A variable property, multiple layer finite element model was developed to predict skin temperatures and times to second and third degree burns under simulated flash fire conditions. A sensitivity study of burn predictions to variations in thermal physical properties of skin was undertaken using this model. It was found that variations in these properties over the ranges used in multiple layer skin models had minimal effects on second degree burn predictions, but large effects on third degree burn predictions. It was also found that the blood perfusion source term in Pennes' bioheat transfer equation could be neglected in predicting second and third degree burns due to flash fires. The predictions from this model were also compared with those from the closed form solution of this equation, which has been used in the literature for making burn predictions from accidents similar to flash fires.

An improved model has been developed to simulate heat transfer in horizontal air spaces between thermal protective fabrics and test sensors in bench top tests, such as the thermal protective performance test. This model calculates the radiation and convection heat transfer from the test specimen to the test sensor. Radiation heat transfer is calculated by treating the bottom boundary of the enclosure as a series of isothermal rectangular pieces. Convection heat transfer is calculated using an empirical correlation and by assuming that convection only occurs over a portion of the cross-section of the enclosure. Predicted times required to exceed the Stoll second degree burn criterion were found to be within 3 % of those measured during actual bench top tests of steel shimstock using air gaps from 6.4 mm (1/4 in.) to 19.1 mm (3/4 in.).

One of the primary differences among various test methods used to evaluate fabrics for thermal protective clothing is the presence or absence of a horizontal air gap between the fabric to be tested and the test sensor. Numerical modeling and flow visualization experiments were used to study the effect of the size of this air space on bench-top test results. The relative magnitudes of conduction, convection and radiation heat transfer in the air gap are shown, and photographs of the flow patterns in these enclosures are included. Applications of this work to other areas of fire protection engineering are dis cussed.

There has been some research into the level of damage and changes to important properties of firefighters' protective clothing after exposure to conditions such as elevated temperature and ultra violet radiation. However, at this time, the results are not comprehensive enough to develop a standard procedure to estimate the remaining useful life of firefighters' protective clothing. There is also a need to develop non-destructive techniques to evaluate clothing, for most tests used to evaluate properties of clothing are destructive, and visual cues cannot completely assess the level of deterioration of the properties of thermal protective fabrics. In this paper, major factors that affect the continuing performance of firefighters' protective clothing and their effects on the service life of the clothing are reviewed. Some nondestructive methods which have been employed in different studies to evaluate the degradation of physical properties of firefighters' protective clothing are also described, along with statistical and probabilistic methods for estimating the useful life of materials. Suggestions for future research, which will assist fire departments in determining the level of damage to clothing, and estimating its remaining useful life are also discussed.

Protective clothing is used in many industries to protect firefighters and other workers from fire and other hazards. While skin burns can occur during a fire, protective fabric temperatures remain high for some time even after a fire ends. Therefore, skin burn injuries can occur during the time in which a fabric is cooling. A heat transfer model has been developed that can predict inherently flame resistant fabric temperatures and skin burn injuries during this cooling phase. This paper describes the heat transfer model, including methods used to calculate the apparent heat capacity and the convection heat transfer coefficient as the fabric cools. The new model has been validated using data from bench top tests of Kevlar R /PBI fabric specimens. Parametric studies using the model demonstrate the importance of selected thermal properties and boundary conditions on fabric temperatures and bench top test results.