The work of the main European research teams in the field of thermal factors was coordinated in order to improve significantly the Required Sweat Rate model published as an international standard. Many significant modifications were brought, in particular concerning the effects of forced convection, body movements and exercise and the prediction of the skin temperature as a function of the rectal temperature and in case of severe conditions of radiation, humidity and clothing. The criteria for acceptable work durations in hot environments were updated concerning the maximum increase in core temperature and the acceptable water loss. The revised model, called Predicted Heat Strain model, was validated through a set of lab and field experiments involving stable and fluctuating conditions with high and low radiation, humidity and air velocity. It is meanwhile adopted as an ISO and CEN standard. In addition, a strategy was developed to assess the risks of heat disorders in any working situation. It is based on the three highest stages of the SOBANE strategy: an "Observation" method for improving simply the thermal conditions of work; an "Analysis" method to evaluate the magnitude of the problem and optimise the choice of solutions and an "Expert" method for in depth analysis of the working situation when needed.