• Doug Stahl

Arc Mapping - Not Valid for Vehicle / Equipment Fire Origin Determination – Part 2 of 3

Last month, in "Arc Mapping - Not Valid for Vehicle / Equipment Fire Origin Determination - Part 1", we discussed Arc Mapping as it is defined in the NFPA 921-2017 Edition. We outlined many reasons why it is not applicable to vehicle / equipment fires for fire origin determination (as arc mapping is defined in 921). Here, we expand on the topic, sharing other recently published literature that questions the validity of Arc Mapping, for origin determination in vehicles and equipment.


PUBLISHED LITERATURE QUESTIONING THE VALIDITY OF ARC MAPPING IN VEHICLES:


In our ISFI 2012 technical paper and presentation titled, "Applicability and Limitations of Arc Mapping in Vehicle and Equipment Fire Investigations", we outlined the following conclusions reached proving why Arc Mapping does not work in vehicles / equipment:

  1. There are a number of significant differences between vehicles/equipment and structures in the configuration and properties of these products and their electrical systems that lead to significantly different behavior in a fire related to the creation of electrical arc marks and other fault evidence.

  2. No testing, analysis, or study verifying the applicability of Arc Mapping as a fire investigation technique utilized to assist in the determination of the fire area of origin in vehicles or equipment was found in the literature.

  3. The different fire behaviors between vehicles/equipment and structures prevent the Arc Mapping technique from being a dependable, robust technique when translated from structures to vehicles and equipment.

  4. Arc Mapping, as a fire origin investigation technique, does not have a scientific basis for use in typical vehicles and equipment when utilized to assist in the determination of the fire area of origin as it can for structures. Surveys and analysis of arc marks and other electrical fault evidence may be important the fire cause determination and hypothesis testing.

  5. Since the term “Arc Mapping” has gained common usage, and is defined in NFPA 921 (2017 & prior), as a fire investigation technique to assist in the determination of the fire origin (in structures), it is proposed that the useful and necessary process of locating, documenting, and analyzing evidence of electrical activity be referred to as “Electrical Activity Survey” (EAS) for distinction and clarification, especially in vehicles and equipment.

  6. Fire investigators need to assure that an investigation technique, method, or process is applicable, reliable, and has a scientific basis when applied outside of the parameters for which it was developed and tested.

"APPLICABILITY AND LIMITATIONS of ARC MAPPING in VEHICLE and EQUIPMENT FIRE INVESTIGATIONS"

DOWNLOAD HERE:

Full Paper Arc Mapping in Vehicles and E
.
Download • 122KB

The Society of Automotive Engineering (SAE) in 2013 published the first peer reviewed experimental study of Arc Mapping in motor vehicles. The paper, "Full Scale Burn Demonstration of Two 2013 Ford Fusions - Arc Mapping Analysis", concluded that a fire investigator must not assume that the mere existence of thermally damaged wires in a post-burn motor vehicle is evidence of the area of origin of a fire or is evidence of the cause of the fire.


Most recently, the technical paper "Arc Mapping: New Science, or New Myth?" published in 2017 by Vytenis Babrauskas, Ph.D. from Fire Science and Technology Inc., and the Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA. Among the conclusions in this paper is one critical of the validity of using arc mapping in vehicles. The article states: "There have been no validation studies of arc mapping in motor vehicles, which also use stranded wires, but typically have low-voltage DC power supplies and sometimes use circuits with no overcurrent protection".


Some investigators implicitly, or explicitly, rely on the applicability of Arc Mapping to vehicles and equipment (and any other nonstructural fire investigations) -- but no analysis, validation, or testing has been found to provide a scientific basis for the reliability and repeatability of Arc Mapping in vehicles and equipment (and even with sometimes questionable usage in building structures). No testing and verification studies are believed to exist for Arc Mapping as applied to vehicles or equipment.

Considering the substantial differences of the electrical systems between structures and vehicles/equipment, and the noted potential differences in fire behaviors attributable to those differences, it should not be expected that Arc Mapping would be a reliable fire investigation technique in vehicles and equipment.


If you disagree, we sincerely ask that you please contact us to discuss! CALL OR EMAIL US NOW!

Next month, Part 3 in this series of articles will share the latest on Arc Mapping and other relevant changes to the NFPA 921 2021, currently scheduled for release on August 21, 2020.


Click here to read our published papers regarding Arc Mapping



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