National Institute of Occupational Safety and Health, Japan.
Ind Health. 2012;50(3):236-8. doi: 10.2486/indhealth.ms1314.
Conventionally, 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, several studies have mentioned that the concentration is not uniform in the breathing zone when a worker is close to the contaminant source. 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. 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. Then, the effects of the sampling location and the body temperature on the exposure were observed. The ratios of nose concentration to chest concentration for the human subject and the mannequin were 0-0.2 and 0.12, respectively. The exposure level of the mannequin was about 5.5-9.3 times higher than that of the human subject.
传统上，“呼吸区”定义为工人的鼻子和嘴周围 0.3 米（或 10 英寸）半径范围内的区域，并且通常假设呼吸区内的污染物是均匀的，其浓度等同于工人吸入的浓度。然而，有几项研究提到，当工人靠近污染物源时，呼吸区内的浓度并不均匀。为了检查工人呼吸区内污染物浓度的空间变异性，在实验室进行了个人暴露的比较测量。在实验中，乙醇蒸气在模型工人（人体模型和模拟人体模型）的前面释放，并且在呼吸区内的两个不同采样点（鼻子和胸部）测量蒸气浓度。然后，观察了采样位置和体温对暴露的影响。人体模型和模拟人体模型的鼻子浓度与胸部浓度之比分别为 0-0.2 和 0.12。模拟人体模型的暴露水平约为人体模型的 5.5-9.3 倍。
