In more realistic conditions, the findings probably would show far smaller differences in concentrations at different sampling sites. A large breathing zone that includes locations on the chest is convenient to industrial hygiene sampling, but it is defensible only. However, these findings should be interpreted with caution because a very dense tracer gas and an unheated, nonbreathing mannequin were used. Results showed significant and substantial differences between concentrations at the nose and lapel. A typical sampling train for personal monitoring would look like this with the sampler mounted in the breathing zone For grab samples of gases, a gas sampling bag is used, e.g. Mannequin movement, done only at the Back orientation, proved important only for the ear location. Download Table Breathing Zone Samples from publication: Evaluation of an Add-on Local Exhaust Ventilation System for an Ethylene Oxide (ETO) Sterilizer. At the Back orientation, the chest sampler provided lower overestimates of C nose at higher velocities than at lower values. Velocity affected the ratios of concentrations. At the Back orientation, C ear was lower than C nose, whereas C ear was higher than C nose at the Side and Facing to flow orientations. The ratio of ear (C ear) and C nose varied with orientation. The breathing zone can be visualized as a hemisphere about 6 to 9 inches around the employees face. For 34 of 36 samples the mean chest concentration (C chest) was higher than the C nose (geometric mean three times higher). Concentrations at the nose were different from concentrations at other sites. Higher velocities significantly increased concentration at the Back orientation and generally reduced it at the Side and Facing orientations. Concentrations at all sampling locations when the mannequin faced to the front and side were less than a tenth of the levels measured at the nose (C nose) when the mannequin faced downstream. For the factorial study design, test conditions included cross-draft velocities of 10, 22, 47, and 80 ft/min three mannequin orientations (facing to, side to, and back to cross-draft), and rotating speed through an 80° arc (fast, slow, and no movement). Simultaneous 15-min time-weighted average samples were taken by drawing air into different sampling bags with sampling pumps. Samplers were placed at the mannequin's mouth, in front of the ear, and at three chest locations at lapel level. Tracer gas concentrations were measured on a 60%-sized mannequin holding a pure sulfur hexafluoride source in its hands at waist height while it stood in a wind tunnel.
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