3 Common Myths About Arc Mapping Forensics

Ellen Eames
May 10, 2023

When an electrical fault or short causes a fire to break out, forensic experts work to locate the source of the fault by employing different investigative techniques. Arc mapping has been in use since the turn of the twenty-first century and is now one of the principal methods used by fire investigators. However, there are some common misconceptions about arc mapping forensics that we at Dreiym Engineering aim to debunk.

Myth #1: Arc Beads Denote Fire Origin

When forensic fire experts perform arc mapping on the scene of a fire, they often find clusters of arc beads in some locations, and none in others. This leads some investigators to believe that if there’s an abundance of arc beads in a given locale, that the fire must have started there.

However, arc beads are not a reliable way of determining the location of a fire’s origin. They can occur at multiple points throughout the fire scene, especially in areas that were severely damaged.

Myth #2: Arc Direction Points Toward the Power Source

When you enlist forensic fire investigation services, the investigator will look at the circuit in question and determine how many arcs are present. If multiple arcs point toward a particular power source, a biased investigator may assume that the fire started there and unofficially end the investigation.

But when dealing with a fire scene with multiple arcs, their direction or location doesn’t automatically point to the source. Multiple arcs can also be found in areas with high ventilation or a heavy concentration of fuel.

Myth #3: Arcs Inside Appliances Indicate Fire Origin

If an electrical appliance was the main location of a fire, investigators may use arc mapping in and around said appliance. Some believe that if arcs are found deep inside the appliance, then the fire must have started there.

Arc mapping, while a popular method of fire investigation, is better at identifying general patterns than pinpointing a specific source or location.

Forensic fire investigators use arc mapping as one of their four main methods of determining the origin of an electrical fire. However, the National Fire Protection Association (NFPA) advises that investigators move away from relying on it, as arc mapping is not specific enough to locate a fire’s ultimate source. These common myths about arc mapping forensics are even believed by some investigators in the industry, but knowing the truth can help you narrow down the evidence to find the source of your fire.

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