Survey of heat stress in industry

In spite of technical progress heat stress remains one of the most frequent complaints of French workers. An analysis of different heat stress conditions in the field shows that heat exposure may be classified under three headings: (a) short exposures to conditions very stressful for unacclimatized workers, (b) short exposures, mainly to radiant heat, of acclimatized subjects currently exposed to warm work situations, and (c) acclimatized workers exposed continuously to hot conditions throughout most of their shift. Unlike laboratory studies, field studies involve very short exposures to constant heat stress. On the other hand, the means of heat prevention vary widely from one place to another, from mainly ad hoc measures in small factories or where exposures are infrequent to major technical improvements in larger plants with regular exposures to heat. When they are quantified, heat stress conditions in the field are in most cases expressed in empirical stress index values. This makes them difficult to compare and is an obstacle to the progressive build up of a data base which might be useful for the abatement of heat stress or the definition of safe and easy to use time limit values. Analytical indices are needed to achieve this objective.