Last Updated: June 29, 2021 10:05:34 AM PDT
Follow these guidelines for working safely in a biological safety cabinet (BSC).
Improper use of a biological safety cabinet can result in contaminated cultures and expose workers to infectious organisms.
When used correctly, a curtain of room air enters the grill at the front edge of the BSC work surface and acts as a protective barrier. The air mixes with the recirculating air stream and passes through a HEPA filter downward toward the work surface, creating a contamination-free zone.
These guidelines aim to preserve the delicate air barrier that protects both the research product and the researcher.
Hands-on training for proper use of a biosafety cabinet is available to researchers. Contact to schedule a class.
- See Biological Safety Cabinets: Overview for a discussion of different types of biosafety cabinets, purpose, placement, certification, and decontamination requirements.
- Do not use the top of the cabinet for storage; this can damage the HEPA filter.
- Keep only necessary equipment or supplies inside the BSC.
- Turn off the ultraviolet sterilizer (if so equipped) as soon as you enter the room.
- Turn on all blowers and cabinet illumination lights.
- Allow 5 minutes of operation to purge the system; check the flow alarm system and visual alarm function (if so equipped).
- Decontaminate readily accessible interior surfaces with a disinfectant appropriate for the agents or suspected agents present.
- Never have the ultraviolet light on when working at the cabinet. It can cause eye damage and skin burns.
- Avoid disrupting airflow:
- Minimize movement (especially rapid movements) into and out of the BSC, or in areas near the BSC.
- Do not block the front grill or rear vents with your arms or other materials.
- Work at least 4 inches from the inside edge of the front vent.
- Bunsen burners, other continuous flame devices, or flammable gases are prohibited in biosafety cabinets.
Safer sterilization methods exist, such as touch-plate microburners equipped with a pilot light, small electric "furnaces," or pre-sterilized loops.
- Beware of fire hazards associated with vaporized ethanol and isopropanol disinfectants.
EH&S Biosafety division strongly discourages UV lamps in BSCs.
National Institutes of Health (NIH), Centers for Disease Control and Prevention (CDC), National Science Foundation/ANSI, and the American Biological Safety Association agree that ultraviolet (UV) lamps are not recommended or necessary for decontamination in BSC’s.
If a UV lamp is used in your BSC, follow the procedures below.
Required:
- Post a warning sign on the front of the BSC indicating the presence of UV light hazards.
- The sign must say CAUTION: Turn off UV light before working.
Be aware of the hazards. Exposure to UV light can cause:
- Painful eye and skin burns
- Damaging exposure levels exist well after the output of the lamp bulb has dropped below the biocidal level.
- Deterioration of some tubing
- This can be dangerous if you're using a touch-o-matic burner with natural gas tubing in a BSC.
Be aware of the limitations:
- Never rely on UV irradiation alone to disinfect a contaminated work area. UV is:
- Not effective on porous materials that are opaque to the light such as wood or foam
- Ineffective if a microbe is protected by dust, dirt, or organic matter
- Affected by the accumulation of dust and dirt on the bulb surface
- Effective only in direct line of site
- UV does not work in shadowed areas, penetrate into cracks or through the grill work of a BSC
- The spill area under the work surface of a BSC is a favorite hide out for fungal spore and hardy bacteria.
- The UV lamp bulb remains lit long after the germicidal effectiveness is gone.
Take precautions during work:
- Turn off UV lamps while the lab is occupied. The stainless steel interior of the BSC can reflect potentially hazardous illumination out of the opening of the cabinet.
- Never have the UV lamp on while an operator is working in the cabinet.
After work is complete:
- Turn the fan off and close the sash, if possible, when the UV lamp is on.
Maintenance:
- Clean UV lamp bulbs frequently by turning off the UV lamp then wiping off the surface of the room temperature lamp bulb with 70% alcohol.
- Before replacing bulbs, clear the BSC of equipment and material, and disinfect it with 10% bleach and then clean with 70% ethanol.
- Install the bulb with gloved hands to prevent oil build up.
- Disinfect lamp bulbs before disposal as universal waste.
When you are done:
- Decontaminate and remove all items from the interior work area.
- Decontaminate readily accessible interior surfaces with a disinfectant appropriate for the agents or suspected agents present.
- Turn on ultraviolet sterilizer (if so equipped). Note: Never rely on UV irradiation of the work area alone to disinfect a contaminated work area.
