NATE Gas Heating Furnace Specialty
Certification Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which type of furnace uses a heat exchanger to transfer heat from
combustion gases to the air?
A. Gas furnace
B. Electric furnace
C. Heat pump
D. Boiler
The heat exchanger in a gas furnace separates combustion gases
from the air being heated, transferring heat safely.
2. What is the primary function of the draft inducer in a gas furnace?
A. Mix gas and air
B. Ensure proper venting of combustion gases
C. Control blower speed
D. Regulate thermostat
The draft inducer creates a draft that pushes combustion gases
out through the venting system.
3. Which component ignites the gas in a modern gas furnace?
A. Thermostat
B. Ignitor
C. Draft inducer
, D. Flame sensor
The ignitor produces the spark or heat necessary to ignite the gas
in the burners.
4. What safety device shuts off the gas if the flame is not detected?
A. Thermocouple
B. Pressure switch
C. Draft inducer
D. Flame sensor
The flame sensor detects the presence of a flame and shuts off gas
if no flame is present, preventing unsafe gas buildup.
5. What is the purpose of the limit switch in a gas furnace?
A. Start the blower motor
B. Prevent overheating
C. Control gas pressure
D. Measure airflow
The limit switch opens to shut off the burners if the furnace
exceeds a safe temperature.
6. Which type of venting system is typically used for high-efficiency
condensing gas furnaces?
A. Chimney vent
B. B-Vent
C. PVC or CPVC vent
D. Metal flue only
High-efficiency condensing furnaces use plastic venting materials
because exhaust gases are cooler and can be safely vented
through PVC.
, 7. What is the main difference between a single-stage and a two-
stage gas furnace?
A. Blower speed
B. Burner operation levels
C. Type of gas used
D. Heat exchanger material
A single-stage furnace operates at full capacity, while a two-stage
furnace can operate at high or low output for efficiency.
8. Which component in a gas furnace detects pressure differences to
confirm inducer operation?
A. Flame sensor
B. Limit switch
C. Pressure switch
D. Thermostat
The pressure switch ensures that the inducer is running and
venting correctly before allowing the furnace to ignite.
9. What could cause a gas furnace to short cycle?
A. Dirty filter
B. Improper gas pressure
C. Oversized furnace
D. Thermostat placement
An oversized furnace heats the space too quickly, triggering the
limit switch and causing frequent on/off cycles.
10. Which fuel type is most commonly used in residential gas
furnaces in the U.S.?
A. Propane only
B. Natural gas
Certification Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which type of furnace uses a heat exchanger to transfer heat from
combustion gases to the air?
A. Gas furnace
B. Electric furnace
C. Heat pump
D. Boiler
The heat exchanger in a gas furnace separates combustion gases
from the air being heated, transferring heat safely.
2. What is the primary function of the draft inducer in a gas furnace?
A. Mix gas and air
B. Ensure proper venting of combustion gases
C. Control blower speed
D. Regulate thermostat
The draft inducer creates a draft that pushes combustion gases
out through the venting system.
3. Which component ignites the gas in a modern gas furnace?
A. Thermostat
B. Ignitor
C. Draft inducer
, D. Flame sensor
The ignitor produces the spark or heat necessary to ignite the gas
in the burners.
4. What safety device shuts off the gas if the flame is not detected?
A. Thermocouple
B. Pressure switch
C. Draft inducer
D. Flame sensor
The flame sensor detects the presence of a flame and shuts off gas
if no flame is present, preventing unsafe gas buildup.
5. What is the purpose of the limit switch in a gas furnace?
A. Start the blower motor
B. Prevent overheating
C. Control gas pressure
D. Measure airflow
The limit switch opens to shut off the burners if the furnace
exceeds a safe temperature.
6. Which type of venting system is typically used for high-efficiency
condensing gas furnaces?
A. Chimney vent
B. B-Vent
C. PVC or CPVC vent
D. Metal flue only
High-efficiency condensing furnaces use plastic venting materials
because exhaust gases are cooler and can be safely vented
through PVC.
, 7. What is the main difference between a single-stage and a two-
stage gas furnace?
A. Blower speed
B. Burner operation levels
C. Type of gas used
D. Heat exchanger material
A single-stage furnace operates at full capacity, while a two-stage
furnace can operate at high or low output for efficiency.
8. Which component in a gas furnace detects pressure differences to
confirm inducer operation?
A. Flame sensor
B. Limit switch
C. Pressure switch
D. Thermostat
The pressure switch ensures that the inducer is running and
venting correctly before allowing the furnace to ignite.
9. What could cause a gas furnace to short cycle?
A. Dirty filter
B. Improper gas pressure
C. Oversized furnace
D. Thermostat placement
An oversized furnace heats the space too quickly, triggering the
limit switch and causing frequent on/off cycles.
10. Which fuel type is most commonly used in residential gas
furnaces in the U.S.?
A. Propane only
B. Natural gas
