Ann. occup. Hyg., Vol. 45, No. 2, pp. 123–135, 2001  2001 British Occupational Hygiene Society Published by Elsevier Science Ltd. All rights reserved Printed in Great Britain. 0003–4878/01/$20.00 PII: S0003-4878(00)00030-2 Development and Validation of the Predicted Heat Strain Model J. MALCHAIRE²*, A. PIETTE², B. KAMPMANN‡, P. MEHNERT§, H. GEBHARDT, G. HAVENITH‡‡, E. DEN HARTOG¶, I. HOLMER²², K. PARSONS‡‡, G. ALFANO§§ and B. GRIEFAHN§ ²Unite´ Hygie `ne et Physiologie du Travail, Universite ´ Catholique de Louvain, Clos Chapelle-aux- Champs 3038, B-1200, Brussels, Belgium; ‡Institut fu ¨r Arbeitswissenschaften der Ruhrkohle Aktiengesellschaft, Hu ¨lshof 28, D-44369, Dortmund, Germany; §Institut fu ¨r Arbeitsphysiologie an der Universita ¨t Dortmund, Ardeystr. 67, D-44139, Dortmund, Germany; Institut fu ¨r Arbeitsmedizin, Sicherheitstechnik und Ergonomie, Corneliusstr. 31, D-42329, Wuppertal, Germany; ¶TNO Human Factors, Department of Work Environment, Thermal Physiology Group, Kampweg 5, P.O. Box 23, NL-3769 ZG, Soesterberg, The Netherlands; ²²National Institute of Working Life (NIWL), S-171 84, Solna, Sweden; ‡‡Human Thermal Environments Laboratory, Loughborough University, Ashby Road, Loughborough, Leicestershire, LE11 3TU, UK; §§DETEC c/o Fac. Ingegneria, Piazzale Tecchio 80, I-80125, Napoli, Italy Eight laboratories participated in a concerted research project on the assessment of hot work- ing conditions. The objectives were, among others, to co-ordinate the work of the main Euro- pean research teams in the field of thermal factors and to improve the methods available to assess the risks of heat disorders at the workplace, and in particular the “Required Sweat Rate” model as presented in International Standard ISO 7933 Standard (1989). The scientific bases of this standard were thoroughly reviewed and a revised model, called “Predicted Heat Strain” (PHS), was developed. This model was then used to predict the minute by minute sweat rates and rectal temperatures during 909 laboratory and field experiments collected from the partners. The Pearson correlation coefficients between observed and predicted values were equal to 0.76 and 0.66 for laboratory experiments and 0.74 and 0.59 for field experiments, respectively, for the sweat rates and the rectal temperatures. The change in sweat rate with time was predicted more accurately by the PHS model than by 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.  2001 British Occupational Hygiene Society. Published by Elsevier Science Ltd. All rights reserved Keywords: heat stress index; required sweat rate INTRODUCTION The ISO 7933 (1989) Standard, entitled Analytical Determination and Interpretation of Thermal stress using Calculation of the Required Sweat Rate was published for the first time in 1989. It was abundantly criticised and many papers were published comparing one version (not always specified) of the Required Received 21 January 2000; in final form 3 May 2000. *Author to whom correspondence should be addressed. Tel.: + 32-2-764-32-29; fax: + 32-2-764-39-54; e-mail: malchai- re@hytr.ucl.ac.be 123 Sweat Rate index to sets of data (for example, Haslam and Parsons, 1987, 1994; Smolander et al., 1991; Kampmann and Piekarski, 2000). Although such comparisons were always limited to a particular set of data, definite limitations were shown concerning:  the prediction of the skin temperature;  the influence of the clothing on convective and evaporative heat exchanges;  the combined effect of clothing and movements;  the increase of core temperature linked to the activity; by guest on January 6, 2015 http://annhyg.oxfordjournals.org/ Downloaded from