| Summary: | 碩士 === 中國醫藥大學 === 職業安全衛生學系 === 96 === This study aimed to evaluate the physiological workloads and subjective discomforts for the most frequently employed full-facepiece respirators with canister and N95 facemasks under thermo environment. Two seperate experiments were conducted. The first experiment evaluated the full-facepiece respirator and using a low respiratory resistance quarter-face mask as the control condition. The second experiment assessed two N95 facemasks with one equipped with valve and the other one without valve. Sixteen physically fit male university students participated in each experiment. The evaluated independent variables were identical in the two experiments including respirator type (RT), workload (WL; light work 45W and moderate work 85W), environmental tepmerature (ET; 25℃ and 35℃) and relative humidity (RH; 50% and 70%). The main mesured dependent variables for both experiments included heart rate at working (HRwork), work pulse (WP), breathing frequence (BF), peak inspiratory and expiratory pressure (PIP/PEP), inspiratory and expiratory time (Ti, Te), tidal volume (VT), minute ventilation (VE), oxygen consumption (VO2), temperature in mask (Tm) and subjective rate of perceptual exertion (RPE).
Results indicated that working in higher ET imposed significant physiological and psychological strain added to that caused by significantly increased HRwork, WP, BF, PIP, Tm, VT (first experiment only), and RPE and decreased Te for same RT, WL and RH. Compared with work at ET = 25℃, work at ET=35℃ and equipped with RF, the HRwork significantly increased 9 to 10 bpm for light WL and 12 to 15 bpm for moderate WL. As for RNV, working at ET = 35℃, the HRwork were reported significantly increased 4 to 6 bpm for light WL and 7 to 8 bpm for moderate WL compared with work at ET = 25℃. Regarding RWV, the increased HRwork were 7 to 8 bmp for light WL and 9 bmp for moderate WL when ET shifted from 25℃ to 35℃. Increased RH were reported with significantly increased VO2, HRwork, WP, BF (experiment 1 only), PIP (experiment 2 only), VE (experiment 2 only) and RPE for same WL, ET, and RT. RPE were found significantly correlated with HRwork, WP, and VO2 for the first experiment and with Tm, BF, and Ti for the second experiment.
When combined the two ET conditions and two RH conditions into 4 corresponded wet bulb globe temperature index (WBGT) levels, it was found that the HRwork significantly increased with higher WBGT. The degree of increased HRwork was significantly higher for moderate WL compared with light WL. It is suggested that the work-rest ratio should be decreased when wearing respirator under thermo work environment.
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