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TABLE 3. COMPARISON OF BIOLOGICAL SAFETY CABINETS.
| Type |
Face velocity (lfpm) |
Airflow Pattern |
Radionuclides/
Toxic Chemicals |
Biosafety Level (s) |
Product Protection |
| Class I*, open front |
75 |
In at front; out rear and top through HEPA filter |
No |
2,3 |
No |
| Class II: Type A |
75 |
70% recirculated through HEPA; exhaust through HEPA |
No |
2,3 |
Yes |
| Type B1 |
100 |
30% recirculated through HEPA; exhaust via HEPA and hardducted |
Yes (Low Levels/volatility) |
2,3 |
Yes |
| Type B2 |
100 |
No recirculation; total exhaust via HEPA and hardducted |
Yes |
2,3 |
Yes |
| Type B3 |
100 |
Same as IIA, but plena under negative pressure to room and exhaust air is ducted |
Yes |
2,3 |
Yes |
| Class III |
NA |
Supply air inlets and exhaust through 2 HEPA filters |
Yes |
3,4 |
Yes |
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