Rectal, oral and 15 skin temperatures and weight loss were measured for 262 subjects before, during and after exposure to heat stress. There were 16 groups--each with 16 or 17 subjects. Four groups were exposed (240 min or until removed) to each of four environments: 30°C and 80% rh (33 ET), 40°C and 30% rh (36 ET), 50°C and 10% rh (38 ET), and 50°C and 20% rh (40 ET). The sedentary subjects wore minimal (0.2 clo) clothing.
At 33 ET, all subjects completed the 240 min heat exposure. At 36 ET, 94% of the young males, 75% of the young females, 100% of the middle-aged males, and 100% of the middle-aged females completed the session. At 38 ET, the respective percentages were 75, 31, 77, and 18. At 40 ET, the respective percentages were 29, 18, 25, and 0.

Rectal temperatures rose at an approximately linear rate for the first 180 min and then increased at a slower rate.

Weight loss g/(h·m2), approximately linear with time, was 49 g/h x m2for 33 ET, 122 for 36 ET, 217 for 38 ET, and 206 for 40 ET.