA filtered. There is a HEPA filter in the exhaust system to protect the environment. Whether air is exhausted outside the building or recirculated depends on the type of work to be done in the cabinet. Class I cabinets may be used to enclose equipment or procedures with a potential to generate aerosols such as tissue homogenization, sonication, or cage cleaning/manipulation.

Class II
Class II biological safety cabinets provide personnel, environmental and product protection. Both room air and interior cabinet air are drawn into a front grille creating an air barrier that provides personnel protection. In addition, downward laminar flow of HEPA-filtered air provides product protection. Air exhaust passes through a certified exhaust HEPA filter and may be recirculated back into the laboratory or exhausted out of the building.

All Class II cabinets are designed for work involving microorganisms assigned to biosafety levels 1,2 and 3. These cabinets provide a suitable environment for cell culture propagation and may also be used for the formulation of nonvolatile antineoplastic or chemotherapeutic drugs. There are several types of Class II cabinets, see the table below for acceptable uses of each and click on Type (Class) to view schematic drawings of biological safety cabinets.

Type (Class) Worker Protection Product Protection Environment Protection Volatile Chemicals Application
I Yes No Yes Yes* Enclose equipment or procedures with a potential to generate aerosols (tissue homogenization, cage cleaning, etc).
II, A1
(was A)
Yes Yes Yes No Cell culture and infectious material procedures that do not include the use of volatile chemicals.
II, A2
(was B3)
Yes Yes Yes Yes (minute
amounts)**
Same as Type A but exhausted to outside. Minute quantities of hazardous chemicals may be used.
II, B1 Yes Yes Yes Yes (minute
amounts)**
Must be hard-ducted to exterior exhaust. Same procedures as Type II,A but manipulations of minute quantities of hazardous chemicals used with in vitro biological systems can be done.
II, B2 Yes Yes Yes Yes (small
amounts)
Cabinet has total-exhaust, no air is recirculated. This cabinet provides simultaneous primary biological and chemical containment. Care must be given as some chemicals can damage the filters or gaskets.

* Special installation venting and/or filters may be needed. Air discharge into a room should not occur if volatile chemicals are to be used.
** Chemical concentrations should not approach the lower explosion limits for the compound.

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