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CETA Application Guide for the Exhaust System Requirements of Class II, Type B Biosafety Cabinets

1. Background

Class II Type B Biosafety Cabinets (BSCs) are unique laboratory ventilation products, in that they protect the operator and their laboratory environment from biohazardous aerosols and volatile toxic chemicals. Type B BSCs also have special exhaust system requirements that set them apart from laboratory chemical fume hoods and other laboratory exhausted devices.

2. Class II BSC use with volatile toxic chemicals

Class II BSC’s integral HEPA or ULPA filters remove particulates, but they do not remove gases. If volatile toxic chemicals are used in a Class II BSC, the cabinet’s exhaust airflow must be removed from the room and subsequently from the facility. The selection and use of volatile toxic chemicals used in any class II BSC should be in small or minute quantities per NSF/ANSI 49. Class II BSC’s in general should never be used as a laboratory chemical fume hood because of material incompatibility and fire protection requirements of NFPA 45.