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Oregon State University

Biosafety Cabinet Comparison

Comparison of Biosafety Cabinet Characteristics

Airflow Pattern Applications
Nonvolatile Toxic
Chemicals and
Volatile Toxic
Chemicals and
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
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