Some aspects of the thermal environment and heat stress

Abstract

This paper deals with the energy exchange between a subject and his surroundings and the consequential physiological response of the body. Although the treatment is in part general, there is emphasis on hot working conditions. The mechanisms by which the human body attempts to maintain a constant core temperature are outlined and the processes of convection, radiation and evaporation are examined. In particular, consideration is given to appropriate numerical values of body heat and mass transfer coefficients and an accurate means of predicting the mass transfer coefficient is brought to the reader's attention. Thereafter, the physical reaction of the body to hot working conditions is dealt with, highlighting the danger of even a small rise in core temperature. An outline is given of the symptoms associated with heat stress, and the need for assessment and control of workers' exposure to hot environments is established. Numerical methods are available for this and these are the subject of a second paper.