ISO DIS 7933

Description / Abstract: The main objective of this International Standard is to describe a mathematical model (the predicted heat strain model) for the analytical determination and interpretation of the thermal stress (in terms of water loss and core temperature) experienced by a subject in a hot environment and to determine the “maximum allowable exposure times”, with which the physiological strain is acceptable for 95% of the exposed population. (the maximum tolerable core temperature and the maximum tolerable water loss are not exceeded by 95% of the exposed people).

The various terms used in this prediction model, and in particular in the heat balance, show the influence of the different physical parameters of the environment on the thermal stress experienced by the subject. In this way, this International Standard makes it possible to determine which parameter or group of parameters can be changed, and to what extent, in order to reduce the risk of physiological strains.

This International Standard does not predict the physiological response of individual subjects, but only considers standard subjects in good health and fit for the work they perform. It is therefore intended to be used by ergonomists, industrial hygienists, etc. Recommendations about how and when to use this model are given in ISO 15265, Ergonomics of the thermal environment -- Risk assessment strategy for the prevention of stress or discomfort in thermal working conditions