The heat and moisture transfer properties determined using this method are calculated from measurements of thermal transport made with the large skin model hot plate instrumentation. As stated in National Fire Protection Association (NFPA) 1971 Standard on Protective Ensemble for Structural Fire Fighting, measurements are made based on the requirements of American Society Testing and Materials (ASTM) F 1868, Standard Test Method for Thermal and Evaporative Resistance of Clothing Materials Using a Sweating Hot Plate, Part C. The reported heat loss parameters are listed and described below.

The measurement of heat transfer is a measure of heat flow from the calibrated test plate (heated to a skin surface temperature of 35°C) through the test material into the test environment (25°C, 65%RH), and is determined for both simulated dry and wet skin conditions. Heat loss parameters, calculated from thermal transport measurements, include:

a. Intrinsic Thermal Resistance (R_cf), (D°C)(m²)/ watt, is an indicator of heat transferred from a dry, heated test plate through a fabric or composite into the test environment.

b. Apparent Intrinsic Evaporative Resistance (R_re^A), (DkPa)(m²)/ watt,
is an indicator of the resistance of a fabric to transport heat and moisture while in contact with a wet, heated plate surface.

c. Total Heat Loss (Q_t), watts/ m², is an indicator of the heat transferred through the test material by the combined dry and evaporative heat loss, from a fully sweating test plate surface into the test environment. Total heat loss, measured at a 100% wet skin condition, indicates the highest predicted metabolic activity level that a wearer may sustain and still maintain body thermal comfort while in a highly stressed state in the test environment.