Heat transfer through clothing systems can mean the difference between life and death for first responders, such as firefighters, who perform intense physical activity in extreme environmental conditions. Total heat loss (THL) is a fabric level test method required by the National Fire Protection Association (NFPA) to assess the thermal burden imposed by materials in the construction of turnout clothing. This methodology, however, does not account for garment fit, construction, or air layers that develop within the clothing. Instead, thermal manikins may be used to measure the THL of entire clothing systems according to ASTM test methods. Environmental test conditions between the two standard methods (fabric versus manikin) differ, creating the need for an adapted heat transfer model for manikin THL comparisons in similar environmental conditions. Therefore, the purpose of this research was to validate the assumptions of a heat transfer model originally developed and published by Ross, Barker, and Deaton (2012) for its accuracy in predicting manikin THL in nonisothermal test conditions. Three protective clothing systems with varying levels of clothing insulation were tested for THL in both isothermal and nonisothermal conditions as well as on the sweating guarded hot plate. Predictive calculations using Ross's heat transfer model, adapted from the original THL hot plate calculation in ASTM F1868, Standard Test Method for Thermal and Evaporative Resistance of Clothing Materials Using a Sweating Hot Plate, were correlated to the actual manikin measurements taken in isothermal conditions to determine if there is any bias present in the current model.
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