Chapter 19 Cause Determination Flashcards
The process of identifying the first fuel ignited, the ignition source, the oxidizing agent, and the circumstances that resulted in the fire.
Fire cause determination.
Fire cause determination generally follows
origin determination.
The determination of the cause of a fire requires
the identification of those factors that were necessary for the fire to have occurred.
The factors that were necessary for the fire to have occurred include
the first fuel ignited
the circumstances, such as failures or human actions, that allowed the factors to come together and start the fire.
The function of the investigator is to
identify those factors that contribute to the fire.
The first fuel ignited is that
which first sustains combustion beyond the ignition source.
The ignition source will be where?
at or near the point of origin at the time of ignition, although in some circumstances, such as the ignitioin of flammable vapors, the two may not appear to coincide.
Generally, the oxidant is
the oxygen in the earth’s atmosphere.
Fire results from the combination of
Fuel
an oxidant
and an ignition source.
The overall methodology for determining the cause of the fire is the
scientific method
The scientific method includes
Recognize the need
defining the problem to be solved
collecting data
analyzing the data
developing a hypothesis
testing the hypothesis
Select Final hypothesis
How many steps are in the scientific method as per NFPA 921?
7
Data should be collected to identify
all potential fuels, ignition sources, and oxidants withing the are or areas of origin.
Identifying the initial fuel is necessary for evaluating the
compentency of potential ignition sources.
The investigator should identify easily ignited items that, once ignited,
could provide the heat source to damage or involve harder to ignite items.
Information should be sought from persons having knowledge (such as occupants) about recent activities in the area of origin and
what fuel items should or should not have been present.
The investigator should develop data that can be used to
analyze the events that brought the fuel and ignition source together.
(ignition sequence)
The fuel must be capable of being ignited by the hypothesized ignition source. The ignition temerpature of the fuel
should be understood.
Ignitioin Source Analysis
the investigator should evaluate all potential ignition sources in the are of origin to determine if they are competent.
A competent ignition source will
have sufficient energy and be capable of transferring that energy to the fuel long enough to raise the fuel to its ignition temperature.
There are times when there is no physical evidence of the ignition source found at the origin, but where an ignition sequence can logically be inferred using other data. This inference may be arrived at
through the testing of alternate hypotheses involving potential ignition sequences, provided that the conclusion regarding the remaining ignition sequence is consistent with all known facts.
Testing of the hypothesis is done by
the principle of deductive reasoning, in which the investigator compares the hypothesis to all known facts as well as the body of knowledge.
Hypotheses Testing Questions
- Is the hypothesized ignition source a compentent ignition source for the first fuel ignited?
- Is the required time for ignition consistent with the time line associated with the cause hypothesis and facts of the incident?
What were the circumstances that brought the ignition source in contact with the first fuel ignited
- What, if any, were the failure modes required for ignition to occur?
The ______ is an intergral part of the scientific method.
Process of elimination.
It is improper to opine a specific fire cause, ignition source, fuel or cause classication that
has no evidence to support it even though all other such hypothesized elements were eliminated.
The cause of a fire is defined as
“the circumstances, conditions, or agencies that bring together a fuel, ignition source, and oxidizer resulting in a fire or a combustion explosion.
The identification of an ignition source and a first fuel is not sufficient to determine?
A cause.
you must consider the relationship between the competency of the ignition source and the first fuel ignited.
If the level of certainty of the opinion is only “possible” or “suspected,” the
fire cause is unresolved and should be classified as “undetermined.”
