Which subtype of Class II BSC is characterized by recirculating all work air?

The subtype of Class II Biological Safety Cabinet (BSC) characterized by recirculating all work air is A1. This type is designed to provide personnel, product, and environmental protection by drawing air through a HEPA filter and recirculating it back into the cabinet. In this process, it helps maintain a sterile environment while ensuring that the air within the cabinet is kept clean of any contaminants that could affect the materials being handled.

In contrast, the other subtypes of Class II BSCs have different air management systems. The A2 subtype also recirculates some air, but it has an increased exhaust system that removes a portion of the air from the cabinet to the outside environment, providing additional protection for volatile agents. The B1 and B2 subtypes use a different air circulation method where a significant portion of the air is exhausted externally rather than recirculated. This makes A1 unique for its characteristics and operation, focusing on full recirculation of air within the cabinet.