- Allow 5 minutes of operation to purge the system.
- Turn off the blower.
Biosafety Cabinet (BSC) - is an enclosed, ventilated laboratory workspace for safely working with materials contaminated with (or potentially conmtaminated with) pathogens requiring a defined biosafety level (BSL). The primary purpose of a BSC is to serve as a means to protect the laboratory worker and the surrrounding environment from pathogens. All air is HEPA-filtered as it exits the BSC, removing harmful bacteria and viruses. Many (but not all) types of BSCs are also designed to maintain the sterility of the materials being worked with.
Note: Chemical fume hoods are not designed nor intended to be used as BSCs. Chemical fume hoods fail to provide the environmental protection that HEPA filtration in a BSC would provide. Likewise, a laminar flow clean bench can not be used as a BSC. A laminar flow clean bench blows unfiltered exhaust air towards the user and is not safe for work with pathogenic agents.
For a thorough description of BSCs, including selection, installation, and use please see Appendix A of the Biosafety in Microbiological and Biomedical Laboratories Guidelines (6th ed.)
If work is being performed in a BSL-2 laboratory, all work in which infectious aerosols may be produced must be conducted in a BSC or other type of physical containment. If work is being performed in a BSL-3 laboratory, all work must be performed in a BSC or other type of physical containment.
Work Practices and Procedures
- Cabinet blowers should be operated at least 3-5 minutes before beginning work to allow the BSC to "purge" particulates.
- Turn off BSC Ultraviolet (UV) light (if present) before beginning work.
- Appropriate personal protective equipment must be worn. Lab coats must be buttoned. Gloves should be pulled over the knitted wrists of the lab coat, not worn inside the coat.
- Place only the necessary materials in the BSC before beginning work.
- Extra supplies (gloves, plates, media, etc.) should be stored outside BSC: material placed inside BSC may cause disruption to the airflow.
- Move arms in and out of BSC slowly, perpendicular to the face opening to reduce disruption of air curtain. Manipulation of materials should be delayed momentarily to allow air circulation to stabilize.
- Do not block front grille with papers or materials or rest arms on front grille. This allows room air to flow directly into the work area rather than being drawn through the front grille. Work with arms raised slightly.
- All operations should be performed at least 4 inches from the front grille on the work surface.
- Interior walls, interior surface of the window, and the surfaces of all materials to be placed in the BSC should be wiped with 70% ethanol or other appropriate disinfectant before and after each use. If bleach is used, make sure that it is followed by sterile water or 70% ethanol. Bleach will eventually ruin the stainless steel surfaces of the BSC.
- Plastic backed absorbent toweling can be placed on the work surface (but not on the front grille) to aid in cleanup and spill containment.
- Active work should flow from the clean to contaminated area across the work surface.
- To minimize frequent in/out arm movement and maintain air barrier, do not tape autoclavable biohazard collections bags to the outside of the BSC and upright pipette collection containers should not be used in the BSC nor placed on the floor outside the BSC (use horizontal discard trays containing an appropriate chemical disinfectant within the BSC).
- Potentially contaminated materials should not be brought out of the BSC until they have been surface decontaminated.
- Use techniques to reduce splatter and aerosol generation: Open bottles or tubes should not be held in a vertical position, hold the lid above open sterile surfaces to minimize direct impact of downward air, open flames create turbulence which disrupts the pattern of air supplied to the work surface and should not be used. If necessary, touch plate microburners which provide a flame on demand or electric furnaces are available. All flames must be off before disinfectants are used.
- Aspirator bottles or suction flasks should be connected to an overflow collection plastic flask containing an appropriate disinfectant, and to an in-line HEPA filter.
- If spilled liquid enters through the front or rear grilles, close the drain valves and pour decontaminating solution into the drain pans. After 20-30 minutes, collect the spilled liquid and disinfectant with paper towels.
Biosafety Cabinet Certifications
- All BSCs should be certified annually. If Biosafety Level 2 or higher materials are used in the BSC, the cabinet must be certified annually.
- If the BSC is relocated, it must be re-certified prior to use.
Reference Source
United States. Department of Health and Human Services. Primary Containment for Biohazards:
Selection, Installation and Use of Biological Safety Cabinets. Washington, D.C: U.S. Government
Printing Office, 1995.
