This research developes a numerical model to predict skin burn injury resulting from heat transfer through a protective garment worn by an instrumented manikin exposed to laboratory-controlled flash fire exposures. This model incorporates characteristics of the simulated flash fire generated in the chamber and the heat-induced changes in fabric thermophysical properties. The model also accounts for clothing air layers between the garment and the manikin. The model is validated using an instrumented manikin fire test system. Results from the numerical model help contribute to a better understanding of the heat transfer process in protective garments exposed to intense flash fires, and to establishing systematic methods for engineering materials and garments to produce optimum thermal protective performance.