NFI EXAM REVIEW 2025 QUESTIONS
AND ANSWERS
Combustion Requirements (3) - ANS Air, Fuel, Heat
Complete Combustion Produces (4) - ANS Water vapor, carbon dioxide, heat, and non
combustible ashes
incomplete combustion produces (3) - ANS carbon monoxide, hydrocarbons, and other gases
rate at which fuel burns is controlled by - ANS the amount of available air
air to fuel ratio is a - ANS critical factor in obtaining optimum fuel combustion
BTU - ANS British Thermal Unit, The amount of energy needed to heat one pound of water
one degree Fahrenheit
wood ignites at - ANS 450-550 F
natural gas ignites at - ANS 1,150 F
propane ignites at - ANS 920-1120 F
electric spark temp - ANS 1,700 F
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,hot surface igniter temp - ANS 2,400 F
butane lighter temp - ANS 3,200 F
stick match temp - ANS 3,000 F
cigarette temp - ANS 500-800 F
For complete combustion: air is ______ % oxygen + _____ % nitrogen - ANS 20 : 80
for complete combustion, __(QTY)__ molecules of __(PART)___ need to be mixed with
___(QTY)__ molecule of _____(PART)____ in the presence of __(PART)__ - ANS 2 oxygen : 1
fuel : heat
When complete combustion happens __(4 things)___ are released - ANS heat, carbon
dioxide (C02), water vapor (H20), and nitrogen (N)
Carbon monoxide is dangerous because (other than senseless) - ANS it mixes with blood and
reduces oxygen carrying capacity
Aldehydes - ANS chemical compounds that have a strong pungent odor
Carbon monoxide is ________ when aldehydes are present - ANS present
Aldehydes result from - ANS flame impingement and through the presence of contaminated
air
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, Efficiency formula - ANS Heat output divided by heat input (percentage of heat transferred
to room)
3 Ts of efficiency - ANS Temperature, turbulence, time
Temperature (efficiency) - ANS minimum ignition temp
Turbulence (efficiency) - ANS fuel must collide with oxygen molecules (refers to the degree
of fuel and air mixing that occurs in combustion zone)
Time (efficiency) - ANS amount of time fuel gases remain in the high temp zone. also known
as "residence time"
Heat Transfer Efficiency - ANS refers to the percentage of heat generated by combustion
actually transferred to room
High heat transfer efficiency is normally associated with: (5 things) - ANS Appliance having
proportionally large exterior surfaces with good heat radiating properties
Long residence time of the hot gases in the Appliance
Adequate turbulence inside the appliance to property transfer heat from the fire chamber to
appliance walls
Rapid heat transfer through the walls of the appliance
Adequate air movement (convection) outside
2 types of factory built fireplaces - ANS radiating and circulating
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AND ANSWERS
Combustion Requirements (3) - ANS Air, Fuel, Heat
Complete Combustion Produces (4) - ANS Water vapor, carbon dioxide, heat, and non
combustible ashes
incomplete combustion produces (3) - ANS carbon monoxide, hydrocarbons, and other gases
rate at which fuel burns is controlled by - ANS the amount of available air
air to fuel ratio is a - ANS critical factor in obtaining optimum fuel combustion
BTU - ANS British Thermal Unit, The amount of energy needed to heat one pound of water
one degree Fahrenheit
wood ignites at - ANS 450-550 F
natural gas ignites at - ANS 1,150 F
propane ignites at - ANS 920-1120 F
electric spark temp - ANS 1,700 F
COPYRIGHT © 2025 BRAINBARTER ALL RIGHTS RESERVED 1
,hot surface igniter temp - ANS 2,400 F
butane lighter temp - ANS 3,200 F
stick match temp - ANS 3,000 F
cigarette temp - ANS 500-800 F
For complete combustion: air is ______ % oxygen + _____ % nitrogen - ANS 20 : 80
for complete combustion, __(QTY)__ molecules of __(PART)___ need to be mixed with
___(QTY)__ molecule of _____(PART)____ in the presence of __(PART)__ - ANS 2 oxygen : 1
fuel : heat
When complete combustion happens __(4 things)___ are released - ANS heat, carbon
dioxide (C02), water vapor (H20), and nitrogen (N)
Carbon monoxide is dangerous because (other than senseless) - ANS it mixes with blood and
reduces oxygen carrying capacity
Aldehydes - ANS chemical compounds that have a strong pungent odor
Carbon monoxide is ________ when aldehydes are present - ANS present
Aldehydes result from - ANS flame impingement and through the presence of contaminated
air
COPYRIGHT © 2025 BRAINBARTER ALL RIGHTS RESERVED 2
, Efficiency formula - ANS Heat output divided by heat input (percentage of heat transferred
to room)
3 Ts of efficiency - ANS Temperature, turbulence, time
Temperature (efficiency) - ANS minimum ignition temp
Turbulence (efficiency) - ANS fuel must collide with oxygen molecules (refers to the degree
of fuel and air mixing that occurs in combustion zone)
Time (efficiency) - ANS amount of time fuel gases remain in the high temp zone. also known
as "residence time"
Heat Transfer Efficiency - ANS refers to the percentage of heat generated by combustion
actually transferred to room
High heat transfer efficiency is normally associated with: (5 things) - ANS Appliance having
proportionally large exterior surfaces with good heat radiating properties
Long residence time of the hot gases in the Appliance
Adequate turbulence inside the appliance to property transfer heat from the fire chamber to
appliance walls
Rapid heat transfer through the walls of the appliance
Adequate air movement (convection) outside
2 types of factory built fireplaces - ANS radiating and circulating
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