Arc mapping

Arc mapping is a technique used in fire investigation and is usually performed by a forensic electrical engineer. It relies on finding the locations of electrical arcs and other electrical faults that occurred during the fire; the locations of the electrical faults can then, under some circumstances, indicate the progression of the fire over time. The basis of the technique is the assumption that, when fire (or hot gases created by the fire) impinges on an electrical line (whether or not protected by a conduit), it will melt the wire insulation and cause an electrical fault at the first point that it reaches on the electrical line. For this to occur, the electrical line must be energized at the time that fire hits it.

The ultimate goal of arc mapping is often to determine the point of origin of the fire. A common assumption used in reaching this goal is that the fire expands uniformly in all directions as it burns, and maintains a circular shape centered on the point of origin; therefore, when an electrical fault occurs on an electrical line, the point of origin is on a perpendicular to that point. Care must be taken with this assumption, however, because in many cases, fire does not extend uniformly; in particular, large local fuel loads, venting, and air currents have a strong effect on fire progression.