Characterizing the tensile strength of outer layer fabrics used in firefighters' protective clothing under radiant heat exposure

Abstract

More than sixty thousand firefighters' injuries have been reported by the National Fire Protection Association (NFPA) in U.S. in 2019. Inadequate protection of the uniform worn by the firefighters could be reason for most of the injuries. Firefighters repeatedly encounter various hazards especially thermal hazards during routine exercise, on-site firefighting, and emergency rescue. Degradation could occur on the bunker gear's fabric, which comes repeatedly in direct contact to thermal hazards when worn in the fire ground. It has also been found that performance of the fabric is extensively affected by the moisture accumulated in the fabric, which may come from the wearers' sweat. Proper evaluation and accurate prediction of the tensile strength of the high-performance fabrics used in both single and multi-layer clothing system could help maintain the overall integrity of the bunker gear and reduce firefighter injuries. This study focuses on evaluation of tensile strength of the fabrics when exposed to 10, 15, and 20 kW/m2 radiant heat fluxes. Different levels of moisture were added to the test samples to simulate the wearers' sweating. In each fabric system, a total of sixty-four different samples were prepared for four different types of fabric, four levels of moisture and exposed to three different heat fluxes for five minutes. Results show that heat flux and moisture levels have significant impact on fabric tensile strength. Moisture had significant more effect on tensile strength in three-layered fabric system compared to the single layer fabric system depending upon the heat flux and fabric properties. This study leads to an understanding on the impact of fabric strength in the presence of fire and moisture; this understanding could lead towards development of new fabrics that could provide better protection for firefighters.