BIOLOGICAL SAFETY CABINETS, FUME HOODS AND FILTRATION SYSTEMS

A.BIOLOGICAL SAFETY CABINETS
Biological safety cabinets are the most widely used and accepted primary containment devices. Class I or II cabinets can provide partial containment, and Class III cabinets have the potential for complete containment. Biological safety cabinets must not be confused with other laminar flow devices or 'clean benches'; in particular, horizontal flow cabinets which direct air towards the operator should not be used for handling infectious, toxic or sensitizing materials.
The correct location, installation, testing and certification of the biological safety cabinet is critical to its performance in containing aerosols.
Cabinets must be annually inspected and tested by trained service personnel to CSA Z316.3-95 or NSF 49 or subsequent modifications.
Laboratory personnel must be trained in the correct use and maintenance of biological safety cabinets to ensure that personnel and product protection (where applicable) are maintained.
CLASS I BIOLOGICAL SAFETY CABINET
This is a ventilated cabinet for personnel protection with an unrecirculated inward airflow away from the operator. This unit should be fitted with a HEPA filter to protect the environment from discharged agents.
Schematic Diagram of a Class I Biological Safety Cabinet

Class I cabinets may be used with or without glove ports.
Class II Biological Safety Cabinet
This is a ventilated cabinet for personnel, product and environmental protection which provides inward airflow and HEPA-filtered supply and exhaust air. The Class II cabinet has four designs: one recirculates most of the air; a second exhausts most of the air; a third provides total exhaust; and a fourth includes cabinets which are convertible between the other designs. Class II cabinets may be of use with low to moderate risk biological agents, minute quantities of toxic chemicals, and trace quantities of radionuclides; however, care must be exercised in selecting the correct Class II cabinet design for these purposes.
Schematic Diagram of a Class II Biological Safety Cabinet

Class III Biological Safety Cabinet
A Class III cabinet is a totally enclosed ventilated cabinet which is gas-tight, and maintained under negative air pressure 120 Pa (0.5 inches water gauge). The supply air is HEPA-filtered and the exhaust air has two HEPA filters in series. Work is performed in the cabinet by the use of attached rubber gloves.
Schematic Diagram of a Class III Biological Safety Cabinet

B. FUME HOODS
Fume hoods must be annually tested by qualified personnel in accordance with Canadian Standards Association CSA Z316.5-94. Auxiliary filters (HEPA, charcoal, etc..) installed in fume hoods must also be tested to appropriate standards.
C. FILTERED SYSTEMS
All filters installed in ventilation systems, vent stacks or primary containment devices must be annually tested.

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