Air Velocities
Downflow velocity plays a critical role in product protection and maintaining an ultra low particulate environment. It can also have an effect on the noise level if set up incorrectly. A risk assessment for product entry and exit of the cabinet should always be carried out.
Both Class I and II BSC have inward face velocities (75-100 linear feet per minute) that provide comparable levels of containment to protect laboratory workers and the immediate environment from infectious aerosols generated within the cabinet.
In the Class I BSC, unfiltered room air is drawn across the work surface. Personnel protection is provided by this inward airflow as long as a minimum velocity of 75 linear feet per minute (lfpm) is maintained through the front opening and appropriate work practices are observed.
In the Class I BSC, unfiltered room air is drawn across the work surface. Personnel protection is provided by this inward airflow as long as a minimum velocity of 75 linear feet per minute (lfpm) is maintained through the front opening and appropriate work practices are observed.
The minimum air velocity of the front window of the class II A1 biosafety cabinet or the measured average value shall be at least 0.38m/s. 70% of the air is recirculated to the work area through the HEPA filter, and 30% of the air is filtered out through the exhaust port.