Installation of a flow control device in an inclined air-curtain fume hood to control wake-induced exposure.

An inclined plate for flow control was installed at the lower edge of the sash of an inclined air-curtain fume hood to reduce the effects of thewake around aworker standing in front of the fume hood. Flow inside the fume hood is controlled by the inclined air-curtain and deflection plates, thereby forming a quad-vortex flowstructure. Controlling the face velocity of the fume hood resulted in convex, straight, concave, and attachment flow profiles in the inclined air-curtain. We used the flow visualization and conducted a tracer gas test with a mannequin to determine the performance of two sash geometries, namely, the half-cylinder and inclined plate designs. When the half-cylinder design was used, the tracer gas test registered a high leakage concentration at V-f <= 57.1 fpm or less. This concentration occurred at the top of the sash opening, which was close to the breathing zone of the mannequin placed in front of the fume hood. When the inclined plate design was used, the containment was good, with concentrations of 0.002-0.004 ppm, at V-f <= 63.0 fpm. Results indicate that an inclined plate effectively reduces the leakage concentration induced by recirculation flowstructures that form in thewake of a worker standing in front of an inclined air-curtain fume hood.