Comparaison of BSC Characteristics
| BSC Class |
Face
Velocity |
Airflow
Pattern |
Applications |
| Nonvolatile Toxic Chemicals
and Radionuclides |
Volatile Toxic Chemicals and
Radionuclides |
| I |
75 |
In at front;
exhausted through HEPA to the outside or into the room through HEPA
(see Fig. 2)
|
YES |
YES (1) |
| 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) |
(1) Installation may require 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 cabinet in to 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.
| Reproduced
from
"Biosafety in Microbiological and Biomedical Laboratories, BMBL 4th
Edition" with permission from the Center for Disease Control (CDC). |
|
