Outdoor air temperature (6 am) °C
Maximum allowable exposure time within which the physiological strain is acceptable (no physical damage is to be expected) calculated as a function of:
max rectal temperature = min
water loss of 5% of the body mass for 95% of the population = min
water loss of 7.5% of the body mass for an average person = min

NOTE: The PHS model (ISO 7933) allows the analytical evaluation of the thermal stress experienced by a subject in a hot environment. The PHS can only be used for dry-bulb temperatures between 15 and 50°C, air speeds between 0 and 3 m/s, metabolic rates between 1.7 and 6.8 met, total clothing insulation between 0.1 and 1.0 clo, and when the difference between the mean radiant temperature and the air temperature is between 0 and 60°C.