Empirical Definition of Limit to work in Hot Environments for Women

Occupational exposure to hot environments can be considered safe if the core body temperature (Tc) does not rise above the expected work-specific equilibrium level. The ambient vapor pressure at which such Tc elevation occurred were tested on female subjects who were exposed to eight air temperatures (Ta) between 36 to 52°C on two series of tests; seminude at metabolic rate of 150 W-m-2 and clothed at 196 W-m-2. Each test started with walking at a given Ta with the vapor pressure (Pa) set to insure Tc equilibrium within 60 minutes. Thereafter, Pa was raised by 1 Torr every 10 minutes for an additional 60 to 70 minutes. The Pa beyond which the monitored rectal temperature (Tre) inflected upwards was considered the limit for the particular Ta for the subject. On the basis of this method, a psychrometrically defined limit was derived as the mean Pa at each Ta for the two series tested. Some of the Pa values could be used to derive the evaporative coefficient applicable to the ambient maximal evaporative capacity.