A performance test for laboratory fume hoods

Existing standards for laboratory fume hoods focus on the face velocity. The influence of room air currents is as important as face velocity in capturing contaminants in such a hood with a worker standing at the face. Further, face velocity standards are not very meaningful for auxiliary air hoods. A performance test was developed, using the measured concentration at the breathing zone of a worker (mannikin) at the face of the hood when known amounts of tracer, mixed with air, were released in the hood. The test method yields a performance rating which includes all parameters, not just face velocity. A performance rating in the form xx AU yyy can be determined, where xx is the tracer gas release rate, Lpm; AU signifies “as used” (in the laboratory); and yyy is the control level, ppm, at the breathing zone of the worker. Similar tests in the absence of a worker or mannikin yield much lower control levels than when a mannikin is present.