The Effect of Moisture on Firefighter Protective Clothing Thermal Insulation: A Review of Industry Research

Despite advances in the new material technology and clothing designs for protecting firefighters, firefighters may still be burned under routine or ordinary fire fighting conditions. Some theories indicate that moisture in the clothing, resulting both internally from firefighters sweating and externally by hose spray or runoff, may be one cause of these injuries. An extensive review of industry research for evaluating the thermal insulation of firefighter protective clothing shows a range of performance for different material systems under both wet and dry conditions. For the various types of heat transfer, using both conventional and modified testing procedures, there is no conclusion that can be generalized for predicting the effect of water on protective clothing materials system thermal insulation. The body of research in the firefighter protective clothing industry shows some conditions where the tolerance times (time-to-pain and time-to-2nd degree burn), or the time for a specific temperature rise, will favor dry systems over wet systems. Other conditions exist where material systems with varying levels of moisture will provide relatively longer tolerance times or specific times to temperature rise as compared to dry systems. Several factors are demonstrated in the literature that affect the performance of clothing that includes moisture. These factors include the amount of water, its location in the material system, the type of heat transfer, the intensity and duration of exposure, and the type of materials and their condition during testing. The industry review demonstrates different effects for each of these factors. Given the variety of exposure conditions that firefighters face, it is likely that no predictive model will ever be developed that fully explains clothing performance under all conditions. This paper is intended to demonstrate the complexity of the subject and how simple claims for effects of moisture on clothing thermal insulation can be misleading or incorrect under many circumstances.