itrc indoor air sampling breathing zone height

This novel design requires neither sash nor baffle. To increase containment efficiency and reduce energy consumption, a sash-less, variable-height inclined air-curtain fume hood (sIAC hood) was developed and tested by a laser-assisted flow visualization technique and tracer-gas detection method. The exposure level of the mannequin was about 5.5-9.3 times higher than that of the human subject. The ratios of nose concentration to chest concentration for the human subject and the mannequin were 0-0.2 and 0.12, respectively. Then, the effects of the sampling location and the body temperature on the exposure were observed. In experiment, ethanol vapor was released in front of a model worker (human subject and mockup mannequin) and the vapor concentrations were measured at two different sampling points, at the nose and at the chest, in the breathing zone. In order to examine the spatial variability of contaminant concentrations in a worker's breathing zone, comparative measurements of personal exposure were carried out in a laboratory. However, several studies have mentioned that the concentration is not uniform in the breathing zone when a worker is close to the contaminant source. In more realistic conditions, the findings probably would show far smaller differences in concentrations at different sampling sites.Ĭonventionally, the 'breathing zone' is defined as the zone within a 0.3 m (or 10 inches) radius of a worker's nose and mouth, and it has been generally assumed that a contaminant in the breathing zone is homogeneous and its concentration is equivalent to the concentration inhaled by the worker. 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. Mannequin movement, done only at the Back orientation, proved important only for the ear location.

At the Back orientation, the chest sampler provided lower overestimates of Cnose, at higher velocities than at lower values. Velocity affected the ratios of concentrations. At the Back orientation, Cear, was lower than Cnose, whereas Cear was higher than Cnose at the Side and Facing to flow orientations. The ratio of ear (Cear) and Cnose varied with orientation. For 34 of 36 samples the mean chest concentration (Cchest,) was higher than the Cnose (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 (Cnose) 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 degrees 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.

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Itrc indoor air sampling breathing zone height