Heat stress management: Case study in an aluminum smelter

Heat stress is a recognized hazard in many industries including aluminum smelters. The emphasis of this case study was on the potroom operations in which molten aluminum was made from alumina ore. The case study presents the methods used to evaluate the heat stress, an overview of the controls and an assessment of their effectiveness. To facilitate the evaluation, environmental data were collected and used to develop a prediction model for WBGT levels at target locations in the potrooms based on the temperature and humidity of air entering the potrooms at a representative (reference) location. The prediction model was largely empirical with an accounting for the nonlinear relationship of wet bulb temperature to air temperature at a fixed vapor pressure. The WBGT prediction in combination with metabolic rate and a task analysis was implemented in a spreadsheet scheme for heat stress evaluation of different jobs. Heat stress guidelines were developed to manage the risk of heat-related disorders. The guidelines mapped out the policy, responsibilities and activities. Important among these activities were training, hygiene practices and medical surveillance. The guidelines included environmental thresholds at the reference location for administrative controls and personal protection. The current level of heat stress was broadcast through the potrooms so that appropriate actions could be taken. The success of the guidelines was seen in the reduction of heat-related disorders and overall injuries. Further, physiological measurements demonstrated that there was good control of heat strain.