19.5 Developing a Cause Hypothesis. The investigator should
use the scientific method (see the Basic Methodology chapter) as the
method for data gathering, hypothesis development, and hypothesis
testing regarding the consideration of potential ignition
sequences. This process of consideration actually involves the development
and testing of alternate hypotheses. In this case, a
separate hypothesis is developed considering each individual
competent ignition source at the origin as a potential ignition
source. Systematic evaluation (hypothesis testing) is then conducted
with the elimination of those hypotheses that are not supportable
(or refuted) by the facts discovered through further examination.
The investigator is cautioned not to eliminate a
potential ignition source merely because there is no obvious evidence
for it. For example, the investigator should not eliminate
the electric heater because there is no arcing in the wires or because
the contacts are not stuck. There may be other methods by
which the heater could have been the ignition source other than
a system failure, such as combustible materials being stored too
close to it. Potential ignition sources should be eliminated from
consideration only if there is reliable evidence that they could
not be the ignition source for the fire. For example, an electric
heater can easily be eliminated from consideration if it was not
energized.

Pat Kennedy, CFEI, CFPS, MIFireE
Fire and Explosion Analyst
Sarasota, Florida
[www.kennedy-fire.com]