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Autoignition / Hot Surface Ignition
Hot surface ignition is governed by the temperature of surfaces in the vehicle, the autoignition properties of the flammable materials, and factors that influence these parameters. While autoignition temperature is measured in a laboratory, the actual temperature of ignition in a vehicle is significantly affected by many factors. Autoignition is dependent on the property of the material being ignited (tendency to ignite at a given temperature) [1], the temperature of the surface in question, and other environmental factors. Environmental factors include air flow, surface condition, and availability of oxygen. Both air flow and surface condition may influence the potential for ignition on surfaces of the same temperature. Air flow may affect air/fuel mixture and the time for transfer of heat. A rough or scaly surface may provide pockets that can increase the time fuel remains in the presence of heat (residence time).
This section will provide information necessary to assess the possibility of autoignition in fire investigations. The following is a list of subtopics covered.
Frequency of autoignition fires
Underhood surface temperatures
Examples of recalls for autoignition
References
Shields, L, Scheibe, R., “Computer-Based Training in Vehicle Fire Investigation-Part 2: Fuel Sources and Burn Patterns,” SAE 2006-01-0548, 2006.