Student Research: Julie Ann Gahn
, Industrial Hygiene & Safety (IH&S) - No longer offered, 1994
A Comparison of Tracer Gas Concentrations Taken in a Wind Tunnel at the Mouth of a Mannikin to Values Found at its Lapel and Cheek
Industrial hygienists use personal samplers to estimate mean breathing zone concentrations of contaminants. The sampling inlet typically is suspended from the worker's lapel. Lapel concentrations are not proven representatives of inhaled concentrations. Researchers have found differences between concentrations at the lapel and at other sites closer to the nose and mouth. Air flow around a boyd is not simple, making predictions of concentration distribution difficult. A zone of reverse flow marked by vortices or eddies forms downstream of a body in a uniform airstream. George, et. al (1990) found that effluent released from a source in the zone of reverse flow is drawn back toward the worker. Thus, source location is an important variable.
A full-sezied (64" tall) female mannikin was used to investigate the effect of nine source locations and three cross draft velocities on the concentrations of tracer gas measured simultaneously at the mouth, lapel, and cheek of the mannikin. The results were complex, and ratios of lapel to mouth concentrations ranged from 0.4 to 3.0. In general, the lapel concentration was higher than the mouth concentration when the source was at waist height and nose height, regardless of the horizontal position. However, when the source was at chest height, the lapel concentrations were usually lower than the mouth concentrations. The cheek concentrations were much more representative of the mouth concentrations for all locations than were the lapel concentrations.
These results support use of the cheek sampling location and raise doubts about the lapel location. Locations more convenient than the cheek should be investigated in further research.