NFI Exam Review || QUESTIONS & ANSWERS RATED
100% CORRECT!!
Combustion Requirements (3) correct answers Air, Fuel, Heat
Complete Combustion Produces (4) correct answers Water vapor, carbon dioxide, heat, and
non combustible ashes
incomplete combustion produces (3) correct answers carbon monoxide, hydrocarbons, and
other gases
rate at which fuel burns is controlled by correct answers the amount of available air
air to fuel ratio is a correct answers critical factor in obtaining optimum fuel combustion
BTU correct answers British Thermal Unit, The amount of energy needed to heat one pound
of water one degree Fahrenheit
wood ignites at correct answers 450-550 F
natural gas ignites at correct answers 1,150 F
propane ignites at correct answers 920-1120 F
electric spark temp correct answers 1,700 F
hot surface igniter temp correct answers 2,400 F
butane lighter temp correct answers 3,200 F
stick match temp correct answers 3,000 F
cigarette temp correct answers 500-800 F
For complete combustion: air is ______ % oxygen + _____ % nitrogen correct answers 20 :
80
for complete combustion, __(QTY)__ molecules of __(PART)___ need to be mixed with
___(QTY)__ molecule of _____(PART)____ in the presence of __(PART)__ correct answers
2 oxygen : 1 fuel : heat
When complete combustion happens __(4 things)___ are released correct answers heat,
carbon dioxide (C02), water vapor (H20), and nitrogen (N)
Carbon monoxide is dangerous because (other than senseless) correct answers it mixes with
blood and reduces oxygen carrying capacity
Aldehydes correct answers chemical compounds that have a strong pungent odor
,Carbon monoxide is ________ when aldehydes are present correct answers present
Aldehydes result from correct answers flame impingement and through the presence of
contaminated air
Efficiency formula correct answers Heat output divided by heat input (percentage of heat
transferred to room)
3 Ts of efficiency correct answers Temperature, turbulence, time
Temperature (efficiency) correct answers minimum ignition temp
Turbulence (efficiency) correct answers fuel must collide with oxygen molecules (refers to
the degree of fuel and air mixing that occurs in combustion zone)
Time (efficiency) correct answers amount of time fuel gases remain in the high temp zone.
also known as "residence time"
Heat Transfer Efficiency correct answers refers to the percentage of heat generated by
combustion actually transferred to room
High heat transfer efficiency is normally associated with: (5 things) correct answers
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 correct answers radiating and circulating
Radiant design correct answers transmits heat energy from firebox opening by direct
radiation to the space in front of it. (do not have grills or louvers on the face, heat moving
blowers not avail.)
circulating design correct answers adds function of heat transfer via heated air convection by
circulating air around the fire chamber and releasing into space to be heated through grills
and louvers
Built-in, high efficiency fireplaces correct answers contain efficient combustion and
convection champers that are enclosed in an insulated metal cabinet. Can be enclosed in close
proximity to combustibles
Fireplace inserts and hearth stoves are correct answers designed to improve the efficiency of
an open fireplace and retain the general appearance of the fireplace while improving its
efficiency
, Hearth appliance construction correct answers modern solid fuel appliance designed to
introduce combustion air through specific and controllable air inlets and are controlled by the
user
Most controlled combustion devices are made of (metals) correct answers cast iron or steel
Cast Iron (fireplace) correct answers made from molds, can be decorative
Steel (fireplace) correct answers welded joints that need no service, some use steel fireboxes
inside decorative cast iron
Soapstone (fireplace) correct answers lower thermal conductivity, delivers heat slowly but
retain and delivers heat longer
Conduction correct answers direct transmission of heat from one surface of solid material to
another surface of solid material
Convection correct answers transfer of heat through a gas or liquid, including air, the transfer
of heated air between areas of unequal density. Natural occurs between heavier, cooler air
and lighter, warmer air
Forced convection occurs correct answers By mechanical means, aka electric blower
Radiation correct answers emission of waves of infrared energy, converted to heat on contact
with solid surfaces
Radiant appliances correct answers single wall, exterior wall is firebox wall. Generally
required for large open spaces than small numerous rooms
Convection appliances (3 things) correct answers double wall construction, allows room air
to circulate, convection currents, blower increases the amount and distance of heated air
circulation
lower surface temperatures of outer wall exposed
less spacious area, may make immediate space too warm/stuffy
Combination appliances correct answers cabinet delivers heated air gradually by convection
currents while exposed surfaces transmit radiant energy waves
Product Standards System (2 things) correct answers specifications that a product manual
must follow and have verified by independent testing
tested appliance, venting performance, safety to strength of materials used
Standards for Hearth Industry Products (organization) correct answers Underwriters
Laboratories Inc (UL) recognized as leader in safety standards
100% CORRECT!!
