BSC
Class |
Face
Velocity |
Airflow Pattern |
Nonvolatile ToxicChemicals andRadionuclides |
Volatile ToxicChemicals andRadionuclides |
| II, A |
75 |
70% recirculated to the cabinet work area through HEPA; 30% balance can be exhausted through HEPA back into the room or to the outside through a thimble unit
|
YES |
NO |
| II, B1 |
100 |
Exhaust cabinet air must pass through a dedicated duct to the outside through a HEPA filter
|
YES |
YES (minute amounts(2)) |
| II, B2 |
100 |
No recirculation; total exhaust to the outside through hard-duct and a HEPA filter
|
YES |
YES (small amounts) |
| II, B3 |
100 |
Same as II, A, but plenums are under negative pressure to room; exhaust air is thimble-ducted to the outside through a HEPA filter
|
YES |
YES (minute amounts(2)) |
| III |
N/A |
Supply air inlets and hard-duct exhausted to outside through two HEPA filters in series
|
YES |
YES (small amounts) |
