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Fire Investigation - Art or Science?

September 22, 2017

Fire investigation has been around for a long time. The destructive nature of fire, and the frequency with which it strikes, makes it a hot topic among insurance professionals, and determining liability, a top priority. But what is fire? How does it work? And what tools does a modern fire investigator have in helping to determine the cause (and liability) of a fire?

In the past, fire investigation was deemed as much an ‘art’ as a science. Investigators would frequently rely solely on past experiences coupled with beliefs passed down from mentors or from previous investigations. And, while there has always been heavy reliance on the visuals of fire patterns, there was not necessarily a focus on how they got there. This has resulted to the propagation of several ‘myths’ in the fire investigation industry, some of which I’ve listed here:

1.    Crazed glass at a scene is indicative of an accelerant: This myth has been long held. Some investigators believed accelerants burned at hotter temperatures than regular household materials and that this would cause glass in the building to fracture into very small pieces known as ‘crazing’. Through experimentation, it has since been discovered that when fire fighters sprayed water onto hot glass, crazing would occur. A normal occurrence in almost all structural fires.

2.    The location with the greatest depth of char is the area of origin: This myth assumed that the greatest depth of char would be where the fire started because it had burned there the longest. However, recent experimentation and research have proven that a fire can burn for longer, and at a greater rate, with good ventilation or fuel loads, which can lead to the greatest depth of char being in an area completely apart from where the fire started. In fact, the area of origin may be starved for oxygen early in the fire’s propagation resulting to a less intense burn pattern.

3.    Lines of demarcation on the floor are caused by accelerant pools: Yes, this is true . . .sometimes. However, lines of demarcation can also be formed by regular household finishes burning. For example, plastic-based carpets can melt, pool and burn very similarly to accelerants in a fire.

4.    The ‘V-Pattern’ is where the fire started: Again, this is true . . .sometimes. Although V-patterns can be caused by the initial flame in a fire event, they can also be caused by many other factors. For example, ventilation patterns, or stacks of fuel igniting late in the fire (i.e. during flashover - the point where a fire goes from being fuel controlled to ventilation controlled, or from a fire within a room to a whole room on fire).

These ‘myths’, and many more, were once widely accepted by fire investigators and were included in reports, opinions, and even court cases. However, the truth of fire investigation is that fire, in and of itself, is a vastly complex scientific phenomenon that incorporates heat transfer, fluid dynamics, chemistry and material sciences. It cannot be understood without understanding the scientific principles behind fire. Modern fire investigators should be up to date with scientific training in order to walk onto a fire scene and begin to understand the scenario behind its ignition and propagation. Anyone can see a ‘V’ on a wall, but it takes science to explain how it got there. The scientific aspects of fire investigation, including material addressed in NFPA 921 driven courses, are now more heavily weighted. As such, it is important when hiring a fire investigator, to make sure that they are current with the science of fire -  make sure they aren’t relying on the “art” of fire investigation. Dig deeper! Work with your investigator to understand the science of what they are seeing. Fire investigation must be based on facts, and facts must be proven with science.

Authored by Ryan Hazlett, EIT


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