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.