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Thermo-physical evaluation of firefighter outer garment in high flux environments

Thermal protective performance tests have been conducted and improved over the years to assess the safety provided by firefighters’ outer thermal garments. Existing evaluation criteria based on empirical relations require an iterative process to estimate skin burn injuries. In this work, the concept of critical time – maximum exposure time before physical failure, is proposed, and utilized to abate this iterative process. The critical time relation to the fabric performance is investigated at an incident heat flux of 41, 84 and 126 kW/m2. Furthermore, parametric studies are performed to characterize the fabric thermo-physical behavior and associated burn degree. The tested specimens consist of an outer shell, a moisture barrier and a thermal liner. The methodology of visual assessment as per ISO 6942 is implemented to approximate the critical time. The critical time relation to increasing incident heat flux displayed a nonlinear performance reduction in the garment. An increase in the second degree burn time was observed for a vertically oriented bench-scale test. The firefighter’s current outer garment failed at a high flux of 126 kW/m2. The concept of relating the critical time to cumulative incident flux will aid the education of firefighters on fluctuating fire environments. This research opens a new domain to analyse the protective garments utilising the critical time.