Biological Safety Cabinets
Biological safety cabinets (BSCs) are among the most effective primary containment devices used in laboratories working with infectious agents. They act as primary barriers to prevent the escape of biological aerosols into the laboratory environment. This is important because most laboratory techniques (e.g.; centrifuging, pipetting, vortexing, sonicating) produce inadvertent aerosols that can be readily inhaled by the laboratory worker.
High Efficiency Particulate Air (HEPA) filters are present in all classes of BSCs. A HEPA filter removes only particulates (including microorganisms), not vapors or gases, from the air. Depending on its quality, a HEPA filter is able to trap up to 99.97% of particles with dimensions equal to or greater than 0.3 micron.
BSCs are designed for:
- Personnel Protection: Protects personnel from harmful agents inside the BSC.
- Product Protection: Protects the work, product, experiment, or procedure performed in the BSC from contaminants in the laboratory environment or from cross contamination inside the cabinet.
- Environmental Protection: Protects the environment from contaminants contained in the BSC.
A comprehensive description of BSC types, performance characteristics, and applications can be found in the publication Biosafety in Microbiological and Biomedical Laboratories, 5th Edition, Appendix A: Primary Containment for Biohazards: Selection, Installation and Use of Biological Safety Cabinets.
Before selecting a cabinet, potential users must evaluate their program and match specific requirements with the appropriate equipment. The Division of Research Safety (DRS) can assist researchers with these evaluations.
To ensure that BSCs are providing adequate personnel and environmental protection, on-site testing and certification of BSCs is required:
- At the time of installation;
- At least annually thereafter;
- At any time the BSC is moved.
Principal Investigators (PIs) are responsible for ensuring that BSCs in their facilities are certified on an annual basis. Most departments have a designated safety contact who will coordinate the certification of BSCs with a qualified vendor. If there is no designated safety contact for the unit, the PI is responsible for contacting a vendor and scheduling the certification. Once certification is completed, cabinet information should be updated in the safety cabinet management system.
PIs will receive email reminders 60 and 30 days prior to the expiration and on the day the certification expires. Safety contacts will receive emails on the 1st of every month listing all BSCs that expire within the next three months. Email reminders will continue until cabinet information has been updated in the safety cabinet management system.
Certifiers must be accredited and have a Certificate of Liability on file. DRS maintains a list of qualified vendors that have certified or repaired BSCs on campus, which is available upon request.
Other accredited certifiers can be located by using the following links:
Note: P-Cards and i-Cards cannot be used as payment for services or repairs of biosafety equipment. Biosafety Cabinet certifications or repairs require a purchase order (P.O.), either “Regular” or “Standing,” in Banner for payment. If you have questions about obtaining a P.O., contact your business office.
Policy on the Use of Uncertified BSCs
If a BSC is no longer certified (due to either certification expiration or failure) it must not be used as a primary safety device. An uncertified biosafety cabinet with the blowers running can disseminate potentially harmful material throughout the environment. Any work with pathogens or potentially infectious materials, even those classified as Risk Group 1, should not be performed in an uncertified cabinet.
Occasionally, there are requests to work with non-pathogenic material (e.g., plant or certain animal tissue cultures) in an uncertified cabinet. This should be considered only if the situation can be carefully managed. The cabinet should have a warning sign, and occupants of the laboratory should be trained on the limitations and potential hazards of using the equipment incorrectly. Such use is strongly discouraged in laboratories where pathogens or potentially infectious materials are also present because the potential for, and risks associated with, using the equipment incorrectly are increased.
For those who wish to work in an uncertified BSC, contact DRS for assistance with developing a risk assessment to determine if the proposed use would qualify for an exemption from the certification requirement.
Chemicals in a BSC
BSCs should not be used in place of a chemical fume hood. Volatile or toxic chemicals should not be used in Class II Type A cabinets without ducting because vapor build-up inside the cabinet presents a fire or explosion hazard. In addition, this type of cabinet recirculates air from the cabinet work space into the room, potentially exposing the operator and other room occupants to toxic chemical vapors
Gas Connections in the BSC
Gas connections to a BSC are not permitted without a written justification for specialized, limited-duration work. Note that routine “flaming” is not considered adequate justification. Approved gas connections should have an additional shut-off valve installed outside of the BSC. Alternatives to continuous flame burners should be used.
