The specific heat-release rate is the molecular-level fire response of a burning polymer. The Federal Aviation Administration obtains the specific heat-release rate of milligram samples by analyzing the oxygen consumed by the complete combustion of the pyrolysis gases during a linear heating program. Dividing the specific heat-release rate (W/g) by the rate of the temperature rise (K/s) of a sample during a test gives a material fire parameter with the units (J/g K) and significance of the heat (release) capacity. The heat-release capacity appears to be a true material property that is rooted in the chemical structure of the polymer and is calculable from additive molar group contributions. Hundreds of polymers of known chemical compositions have been tested to date, providing over 40 different empirical molar group contributions to the heat-release capacity. Measured and calculated heat-release capacities for over 80 polymers agree to within +/-15%, suggesting a new capability for predicting flammability from the polymer chemical structure.