Evaluating the Efficacy of a Thermal Exposure Chamber Designed for Assessing Workers’ Thermal Hazard

Abstract

low thermal impact condition, the exposure chamber studied can still be regarded as a feasible one for assessing workers' thermal hazard. (J Occup Health 2003; 45: 153-159) K e y w o r d s : T h e r m a l e x p o s u r e c h a m b e r, Environmental factors, Uniformity, Monte Carlo simulation, Sensitivity analysisThe four environmental factors, air temperature (T a ), air velocity (V a ), relative humidity (RH) and globe temperature (T g ), together with workers' workload and clothing, were known to be the main factors affecting the extent of the thermal hazard for workers in thermal environments. Based on this concept, the ISO 7933 Standard entitled Analytical Determination and Interpretation of Thermal Stress Using Calculation of Required Sweat Rate proposed a physiologically-based approach in 1989 for estimating the allowable exposure times (AETs) for workers in various thermal environments 1) . In principle, the use of the above approach for determining workers' AETs requires no direct measurement of workers' physiological responses (such as the worker's sweat rate, metabolic rate and skin temperature etc.) in the field. Instead, it allows us to estimate workers' physiological responses by incorporating the on-site measured environmental factors into the empirical equations proposed in ISO 7933. Indeed, the above approach has been criticized by many researchers [2][3][4][5][6] . Nevertheless, recently the American Conference of Governmental Industrial Hygienists (ACGIH) has incorporated it into its work/rest-time regimen determination process 7) . But because the physiological responses could not be directly measured in the field, it can be expected that the above approach might have some inherent uncertainties, which warrants the need for establishing a thermal exposure chamber that can accurately simulate various thermal environments. Abstract: Evaluating the Efficacy of a ThermalExposure Chamber Designed for Assessing Workers' Thermal Hazard: Perng-Jy TSAI, et al. Department of Environmental and OccupationalHealth, Medical College, National Cheng Kung University, Taiwan-This study was conducted on a thermal exposure chamber designed for assessing workers' thermal hazard. In order to assess the efficacy of the studied chamber, three environmental conditions were selected to simulate high, middle and low thermal impact situations, with air temperatures (T a ) of 43.12, 36.23 and 25.77°C, globe temperatures (T g ) of 44.41, 41.07 and 29.24°C, relative humidity (RH) of 77, 59 and 39 %, and air flow velocities (V a ) of 1.70, 0.91 and 0.25 m/s, respectively. For the three specified thermal impact conditions, results show that the coefficients of variation (CVs) for T a , T g , RH and V a measured in the chamber studied were consistently less than 10%, except for V a under the low thermal impact condition (=50%). For each specified thermal impact condition, we generated 1,000 environmental combinations by using the Monte Carlo simulation approach according to the variations obtained from the four environmental ...

Evaluation of Auditory Fatigue in Combined Noise, Heat and Workload Exposure

“…A digitally controlled thermal exposure chamber with evaluated efficacy 37) was used to simulate the heat stress. All driving units were adjustable using an automatic feedback control system to simulate air temperature (T a ), relative humidity (RH), globe temperature (T g ), and air velocity (V a ), respectively, for the determination of specified wet bulb globe temperature (WBGT).…”

Prioritizing Factors Associated with Thermal Stresses Imposed on Workers in Steel and Iron Casting Industries Using the Monte Carlo Simulation and Sensitivity Analysis

“…Sensitivity analysis was used to prioritize the sensitivities of the above five factors in determining AET based on the PHS model. The above approach was successfully used in our previous research 12) (Tsai et al 2003) to identify the significant environmental factors affecting the efficacy of a thermal exposure chamber designed for assessing the thermal hazards for workers.…”