When the rescue crews have departed and the forensic engineer arrives at the scene of a vehicular fire, the engineer often faces a much greater and more complex challenge in determining the fire’s origins than they do in a building fire scenario. According to the U.S. Fire Administration’s (USFA) most recent report, 23% of highway fires fall under the category of “no cause determined” and some engineers believe that is a generous statistic and would not be surprised if the number was closer to double that, or 46%. Often, cars are completely burned and gutted – and even if an engineer can narrow it down to two possible specific sources of ignition, the ignition source still falls into the “undetermined” category by default. In other words, following the guidelines established by the National Fire Protection Association (NFPA), the bar is set very high in establishing an absolute burden of proof. Furthermore, variables like wind and ventilation frequently have a huge impact on car fires because these factors increase the ferocity and speed of the fire’s destruction. For example, if a car’s windows are open, the fire’s progression path will be altered, exacerbating an already complex investigation.
From 2014-16, USFA records indicated that 83% of highway vehicle fires occurred in passenger vehicles — for a total of one in eight fires for fire department responses across the nation (USFA 7/2018 Vol 19, Issue 2). About 60% of roadway fires are the direct result of a collision, a more cut and dry cause and origin. But for the other 40%, where the fire’s origins are questionable, the identification process can be like solving a complex and vague puzzle. One of the main reasons for this is because there is seldom one isolated cause; instead, a sequence of events occurred – often over some period of time…which resulted, eventually, in the perfect condition for a blaze to ignite.
So, for investigators, it becomes a chicken-or-the-egg scenario; which part malfunctioned first and for how long? There are many different types of combustible liquids under the hood of a car, gasoline being the most dangerous and volatile by far…and leaks in the fuel system are the most common cause of vehicle fires (auto.howstuffworks.com/Top 10 causes of car fires). But which part over-heated causing which fluid to leak throughout the engine, waiting for a spark? It’s likely that a combination of human, mechanical and chemical factors worked together to create any given blaze. Sloppy or inadequate maintenance contributes to ripe conditions for a fire; a bad gasket is more likely to drip hazardous, flammable fluids, for instance. Frayed wiring is more likely to spark and make contact with such fluids. Overheating, also included in the top five causes of car fires, is often the impetus in the ignition and spread of fire, where these dangerously hot leaky fluids flow onto the exhaust system, or land on other hot parts.
CED’s mechanical engineers have exhaustive experience (pun intended) in vehicular fires.
If you are or become involved in a vehicular fire case, CED has qualified engineers with vast experience in the field. Call us at 1-800-780-4221 or submit an assignment on line HERE.
Senior Mechanical Engineer
Materials Science Engineer