The Ability of the U.S. Army Heat Strain Decision Aid (HSDA) to Predict a Limiting Heat Stress Exposure

Working below the threshold limit value (TLV) for heat stress is not always feasible. When work above the TLV is required, an exposure method is needed that can help protect workers from time limiting heat stress by calculating a safe time for work at certain heat exposures. The purpose of this paper is to determine whether the USARIEM Heat Strain Decision Aid (HSDA) can be used to predict time limiting heat stress exposure in an occupational setting. Twelve adults participated in time limited heat stress exposures. A range of heat stress conditions were designed using three different ensembles and five different heat stress levels. Safe exposure times were assigned based on limiting criteria for core temperature (38.5°C), high heart rate (90% of age-estimated maximum), or willingness to continue. The HSDA process was adapted to an Excel function using Visual Basic for Applications (VBA) and trial data were input data to the HSDA function. A second HSDA function was used to find a predicted core temperature for fixed a standard person using a height of 170cm, a weight of 70kg, and an initial core temperature of 37°C. The logistic regression and probability of the individual data as well as the fixed data were compared. We found that the HSDA could be used to assess time limiting exposures in an occupational setting when workers are working above the TLV