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The effect of a worker's presence in a room on contaminant dispersion.

Lee-E; Feigley-C; Khan-J; Tamanna-S
American Industrial Hygiene Conference and Exposition, May 21-26, 2005, Anaheim, California. Fairfax, VA: American Industrial Hygiene Association, 2005 May; :19
Previous studies have shown that contaminant concentrations in the breathing zone strongly depended on the worker's position relative to a contaminant source. However, most investigations were performed in a wind tunnel or in rooms with displacement ventilation-air flow patterns that are not typical of workrooms in the U.S. Here the effect of worker presence near a source was investigated in an experimental room (2.86 m(L) x 2.35 m(H) x 2.86 m(W)) to determine if one worker's presence could influence contaminant dispersion patterns in a room, and thus potential exposure levels of others in the room. A heated mannequin was placed in four locations near a source for a wall jet (WJ) air inlet and one location for the ceiling diffuser (CD) inlet. Tracer gas (99.5% propylene) concentrations were monitored automatically at 144 sampling points with a photo ionization detector. Two flowrates (5.5 and 3.3 m3/min) were employed. The worker presence influenced the contaminant dispersion pattern in the occupied portion of the room for all conditions investigated, except for CD-S.S m3/min; for WJ-S.S m3/min, concentrations were higher near the source pedestal for all worker locations compared to those without a worker present. Relatively more variation of contaminant concentrations was observed in the occupied zone of WJ-5.5 m3/min (CVs = 0.42-0.58) than those of WJ- 3.3 m3/min (CVs = 0.2-0.28). For the CD-3.3 m3/min, the worker present north of the source generated better mixing of room air (CV = 0.17) in the breathing zone compared to when the worker was absent (CV = 0.49). Perhaps, thermal convection from the heated worker promoted better mixing of room air. These experimental results indicate that contaminant dispersion patterns depend upon the location of the worker and the worker's interaction with the air velocity field. Also, they suggest that a greater understanding of concentration variability in workrooms is needed to develop more sophisticated methods of exposure estimation.
Workers; Work-environment; Air-contamination; Ventilation; Air-flow; Air-sampling; Air-quality; Exposure-levels; Indoor-air-pollution; Indoor-environmental-quality
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American Industrial Hygiene Conference and Exposition, May 21-26, 2005, Anaheim, California
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University of South Carolina at Columbia, Columbia, South Carolina