Selection
The protection of personnel from aerosols created by experimental procedures is necessary with use of biological agents. The biological safety cabinet is a primary barrier that protects the work by controlling the aerosols.
Biological safety cabinets can only protect the worker and the experiment if they have been properly selected for the intended containment function. Selection is dependent on:
Class I
Designed as a partial containment cabinet offering adequate personnel protection but no product or experiment protection. Cross contamination may result from contaminated air flowing over the work area.
NIH (National Institute of Health) recommends the use of this type cabinet for low to moderate risk infectious biological agents (CDC Class 1,2).
Air velocity through this opening must be a minimum of 75 linear feet per minute (lfpm).
Class II
A laminar flow safety cabinet developed to protect the worker, the research material and environment. The essential components of Class II cabinets are:
Class III
Class III cabinets are gas tight, closed-front, self-contained, ventilated safety cabinets. They operated at a negative pressure thus providing a physical barrier between the agent and worker. Of all the safety cabinets these provide the greatest degree of personnel protection.
Work in these cabinets require arm length rubber gloves attached to a sealed front panel. Although it may be awkward to work with this system because all manipulations must be performed through rubber gloves, the protection and sense of security afforded is well worth the slight inconvenience.
Class III systems are used to contain highly infectious materials such as those classified as Class 4 by CDC.
Certification
Since contamination control depends on proper mechanical performance, certification is necessary:
Effective Use of a Class II Cabinet
1. Wash hands well with a germicidal soap before and after work in the cabinet
2. Use gloves and long-sleeve lab coats to avoid shedding of skin flora and for protection
3. Disinfect the interior work surfaces by wiping it down with an appropriate disinfectant
4. Place everything needed for the complete procedure in the cabinet prior to beginning work
5. Keep the front intake and rear exhaust grill free of equipment and material
6. Turn on airflow and wait 5-10 minutes before working after materials are in the cabinet. This allows the cabinet time to purge airborne contaminates from the work areas
7. Minimize traffic in the area during operation of the cabinet. Unnecessary activity may create disruptive air currents
8. Place the Bunsen burner to the rear of the cabinet. The flame can disrupt unidirectional airstream when in the front.
9. Let the cabinet run for 15 minutes with no activity after completion of work. This allows time for the cabinet to purge air contaminants
10. Decontaminate the interior surface after removal of all materials
11. Shut down by turning off the fan and light
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