Abstract
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.