Abstract
In the threshold limit values (TLVs) for heat and cold stress published by the American Conference of Governmental Industrial Hygienists, the main approach for prevention is similar: the frequency and length of required rest periods depend on the climatic conditions of the working area and the work metabolism. Whereas methods and instruments for measuring the climatic conditions are fairly well established for practical application, the methods available for assessing the effects of clothing and work metabolism at the job site are cumbersome and/or inaccurate. Both TLVs stipulate that the recommended work-rest regimens are valid only if the Workers' clothing is adapted to the climatic conditions of the working area. Yet there is no standard method to measure the insulation, vapor permeability, and ventilation of working uniforms and different protective garments. Some new methods are described which hold promise to solve these problems. Recommendations on methods to assess metabolism include qualitative and quantitative task analysis, depending on the degree of accuracy required. For heat stress, individual variability in tolerance can be accounted for through personal monitoring of physiological strain. Meanwhile, a management strategy is outlined to help mitigate the effects of variability among workers and the uncertainty in determining clothing effects and metabolism.