HESI PN Exit Exam NGN | 2026–2027 |
Actual Exam Screenshot- Based
Questions with Verified Correct Answers |
GRADED A+
1. A rapid oxidation process resulting in the evolution of light and heat is the
definition of which term?
A. Energy
B. Explosion
C. Fire
D. Flame
Correct Answer: C
Rationale: Fire is scientifically defined as a rapid, self-sustaining oxidation process that
releases heat and light. An explosion is a rapid oxidation event specifically characterized
by a pressure wave. Energy is the capacity to do work, and a flame is the visible gaseous
component of the fire.
2. What are the four components of the fire tetrahedron?
A. Fuel, Oxygen, Heat, Chemical Chain Reaction
B. Fuel, Oxygen, Carbon Dioxide, Ignition Source
C. Heat, Light, Smoke, Flame
D. Combustible Material, Air, Spark, Flame
Correct Answer: A
Rationale: The fire tetrahedron represents the four essential elements required for
combustion: fuel, oxygen, heat, and the chemical chain reaction. The older fire triangle
excluded the chain reaction.
3. The chemical and physical changes that occur in gypsum wallboard surfaces
during a fire is called:
A. Spalling
B. Calcination
,C. Crazing
D. Pyrolysis
Correct Answer: B
Rationale: Calcination refers to the chemical and physical changes that occur in gypsum
wallboard surfaces during a fire. This is an important fire effect that investigators
examine to determine heat exposure.
4. What is pyrolysis?
A. Rapid flame spread
B. Decomposition of material by heat
C. Ignition temperature
D. Fire suppression
Correct Answer: B
Rationale: Pyrolysis is the thermal decomposition of materials before ignition, occurring
when materials are heated to the point where they begin to break down chemically,
releasing combustible gases.
5. A liquid with a flash point ABOVE 100°F is classified as:
A. Flammable liquid
B. Combustible liquid
C. Ignitable liquid
D. Volatile liquid
Correct Answer: B
Rationale: Combustible liquids have a flash point above 100°F. Flammable liquids have
flash points below 100°F. This distinction is critical for fire investigators to understand
the fire hazard and ignition potential of liquids found at scenes.
6. What is the term for the ability of matter to perform work by moving objects or
transforming heat?
A. Power
B. Energy
C. Current
D. Force
Correct Answer: B
Rationale: Energy is defined as the capacity to do work. Power is the rate at which work
,is done, current is the flow of electrical charge, and force is an interaction that causes a
change in motion.
7. What is the term for the propagation of a combustion zone at a velocity less
than the speed of sound?
A. Detonation
B. Conflagration
C. Deflagration
D. Smoldering
Correct Answer: C
Rationale: Deflagration is a subsonic combustion wave, the typical type of combustion
seen in ordinary fires. Detonation is supersonic. Conflagration is a large destructive fire,
and smoldering is slow, flameless combustion.
8. What is the acronym for a Boiling Liquid Expanding Vapor Explosion?
A. BLEVE
B. BLIVE
C. BELEV
D. BLEV
Correct Answer: A
Rationale: BLEVE is the widely recognized acronym for Boiling Liquid Expanding Vapor
Explosion, a specific type of explosion that occurs when a vessel containing a
pressurized liquid above its boiling point ruptures.
9. A distinct fire effect on noncombustible surfaces after burning off combustible
layers is called a:
A. Heat Shadow
B. Clean Burn
C. Spalling
D. Calcination
Correct Answer: B
Rationale: A "clean burn" is a specific fire pattern that occurs when intense radiated
heat or direct flame contacts a surface during the fire, burning away deposits. This
pattern is crucial for determining fire intensity and duration.
, 10. The minimum temperature needed to heat a fuel so as to ignite and begin self-
sustained combustion is called:
A. Flash point
B. Ignition temperature
C. Auto-ignition temperature
D. Piloted ignition temperature
Correct Answer: B
Rationale: Ignition temperature is the minimum temperature needed to heat a fuel to
ignite and begin self-sustained combustion.
11. A deflagration resulting from the sudden introduction of air into a confined
space containing oxygen-deficient products of incomplete combustion is called:
A. Flashover
B. Backdraft
C. BLEVE
D. Smoke explosion
Correct Answer: B
Rationale: A backdraft occurs when sudden introduction of air into a confined space
containing oxygen-deficient products of incomplete combustion causes a deflagration.
12. At approximately what temperature in the upper gas layer does the onset of
flashover occur?
A. 800°F
B. 1100°F
C. 1400°F
D. 1800°F
Correct Answer: B
Rationale: The onset of flashover occurs when the upper gas layer temperature reaches
approximately 1100°F.
