NFI Exam Review Questions with Detailed Verified Answers

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NFI Exam Review Questions with Detailed
Verified Answers

Question: Combustion Requirements (3)

Ans✅ ✅: Air, Fuel, Heat

Question: Complete Combustion Produces (4)

Ans✅ ✅: Water vapor, carbon dioxide, heat, and non combustible ashes

Question: incomplete combustion produces (3)

Ans✅ ✅: carbon monoxide, hydrocarbons, and other gases

Question: rate at which fuel burns is controlled by

Ans✅ ✅: the amount of available air

Question: air to fuel ratio is a

Ans✅ ✅: critical factor in obtaining optimum fuel combustion

Question: BTU

Ans✅ ✅: British Thermal Unit, The amount of energy needed to heat one pound of
water one degree Fahrenheit

Question: wood ignites at

Ans✅ ✅: 450-550 F

Question: natural gas ignites at

Ans✅ ✅: 1,150 F

Question: propane ignites at

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Ans✅ ✅: 920-1120 F

Question: electric spark temp

Ans✅ ✅: 1,700 F

Question: hot surface igniter temp

Ans✅ ✅: 2,400 F

Question: butane lighter temp

Ans✅ ✅: 3,200 F

Question: stick match temp

Ans✅ ✅: 3,000 F

Question: cigarette temp

Ans✅ ✅: 500-800 F

Question: For complete combustion: air is ______ % oxygen + _____
% nitrogen

Ans✅ ✅: 20 : 80

Question: 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

Question: When complete combustion happens __(4 things)___ are
released

Ans✅ ✅: heat, carbon dioxide (C02), water vapor (H20), and nitrogen (N)

Question: Carbon monoxide is dangerous because (other than
senseless)

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Ans✅ ✅: it mixes with blood and reduces oxygen carrying capacity

Question: Aldehydes

Ans✅ ✅: chemical compounds that have a strong pungent odor

Question: Carbon monoxide is ________ when aldehydes are present

Ans✅ ✅: present

Question: Aldehydes result from

Ans✅ ✅: flame impingement and through the presence of contaminated air

Question: Efficiency formula

Ans✅ ✅: Heat output divided by heat input (percentage of heat transferred to
room)

Question: 3 Ts of efficiency

Ans✅ ✅: Temperature, turbulence, time

Question: Temperature (efficiency)

Ans✅ ✅: minimum ignition temp

Question: Turbulence (efficiency)

Ans✅ ✅: fuel must collide with oxygen molecules (refers to the degree of fuel and
air mixing that occurs in combustion zone)

Question: Time (efficiency)

Ans✅ ✅: amount of time fuel gases remain in the high temp zone. also known as
"residence time"

Question: Heat Transfer Efficiency

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Ans✅ ✅: refers to the percentage of heat generated by combustion actually
transferred to room

Question: 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

Question: 2 types of factory built fireplaces

Ans✅ ✅: radiating and circulating

Question: Radiant design

Ans✅ ✅: 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.)

Question: circulating design

Ans✅ ✅: 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