Development and validation of the predicted heat strain model

Eight laboratories participated in a concerted research project on the asse ssment of hot working conditions. The objectives were, among others, to co- ordinate the work of the main European research teams in the field of therm al factors and to improve the methods available to assess the risks of heat disorders at the workplace, and in particular the "Required Sweat Rate" mo del as presented in International Standard ISO 7933 Standard (1989), The sc ientific bases of this standard were thoroughly reviewed and a revised mode l, called "Predicted Heat Strain" (PHS), was developed. This model was then used to predict the minute by minute sweat rates and rectal temperatures d uring 909 laboratory and field experiments collected from the partners, The Pearson correlation coefficients between observed and predicted values wer e equal to 0.76 and 0.66 for laboratory experiments and 0.74 and 0.59 for f ield experiments, respectively, for the sweat rates and the rectal temperat ures. The change in sweat rate with time was predicted more accurately by t he PHS model than hy the required sweat rate model, This suggests that the PHS model would provide an improved basis upon which to determine allowable exposure times from the predicted heat strain in terms of dehydration and increased core temperature. (C) 2001 British Occupational Hygiene Society, Published by Elsevier Science Ltd. All rights reserved.