The effects of moisture on the thermal protective performance of firefighter protective clothing under medium intensity radiant exposure

Abstract

Current firefighter protective clothing is composed of multilayer fabric systems. The outer shell fabrics inevitably become wet in the process of firefighters performing their duties, and sweat may also increase moisture in the inner layers of protective clothing. In this study, two kinds of outer shell fabrics (aramid IIIA fabric and aramid 1313 and flame-retardant viscose-blended fabric) and two kinds of thermal liner fabrics with different thicknesses were selected. Three wetness conditions were simulated for the outer shell fabric, thermal liner fabric and both fabrics together. A modified thermal protective performance (TPP) tester was applied to assess TPP provided by these wetted fabrics; in addition, second-degree skin burn time was predicted and absorbed energy indexes were calculated. The regression method was employed to create fitting curves for absorbed energy and second-degree burn time in different configurations and the Pearson correlation was established to analyze their relationship, in which the lowest R2 value could reach 0.9122 and p-values were all much less than 0.05. Performance results for both wet conditions indicated that outer shell moisture and a thicker thermal liner have a positive and increased negative effect, respectively, on fabric TPP. When the sample S-3-D (aramid 1313 and flame-retardant viscose-blended fabric, moisture barrier and the thin thermal liner) was both wetted in the outer shell and thermal liner, its second-degree burn time was improved by 12.8% over performance in dry conditions. These findings may have important applications for the design and manufacture of optimal protective performance clothing systems.