The Class II Type B2 cabinet is a total exhaust, non-recirculating, vertical laminar flow biological safety fume hood. It was developed in order to provide protection from diverse types of biohazardous material as well as gases and fumes in the work area (that are an adjunct of biological work).

The conventional fume hood only protects the user. The Class II, Type A 70% recirculating hood, in addition to protecting the user, also protects work in progress and the environment from all particulates. The Class II, Type B2 Biological Safety Cabinet carries this protection one step further by ducting (venting) to the outside of the building 100% of the air entering the hood. This total exhaust feature makes the B2 hood suitable for not only handling particulates, but also fumes and gases. It is especially desirable for work with radionuclides, effluents from subliming particulates and noxious odors.

The Class II, Type B2 cabinet provides 100% exhaust, with absolutely no recirculation of air in the cabinet. Germfree invented and patented the total exhaust BSC which was later classified as a Class II B2 Cabinet.