Because of the dangers associated with occupational heat stress, the exposure of individuals working in high -temperature environments must be carefully controlled. This paper describes how an acceptable work pattern, which restricts exposure to a safe limit, can be established. The method adopts a rational heat transfer approach. It is based on calculating the rates of energy exchange between an individual and the surroundings. The processes involved — convection, radiation, evaporation and conduction — are examined and the defining equations explained. Thereafter, the physiological constraints appropriate to hot exposures are considered and, on this basis, a numerical assessment procedure is proposed which allows the evaluation of maximum exposure and minimum recovery periods for acclimatised workers. An example is given illustrating the application of the procedure.
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