Scientists wanted to compare a new thermal stress index called Air Cooling Power (ACP), to the required sweat rate (ISO 7933) and the WBGT (wet bulb globe temperature) in the hot and humid thermal environment of deep mines. Relevant physical parameters were measured in a range of representative situations in order to analyze the performance of each of these indexes in relation to the proper protection of workers in deep mines. Comparative analysis of the exposure level permitted by each index was done in parallel with the cardiac stress levels recorded with experienced workers. The three indexes show comparable exposure limits and several recordings show severe stress levels. The WBGT and sweat rate indexes are preferred to the Air Cooling Power because they are supported by recognized standardization organizations. The authors emphasize the need for strict control of working conditions in deep mines. The results suggest approaches that are applicable to all similar thermal environments.
