NFPA 921 EXAM SET 2025 QUESTIONS AND ANSWERS
RATED A+
✔✔3.3.116 Incendiary Fire - ✔✔A fire that is intentionally ignited in an area or under
circumstances where and when there should not be a fire.
✔✔3.3.117 Inductive Reasoning - ✔✔The process by which a person 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.
✔✔3.3.121 Isochar - ✔✔A line on a diagram connecting points of equal char depth.
✔✔3.3.142 Point of Origin - ✔✔The exact physical location within the area of origin
where a heat source and a fuel first interact, resulting in a fire or explosion.
✔✔3.3.148 Proximate Cause - ✔✔The cause that directly produces the effect without
the intervention of any other cause.
✔✔3.3.159 Scene - ✔✔The general physical location of a fire or explosion incident
(geographic area, structure or portion of a structure, vehicle, boat, piece of equipment,
etc.) designated as important to the investigation because it may contain physical
damage or debris, evidence, victims, or incident-related hazards.
✔✔3.3.160 Scientific Method - ✔✔The systematic pursuit of knowledge involving the
recognition and definition of a problem; the collection of data through observation and
experimentation; analysis of the data; the formulation, evaluation and testing of
hypotheses; and, where possible, the selection of a final hypothesis.
✔✔3.3.168 Site - ✔✔The general physical location of the incident, including the scene
and the surrounding area deemed significant to the process of the investigation and
support areas.
✔✔3.3.178 Spoliation - ✔✔Loss, destruction, or material alteration of an object or
document that is evidence or potential evidence in a legal proceeding by one who has
the responsibility for its preservation.
✔✔4.1* Nature of Fire Investigations - ✔✔With few exceptions, the proper methodology
for a fire or explosion investigation is to first determine and establish the origin(s), then
investigate the cause: circumstances, conditions, or agencies that brought the ignition
source, fuel, and oxidant together.
✔✔4.3.1 Recognize the Need - ✔✔First, one should determine that a problem exists. In
this case, a fire or explosion has occurred and the cause should be determined and
listed so that future, similar incidents can be prevented.
, ✔✔4.3.2 Define the Problem - ✔✔Having determined that a problem exists, the
investigator or analyst should define the manner in which the problem can be solved.
✔✔4.3.3 Collect Data - ✔✔Facts about the fire incident are now collected by
observation, experiment, or other direct datagathering 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.
✔✔4.3.4* Analyze the Data - ✔✔The scientific method requires that all data collected
be analyzed. This is an essential step that must take place before the formation of the
final hypothesis. The identification, gathering, and cataloging of data does not 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.
✔✔4.3.5* Develop a Hypothesis (Inductive Reasoning) - ✔✔Based on the data
analysis, the investigator produces a hypothesis, or hypotheses, to explain the
phenomena, whether it be the nature 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.
✔✔4.3.6* Test the Hypothesis (Deductive Reasoning) - ✔✔The investigator does not
have a valid or reliable conclusion unless the hypothesis can stand the test of careful
and serious challenge. 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 scientific knowledge associated with the phenomena relevant to the
specific incident. Testing of a hypothesis should be designed to disprove, or refute, the
hypothesis. This may also be referred to as falsification of the hypothesis. Working to
disprove a hypothesis is an attempt to find all the data or reasons why the hypothesis is
not supported or not true, rather than simply finding and relying on data that support the
hypothesis or why the hypothesis is true. This method of testing the hypothesis can
prevent "confirmation bias," which can occur when the hypothesis or conclusion relies
only on supporting data (see 4.3.10). 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
RATED A+
✔✔3.3.116 Incendiary Fire - ✔✔A fire that is intentionally ignited in an area or under
circumstances where and when there should not be a fire.
✔✔3.3.117 Inductive Reasoning - ✔✔The process by which a person 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.
✔✔3.3.121 Isochar - ✔✔A line on a diagram connecting points of equal char depth.
✔✔3.3.142 Point of Origin - ✔✔The exact physical location within the area of origin
where a heat source and a fuel first interact, resulting in a fire or explosion.
✔✔3.3.148 Proximate Cause - ✔✔The cause that directly produces the effect without
the intervention of any other cause.
✔✔3.3.159 Scene - ✔✔The general physical location of a fire or explosion incident
(geographic area, structure or portion of a structure, vehicle, boat, piece of equipment,
etc.) designated as important to the investigation because it may contain physical
damage or debris, evidence, victims, or incident-related hazards.
✔✔3.3.160 Scientific Method - ✔✔The systematic pursuit of knowledge involving the
recognition and definition of a problem; the collection of data through observation and
experimentation; analysis of the data; the formulation, evaluation and testing of
hypotheses; and, where possible, the selection of a final hypothesis.
✔✔3.3.168 Site - ✔✔The general physical location of the incident, including the scene
and the surrounding area deemed significant to the process of the investigation and
support areas.
✔✔3.3.178 Spoliation - ✔✔Loss, destruction, or material alteration of an object or
document that is evidence or potential evidence in a legal proceeding by one who has
the responsibility for its preservation.
✔✔4.1* Nature of Fire Investigations - ✔✔With few exceptions, the proper methodology
for a fire or explosion investigation is to first determine and establish the origin(s), then
investigate the cause: circumstances, conditions, or agencies that brought the ignition
source, fuel, and oxidant together.
✔✔4.3.1 Recognize the Need - ✔✔First, one should determine that a problem exists. In
this case, a fire or explosion has occurred and the cause should be determined and
listed so that future, similar incidents can be prevented.
, ✔✔4.3.2 Define the Problem - ✔✔Having determined that a problem exists, the
investigator or analyst should define the manner in which the problem can be solved.
✔✔4.3.3 Collect Data - ✔✔Facts about the fire incident are now collected by
observation, experiment, or other direct datagathering 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.
✔✔4.3.4* Analyze the Data - ✔✔The scientific method requires that all data collected
be analyzed. This is an essential step that must take place before the formation of the
final hypothesis. The identification, gathering, and cataloging of data does not 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.
✔✔4.3.5* Develop a Hypothesis (Inductive Reasoning) - ✔✔Based on the data
analysis, the investigator produces a hypothesis, or hypotheses, to explain the
phenomena, whether it be the nature 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.
✔✔4.3.6* Test the Hypothesis (Deductive Reasoning) - ✔✔The investigator does not
have a valid or reliable conclusion unless the hypothesis can stand the test of careful
and serious challenge. 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 scientific knowledge associated with the phenomena relevant to the
specific incident. Testing of a hypothesis should be designed to disprove, or refute, the
hypothesis. This may also be referred to as falsification of the hypothesis. Working to
disprove a hypothesis is an attempt to find all the data or reasons why the hypothesis is
not supported or not true, rather than simply finding and relying on data that support the
hypothesis or why the hypothesis is true. This method of testing the hypothesis can
prevent "confirmation bias," which can occur when the hypothesis or conclusion relies
only on supporting data (see 4.3.10). 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
