Performance evaluation of thermal protective clothing
Fire-resistant/retardant fibers are processed through various steps (eg, yarn processing, fabric and garment engineering) to manufacture thermal protective clothing for firefighters. The main function of this clothing is to resist heat transfer from firefighters’ ambient environment towards their bodies to protect them from burn injuries. To accomplish this function, the clothing must have thermal stability and insulative characteristics when exposed to thermal environments (eg, radiant heat, flame, hot surfaces) for determined durations [37,38,304,305]. On the other hand, the clothing should properly transmit and evaporate the metabolic heat and sweat- vapor from firefighters’ bodies towards their ambient environment. This function of the clothing helps to maintain a constant core temperature of firefighters’ bodies at 37°C in a range of thermal environments and levels of activity, which can provide physiological comfort to firefighters by reducing their heat stress [306-310].
One of the main requirements to confirm the thermal stability of the clothing is determination of softening and melting temperatures of the fire-resistant/retardant fibers. This further requires the determination of combustibility or flammability of these fibers or fabrics. The determination of softening and melting temperatures, along with the flammability, helps to verify how well the integrity of the clothing can be maintained during exposure to thermal environments and, therefore, prevent firefighters from burn injuries [220,245]. The next critical feature for protective clothing is its thermal insulation characteristics. By testing its thermal protective performance , researchers can establish if it provides effective protection for firefighters from burn injuries [75,76]. Finally, the physiological comfort provided by thermal protective clothing should be tested by evaluating its thermal and evaporative resistance along with total heat loss (THL) through the clothing; the results of these tests will help in understanding the metabolic heat and sweat-vapor transfer characteristics of thermal protective clothing to prevent/reduce the heat stress of firefighters [306,307,311]. In this context, it is necessary to mention that THL is commonly evaluated in North America using the ASTM F 1868 standard. Contextually, it is necessary to mention that ISO is currently working on a standard (ISO CD 18640) using sweating torso developed by Psikuta, Wang, and Rossi . This standard can more realistically evaluate the physiological comfort properties of protective clothing.