 ASHRAE 55-2010 defines SET as "the temperature of an imaginary environment at 50% relative humidity, < average air speed, and mean radiant temperature equal to average air temperature, in which total heat loss from the skin of an imaginary occupant with an activity level of 1.0 met and a clothing level of 0.6 clo is the same as that from a person in the actual environment, with actual clothing and activity level".