Experimental research on physiological index at the heat tolerance limits in China

In this study, the heat stress and heat tolerance of 148 male volunteers were examined under different climatic conditions in a stainless steel climatic chamber. The conditions were 30 to 42° dry bulb temperature and 40 to 80 percent relative humidity. The subjects, aged from 19 to 26 years old, performed various activities at the metabolic heat of 175, 349 and 580 W, respectively. The exposure durations and resulting heat stress were determined by measuring oral temperature, skin temperature, heart rates, blood pressure and sweating responses. The study proposed physiological limit values at exposure limits. Moreover, the study suggested that physiological measures from the experiments should be applied to evaluate the classification of extreme heat working environments in China.