A chemical fume hood is the main thing standing between your staff and solvent vapors, formalin and xylene. It only works if it is moving enough air, in the right pattern, at the sash height people actually use. Certification is how you prove it does, and it is one of the first safety records an inspector asks for in a pathology or histology lab.
How often fume hoods must be certified
Fume hoods are typically certified at least once a year. The ANSI/ASSP Z9.5 laboratory ventilation standard calls for routine performance testing, and most safety programs and accrediting bodies treat annual as the minimum. A hood should also be tested:
- When it is first installed, before use
- After it is moved, even within the same room
- After changes to the building exhaust or HVAC system
- After repairs to the hood, sash or airflow monitor
- Whenever users suspect a problem, such as odors at the sash
What the test measures
Face velocity
The certifier measures air speed across a grid of points over the sash opening at the working sash height, then averages it. Most conventional hoods are held to an average of roughly 80 to 120 feet per minute, though your facility or the manufacturer may set a different target. Individual low readings matter as much as the average.
Airflow visualization
Smoke is released around the sash edges, work surface and inside the hood to show that air flows in and stays in. Smoke rolling back out at the sash is a containment failure even if the face velocity looks fine.
Sash and alarm
The sash should move smoothly and hold its position, and the airflow monitor or low-flow alarm should trip when airflow drops. A muted or disabled alarm is one of the most common findings.
Containment testing
For new installations, or where your safety program requires it, testing to ASHRAE 110 adds a tracer gas test that measures how much escapes the hood under controlled conditions.
What you should receive
- A report with every face-velocity reading, the average and the target
- Sash height at which the hood was tested
- Smoke test and alarm results
- Date, certifier and next-due date
- A label on the hood that matches the report, showing the maximum safe sash height
Fume hood or biosafety cabinet?
They are not interchangeable. A chemical fume hood protects the user from chemical vapors and exhausts air out of the building. A biosafety cabinet uses HEPA filters to protect the user, the sample and the room from biological material. They are certified to different standards: fume hoods to Z9.5 and ASHRAE 110, biosafety cabinets to NSF/ANSI 49. See biosafety cabinet certification for the cabinet side.
BMCA schedules and documents fume hood certification across Florida and Puerto Rico, usually on the same visit as your biosafety cabinets and calibrations. The field testing is performed by our certification partner, Medrep Technologies.