Open flames in BSCs:
- Create turbulence in the airflow, compromising protection of both the worker and the work;
- Present a potential fire or explosion hazard, especially when using a gas burner in conjunction with ethanol;
- Cause excessive heat build-up, which may damage HEPA filters and compromise the cabinet’s integrity;
- May inactivate the manufacturer’s warranty.
Ultraviolet Lamp Usage
The primary method of decontamination should be to use an effective, EPA registered disinfectant such as 10% bleach for 10 minutes. For corrosive chemicals such as bleach, disinfection should be followed by rinsing with sterile water or 70% ethanol to remove chemical residue that may otherwise damage stainless steel surfaces.
Ultraviolet (UV) lamps are not recommended in BSCs nor are they necessary. If installed, UV lamps must be cleaned weekly to remove any dust and dirt that may reduce their germicidal effectiveness. The lamps should be checked weekly with a UV meter to ensure that the appropriate intensity of UV light is being emitted. UV lamps must be turned off when the room is occupied to protect eyes and skin from UV exposure, which can burn the cornea and cause skin cancer. If the cabinet has a sliding sash, close the sash when operating the UV lamp.
A few BSCs have UV lamps. When used, they must be tested periodically to ensure that their energy output is sufficient to kill microorganisms. The surface on the bulb should be cleaned with 70% ethanol prior to performing this test. Five minutes after the lamp has been turned on, the sensor of the UV meter is placed in the center of the work surface. The radiation output should not be less than 40 microwatts per square centimeter at a wavelength of 254 nanometers (nm).
Use of Cabinets
- Thoroughly understand procedures and equipment required before beginning work.
- Minimize disruptions, such as room traffic or entry into the room, while the cabinet is in use.
- Turn off the UV light if in use. Ensure that the sash is set in the correct operating position.
- Turn on the fluorescent light and cabinet blower.
- Check the return air grilles, especially in the back of the workspace, for obstructions, and note the pressure gauge reading.
- Allow the cabinet to operate unobstructed for at least fifteen minutes.
- Wash hands and arms thoroughly with soap.
- Wear a long-sleeved lab coat with knit cuffs and over-the-cuff gloves.
Surface Decontamination Before Work
- Wipe down the interior surfaces of the cabinet with 10% bleach, followed with 70% ethanol after 5 to 10 minutes to prevent pitting of the stainless steel, and allow to dry.
Loading Materials and Equipment
- Load only the materials required for the procedure. Do not overload the cabinet.
- Do not obstruct the front, side, or rear return air grilles.
- Large objects should not be placed close together. After loading the cabinet, wait two to three minutes to purge airborne contaminants from the work area.
- Keep all materials at least four inches inside the sash, and perform all operations with contaminate material as far to the rear of the work area as possible.
- Segregate all clean and contaminated materials in the work area and arrange materials to minimize the movement of contaminated materials into clean areas.
- Keep all discarded, contaminated material to the rear of the cabinet.
- Avoid moving materials or excessive motion of the operator’s hands and arms through the front access opening during use.
- Open flames SHOULD NOT be used.
- Use proper aseptic technique.
- Avoid using techniques or procedures that disrupt the air flow pattern of the cabinet.
- If there is a spill or splatter during use, all objects in the cabinet should be surface-decontaminated before removal. Thoroughly disinfect the work surfaces of the cabinet while it is still on. This will prevent the release of contaminants from the cabinet.
- When work is completed, the cabinet should be allowed to operate for three to five minutes undisturbed to purge airborne contaminants from the work area.
Unloading Materials and Equipment
- Disposable contaminated objects, including gloves, should be placed in disposal pans or autoclave bags inside the BSC after use.
- Reusable objects in contact with contaminated material should be surface-decontaminated before removal from the cabinet.
- All open trays or containers should be covered before being removed from the cabinet.
Surface Decontamination After Work
- Wipe down the interior surfaces of the cabinet with 10% bleach or other EPA-registered disinfectant, followed in 10 minutes with 70% ethanol to prevent pitting of the stainless steel, and allow to dry.
- Turn off the fluorescent light and cabinet blower, if desired.