Assessment of Water Vapor Diffusion in Firefighters Protective Clothing
Shonali Nazare, Christopher W. Meyer, Daniel M. Madrzykowski
Structural firefighters often encounter hot and humid environments during interior firefighting. The water vapor transfer to and from the skin has great influence on thermo-physiological comfort of the firefigher. Quantitative information on water vapor transfer through protective clothing can provide significant insight into conditions that develop in the microclimate between the fabric layer and the skin. An experimental set-up has been developed to assess water vapor transfer through firefighter protective clothing when exposed to hot and humid environments. With suitable manipulation of test conditions and selection of test fabrics, the test method facilitates water vapor transfer via pure diffusion under dynamic conditions. Exposure conditions are selected such that the fabric specimen is exposed to water vapor with dew point temperatures that are likely to cause steam burns. This work examines the water vapor transport phenomena and the accumulation of water vapor in the microclimate i.e., the air space between the skin and the fabric layer. The experimental data provides temperature and humidity conditions in the microclimate between the fabric layer and the skin. The results demonstrate the ability of the test method to characterize test materials based on their permeability to water vapor. Different materials, including aluminum foil, knitted fabric, three-layered turnout gear composite, and a densely woven glass fabric, were exposed to hot and humid conditions. The aluminum foil displayed negligible water vapor diffusion while knitted hood fabric exhibited the highest rate of water vapor diffusion. Three layered turnout gear composite and a densely woven glass fabric revealed intermediate rate of water vapor diffusion.