Full Scale Burn Demonstration of Two 2013 Ford Fusions - Arc Mapping Analysis 2018-01-1439

Vehicle fire investigators sometimes use the existence and location of thermally damaged wiring (arced, shorted, melted, & beaded) discovered in a post burn analysis of a vehicle as an indication of the fire origin and its cause. One systematic method of analysis is to use the process of arc mapping.

To examine the reliability of arc mapping in motor vehicle fires, two full scale burn demonstrations were conducted on 2013 Ford Fusions. Both vehicles had similar fire origins artificially initiated in the interior of the vehicles near the driver’s front seat. The engines were running and all accessories were off. During the burn sequence, occurrences of fire induced unintended electrical activity were captured with video and still photography. Examples of this unintended activity include lights, horn, wipers, and decklid latch activation. The burn concluded when the measured battery voltage went to zero in demonstration 1. The burn concluded in demonstration 2 after the measured battery voltage went to zero and the fire consumed the passenger compartment and most of the engine compartment. During the burn duration, passenger and engine compartment temperatures were recorded. A post burn arc mapping analysis of the vehicles was performed and thermally damaged electrical wires were identified. An attempt was made to analyze the circuits associated with thermally damaged wires to determine if the circuit was powered at the time of the fire or if the circuit became powered due to the fire. However, because of the extensive burn damage, specific circuits could not be identified. The findings on the two vehicles were compared to each other. The demonstrations concluded that arc mapping in a post burn vehicle is not indicative of the fire’s origin or causation consistent with NFPA 921 section 27.5.3.3.4. Arc mapping may be an effective method to determine origin and cause when thermally damaged wires can be identified, given that arcing can be confirmed, the electrical circuits can be identified, and a chronological map can be created indicating the origin and cause, however this is beyond the scope of this paper.