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Appendix II: Biological Safety Cabinets

Laminar Flow Hoods

“Biological safety cabinets (BSC) are among the most effective and most commonly used primary containment devices.” Three types exist, Class I, Class II and Class III. Class III provides the maximum protection, and Class I the least. The biological safety cabinets used in the CSB/SJU biology department are Class II BSC and are located in NSC 203 and 223.

“Class II BSC have inward face velocities (75-100 linear feet per minute) that provide comparable levels of containment.” Class II BSC have high efficiency particulate air filtration (HEPA filtration) of the flow of air over the work surface (vertical laminar flow) which protects the material being manipulated from contamination. The exhaust air is also HEPA filtered to protect the environment.

Two types of Class II BSC exist, A and B. The BSC in the biology department are type A which is “suitable for microbiological research in the absence of volatile or toxic chemicals” or radioactive materials because the air is recirculated within the cabinet. Class IIA biological safety cabinets are suitable for Biosafety levels 2 and 3.

Biological safety cabinets need to tested and certified at installation, moving and annually thereafter.

Training of personnel using the BSC is important in recognizing activities that can disrupt the inward directional flow of air into the cabinet. The disruption of airflow can allow aerosolized particles to escape. Some activities that can disrupt air flow include:

  • Repeated insertion and withdrawal of workers arms in and out of the BSC
  • Opening and closing doors to the laboratory.
  • Improper placement or operation of materials or equipment in the BSC
  • Brisk walking past the BSC

Class II biological safety cabinets should be located away from traffic patterns and doors. The air flow from fans, room air supply louvers should be carefully considered.

Horizontal laminar flow clean benches

These hoods are used for product protection, e.g. pouring sterile agar plates. It does not provide protection for personnel using the hood because the downstream exhaust is directed at them while they are working. The clean bench should never be used for handling toxic, infectious, radioactive or sensitizing materials.