Heat-related illnesses can affect both indoor and outdoor workers who work in a hot environment with limited air movement. The risk exists whether working on a mine site or exploration operation, in a processing plant, refinery, building or undercover structure in hot weather. Working in the vicinity of a heat source, such as machinery, vehicles, heavy mobile equipment, or a furnace or gold room, can also increase the risk.
People are normally able to maintain a constant internal body temperature (37.2oC) by balancing heat gain with heat loss. While heat is gained from metabolism, physical activity and the environment, the body cools through heat loss from the skin by thermal conduction, convection and radiation, with hydration and sweat playing a major role. Under warm or hot conditions, evaporation of sweat from the skin is most effective in dissipating heat from the body. However, when humidity exceeds 75 per cent, evaporation does not occur.
When the body works hard and is not able to cool down under hot conditions, it can overheat, resulting in heat-related illness. There is a range of progressive heat-related conditions, including dehydration, heat rash, heat cramps, fainting (heat syncope), heat exhaustion and heat stroke which can be fatal. If the internal body temperature rises and exceeds 40oC, damage to critical organs (including brain, liver, kidneys and muscle) can occur with devastating results.