NATE Gas Heating (Air) Installation Technician
Certification | Exam Questions And Correct Answers
(Verified Answers) Plus Rationales | Latest Update
2026/2027 | Graded A+.
1. Which of the following is the primary function of a gas furnace heat
exchanger?
a) To circulate air through the duct system
b) To ignite the gas burner
c) To transfer heat from combustion gases to the air without mixing
the gases with the air
d) To filter airborne contaminants
Rationale: The heat exchanger allows heat to pass to the air while
keeping combustion gases separate from the indoor air.
2. What type of gas is most commonly used in residential gas furnaces in
the U.S.?
a) Propane
b) Natural Gas
c) Butane
d) Methane
Rationale: Natural gas (methane) is the primary fuel source for
residential furnaces due to availability and safety.
3. The purpose of a draft inducer motor is to:
, a) Control the thermostat signal
b) Ensure proper venting of combustion gases
c) Increase blower efficiency
d) Filter the air before heating
Rationale: The inducer motor helps remove combustion gases and
establishes proper draft for safe venting.
4. A 90% AFUE gas furnace achieves what efficiency level?
a) 75%
b) 80%
c) 90%
d) 95%
Rationale: AFUE (Annual Fuel Utilization Efficiency) represents the
percentage of fuel converted to heat for the home.
5. Which component regulates the flow of gas into the burner?
a) Gas manifold
b) Draft inducer
c) Gas valve
d) Flame sensor
Rationale: The gas valve meters the correct amount of gas to the
burners for safe combustion.
6. What is the correct sequence of operation for a gas furnace?
a) Blower → Gas valve → Igniter → Burner
b) Thermostat call → Inducer motor → Igniter → Gas valve →
Flame
, → Blower
c) Gas valve → Igniter → Flame sensor → Blower
d) Thermostat call → Blower → Gas valve → Igniter
Rationale: Proper sequence ensures safety and efficiency: call for
heat, draft established, ignition, flame detection, and airflow.
7. The main purpose of a limit switch in a gas furnace is to:
a) Control blower speed
b) Prevent overheating of the heat exchanger
c) Regulate gas pressure
d) Measure room temperature
Rationale: The limit switch turns off the burner if the furnace
temperature exceeds safe limits.
8. A flame rollout switch is activated by:
a) Low gas pressure
b) Improper thermostat signal
c) Flame leaving the combustion chamber
d) Blower motor failure
Rationale: Flame rollout occurs when the flame is not properly
contained, triggering the safety switch.
9. What is the standard pressure for natural gas in residential
systems?
a) 3 psi
b) 10 psi
, c) 7 inches of water column (≈0.25 psi)
d) 1 atm
Rationale: Residential natural gas is delivered at low pressure for
safety and controlled combustion.
10. Which of the following materials is commonly used for venting
high-efficiency condensing furnaces? a) Black steel
b) Aluminum
c) PVC or CPVC
d) Copper
Rationale: Condensing furnaces produce acidic condensate,
requiring corrosion-resistant PVC or CPVC venting.
11. Which safety device prevents a gas furnace from operating if the
inducer motor is not running? a) Limit switch
b) Thermostat
c) Pressure switch
d) Rollout switch
Rationale: The pressure switch ensures the inducer creates the
correct draft before allowing the furnace to ignite.
12. What is the primary purpose of the blower in a gas furnace?
a) Ignite the gas
b) Control the gas valve
Certification | Exam Questions And Correct Answers
(Verified Answers) Plus Rationales | Latest Update
2026/2027 | Graded A+.
1. Which of the following is the primary function of a gas furnace heat
exchanger?
a) To circulate air through the duct system
b) To ignite the gas burner
c) To transfer heat from combustion gases to the air without mixing
the gases with the air
d) To filter airborne contaminants
Rationale: The heat exchanger allows heat to pass to the air while
keeping combustion gases separate from the indoor air.
2. What type of gas is most commonly used in residential gas furnaces in
the U.S.?
a) Propane
b) Natural Gas
c) Butane
d) Methane
Rationale: Natural gas (methane) is the primary fuel source for
residential furnaces due to availability and safety.
3. The purpose of a draft inducer motor is to:
, a) Control the thermostat signal
b) Ensure proper venting of combustion gases
c) Increase blower efficiency
d) Filter the air before heating
Rationale: The inducer motor helps remove combustion gases and
establishes proper draft for safe venting.
4. A 90% AFUE gas furnace achieves what efficiency level?
a) 75%
b) 80%
c) 90%
d) 95%
Rationale: AFUE (Annual Fuel Utilization Efficiency) represents the
percentage of fuel converted to heat for the home.
5. Which component regulates the flow of gas into the burner?
a) Gas manifold
b) Draft inducer
c) Gas valve
d) Flame sensor
Rationale: The gas valve meters the correct amount of gas to the
burners for safe combustion.
6. What is the correct sequence of operation for a gas furnace?
a) Blower → Gas valve → Igniter → Burner
b) Thermostat call → Inducer motor → Igniter → Gas valve →
Flame
, → Blower
c) Gas valve → Igniter → Flame sensor → Blower
d) Thermostat call → Blower → Gas valve → Igniter
Rationale: Proper sequence ensures safety and efficiency: call for
heat, draft established, ignition, flame detection, and airflow.
7. The main purpose of a limit switch in a gas furnace is to:
a) Control blower speed
b) Prevent overheating of the heat exchanger
c) Regulate gas pressure
d) Measure room temperature
Rationale: The limit switch turns off the burner if the furnace
temperature exceeds safe limits.
8. A flame rollout switch is activated by:
a) Low gas pressure
b) Improper thermostat signal
c) Flame leaving the combustion chamber
d) Blower motor failure
Rationale: Flame rollout occurs when the flame is not properly
contained, triggering the safety switch.
9. What is the standard pressure for natural gas in residential
systems?
a) 3 psi
b) 10 psi
, c) 7 inches of water column (≈0.25 psi)
d) 1 atm
Rationale: Residential natural gas is delivered at low pressure for
safety and controlled combustion.
10. Which of the following materials is commonly used for venting
high-efficiency condensing furnaces? a) Black steel
b) Aluminum
c) PVC or CPVC
d) Copper
Rationale: Condensing furnaces produce acidic condensate,
requiring corrosion-resistant PVC or CPVC venting.
11. Which safety device prevents a gas furnace from operating if the
inducer motor is not running? a) Limit switch
b) Thermostat
c) Pressure switch
d) Rollout switch
Rationale: The pressure switch ensures the inducer creates the
correct draft before allowing the furnace to ignite.
12. What is the primary purpose of the blower in a gas furnace?
a) Ignite the gas
b) Control the gas valve
