Appendix E

 

Comparison of Biosafety Cabinet Characteristics (BMBL, 5th edition, page 311)

 

BSC Class

Face Velocity

Airflow Pattern

Applications

Nonvolatile Toxic Chemicals and Radionuclides

Volatile Toxic Chemicals and Radionuclides

I

75

In at front through HEPA to the outside or into the room through HEPA

Yes

When exhausted outdoors *

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 connection

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) *

I, B2

100

No recirculation; total exhaust to the outside through a HEPA filter and hard ducted connection

Yes

Yes

(small amounts) *

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 connection

Yes

When exhausted outdoors (formally known as “B3”) (minute amounts) *

III

N/A

Supply air is HEPA filtered. Exhaust air passes through two HEPA filters in series and is exhausted to the outside via a hard ducted connection

Yes

Yes

(small amounts) *

* 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. In no instance should the chemical concentration approach the lower explosion limits of the compounds.