These are bio-enclosures that are commonly used for microbiological analysis. These cabinets are suitable for Biosafety levels I to IV where samples being handled range from non-pathogenic to those with lethal effects.
In a B1 cabinet, 70% of the air is exhausted while only 30% is recirculated in the work zone. It has a special exhaust feature that eliminates re-circulation when work is performed towards the back within the interior of the cabinet. A type B2 cabinet on the other hand has total air exhaustion design. This type is suitable for analysis that involve use of toxic chemicals since the absence of air recirculation provides protection for the user. Type B2 cabinet requires installation of a ducting system to allow filtered exhaustion in the environment.