Thermal stress and thermal comfort.

The factors which determine the level of heat stress and the difficulties inherent in its measurement are discussed. The degree of thermal comfort or discomfort is shown to he a useful measure of thermal stress and methods for the determination of the preferred temperature are described. Objective measures of heat stress such as its interference with sleep and its effect on mortality in the aged are shown to agree with the subjective measure of thermal comfort. Means for the mitigation of heat stress in hot climates are outlined.