NFI Core Knowledge Exam Questions and Answers Latest Update 2025 Already Passed
AHJ stands for: - Answers Authority Having Jurisdiction
ASTM stands for: - Answers American Society for Testing and Materials
HUD stands for: - Answers U.S. Department of Housing and Urban Development
NFPA stands for: - Answers National Fire Protection Association
IRC stands for: - Answers International Residential Code
What are the three REQUIREMENTS of combustion? - Answers Oxygen or air, fuel and ignition or heat
(Combustion Triangle)
What is the fourth necessary component of fire/combustion? - Answers Chemical Reactions (Fire
Tetrahedron)
Fuel is ignited by _____________, not necessarily with spark or flame present. - Answers Heat
Wood ignites at what temperature? - Answers 450-550 degrees Fahrenheit
Natural gas ignites at what temperature? - Answers 1,150 degrees Fahrenheit
Propane gas ignites at what temperature? - Answers 920-1,120 degrees Fahrenheit
Hot surface ignitor ignites at what temperature? - Answers 2,400 degrees Fahrenheit
Electric spark ignites at what temperature? - Answers 1,700 degrees Fahrenheit
Air contains ____% of _____________ and _____% of _______________. - Answers 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? - Answers Nitrogen
What are the four products of combustion? - Answers Heat, Carbon Dioxide, water vapor and Nitrogen
What causes incomplete combustion? - Answers 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 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 _______________. - Answers Toxic and combustible.
What are Aldehydes? - Answers 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. - Answers Carbon
Monoxide.
What are the four products of incomplete combustion? - Answers Carbon Monoxide, Hydrocarbons,
water, and non-combustible ash.
What are the three T's affecting efficiency? - Answers Temperature, Turbulence and Time
High heat transfer efficiency is normal associated with these five things: - Answers The appliance having
large exterior surfaces and good heat radiation, long residence time, adequate turbulence, rapid heat
transfer, and adequate air movement.
Fireplaces and freestanding wood stoves will not perform properly if the venting is
___________________ or has too many __________________ or _____________________. - Answers
too short, bends, horizontal runs.
Heat transfer efficiency is increased by: - Answers Adequate turbulence inside the appliance.
100% heat transfer efficiency would create problems with: - Answers draft and water condensation.
Heat transfer efficiency has a direct influence on: - Answers Overall efficiency.
What are the four factors determining natural draft? - Answers Vent gas temperature, outdoor
temperature, ability of the vent to hold heat and height of the vent.
Natural Draft: - Answers The force of pressure difference created in a venting system by the
temperature difference between the gases in the venting system and the outdoor air.
Mechanical Draft: - Answers The force of the pressure difference created in a venting system by an
electrically powered fan.
Flow: - Answers The volume of gases that pass through a venting system because of draft.
Negative pressure: - Answers less than normal atmospheric pressure.
Positive pressure: - Answers greater than normal atmospheric pressure.
________ is the force that moves gases, the amount of ________ determines whether the venting
system performs successfully. - Answers Draft, flow.
Cross-sectional area: - Answers The size of the flue for the amount of gases that can move through the
system in a given time period.
Resistance to flow: - Answers Elbows, tees, offsets, horizontal runs, obstructions, wind and competing
sources of negative pressure.
AHJ stands for: - Answers Authority Having Jurisdiction
ASTM stands for: - Answers American Society for Testing and Materials
HUD stands for: - Answers U.S. Department of Housing and Urban Development
NFPA stands for: - Answers National Fire Protection Association
IRC stands for: - Answers International Residential Code
What are the three REQUIREMENTS of combustion? - Answers Oxygen or air, fuel and ignition or heat
(Combustion Triangle)
What is the fourth necessary component of fire/combustion? - Answers Chemical Reactions (Fire
Tetrahedron)
Fuel is ignited by _____________, not necessarily with spark or flame present. - Answers Heat
Wood ignites at what temperature? - Answers 450-550 degrees Fahrenheit
Natural gas ignites at what temperature? - Answers 1,150 degrees Fahrenheit
Propane gas ignites at what temperature? - Answers 920-1,120 degrees Fahrenheit
Hot surface ignitor ignites at what temperature? - Answers 2,400 degrees Fahrenheit
Electric spark ignites at what temperature? - Answers 1,700 degrees Fahrenheit
Air contains ____% of _____________ and _____% of _______________. - Answers 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? - Answers Nitrogen
What are the four products of combustion? - Answers Heat, Carbon Dioxide, water vapor and Nitrogen
What causes incomplete combustion? - Answers 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 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 _______________. - Answers Toxic and combustible.
What are Aldehydes? - Answers 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. - Answers Carbon
Monoxide.
What are the four products of incomplete combustion? - Answers Carbon Monoxide, Hydrocarbons,
water, and non-combustible ash.
What are the three T's affecting efficiency? - Answers Temperature, Turbulence and Time
High heat transfer efficiency is normal associated with these five things: - Answers The appliance having
large exterior surfaces and good heat radiation, long residence time, adequate turbulence, rapid heat
transfer, and adequate air movement.
Fireplaces and freestanding wood stoves will not perform properly if the venting is
___________________ or has too many __________________ or _____________________. - Answers
too short, bends, horizontal runs.
Heat transfer efficiency is increased by: - Answers Adequate turbulence inside the appliance.
100% heat transfer efficiency would create problems with: - Answers draft and water condensation.
Heat transfer efficiency has a direct influence on: - Answers Overall efficiency.
What are the four factors determining natural draft? - Answers Vent gas temperature, outdoor
temperature, ability of the vent to hold heat and height of the vent.
Natural Draft: - Answers The force of pressure difference created in a venting system by the
temperature difference between the gases in the venting system and the outdoor air.
Mechanical Draft: - Answers The force of the pressure difference created in a venting system by an
electrically powered fan.
Flow: - Answers The volume of gases that pass through a venting system because of draft.
Negative pressure: - Answers less than normal atmospheric pressure.
Positive pressure: - Answers greater than normal atmospheric pressure.
________ is the force that moves gases, the amount of ________ determines whether the venting
system performs successfully. - Answers Draft, flow.
Cross-sectional area: - Answers The size of the flue for the amount of gases that can move through the
system in a given time period.
Resistance to flow: - Answers Elbows, tees, offsets, horizontal runs, obstructions, wind and competing
sources of negative pressure.