13. What is the heat flux measurement that indicates the onset of flashover?
A. 1 W/cm²
B. 2 W/cm²
C. 3 W/cm²
D. 4 W/cm²
Actual Exam Screenshot- Based
Questions with Verified Correct Answers |
GRADED A+
1. A rapid oxidation process resulting in the evolution of light and heat is the
definition of which term?
A. Energy
B. Explosion
C. Fire
D. Flame
Correct Answer: C
Rationale: Fire is scientifically defined as a rapid, self-sustaining oxidation process that
releases heat and light. An explosion is a rapid oxidation event specifically characterized
by a pressure wave. Energy is the capacity to do work, and a flame is the visible gaseous
component of the fire.
2. What are the four components of the fire tetrahedron?
A. Fuel, Oxygen, Heat, Chemical Chain Reaction
B. Fuel, Oxygen, Carbon Dioxide, Ignition Source
C. Heat, Light, Smoke, Flame
D. Combustible Material, Air, Spark, Flame
Correct Answer: A
Rationale: The fire tetrahedron represents the four essential elements required for
combustion: fuel, oxygen, heat, and the chemical chain reaction. The older fire triangle
excluded the chain reaction.
3. The chemical and physical changes that occur in gypsum wallboard surfaces
during a fire is called:
A. Spalling
B. Calcination
,C. Crazing
D. Pyrolysis
Correct Answer: B
Rationale: Calcination refers to the chemical and physical changes that occur in gypsum
wallboard surfaces during a fire. This is an important fire effect that investigators
examine to determine heat exposure.
4. What is pyrolysis?
A. Rapid flame spread
B. Decomposition of material by heat
C. Ignition temperature
D. Fire suppression
Correct Answer: B
Rationale: Pyrolysis is the thermal decomposition of materials before ignition, occurring
when materials are heated to the point where they begin to break down chemically,
releasing combustible gases.
5. A liquid with a flash point ABOVE 100°F is classified as:
A. Flammable liquid
B. Combustible liquid
C. Ignitable liquid
D. Volatile liquid
Correct Answer: B
Rationale: Combustible liquids have a flash point above 100°F. Flammable liquids have
flash points below 100°F. This distinction is critical for fire investigators to understand
the fire hazard and ignition potential of liquids found at scenes.
6. What is the term for the ability of matter to perform work by moving objects or
transforming heat?
A. Power
B. Energy
C. Current
D. Force
Correct Answer: B
Rationale: Energy is defined as the capacity to do work. Power is the rate at which work
,is done, current is the flow of electrical charge, and force is an interaction that causes a
change in motion.
7. What is the term for the propagation of a combustion zone at a velocity less
than the speed of sound?
A. Detonation
B. Conflagration
C. Deflagration
D. Smoldering
Correct Answer: C
Rationale: Deflagration is a subsonic combustion wave, the typical type of combustion
seen in ordinary fires. Detonation is supersonic. Conflagration is a large destructive fire,
and smoldering is slow, flameless combustion.
8. What is the acronym for a Boiling Liquid Expanding Vapor Explosion?
A. BLEVE
B. BLIVE
C. BELEV
D. BLEV
Correct Answer: A
Rationale: BLEVE is the widely recognized acronym for Boiling Liquid Expanding Vapor
Explosion, a specific type of explosion that occurs when a vessel containing a
pressurized liquid above its boiling point ruptures.
9. A distinct fire effect on noncombustible surfaces after burning off combustible
layers is called a:
A. Heat Shadow
B. Clean Burn
C. Spalling
D. Calcination
Correct Answer: B
Rationale: A "clean burn" is a specific fire pattern that occurs when intense radiated
heat or direct flame contacts a surface during the fire, burning away deposits. This
pattern is crucial for determining fire intensity and duration.
, 10. The minimum temperature needed to heat a fuel so as to ignite and begin self-
sustained combustion is called:
A. Flash point
B. Ignition temperature
C. Auto-ignition temperature
D. Piloted ignition temperature
Correct Answer: B
Rationale: Ignition temperature is the minimum temperature needed to heat a fuel to
ignite and begin self-sustained combustion.
11. A deflagration resulting from the sudden introduction of air into a confined
space containing oxygen-deficient products of incomplete combustion is called:
A. Flashover
B. Backdraft
C. BLEVE
D. Smoke explosion
Correct Answer: B
Rationale: A backdraft occurs when sudden introduction of air into a confined space
containing oxygen-deficient products of incomplete combustion causes a deflagration.
12. At approximately what temperature in the upper gas layer does the onset of
flashover occur?
A. 800°F
B. 1100°F
C. 1400°F
D. 1800°F
Correct Answer: B
Rationale: The onset of flashover occurs when the upper gas layer temperature reaches
approximately 1100°F.
13. What is the heat flux measurement that indicates the onset of flashover?
A. 1 W/cm²
B. 2 W/cm²
C. 3 W/cm²
D. 4 W/cm²
