Motor Vehicle Fire Investigations

roarengineering Articles, Fire & Explosion Investigation

Heavy equipment fire outside a structure

Investigating motor vehicle fires can be a complex task since there is such a wide variety of vehicles included in this specialized category of fire investigations. Chapter 21 of the National Fire Protection Association, Guide for Fire and Explosion Investigations (NFPA 921), deals specifically with motor vehicle fires that involve automobiles, trucks, heavy equipment, farm implements, and recreational vehicles (motor homes). If you take a moment to think about the types of vehicles that ‘fit’ these categories, the list can include forklifts, tractor/trailers, buses, cube vans, forestry equipment, etc.

Electrical systems in a modern vehicle

Motor vehicles have become more sophisticated and more costly, so a fire in a vehicle can easily cause $100,000 in damages. If the vehicle is stored indoors or is close to a structure, a vehicle fire can easily spread to the structure an cause significantly more damage.

Fire spread from a vehicle to a house

Investigating a motor vehicle fire is not a simple task and it requires specialized training and expertise. Becoming a Certified Vehicle Fire Investigator (CVFI) is a start, but technical training is required for the majority of modern motor vehicle fires. Consider the various ignitable liquids contained in a vehicle (gasoline, diesel, brake fluid, power steering fluid, engine oil, gear oil, automatic transmission fluid, glycol, and methanol) and the numerous common plastics found in the construction of motor vehicles (acrylic fibers, ABS, fiberglass, nylons, polycarbonate, polyethylene, polypropylene, polystyrene, polyurethane, vinyl (PVC)). Now consider that all the ignitable liquid, plastics, and rubbers are encapsulated in one package and a motor, electrical system and mechanical systems get shoved into the package. The engineers that design motor vehicles have to deal with functionality, performance and design but they also have to consider many other issues including,

  1. Hot surfaces including exhaust piping, engine manifolds, turbo chargers, mechanical braking systems, spinning shafts and bearings,
  2. Electrical issues including high resistance faults, overloading, and arcing,
  3. High pressure fugitive fuel release caused by wear or abrasion. Atomized fuel requires little ignition energy to ignite (i.e. a spark).

Dash fire in a new truck

The physical size of a motor vehicle will dictate the amount of space that is available to run electrical wires and provide adequate separation between hot surfaces and combustibles. Engineers must also consider the possibility of abrasion of hoses and electrical conductors that are routed through tight spaces within the vehicle. Finally, consideration must be given to the extreme temperatures that a vehicle operates under and the corrosive environment that vehicles operate in, especially in northern climates and close to large bodies of salt water.

Many motor vehicles can be powered by a fuel (gasoline, diesel, LPG, natural gas, bio-fuels, etc.) but more and more motor vehicles are being powered by stored energy (batteries). New battery operated and hybrid vehicles utilize specially designed batteries and incorporate sophisticated charging systems (shore power and/or braking energy recovery). Shore power systems include battery chargers, block heaters, and other AC powered equipment. These electrical systems require a specific expertise in order to properly interpret and assess their role in initiating a fire. For example, luxury motor vehicle manufacturers use fuses as well as triacs (bidirectional electronic switches) that can react more quickly than conventional fuses and breakers to cut off power to a particular circuit with in the vehicle. A proper investigation will include a thorough analysis of fuses, breakers, triacs and computer storage devices that will contain data that can assist in determining the origin and cause for the fire.

Electrical arcing damage of a wiring harness

Vehicle fire investigators must possess the technical expertise to be able to analyze the complex systems within a vehicle in order to determine the origin and be able to identify all the possible ignition sources. It is a process that requires specialized technical knowledge and expertise in the areas of vehicle fire dynamics, fire chemistry, mechanical systems, and electrical systems. It also requires continual education since vehicle technology changes at a rapid pace.

The motor vehicle fire investigators at Roar Engineering are Certified Vehicle Fire Investigators (CVFI) and have the specialized engineering expertise to provide a proper and thorough analysis of complex electrical, mechanical and fuel delivery (storage) systems in today’s complex motor vehicles. Feel free to contact Vincent Rochon, Jason D’Ornellas or Darryl Schnarr with any question(s) you have regarding Motor vehicle fire investigation.

Authored by Vincent Rochon P.Eng, Consulting Engineer