See also Maintain, Move & Transfer a Class II Biological Safety Cabinet (BSC).

Biological safety cabinets (BSCs), often referred to as tissue culture hoods, are the primary method of laboratory containment for working with infectious microorganisms. When used appropriately and in combination with good microbiological practices, they provide worker, environmental and product protection.

The Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH) have categorized three classes of BSCs: Class I, II, and III - all which offer different degrees of protection to handle the hazards imposed within each biosafety level. One of the main components of each class is one or more high efficiency particulate air (HEPA) filters, which removes microscopic contaminants equal to and greater than 0.3 μm with an efficiency of 99.97%.

Class II Biological Safety Cabinets are the most commonly used BSCs. Their open front design with inward airflow protects the researcher; downward, laminar HEPA filtration protects the product; and HEPA filtered exhaust protects the environment.

The subtypes typically found in Vanderbilt research laboratories include:

  • Class II A1 - recirculates 70% of the HEPA-filtered air back into the laboratory and should never be used for work involving volatiles or radio-nucleotides. Airflow is a minimum of 75 lfpm.
  • Class II A2 - also recirculates 70% of the HEPA-filtered air but can be ducted or unducted back into the cabinet. For minimal use with toxic chemicals, it can be operated safely. Airflow is 100 lfpm.
  • Class II B - is designed for use with BSL2 or BSL3 agents and minute quantities of volatile chemicals. Airflow is 100 lfpm and 70% of air is HEPA-filtered to the outdoors while 30% is HEPA-filtered and recirculated back into the cabinet. For maximum performance, experiments should be conducted as centrally located into the cabinet as possible.

Proper use of a Class II Biological Safety Cabinet

  • The cabinet should be certified yearly to ensure proper function. (Contact VEHS for names of accredited field certifiers.)
  • If not already running, turn on the blowers in the cabinet and let them run for 15 minutes before starting work.
  • Wear appropriate personal protective equipment (typically gloves and buttoned lab coat) while working at the cabinet.
  • After loading the cabinet with your research materials, let the blowers circulate the air for at least 5 minutes to remove contaminants that could be on the outside of the materials.
  • When first placing hands and arms into cabinet, pause briefly so that airflow can stabilize.
  • Limit movements into and out of the cabinet to reduce the possibility of bringing-in or letting-out contaminants.
  • Avoid blocking airflow slots, or grills, with research materials such as pipette aids, biowaste bags, flasks, etc.
  • Keep all materials at least four inches inside the sash opening. This will provide the most product protection.
  • Conduct research in a ‘clean to dirty’ (left to right) work pattern.
  • Keep head out of the work area.
  • Do not use an open flame in the cabinet as it disrupts airflow and could damage the HEPA filter.
  • The use of UV lights in BSCs is not recommended by safety professionals due to their limited effectiveness and potential harm to those exposed.
  • Clean and decontaminate all visible surfaces and front sash before and after each use. A disinfectant more stringent than 70% ethanol is necessary if conducting research with human cell lines, viral vectors, and other pathogenic microorganisms.  Refer to Maintaining a BSC for more information on proper disinfection procedures.
  • Chemical fume hoods and clean air benches are NOT the same as a BSC, and they should not be used as a substitute for a BSC! Neither should a non-ducted BSC be used with large quantities of volatile chemicals.

For more detailed information on BSCs and their application, please refer to the following texts:

Appendix A. Biosafety for Microbiological and Biomedical Laboratories, 5th edition. U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, and National Institutes of Health, December 2009.

Fleming, D.O. and D.L. Hunt. 2006. Biological Safety: principles and practices. 4th edition. ASM Press: pgs.303-323.