cert with high current, caused excessive
heating of the outer nut and severe arc
damage. This is not a result of soldering,
which supplies insufficient heat to cause
such damage to iron. Rather, it was most
likely a result of high current flow, characteristic of a lightning strike.
Figure 10 depicts a door frame in a basement area with a fire origin at the upper
part of the frame. Char depth is most severe
in this area (red arrow). Electrical wiring
above, at the door frame, shows evidence
of arcing, probably as a result of continuously chaffing against the door, causing insulation breakdown, electrical malfunction
and a fire. Char damage to wood members
tends to decrease as one moves away in any
direction from the location of the red arrow,
a good fire origin indicator.
Figure 11 shows a burn pattern on a
clothes dryer with an approximate origin
at the red arrow. The low burn and badly
oxidized sheet metal on the dryer suggest that a malfunction inside the dryer
caused a fire. There is relatively little damage around the dryer which supports the
opinion that the dryer caused the fire.
A fire originated on a plumbing stack
in a home after a lightning strike (Figure
12). There was evidence of burning in the
form of char on roof sheathing around
the plumbing vent only, with the absence
of any other burn patterns throughout
the home. There were no man-made electrical or mechanical ignition sources in
this area. Char depth is most severe right
next to the plumbing vent and decreases
away from the vent.
Figure 13 depicts a relatively small
burn pattern inside of a heating unit. The
fire origin (red arrow) was located at severely damaged electrical wire (green arrow) that was routed around a sharp metal corner where a wire had chaffed and
shorted. The blower had sucked burning debris and smoke into its intake and
spread it around the apartment, causing
significant smoke-related damage. Note
the forced air flow has affected the natural convective V pattern, which was distorted to the left as a result of the blower.
Thermal patterns on overheated boilers
tend to be uniform since the whole unit
tends to be overheated. In Figure 14, we
see a boiler that overheated, causing a fire
and severe damage to a building. A low
water cut off control was found to have
malfunctioned, causing the over heating.
The dark grey, high temperature oxide
is noted on the outer shell of the boiler,
which is consistent with overheating.
Figure 15 is a photo of a badly dam-
aged electronic processing machine
which shows uniform burn patterns
throughout the machine and duct work
(red arrows). This is indicative of ignition
of combustible vapors in the machine
and exhaust duck work. Burn patterns
of this nature are often not definitive as
to the origin of the fire, other than that a
combustible vapor was ignited inside the
1 “Burn Pattern Recognition for Fire
Origin Analysis,” appeared in Insurance
Adjuster Magazine (later Claims Magazine), July 1987. http://croberts.com/burn-
2“Thermal Pattern Analysis: Investigating
Fire’s Fingerprints,” Claims Magazine,
June 2000. http:/ croberts.com/burn.htm.