Chemical: chemical reaction; exothermic and endothermic.
Electrical: Converted to heat energy; flowing through a conductor.
Nuclear: splitting the nucleus of an atom into two smaller nuclei (nuclear fission)
Loose connections: high resistance with increased heating at the contact.
2. Fire Patterns
3. Arc Mapping
4. Fire Dynamics
Heat is transferred by convection to a solid when hot gases pass over cooler surfaces. The rate of heat transfer to the solid is a function of the temperature difference, the surface area exposed to the hot gas, and the velocity of the hot gas. The higher the velocity of the gas, the greater the rate of convective transfer.
starts from a particular experience and proceeds to generalizations. The process by which hypotheses are developed based upon observable or known facts and the training, experience,
knowledge, and expertise of the observer.
are drawn by logical inference from given premises. Testing of the hypothesis is done by the principle of deductive reasoning, in which the investigator compares the hypothesis to all the known facts as well as the body
of scientific knowledge associated with the phenomena relevant
to the specific incident.
breaking down an event into causal component parts. These
components are then placed in a logical sequence of events or
conditions necessary to produce the event. If the conditions or
sequence are not present then the hypothesis is disproved.
across a gap or through a medium such as charred insulation.
reaction resulting in the evolution of light and heat in varying intensities.
has sufficient energy and is capable of transferring that energy to the fuel long enough to raise the fuel to its ignition temperature.
to answer questions of interest to the legal system.
kinetics, fluid mechanics, fire safety) and their interaction
with people, structures, and the environment.
Define the problem
Analyze the Data
Develop a Hypothesis
Test the Hypothesis (if fail, go back to collect data)
Select the Hypothesis
similar incidents can be prevented.
which the problem can be solved. In this case, a proper origin and cause investigation should be conducted. This is done by an examination of the scene and by a combination of other data collection methods, such as the review of previously conducted
investigations of the incident, the interviewing of witnesses
or other knowledgeable persons, and the results of scientific testing.
means. The data collected is called empirical data because it is based on observation or experience and is capable
of being verified or known to be true.
equate to data analysis. Analysis of the data is based on the knowledge, training, experience, and expertise of the individual doing the analysis. If the investigator lacks expertise to properly attribute meaning to a piece of data, then assistance
should be sought. Understanding the meaning of the data will enable the investigator to form hypotheses based on the evidence, rather than on speculation.
of fire patterns, fire spread, identification of the origin,
the ignition sequence, the fire cause, or the causes of damage or responsibility for the fire or explosion incident. This process is referred to as inductive reasoning. These hypotheses should be based solely on the empirical data that the investigator has collected through observation and then developed into explanations for the event, which are based upon the
investigator’s knowledge, training, experience, and expertise.
Test the Hypothesis (Deductive Reasoning)
associated with the phenomena relevant to the specific incident. A hypothesis can be tested physically by conducting experiments,
analytically by applying accepted scientific principles,
or by referring to scientific research. When relying on
the research of others, the investigator or analyst must ensure that the conditions, circumstances, and variables of the research and those of the hypothesis are sufficiently similar.
Whenever the investigator relies on research as a means of hypothesis testing, references to the research relied upon should be acknowledged and cited. If the hypothesis is refuted or not supported, it should be discarded and alternate hypotheses should be developed and tested. This may require the collection of new data or the reanalysis of existing data. The testing process needs to be continued until all feasible hypotheses
have been tested and one is determined to be uniquely
consistent with the facts and with the principles of science. If no hypothesis can withstand an examination by deductive reasoning, the issue should be considered undetermined.
developed based on the absence of data is an example of a hypothesis that is incapable of being tested. The inability to refute a hypothesis does not mean that the hypothesis is true.
and examining all of the data in a logical and unbiased
manner to reach a scientifically reliable conclusion, the investigator(s) uses the premature determination to dictate investigative processes, analyses, and, ultimately, conclusions, in a
way that is not scientifically valid. The introduction of expectation bias into the investigation results in the use of only that data that supports this previously formed conclusion and often
results in the misinterpretation and/or the discarding of data that does not support the original opinion. Investigators are strongly cautioned to avoid expectation bias through
proper use of the scientific method.
(falsification of the hypothesis). Confirmation bias
occurs when the investigator instead tries to prove the hypothesis. This can result in failure to consider alternate hypotheses, or prematurely discounting seemingly contradictory data without an appropriate assessment. A hypothesis can be said to
be valid only when rigorous testing has failed to disprove the hypothesis.
assurance requirements. An administrative reviewer will determine whether all of the steps outlined in an organization’s procedure manual, or required by agency policy, have been followed and whether all of the appropriate documentation is present in the file, and may check for typographical or grammatical
proper fire investigation and should, at a minimum, have access to all of the documentation available to the investigator whose work is being reviewed. If a technical reviewer has been asked to critique only specific aspects of the investigator’s work product, then the technical reviewer should be qualified
and familiar with those specific aspects and, at a minimum, have access to all documentation relevant to those aspects. A technical review can serve as an additional test of the various
aspects of the investigator’s work product.
employed in prepublication review of scientific or technical
documents and screening of grant applications by
research-sponsoring agencies. Peer review carries with it connotations of both independence and objectivity. Peer reviewers should not have any interest in the outcome of the review.
The author does not select the reviewers, and reviews are often conducted anonymously. As such, the term “peer review”
should not be applied to reviews of an investigator’s work by coworkers, supervisors, or investigators from agencies conducting
investigations of the same incident. Such reviews are
more appropriately characterized as “technical reviews,” as described
conductivity (k), density (ρ), and heat capacity (c) — play a role. Multiplied together as a mathematical product, these properties are called the thermal inertia, kρc, of a material. The thermal inertia
of a material is a measure of how easily the surface temperature of the material will increase when heat flows into the material. Low-density materials like polyurethane foam have a low thermal inertia and the surface temperature will increase quickly upon exposure to a heat flux. Conversely, metals have a high thermal inertia due to their high thermal conductivity and high
density. As such, when exposed to a flame, the surface temperature
of a metal object increases relatively slowly compared to the surface temperature of a plastic or wood object. Table 188.8.131.52 provides data for some common materials at room temperature. Thermal properties are generally a function of temperature.