Does your hood really need to be ducted?

 

Many biological safety cabinets and chemo hoods used in hospitals today are ducted to the outside. This is the only way to protect the user from many non-particulate hazards like chemical fumes.

Venting of the unit’s exhaust to outside the building can make solving airflow problems a lot harder for you. A ducted hood with a problem involves people from different areas of the facility. It’s like a computer problem, with the hardware people blaming the software people, the software people blaming the hardware, and you stuck in the middle.

If your hood won’t come on because of insufficient exhaust or your certifier can’t certify it because the exhaust is too low, the hardest battle can be getting everyone to understand. The certifier says it’s too low, the facilities person says it’s more than enough and you just want to get your hood certified. Controlled Environment Testing Association (CETA) has 2 application guides that will provide helpful hints on understanding and dealing with these and other kinds of problems.

  • CAG-007: Exhaust System Requirements of Class II Biosafety Cabinets
  • CAG-010: Application Guide for Informational Notes to Meet the NSF/ANSI 49:2010a Standard Requirements

LTS can provide a copy of these 2 documents upon request.

There are three types of Biological Safety Cabinets. A Class I is basically a fume hood with a filter. You can’t use large amounts of chemicals in a Class I because they can eat through the filter. Class I cabinets are great for personal protection, but offer no product protection. A Class III cabinet is a ventilated glovebox. Air is filtered in and out and you use gloves mounted in glove ports to work with materials inside the hood.

The five types of Class II cabinets, A1, A2, B1, B2, and C1 are what most of us refer to when we think of a chemo hood or biohood. You reach in through an 8 or 10 high opening below a window. Air is drawn into the hood through that opening like a fume hood. Unlike a Class I cabinet, filtered air is also blown onto the work area from above, so your product is protected from outside contaminates. (Another similar type of equipment is a laminar air flow workstation which blows filtered air over the work space. Since you get product protection but no personnel protection, this isn’t considered a safety cabinet.)

Not all Class II cabinets need to be connected to your building’s exhaust. The Class II types A1 and A2 cabinets do not have to be connected to an exhaust duct to function properly. However, if they are connected to an external exhaust they must be canopy(thimble) connected. The other three types – B1 (sometimes called an NCI hood after the National Cancer Institute), B2 (commonly called a Total Exhaust hood), and the newest C1 all need to be connected to an external exhaust system to function.

If you have the A1 or A2 type, it may be possible to solve your exhaust problem by allowing the unit to vent to the room. If you are dealing with only particulate hazards, the cabinet’s filters should be able to capture the hazard. If those particulates might offgas or if you are using non-particulate hazards like low amounts of ether or other gases, the cabinet’s exhaust may need to be ducted outside. Your facility’s safety officer can help determine this with you.

As a customer, what do I need to do to prepare for a BSC certification?

 

Before our technician can begin to test your cabinet, all removable nonessential to cabinet operation (acceptable option components) need to be removed from the cabinet. You should also wipe down the work surface, interior walls and grille with an appropriate disinfectant for the type of work you are doing.

How long does a certification take?

 

Depending on the tests performed, a standard certification of a Class II, Type A1 or A2 BSC will generally take approximately 45 minutes to 1 hour. A standard certification of any Class II, Type B1, B2, or A2-Exhausted BSC will generally take approximately 1.25 to 1.75 hours. Additional time would be required to perform a degradation inspection, cabinet integrity test, decontamination or other maintenance.

What does field certification involve?

 

Field certification consists of required tests related to containment (personnel, product and environmental protection), and optional tests related to worker comfort and safety.

Required tests include:

  • Airflow velocity profiles (downflow and inflow)*
  • Airflow smoke patterns*
  • HEPA/ULPA filter leak test*
  • Site installation assessment tests*
    • Alarm functions*
    • Blower interlock*
    • Exhaust system performance* (proper exhaust duct negative pressure and canopy performance)
  • Cabinet integrity test (positive plenum cabinets only)

Worker comfort and safety tests include:

  • Lighting intensity*
  • Vibration
  • Noise level*
  • Electrical leakage, ground circuit resistance*, and polarity*

*Part of LTS Standard Certification Report
In addition to the above NSF/ANSI 49 recommends the lifespan of a unit be 15 years. Starting at age 16 Lewis Testing Services requires a degradation inspection be performed to reduce the safety risks that an aging unit generates.

When does my biosafety cabinet need to be certified?

Class I and II biosafety cabinets should be tested and certified at the time of installation and at least annually thereafter. In addition, whenever HEPA/ULPA filters are changed, maintenance repairs are made to internal parts, or a cabinet is relocated. More frequent field recertification should be considered for particularly hazardous or critical applications or workloads.

USP 797 requires testing on a semi-annual basis.

Who requires that my biosafety cabinet be certified?

The most important question is why you wouldn’t have your cabinet certified. Certification is both a safety and quality assurance function. Reestablishing the proper cabinet settings gives you the peace of mind that the cabinet will provide its specified personnel, product and environmental protections.

Recommendations and requirements to certify biosafety cabinets come from a variety of sources. All manufacturers and NSF International recommend field certification of biosafety cabinets at installation and at least annually thereafter. In addition, whenever HEPA/ULPA filters are changed, maintenance repairs are made to internal parts, or a cabinet is relocated. JCAHO has now required proper maintenance (certification) of BSCs. CDC and NIH state that it is “imperative” that Class I and II biosafety cabinets be tested and certified (BMBL, 5th edition) and NIH funded research grants require cabinet certification. Individual state boards of pharmacy require certification of biosafety cabinets used in pharmacies in accordance to USP 797. Finally, proper maintenance, including certification, of biosafety cabinets falls under the OSHA General Duty clause.

What are you actually certifying/testing?

A field certification confirms that an installed cabinet is operating in accordance with the field test specifications of NSF Standard 49 (if currently listed by NSF) or the manufacturer. Field certification does not include the microbiological challenge and cross contamination tests that are performed in the factory by the manufacturer.

Required Test Optional Test
  • Downflow velocity profile test*
  • Inflow velocity test*
  • Airflow smoke patterns test*
  • HEPA/ULPA filter leak test*
  • Site installation assessment tests*
    • Alarm functions*
    • Blower interlock*
    • Exhaust system performance* (proper exhaust duct negative pressure and canopy performance)
  • Cabinet integrity test (positive pressure plenum cabinets only)
  • Lighting intensity*
  • Vibration
  • Noise level*
  • Electrical leakage, ground circuit resistance*, and polarity*

*Part of LTS Standard Certification Report
In addition to the above NSF/ANSI 49 recommends the lifespan of a unit be 15 years. Starting at age 16 Lewis Testing Services requires a degradation inspection be performed to reduce the safety risks that an aging unit generates.