Windows and Doors
The position of windows and doors can often be determined by studying fire patterns. Open windows and doors create large propagation paths and often leave distinctive heat patterns around the openings. It can be a challenge to determine whether the opening from the door or window existed prior to the fire.
Discontinuities in heat pattern between the trailing edge of a door and the adjoining body panel may indicate whether the door was open during the fire. Doors may change position during the course of the fire; they may have been opened by the occupants in an effort to escape the fire or by emergency personnel during a rescue.
As with structural fires, windows often break from heat; it is sometimes possible to ascertain whether the broken window pre-existed the fire or was the result of fire. If there are window fragments inside the car (or at the fire site) that are not heat damaged or covered with soot, then there is a higher possibility that the broken glass preceded the fire. Glass fragments and loose components found on the ground at the scene are often swept up and put in the vehicle during salvage.
In some cases the position of the openable windows may be determined by noting the position of the window lift mechanism inside the door. In extreme fires, where lift mechanisms distort or few consumables remain, it is often impossible to make a reliable determination of window position based on this technique.
Fire can penetrate around the polymeric
materials surrounding windows, or break windows propagating fire across the
The response of the vehicle windshield can be indicative of fire origin. A fire originating rear of the instrument panel in the passenger compartment will often damage the top of the windshield first. Fire patterns may then radiate outward (on the hood) from the windshield. Engine compartment fires tend to cause damage to the base of the windshield, near the cowling.
For another example, you can revisit the Grand Am case study by clicking here.
Contrary to this observation, fires that occur in the instrument panel (vehicle interior) may also tend to damage the lower part of the windshield first. Crush damage to the hood may provide a path for fire either toward or away from the windshield which will alter the propagation path.
It should also be noted that the body panels of some vehicles are composed of aluminum or fiberglass. Propagation dynamics will inexorably change (when compared to steel) if the panels deform during the fire.
|Gas filled hood strut that burst from internal pressure during a vehicle fire.