Working under warm and hot conditions are to be found in a lot of industrial working places and also in service areas. Besides, it is frequently associated with expositions, which are required only occasionally, then, however, with clear heat loads, for example maintenance works on hot machines and generators. The temporal organization of the working phases and a sufficient time of cooling phases here forms a measure to guarantee health protection. Based on a suggestion by Pangert et al. (2003) in a first step orienting physiological laboratory tests under defined conditions were performed, which in their result showed a good agreement with the recommendations. Besides, a period of one hour was taken in each case which became partitioned in working and cooling phases. With a look at the multiplicity of the parameters to be considered - besides the climate parameters particularly the work load, the clothing and also the cycle time - which naturally can only be covered incompletely within the framework of physiological experiments, in a next step the application of the Predicted Heat Strain (PHS) model (cf DIN EN ISO 7933) was examined. Based on the parameters given above, this model allows the prediction of the body core temperature and sweat production as the fundamental strain parameters for the assessment of working under hot environmental conditions and can be considered as the "state of the art" concerning the prediction of physiological parameters for thermal stress. Particularly work sequences and therefore also changes between exposition and resting phases can be examined. As a result indications of the practical application of the model concerning the organization of work and cooling phases are given. The results of the performed laboratory studies as well as the Pangert-suggestion found consideration. Besides, in the result the fundamental aptitude of the model could be shown by which the given parameters of influence can be considered in specified form when organizing required cooling phases.

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