A fume hood is engineered containment: it protects the person at the sash by pulling contaminated air away at a specified face velocity. Too low and it does not contain; counter-intuitively, too high creates turbulence at the sash that rolls contaminant back out. The hood gives no indication either way, and in a teaching lab the person relying on it is usually a student.
The steps ChatterFix schedules for this PM. Every step is a checkable item on the work order — a technician can speak their way through it without touching a keyboard.
A fume hood is engineered containment: it protects the person at the sash by pulling contaminated air away at a specified face velocity. Too low and it does not contain; counter-intuitively, too high creates turbulence at the sash that rolls contaminant back out. The hood gives no indication either way, and in a teaching lab the person relying on it is usually a student.
The hood looks and sounds like it is working while containment has failed, so exposure occurs with no signal at all. Airflow monitors drift or get ignored after nuisance alarms. Because the whole exhaust system is shared, one modification elsewhere — a new fan, a rebalanced building — can silently change every hood on the run.
Annual certification at minimum, which is what most standards and insurers expect. Re-test immediately after any change to the hood, the ductwork, the exhaust fan or the building's air balance, and treat a persistent monitor alarm as a test trigger rather than a nuisance.
This procedure — and every other PM for your industry — is already built into ChatterFix. Pick your industry and it lands on the right equipment, on the right interval, in about three minutes.