OSHA heat stress standards were developed in an attempt to establish work conditions which would insure that workers'deep body temperature would not exceed 38°C .(100.4°F). The 38°C limit was based on the recommendations of a panel of experts of the World Health Organization (WHO). The standards consider the wet-bulb globe temperature (WBGT) index as the most suitable index to specify the work environment. In these standards threshold WBGT values, for three different work load ranges at two different air velocity ranges, were recowmended. The WBGT index3 was chosen to identify the environment because it is simple as far as measurements needed for its determination.