These include air temperature, humidity, radiant temperature, air movement and the level of personal activity, the clothing worn, the body's fluid and salt balance and acclimatisation. Individual responses also vary, depending on perception, physical fitness, fluid intake, medications etc. To achieve an acceptable thermal environment, each of these factors must be considered.
Heat stress occurs when more heat is being absorbed into the body than can be dissipated.
In the short term, concentration is affected which increases the likelihood of accidents, and heat illness may develop. Severe illness or heat stroke can occur, which can result in death if not addressed. Cold Stress occurs when the rate of the body heat loss exceeds the rate of heat production. Cold related injuries include frostnip, frostbite, chilblains and, when severe, hypothermia, again with the possibility of death if not addressed. Hence, exposure to temperatures above 30 Deg.