The effect of temperature differences on the distribution of an airborne contaminant in an experimental room.
The effect of temperature differences on the distribution of an airborne contaminant in an experimental room.
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DOI：
10.1093/annhyg/mel017
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发表时间：
2006-07
期刊：
影响因子：
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通讯作者：
Eungyoung Lee;C. Feigley;J. Khan;J. Hussey
中科院分区：
文献类型：
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作者：
Eungyoung Lee;C. Feigley;J. Khan;J. Hussey
估计暴露于排放到工作室空气中的污染物对工人保护至关重要。虽然污染物浓度在工作室内往往不是空间上均匀的，但许多估计暴露的方法都没有充分考虑到这种变化。在这里，一个房间内的温度差异对空间污染物分布的影响进行了研究。示踪气体（99.5%丙烯）浓度自动监测在144个采样点与光电离检测器。一面墙被选择来代表建筑物的外墙，并被加热或冷却以模拟夏季或冬季的条件。实验在两个流速（5.5和3.3米（3）分钟（-1））和六个热条件（等温，三个夏季条件和两个冬季条件）。对于5.5 m（3）min（-1）和所有热条件，变异系数（CV）范围为0.34 - 0.45，归一化平均浓度相似。对于3.3 m（3）min（-1），冬季条件产生的浓度空间变异性（CV = 0.72和1.10）大于等温或夏季条件（CV范围= 0.29-0.34）。模拟冬季条件的试验表明，由此产生的稳定温度结构抑制了示踪剂的稀释，并增强了示踪剂在房间下部的分离，特别是对于较低的流速（3.3 m（3）min（-1））。因此，当用于非等温且混合不充分的房间时，在暴露建模中未明确解决热效应可能会影响估计的准确度和精度。这些发现对空气监测也有影响。分散模式为不同的热条件下，被发现有很大的不同，即使当平均浓度几乎相同。因此，当夏季和冬季条件在室内产生温度梯度时，不应将单个季节的监测数据视为全年的代表。
Estimating exposure to contaminants emitted into workroom air is essential for worker protection. Although contaminant concentrations are often not spatially uniform within workrooms, many methods for estimating exposure do not adequately account for this variability. Here the impact of temperature differences within a room on spatial contaminant distribution was studied. Tracer gas (99.5% propylene) concentrations were monitored automatically at 144 sampling points with a photoionization detector. One wall was chosen to represent a building's external wall and was heated or cooled to simulate summer or winter conditions. Experiments were preformed at two flow rates (5.5 and 3.3 m(3) min(-1)) and six thermal conditions (isothermal, three summer conditions and two winter conditions). For 5.5 m(3) min(-1) and all thermal conditions, the coefficient of variation (CV) ranged from 0.34 to 0.45 and the normalized average concentrations were similar. For 3.3 m(3) min(-1), winter conditions produced greater spatial variability of concentration (CV = 0.72 and 1.10) than isothermal or summer conditions (CV range = 0.29-0.34). Tests simulating winter conditions suggest that the resulting stable temperature structure inhibited the dilution of the tracer and enhanced its segregation in the lower portion of the room, especially for the lower flow rate (3.3 m(3) min(-1)). Therefore, not explicitly addressing thermal effect in exposure modeling may impact the estimated accuracy and precision when used for rooms that are non-isothermal and not well mixed. These findings also have implications for air monitoring. Dispersion patterns for different thermal conditions were found to be substantially different, even when the mean concentrations were nearly the same. Thus, monitoring data from a single season should not be taken as representative of the entire year, when summer and winter conditions create temperature gradients in a room.