Comparison of Biosafety Cabinet Characteristics
BSC Class |
Face Velocity |
Airflow Pattern | Applications | |
Nonvolatile Toxic Chemicals and Radionuclides |
Volatile Toxic Chemicals and Radionuclides |
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I | 75 | In at front; exhausted through HEPA to the outside or into the room through HEPA. | YES | When exhausted outdoors (1,2) |
II, A1 | 75 | 70% recirculated to the cabinet work area through HEPA; 30% balance can be exhausted through HEPA back into the room or to outside through a canopy unit | Yes (minute amounts) |
NO |
II, B1 | 100 | 30% recirculated, 70% exhausted. Exhaust cabinet air must pass through a dedicated duct to the outside through a HEPA filter | YES | Yes (minute amounts) (1,2) |
I, B2 | 100 | No recirculation; total exhaust to the outside through a HEPA filter | YES | Yes (small amounts) (1,2) |
II, A2 | 100 | Similar to II, A1, but has 100 Ifm intake air velocity and plenums are under negative pressure to room; exhaust air can be ducted to the outside through a canopy unit. FORMERLY “B3” | YES | When exhausted outdoors (minute amounts) (1,2) |
III | N/A | Supply air is HELP filtered. Exhaust air passes through two HEPA filters in series and is exhausted to the outside via a hard connection | YES | Yes (small amounts) (1,2) |
(1) Installation requireS a special duct to the outside, an in-line charcoal filter, and a spark proof (explosion proof) motor and other electrical components in the cabinet. Discharge of a Class I or Class II, Type A2 cabinet into a room should not occur if volatile chemicals are used.
(2) In no circumstances should the chemical concentration approach the lower explosion limits of the compound.
Last update 4/19/2010