Fire Behavior of Materials in Vehicle Crash Fires and Survivability of the Passengers

Results from the research projects sponsored by General Motors, Motor Vehicle Fire Research Institute and National Highway Traffic Safety Administration are discussed. In the projects, thermophysical and fire properties of engine compartment fluids and polymer parts of the vehicle were quantified. Burning behaviors of the actual vehicle parts and front and rear crashed vehicle were also examined.

Penetration of flames into the passenger compartment was the most critical stage in vehicle crash fire tests. Pain, 2^nd and 3^rd degree burns, flashover, toxicity, and lethality followed in that order very shortly after the flame penetration. The flame penetration into the passenger compartment from the engine compartment fires in front vehicle crashes was significantly longer (10 to 24 minutes post ignition) than from gasoline pool fires under the vehicle (0.5 to 3.0 minutes post ignition). Thus, prevention of the penetration of flames into the passenger compartment is the most important step for passenger survivability. Thermal hazard appears to be more critical than the toxic hazard for the survivability of the passenger.

For the prevention of the flames to enter the passenger compartment from the engine compartment fire and from the gasoline pool fire under vehicle, large-scale vehicle burn tests were performed using fire retarded HVAC unit and a vehicle undercoated by an intumescent paint. The fire retardant treatment and the intumescent paint used in the tests, however, were found to be ineffective in the tests.

Amongst the thermophysical and fire properties quantified for the polymers parts, critical heat flux, thermal response parameter, and fire propagation index were identified as important for the hazard classification.

The test data suggest that for realistic assessment of the fire behavior of motor vehicle polymer parts, tests where entire polymer surfaces are exposed are needed. Two ASTM tests, E1354 Cone Calorimeter and ASTM 2058 FPA are able to satisfy this condition and could replace the NHTSA's FMVSS 571.302 Standard Test.