Chapter 4: Using Proper Procedures and Techniques with the Biological Safety Cabinet
The use of proper procedures and equipment cannot be overemphasized in providing primary personnel and environmental protection. The Biological Safety Cabinet is not a substitute for good laboratory practice and proper aseptic technique. Aerosols can escape with poor laboratory procedure & technique. Chemical vapors will pass through HEPA filters and most biological safety cabinets do not provide protection from volatile toxic chemicals or radionuclides. (note: when working with harmful aerosols or vapors it is required to use a Class II, Type B2 Biological Safety Cabinet that exhausts all air through the facilities house exhaust system. Click here to learn about how Class II Cabinets work
Location of the Cabinet
Proper use begins with the proper location and installation of your Biological Safety Cabinet. It was developed as a workstation to provide personnel, product and environmental protection during the manipulation of infectious microorganisms and hazardous aerosols. In order to accomplish this task, location considerations must be met to ensure maximum effectiveness.
The Ideal Location
The ideal location for any Biological Safety Cabinet is remote from the entry points of your laboratory since people walking parallel to the face of a BSC can disrupt the air curtain. The air curtain created at the front of the cabinet is quite fragile. Open windows, air supply registers, or laboratory equipment that creates air movement, such as centrifuges and vacuum pumps, should not be located near the Biological Safety Cabinet. Similarly, chemical fume hoods must not be located close to Biological Safety Cabinets.
Clearance Around the Biological Safety Cabinet
A 12 inch (30 cm) clearance should be provided behind and on each side of the cabinet. At minimum a 3 inch (8 cm) clearance on each side and 1.5 inch (3.8 cm) clearance in back are recommended. The electrical outlet for the cabinet should be accessible for the cabinet service and electrical safety testing without moving the cabinet.
When the cabinet is connected by a canopy or thimble transition to the ventilation system, adequate space must be provided so that the configuration of the ductwork will not interfere with airflow. The canopy or thimble transition unit must provide access to the exhaust filter for testing of the HEPA filter. Also, Biological Safety cabinets should not be installed as an integral part of a rooms supply and exhaust system.
System fluctuations of the room supply and exhaust air will cause the Biological Safety Cabinet to operate incorrectly. The exception to this would be the Class II, type A2 with a canopy connection for room exhaust, since the canopy's air gap will allow for exhaust system fluctuations without affecting containment performance.
Biological Safety Cabinets that are hard connected (Class II, type B1 and B2) should not be used as the sole source of room exhaust. A supplemental room exhaust should be present to aid in room air balance.
Class II, type B2 Biological Safety Cabinets that are hard connected to supply air should be equipped with an interlocked damper to prevent the work zone from being positively pressurized.CETA Whitepaper on installation of Type B2 Biological Safety Cabinets
To review, cabinets should be located away from doors, away from windows that can be opened, away from room supply air and away from heavily-traveled laboratory areas.
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