Evaluating Fire Propagation into the Passenger Compartment via Full-Scale Burn Testing

Two full-scale burn tests were conducted to evaluate the propagation of an engine compartment fire into the passenger compartment of consumer vehicles. In particular, the effect of penetrations in the bulkhead separating the engine compartment from the passenger compartment was examined. The first burn test involved two vehicles of the same year, make, and model. One of the vehicles was left in the original equipment manufacturer (OEM) configuration. The other vehicle was modified by welding steel plates over the pass-through locations in the bulkhead between the engine and passenger compartments. After the fire was initiated in the engine compartment and had reached the onset of flashover, the heat and flames from this fire began to effect the passenger compartment. At about this same time, flames extending from the engine compartment around the hood began impinging directly on the outer face of the windshield. The passenger compartment temperature first increased on both vehicles at an under-dash location near the bulkhead. Once the windshields failed the temperature of the airspace in occupant compartment that the driver or passengers would occupy and the headrest heat flux rapidly increased. A second burn demonstration involved a single mini-van with a windshield that had been fractured in a way similar to what would be expected during a front-end collision. As the fire that was initiated in the engine compartment interacted with the windshield, it failed in locations where there was existing mechanical damage to the windshield. The fire propagated into the vehicle via the broken windshield when the engine compartment fire was visually smaller than in testing in which the windshield was undamaged before the fire.