Combustion Requirements (3) correct answers Air, Fuel, Heat
Complete Combustion Produces (4) correct answers Water vapor, carbon dioxide, heat, and
non combustible ashes
incomplete combustion produces (3) correct answers carbon monoxide, hydrocarbons, and
other gases
rate at which fuel burns is controlled by correct answers the amount of available air
air to fuel ratio is a correct answers critical factor in obtaining optimum fuel combustion
BTU correct answers British Thermal Unit, The amount of energy needed to heat one pound
of water one degree Fahrenheit
wood ignites at correct answers 450-550 F
natural gas ignites at correct answers 1,150 F
propane ignites at correct answers 920-1120 F
electric spark temp correct answers 1,700 F
hot surface igniter temp correct answers 2,400 F
butane lighter temp correct answers 3,200 F
stick match temp correct answers 3,000 F
cigarette temp correct answers 500-800 F
For complete combustion: air is ______ % oxygen + _____ % nitrogen correct answers 20 :
80
for complete combustion, __(QTY)__ molecules of __(PART)___ need to be mixed with
___(QTY)__ molecule of _____(PART)____ in the presence of __(PART)__ correct answers
2 oxygen : 1 fuel : heat
When complete combustion happens __(4 things)___ are released correct answers heat,
carbon dioxide (C02), water vapor (H20), and nitrogen (N)
Carbon monoxide is dangerous because (other than senseless) correct answers it mixes with
blood and reduces oxygen carrying capacity
Aldehydes correct answers chemical compounds that have a strong pungent odor
,Carbon monoxide is ________ when aldehydes are present correct answers present
Aldehydes result from correct answers flame impingement and through the presence of
contaminated air
Efficiency formula correct answers Heat output divided by heat input (percentage of heat
transferred to room)
3 Ts of efficiency correct answers Temperature, turbulence, time
Temperature (efficiency) correct answers minimum ignition temp
Turbulence (efficiency) correct answers fuel must collide with oxygen molecules (refers to
the degree of fuel and air mixing that occurs in combustion zone)
Time (efficiency) correct answers amount of time fuel gases remain in the high temp zone.
also known as "residence time"
Heat Transfer Efficiency correct answers refers to the percentage of heat generated by
combustion actually transferred to room
High heat transfer efficiency is normally associated with: (5 things) correct answers
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 correct answers radiating and circulating
Radiant design correct answers transmits heat energy from firebox opening by direct
radiation to the space in front of it. (do not have grills or louvers on the face, heat moving
blowers not avail.)
circulating design correct answers adds function of heat transfer via heated air convection by
circulating air around the fire chamber and releasing into space to be heated through grills
and louvers
Built-in, high efficiency fireplaces correct answers contain efficient combustion and
convection champers that are enclosed in an insulated metal cabinet. Can be enclosed in close
proximity to combustibles
Fireplace inserts and hearth stoves are correct answers designed to improve the efficiency of
an open fireplace and retain the general appearance of the fireplace while improving its
efficiency
, Hearth appliance construction correct answers modern solid fuel appliance designed to
introduce combustion air through specific and controllable air inlets and are controlled by the
user
Most controlled combustion devices are made of (metals) correct answers cast iron or steel
Cast Iron (fireplace) correct answers made from molds, can be decorative
Steel (fireplace) correct answers welded joints that need no service, some use steel fireboxes
inside decorative cast iron
Soapstone (fireplace) correct answers lower thermal conductivity, delivers heat slowly but
retain and delivers heat longer
Conduction correct answers direct transmission of heat from one surface of solid material to
another surface of solid material
Convection correct answers transfer of heat through a gas or liquid, including air, the transfer
of heated air between areas of unequal density. Natural occurs between heavier, cooler air
and lighter, warmer air
Forced convection occurs correct answers By mechanical means, aka electric blower
Radiation correct answers emission of waves of infrared energy, converted to heat on contact
with solid surfaces
Radiant appliances correct answers single wall, exterior wall is firebox wall. Generally
required for large open spaces than small numerous rooms
Convection appliances (3 things) correct answers double wall construction, allows room air
to circulate, convection currents, blower increases the amount and distance of heated air
circulation
lower surface temperatures of outer wall exposed
less spacious area, may make immediate space too warm/stuffy
Combination appliances correct answers cabinet delivers heated air gradually by convection
currents while exposed surfaces transmit radiant energy waves
Product Standards System (2 things) correct answers specifications that a product manual
must follow and have verified by independent testing
tested appliance, venting performance, safety to strength of materials used
Standards for Hearth Industry Products (organization) correct answers Underwriters
Laboratories Inc (UL) recognized as leader in safety standards
