Experimental Characterization of the Thermal Response of Firefighter Protective Ensembles Under Non-Flaming Convective Exposure

Abstract

Thermal burns are one of the most serious injuries a firefighter can sustain while operating in a structure fire despite being fully covered in gear designed to protect them from thermal exposure. Extensive experimentation has been conducted into the performance of a firefighter’s protective ensemble when caught in a high radiative heat flux environment to ensure the wearer has enough time to escape to safety. High heat flux tests are beneficial in estimating safe operating times, but firefighters are also getting burned in fire environments that are thought to be routine exposures. The current study explored the thermal response of three-layer firefighter protective ensembles exposed to a majority convective, low-level heat flux in an oven. Through experimentation, the temperature of a copper calorimeter simulating skin beneath two different protective ensembles were measured while exposed to temperatures of 100°C, 150°C, 200°C, 250°C, and 300°C. The time for the copper calorimeter to reach a temperature of 55°C (the temperature a second-degree burn has the potential to occur to human skin) was recorded and compared to currently accepted thermal operating time limits for firefighters. Results show that once exposure reached above 100°C the time for a potential burn injury to occur fell below the predicted safe operational time for firefighters of 15–20 minutes when the PPE was in contact with the copper disk. The time to potential burn injury and test temperature exhibited an exponentially decaying relationship which is expected to continue as temperatures increase beyond those tested in the current study. Although consisting of different layers of material, both types of protective ensembles tested responded similarly and demonstrated no significant differences in time to potential burn injury at every temperature. Additional tests were conducted in the oven with an air gap placed below the protective ensemble as well as using the original test set up with a mostly radiative heat source to compare results and evaluate different exposures and conditions for future experimentation.