IMPORTANT - This version of the tool (v2.5.4) complies with the ASHRAE 55 2020 Standard. This version is no longer supported and may contain errors that have been fixed in newer releases. Please visit the CHANGELOG page to find out more.

Inputs
m/s
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.