Factors Affecting the Design of Local Exhaust Ventilation for the Control of Contaminants from Hand-Held Sources

Abstract

Tracer gas concentrations generated from a hand-held source are measured in the breathing zone of a mannequin positioned in front of flanged circular exhaust hoods in various configurations. Statistical analyses suggest that, other things being equal, it is preferable to position the mannequin (worker) to the side of the hood rather than in the conventional orientation with source between the body and the hood. The experiments show an unexpected increase in exposure as the source-to-hood distance decreases for small hoods. The importance of work practices used in conjunction with engineering controls is indicated.