A Class II biological safety cabinet (BSC) is a ventilated containment device found in laboratories around the world. BSCs are used in many applications, including cell culture, pharmaceutical, clinical and microbiological work. Due to the critical nature accomplished inside these commonly used laboratory products, BSCs are regulated through rigorous standards and compliance. Engineered controls are built into the design of BSCs providing protection to the operator, product and environment.
Globally, different regions have their own standards applicable to BSCs, and manufacturers build and test to the criteria set out in these standards. In a Class II, Type A2 BSC air is drawn in through the front aperture, which provides operator protection. The inflow air mixes with the downflow air as it enters the front intake grille and then passes through the plenum where the air splits. Approximately 60% to 70% of the air is recycled and pushed back into the BSC work area through the downflow, and the remaining 40% to 30% is exhausted through the exhaust HEPA filter. This filtered exhaust air can be externally extracted with a thimble system, direct duct or simply extracted back into the laboratory. However, if volatile chemicals are used within the BSC as an adjunct to microbiological work, exhaust must be released into the atmosphere through a thimble system or direct duct.