NFI Core Knowledge Exam 2026
Questions and Answers
AHJ stands for: - Correct answer-Authority Having Jurisdiction
ASTM stands for: - Correct answer-American Society for Testing and Materials
HUD stands for: - Correct answer-U.S. Department of Housing and Urban
Development
NFPA stands for: - Correct answer-National Fire Protection Association
IRC stands for: - Correct answer-International Residential Code
What are the three REQUIREMENTS of combustion? - Correct answer-Oxygen or
air, fuel and ignition or heat (Combustion Triangle)
What is the fourth necessary component of fire/combustion? - Correct answer-
Chemical Reactions (Fire Tetrahedron)
Fuel is ignited by _____________, not necessarily with spark or flame present. -
Correct answer-Heat
Wood ignites at what temperature? - Correct answer-450-550 degrees Fahrenheit
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,Natural gas ignites at what temperature? - Correct answer-1,150 degrees
Fahrenheit
Propane gas ignites at what temperature? - Correct answer-920-1,120 degrees
Fahrenheit
Hot surface ignitor ignites at what temperature? - Correct answer-2,400 degrees
Fahrenheit
Electric spark ignites at what temperature? - Correct answer-1,700 degrees
Fahrenheit
Air contains ____% of _____________ and _____% of _______________. -
Correct answer-20% of Oxygen and 80% of Nitrogen
What is the only product of combustion that does not combine with any other
elements and is unaffected by combustion? - Correct answer-Nitrogen
What are the four products of combustion? - Correct answer-Heat, Carbon
Dioxide, water vapor and Nitrogen
What causes incomplete combustion? - Correct answer-Inadequate air due to
blockage of air openings from poor maintenance, cooling from a poorly built fire
in a woodburning appliance or flames improperly contacting logs in a gas
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
, appliance (flame impingement), inadequate secondary air due to poor venting in a
gas appliance or inadequate draft in a woodburning appliance.
Carbon Monoxide is a gas that is ___________ and _______________. - Correct
answer-Toxic and combustible.
What are Aldehydes? - Correct answer-Chemical compounds that have a strong,
pungent odor, and are produced in incomplete or interrupted combustion.
When the odor of aldehydes is present, _________ ___________ is also present. -
Correct answer-Carbon Monoxide.
What are the four products of incomplete combustion? - Correct answer-Carbon
Monoxide, Hydrocarbons, water, and non-combustible ash.
What are the three T's affecting efficiency? - Correct answer-Temperature,
Turbulence and Time
High heat transfer efficiency is normal associated with these five things: - Correct
answer-The appliance having large exterior surfaces and good heat radiation, long
residence time, adequate turbulence, rapid heat transfer, and adequate air
movement.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
Questions and Answers
AHJ stands for: - Correct answer-Authority Having Jurisdiction
ASTM stands for: - Correct answer-American Society for Testing and Materials
HUD stands for: - Correct answer-U.S. Department of Housing and Urban
Development
NFPA stands for: - Correct answer-National Fire Protection Association
IRC stands for: - Correct answer-International Residential Code
What are the three REQUIREMENTS of combustion? - Correct answer-Oxygen or
air, fuel and ignition or heat (Combustion Triangle)
What is the fourth necessary component of fire/combustion? - Correct answer-
Chemical Reactions (Fire Tetrahedron)
Fuel is ignited by _____________, not necessarily with spark or flame present. -
Correct answer-Heat
Wood ignites at what temperature? - Correct answer-450-550 degrees Fahrenheit
©COPYRIGHT 2025, ALL RIGHTS RESERVED 1
,Natural gas ignites at what temperature? - Correct answer-1,150 degrees
Fahrenheit
Propane gas ignites at what temperature? - Correct answer-920-1,120 degrees
Fahrenheit
Hot surface ignitor ignites at what temperature? - Correct answer-2,400 degrees
Fahrenheit
Electric spark ignites at what temperature? - Correct answer-1,700 degrees
Fahrenheit
Air contains ____% of _____________ and _____% of _______________. -
Correct answer-20% of Oxygen and 80% of Nitrogen
What is the only product of combustion that does not combine with any other
elements and is unaffected by combustion? - Correct answer-Nitrogen
What are the four products of combustion? - Correct answer-Heat, Carbon
Dioxide, water vapor and Nitrogen
What causes incomplete combustion? - Correct answer-Inadequate air due to
blockage of air openings from poor maintenance, cooling from a poorly built fire
in a woodburning appliance or flames improperly contacting logs in a gas
©COPYRIGHT 2025, ALL RIGHTS RESERVED 2
, appliance (flame impingement), inadequate secondary air due to poor venting in a
gas appliance or inadequate draft in a woodburning appliance.
Carbon Monoxide is a gas that is ___________ and _______________. - Correct
answer-Toxic and combustible.
What are Aldehydes? - Correct answer-Chemical compounds that have a strong,
pungent odor, and are produced in incomplete or interrupted combustion.
When the odor of aldehydes is present, _________ ___________ is also present. -
Correct answer-Carbon Monoxide.
What are the four products of incomplete combustion? - Correct answer-Carbon
Monoxide, Hydrocarbons, water, and non-combustible ash.
What are the three T's affecting efficiency? - Correct answer-Temperature,
Turbulence and Time
High heat transfer efficiency is normal associated with these five things: - Correct
answer-The appliance having large exterior surfaces and good heat radiation, long
residence time, adequate turbulence, rapid heat transfer, and adequate air
movement.
©COPYRIGHT 2025, ALL RIGHTS RESERVED 3
