Firefighters putting out car fire


Author: Gordon E. Ivory, CFEI, CVFI, CFII, RL

Make the Most of Your Investigation, Whether Accidental or Incendiary in Nature

Modern day vehicles are much more complex in design than of earlier days. The fire investigator - either paid, volunteer, public, or private sector - must base his opinion on training, education, and experience when investigating these types of fires. The information he/she gathers must be reported accurate and factual. What was once called Cause and Origin has now been re-defined as Origin and Cause since the fire’s Origin (where the fire originated) must be determined before the cause can be established. Knowing what to look for in a reported stolen burn and recovered vehicle and/or accidental fire in a vehicle is only half the battle.

Finding the Origin of the Vehicle Fire

The origin of fires can be broken down into three main areas, of which can be later subdivided further: the engine compartment, the occupant compartment, and the cargo area or bed of the truck or vehicle. Each area might have burn patterns such as lines of demarcation or radial burn patterns pointing towards the fire’s origin. All investigations should be conducted from areas with the least damage and progress to most severe.

Windshield Evidence

The windshield contains a plastic laminate which keeps the pieces of broken glass from being dispersed into the passenger compartment during an accident or fire. The manufacturer inserts a thin piece of vinyl or laminate between the two sheets of shaped glass to form the windshield. This is called laminated safety glass. This surface can withstand great impact, bulls eyes, and cracks resulting from stones or pebble pings on the road.

Close examination of the windshield might reveal substantial information as to the location where the fire originated. NFPA Guide for Fire and Explosion Investigators 2017 Edition states: A passenger compartment fire will frequently cause failure at the top of the windshield and will leave radial fire patterns (fire patterns that appear to radiate from an area) on the hood. These patterns are created as the fire progresses and consumes the surface coatings. Engine fires, on the other hand, may spread into the passenger compartment through preexisting penetrations in the bulkhead, and typically cause failure at the bottom of the windshield. Radial burn patterns from an engine fire might be observed on the doors.

Engine or Passenger Compartment?

When the fire is suspected to have originated in the engine compartment, look for large burn patterns on the hood, with radial burns pointing toward the firewall, or bulkhead, as it is otherwise known, where it most likely will have vented. The windshield will generally show burn patterns at the bottom, while leaving the top intact, depending on the intensity of the fire. Fires that originate in the interior of the vehicle will generally affect the top of the window, causing it to break and fall inward, leaving a fracture line at the base. These glass fragments will sometimes be held intact by the rubber sealant around the window frame. Fire inside the vehicle will burn vertically and later horizontally once it reaches the ceiling or headlining material. As with all fires involving vehicles, the construction method and items utilized will sometimes play a significant role on the burn patterns present; therefore, the investigator must be keenly aware of how the vehicle was constructed and what items were stored where at the time of the fire.

Vehicle Identification

The first thing that needs to be done even before starting the investigation is to confirm the identification of the vehicle you will be examining. The VIN tag, which is the vehicle identification number located on the driver’s side of the dashboard, is the easiest way to identify the vehicle. VIN numbers can also be found on the driver side on the compliance sticker. A partial VIN can sometimes be found on an engine, or bulkhead, as it is otherwise known. The license plate might also aide the investigator in the identification of the vehicle. The website I use frequently is This will help confirm the vehicle’s year and engine type. The second thing that must be considered to document is the condition of the battery, and to make sure it is disconnected, eliminating any power surges to the vehicle in an uneventful, unexpected deployment of the airbag. If you get hurt at the fire scene examination, you are no longer part of the solution, but become part of the problem.

