Class II, Type A2 Biosafety Cabinet
User Manual
6
Control of Airflow
To be sure your unit is functioning properly, the air velocity should be measured directly by a qualified third party
certification professional. Readings of air velocity, measured in feet per minute, can be made with a velometer
or thermoanemometer to determine if the unit is within specification and when the filters should be changed.
This certification should be performed at least annually, and many regulatory bodies recommend semi-annually.
The unit must also be recertified any time that it is relocated. The following chart represents the acceptable
range of air velocities that are measured in your unit.
Unit Inflow (fpm) Downflow (fpm) Volume (cfm) Exhaust Flow (fpm)
BBF 2 87-102 65-80 114-134 154-181
BBF 3 102-112 67-82 147-161 123-134
BBF 4 102-112 67-82 215-236 130-142
BBF 6 102-112 70-85 353-388 106-117
Eventually, the HEPA filters will be loaded with particulates to a point where the blower can no longer overcome
the resistance to provide the proper air velocities. At this point new HEPA filters must be installed. Replacement
HEPA filters can be ordered ahead of time so that they are available in advance of changing. Because viable
particles may be trapped and survive for a period of time in the filters, the Class II, Type A2 Biosafety Cabinet
must be decontaminated, if any biological agents have been manipulated within the cabinet, before any HEPA
filters are changed.
A low flow alarm will indicate when the inflow has fallen below acceptable levels. This can indicate that
maintenance needs to be performed on the cabinet.
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