Biosafety Cabinets

• Biosafety Cabinets (BSCs) are specialized pieces of lab equipment designed to safely contain biohazardous agents/ materials. Also, all but one class of BSCs protect sterile items and culture materials from contamination when they are manipulated in the BSC workspace. Different classes and types of BSCs meet different, specific needs. Choosing the right BSC for purchase should be based on a thorough risk assessment of all material (biological and chemical) being handled and the procedures involved with the work. 
• BSCs must not be confused with chemical fume hoods, laminar flow hoods, or tissue culture hoods. In most cases, BSCs and chemical fume hoods have distinctly different functions and cannot be used interchangeably.
  • Chemical fume hoods utilize directional airflow to protect lab workers from exposure to toxic chemical fumes or particulates by venting them to the outside.
  • Material or items inside a chemical fume hood are not protected from room air contamination. 
  • Chemical fume hoods should never be used for the containment of biologicals.
  • Minute amounts of volatile chemicals/radionuclides may be used ONLY with certain types of BSCs which exhaust them to the outside.

HEPA filters:

• The HEPA filters are important features of the BSC, capturing potentially infectious particles from your work as well as room air contaminants, and contaminants that you may shed. HEPA filters should be replaced by the BSC's service provider every 3-5 years, depending on cumulative hours of operation, the cleanliness of the lab, and the materials being used in the BSC. Changing or cleaning the pre-filter on a regular basis extends the life of a HEPA filter.
• The HEPA-filtered directional airflow in a BSC: 
  1. Protects the work material from contaminants,
  2. Protects the worker from exposure to aerosols, and
  3. Prevents the release of aerosolized material into the environment. IMPORTANT: BSC HEPA filters do not entrap or filter chemical vapors or gases; they entrap particulates.

Magnehelic gauge:

• The magnehelic gauge on the BSC shows the air pressure difference across the HEPA filter and can indicate when the airflow system and filter are not operating properly. 
• BSC users should know their BSC's acceptable gauge readings and limits; ask your service provider, or look on the BSC certification label for this information. 
• Before each work session, check the gauge and look for changes higher or lower than this acceptable range. A higher resistance reading indicates the filter is loaded or blocked; a lower resistance reading may indicate a hole or tear in the HEPA filter. In either instance, do not use the BSC; contact a service provider.

SIDE-BY-SIDE BSC CLASS COMPARISON

SIDE-BY-SIDE COMPARISON OF BSC CLASS II TYPES

C1 biosafety cabinets:

• The Labconco Purifier Axiom Class II, Type C1 biosafety cabinet is designed to be more flexible than other biosafety cabinets. It can be used as a re-circulating Class II Type A2 cabinet for standard microbiological work, or it can be ducted to the outside (or used with a manifold exhaust system) for working with small amounts of volatile chemicals and radionuclides, as with a Type B2 cabinet. 
• This cabinet does not have the full functionality of a chemical fume hood, and must not be used as a substitute for a chemical fume hood.
• Special HVAC requirements may be involved with the installation of this type of cabinet and all manufacturer's recommendations must be followed. 
• Specific EHS training is required for new users of C1 biosafety cabinets to ensure a full understanding of the limitations and proper uses of the C1 cabinet.

Using volatile chemicals/radionuclides in a BSC:

• In general,
  • Minute amounts can be handled in Class II Type A2 or B1 BSCs vented to outside.
  • Small amounts can be handled in Class II Type B2 BSCs vented to outside.
• Specifically,
  • Check the Safety Data Sheets for volatile chemicals to learn explosion limits, and avoid approaching those concentrations, as chemicals can volatilize and concentrate to hazardous levels inside a BSC, or in ductwork after being pulled through HEPA filters.
  • Make sure the volatile chemicals you use will not damage HEPA filters.
• You have exceeded the quantity of a volatile chemical you can safely use in your BSC if you can smell or otherwise detect chemical fumes out in the lab. In these circumstances, discontinue use of that BSC; instead, locate and use a BSC that exhausts most or all air to the outside.

Purchasing:

• Choosing the right BSC for purchase should be based on a thorough risk assessment of all material (biological and chemical) being handled and the procedures involved with the work.
• Key questions to consider:
  • What type and quantity of biological and chemical material will be used in the BSC?
  • What biosafety level (and containment level) will be required?
  • Are you working with biologicals only, or with minute/small amounts of volatile chemicals/radionuclides?
  • What type of exhaust (recirculating, or ducted to the outside) will be needed?
• Contact EHS (540-231-3600) for assistance in evaluating needs for a BSC purchase.

Room location:

• Room location is important to the proper functioning of a BSC:
  • Ideally, BSCs should occupy lab space that is removed from other work areas, especially high traffic areas. 
  • The cabinet should be placed 12-14 inches from the ceiling and walls.
  • The cabinet should be placed away from windows, air supply vents, the lab features creating air movement (chemical fume hoods, centrifuges, vacuum pumps), and entry points into the lab.

Required certification:

• All new BSCs to be used for handling potentially infectious/biohazardous material (BSL-2, BSL-3; ABSL-2, ABSL-3; ACL-2, ACL-3) must be certified before being used; certification involves a standardized check of proper function, performed by a qualified technician.
• YEARLY CERTIFICATION IS REQUIRED FOR ANY BSC BEING USED WITH POTENTIALLY INFECTIOUS MATERIALS.
• Cabinets must be re-certified: 
  1. following a major relocation (change of building, campus, state, country); 
  2. when a HEPA filter is replaced; 
  3. following any other repair or service to the unit.  

BSC certification vendors at Virginia Tech:

• Vendors who supply certification services hold contracts with the university; contracts are negotiated every 5 years and are renewed annually. 
• These contractors also provide:
  • Repair services
  • Decontamination services for all HEPA-filtered equipment, and room/area decontamination.
• Current list of Laboratory Engineering Controls Maintenance Service Vendors

• Principal Investigators can choose from these three providers for cabinet certification services.
• A Purchase Order (PO) must be obtained through the PI's departmental business office for this service; the procedure for this is outlined in the next item.

Decontamination procedures for BSCs:

• Biosafety cabinets must be properly decontaminated prior to: 
  • certification technician's arrival
  • any service visit for in situ repairs
  • moves within a building.
• Prepare a BSC for these events by removing all items and disinfecting all work area surfaces, including vertical side and back surfaces, and sash glass.
• Gas or vapor decontamination of the entire unit (including inaccessible areas--plenums, etc.) by a qualified contractor is required:
  • prior to a major relocation to another building, campus, state, country, etc.
  • prior to going to surplus 
  • after receiving extensive repairs
  • following a high-volume spill 
  • if the unit will be used in a lower containment lab (e.g., from BSL-3 to BSL-2)
• Disinfecting agents typically used by professionals include formaldehyde gas and vaporized chlorine dioxide.
• If you need assistance in determining whether whole-unit decontamination is needed, or for information on scheduling decontamination service with a contractor, contact EHS.
• Whenever you have decontaminated a BSC (by either method listed above), you must attach a completed Lab Equipment Decontamination Form to the unit prior to the date you are expecting the movers, certification vendor, etc. Please follow the directions on the back of the form.