A new environmental heat stress index for indoor hot and humid environments based on Cox regression

Physical work in hot and humid environments imposes health risks, productivity falling and safety problems on workers. Protection of workers from heat related problems requires quantitative heat stress assessment of the workplace. In this paper, a new index-equivalent temperature (ET) is proposed to measure the environmental heat stress in indoor hot and humid environments. A climate chamber was built to simulate the indoor hot and humid environment. And the safe working time of 144 male volunteers were studied under different climatic conditions in the chamber. Cox regression method is adopted to obtain the impacts of variables on the safe working time. Then the new index-ET is proposed based on the Cox regression results. The correlations between the ET and the common used indexes are determined to test the validity of this new index. Finally the safe working time concerned with the ET is summarized. The results show that the new index gives physiological correlates and physical means. The ET developed in this paper has the potential to be a practical index to measure the environmental heat stress in indoor hot and humid environments.