Exposure to heat is common in work-places in many branches of industry. Acute disorders may result either from excessive demands on, or failure of, the human temperature control mechanism or from a combination of the two. The complex interactions between temperature at the work-place, physical work and climatic conditions are such that each of these types of stress reduces the ability to tolerate the other two. Some individuals may react to hot work with impairments of cardiovascular and renal functions. It is known that heat may adversely affect alertness, reaction times and psychomotor coordination; this would account for a higher accident rate among workers exposed to heat. Accidents are particularly frequent among workers who are not acclimatized.
Heat is one of the commonest potentially harmful physical environments. In industries such as mining, steel or glass manufacture, agriculture and road building, workers are often exposed to severe environmental heat stress, which may even threaten survival. Hard physical work or exercise in hot surroundings is the main hazard, for the total heat load and the body is in fact the sum of environmental and metabolic heat.