In which subtype of BSC Class II is all of the work surface area exhausted outside?

The subtype of Biohazard Safety Cabinet (BSC) Class II in which all of the work surface area is exhausted outside is B2. This type of cabinet is designed to provide maximum protection against contaminants by ensuring that all air circulating within the cabinet is vented directly to the outside environment. This design is particularly important in settings where highly hazardous materials are handled, as it prevents the potential buildup of toxic fumes or contaminants within the controlled environment.

In contrast, other subtypes such as A1 and A2 recirculate some of the air back into the cabinet, which limits their use to less hazardous materials or situations where maximum exhaust to the outside is not as critical. B1 also includes some recirculated air but has a different filtration system. The B2 cabinet’s configuration provides a higher level of safety for both the worker and the environment, making it essential for specific applications.