NFPA 921 FIRE AND EXPLOSION
INVESTIGATIONS (ACTUAL 2025) | Q&A LATEST
/2026 | 100% PASS
Absolute Temperature
A temperature measured in Kelvins (K) or Rankines (R).
Accelerant
A fuel or oxidizer, often an ignitible liquid, intentionally used
to initiate a fire or increase the rate of growth or spread of fire.
Conduction
Heat transfer to another body or within a body by direct
contact.
Convection
Heat transfer by circulation within a medium such as a gas or
a liquid.
,Creep
The tendency of a material to move or deform permanently to
relieve stresses.
Current
A flow of electric charge.
Deductive Reasoning
The process by which conclusions are drawn by logical
inference from given premises.
Deflagration
Propagation of a combustion zone at a velocity that is less
than the speed of sound in the unreacted medium.
Density
The mass of a substance per unit volume, usually specified at
standard temperature and pressure. The density of water is
approximately one gram per cubic centimeter. The density of
air is approximately 1.275 grams per cubic meter.
,Detection
1) Sensing the existence of a fire, especially by a detector
from one or more products of the fire, such as smoke, heat,
infrared radiation, and the like. (2) The act or process of
discovering and locating a fire.
Detonation
Propagation of a combustion zone at a velocity greater than
the speed of sound in the unreacted medium.
Ceiling Layer
A buoyant layer of hot gases and smoke produced by a fire in
a compartment.
Diffuse Fuel
A gas, vapor, dust, particulate, aerosol, mist, fog, or hybrid
mixture of these, suspended in the atmosphere, which is
capable of being ignited and propagating a flame front.
, Diffusion Flame
A flame in which fuel and air mix or diffuse together at the
region of combustion.
Drop Down or "fall down."
The spread of fire by the dropping or falling of burning
materials.
Effective Fire Temperatures
Temperatures reached in fires that produce physical effects
that can be related to specific temperature ranges.
Spark
A small, incandescent particle created by some arcs.
Empirical Data.
Factual data that is based on actual measurement, observation
or direct sensory experience rather than on theory.
INVESTIGATIONS (ACTUAL 2025) | Q&A LATEST
/2026 | 100% PASS
Absolute Temperature
A temperature measured in Kelvins (K) or Rankines (R).
Accelerant
A fuel or oxidizer, often an ignitible liquid, intentionally used
to initiate a fire or increase the rate of growth or spread of fire.
Conduction
Heat transfer to another body or within a body by direct
contact.
Convection
Heat transfer by circulation within a medium such as a gas or
a liquid.
,Creep
The tendency of a material to move or deform permanently to
relieve stresses.
Current
A flow of electric charge.
Deductive Reasoning
The process by which conclusions are drawn by logical
inference from given premises.
Deflagration
Propagation of a combustion zone at a velocity that is less
than the speed of sound in the unreacted medium.
Density
The mass of a substance per unit volume, usually specified at
standard temperature and pressure. The density of water is
approximately one gram per cubic centimeter. The density of
air is approximately 1.275 grams per cubic meter.
,Detection
1) Sensing the existence of a fire, especially by a detector
from one or more products of the fire, such as smoke, heat,
infrared radiation, and the like. (2) The act or process of
discovering and locating a fire.
Detonation
Propagation of a combustion zone at a velocity greater than
the speed of sound in the unreacted medium.
Ceiling Layer
A buoyant layer of hot gases and smoke produced by a fire in
a compartment.
Diffuse Fuel
A gas, vapor, dust, particulate, aerosol, mist, fog, or hybrid
mixture of these, suspended in the atmosphere, which is
capable of being ignited and propagating a flame front.
, Diffusion Flame
A flame in which fuel and air mix or diffuse together at the
region of combustion.
Drop Down or "fall down."
The spread of fire by the dropping or falling of burning
materials.
Effective Fire Temperatures
Temperatures reached in fires that produce physical effects
that can be related to specific temperature ranges.
Spark
A small, incandescent particle created by some arcs.
Empirical Data.
Factual data that is based on actual measurement, observation
or direct sensory experience rather than on theory.
