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