Stolen & Burned Vehicles

When the reported theft and recovery of a vehicle fire is found, the position of the windshield glass is critical as the location of the ignition switch and/or lock assembly, when the vehicle is examined, to determine if the ignition lock assembly and/or components were on the column at the time of the fire. Most vehicle fires, when intentionally set, are done so in the interior, causing the windshield to fail and fall inward. Anything on the floor at the time of the fire will generally be covered with windshield glass. If the keys or lock assembly of the ignition are found on top of the glass, it can be readily assumed they were on the column at the time of the fire. Therefore, during the examination and delayering of the interior of the vehicle, it is important to record the location of the components of the lock assembly. When a vehicle is stolen and recovered burnt, a qualified forensic locksmith should examine the vehicle locks and ignition to determine signs of manipulation such as picking, prying, impressioning, rotational tool marks, or drilling. Once the origin of the fire has been established, the cause will generally be close by.

Know The Vehicle's Components

When you come across a device or component in which you do not know its function, there are several web sites available for identification process of these items:,, and

Glass Fragments Tell a Story

The investigator should always examine the site where the fire occurred, if possible, to document the scene, and to determine if any glass fragments are on the grass or pavement. Door glass is designed to shatter into small pieces when impacted with an object to break the plain of the glass these glass fragments could be an indication of forced entry. Likewise, the position of the glass inside the doorframe or cavity should always be examined. Vehicles involving electric window glass motors, however, are sometimes, subject to cross shorting of the wires, causing the windows to motor down or up. Fires involving manual crank windows will generally show the position of the windows at the time of the fire, after the window jig is repositioned and examined.

The position, location and condition of the glass in the vehicle can be considered valuable when examining a vehicle, whether accidental or incendiary. In all cases involving fire investigation of vehicle fires, they should and must be performed by a properly educated and trained fire investigator.

Understanding Vehicle Construction

In reconstructing the flame spread and burn patterns, it’s important to keep in mind those plastic heater/air conditioner housings, dashboards, instrument clusters, glove boxes and their contents, louver vents and door trim panels represent a large accumulation of combustible material and can generate substantial heat. It may take extensive and considerate time and effort to understand both materials and the vehicle construction to establish for each location whether it is a hot spot (area of heavy and long burning) or the point of origin.

Flame Propogation Rate

FMVSS302 - Federal Motor Vehicle Safety Standard 302 is a Department of Transportation standard for textile materials. This standard state that a material shall not burn or propagate flame across its surface at a rate of more than 4” per minutes. This was designed to prohibit the flame spread when a small fire occurs in the interior of the vehicle from growing out of control such as when a cigarette is dropped. Therefore, during your investigation, this must be considered as to how the fire growth occurred and what was the fuel and heat source.

Oxidation Patterns

Oxidation patterns (rusting) are important in identifying the point of origin, but they can last only for a few weeks or months when exposed to the weather elements such as rain and snow and rapidly degrade the information they have to offer. It is recommended that if the vehicle is to be stored outside in substandard weather conditions that it be covered; this is not only to protect the metal from the oxidation process, but to keep the rain and snow out of the vehicle if it is an interior fire, and until it can be properly examined.

Fluid Analysis

The investigator might want to consider taking fluid sample of the engine oil and transmission and have them tested at a laboratory. Oil analysis is a speedy, nondestructive way to gauge the health of an engine by looking at what's in the oil. One lab that I use is Blackstone Laboratories (260)744-2380 but there are several more.

Testing of the oil can show the following:

  • Spectral Exam: Establishes the amounts of wear metals, silicon, and additives present in the oil. Also checks for coolant.
  • Viscosity: Determines the grade of oil.
  • Insolubles: Measures the percentage of solids present in the oil.
  • Flashpoint: The flashpoint is the temperature at which the vapors from the oil ignite. This test also looks for moisture contamination.

Lets say after testing of the oil sample the results show the present of Antifreeze, this is a sign of an internal leak, usually caused by a bad gasket or engine failure and should not be present in the oil. While the testing of the transmission fluid sample it showed high levels of Aluminum, Chromium, Iron, Copper, Lead, Tin, Nickel, Silver, Manganese, Potassium or Sodium this could be an indication of a transmission problem was present. In either case, this will provide the investigator with some of the needed facts as to the condition of the engine and transmission at the time of the fire.