NATE Gas Heating (Air) Specialty
Certification Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
Pdf
1. What is the primary purpose of a furnace heat exchanger?
A. Increase blower speed
B. Transfer heat from combustion gases to the circulating air without mixing the
two
C. Regulate gas pressure
D. Remove moisture from indoor air
Answer: Transfer heat from combustion gases to the circulating air without
mixing the two
Rationale: The heat exchanger transfers combustion heat to the air stream while
keeping combustion products separated from indoor air.
2. Which gas is commonly used as the odorant added to natural gas?
A. Oxygen
B. Nitrogen
C. Mercaptan
D. Carbon monoxide
,Answer: Mercaptan
Rationale: Mercaptan is added to otherwise odorless natural gas so leaks can be
detected by smell.
3. What is the normal primary purpose of a furnace pressure switch?
A. Measure indoor static pressure
B. Prove proper draft or pressure conditions before allowing ignition
C. Control blower speed
D. Measure gas temperature
Answer: Prove proper draft or pressure conditions before allowing ignition
Rationale: The pressure switch verifies that the inducer and venting system are
producing the required pressure conditions for safe operation.
4. What component normally initiates the ignition sequence on a modern
induced-draft furnace?
A. Limit switch
B. Thermostat call for heat
C. Flame sensor
D. Gas valve
Answer: Thermostat call for heat
Rationale: When the thermostat calls for heat, the control board begins the
programmed ignition sequence.
5. What is the purpose of an induced-draft blower?
,A. Increase return-air temperature
B. Establish proper combustion airflow and assist in exhausting combustion
products
C. Circulate room air
D. Increase gas pressure
Answer: Establish proper combustion airflow and assist in exhausting
combustion products
Rationale: The inducer creates the draft needed for combustion and venting
before and during burner operation.
6. A furnace has a 100,000 Btu/h input rating and an 80% AFUE. Approximately
how much useful heat is delivered?
A. 20,000 Btu/h
B. 50,000 Btu/h
C. 80,000 Btu/h
D. 125,000 Btu/h
Answer: 80,000 Btu/h
Rationale: An 80% efficiency applied to a 100,000 Btu/h input gives
approximately 80,000 Btu/h of useful heat output.
7. What is the purpose of the furnace rollout switch?
A. Increase blower speed
B. Detect abnormal flame or heat rollout from the burner area
C. Control room humidity
D. Measure supply-air temperature
Answer: Detect abnormal flame or heat rollout from the burner area
, Rationale: A rollout switch is a safety device designed to shut down the furnace
if flame or excessive heat escapes from the intended combustion area.
8. What should a technician do if a manual-reset rollout switch has tripped?
A. Immediately reset it repeatedly
B. Bypass it temporarily
C. Determine and correct the cause before resetting it
D. Increase gas pressure
Answer: Determine and correct the cause before resetting it
Rationale: Repeated resetting without finding the cause can allow a dangerous
combustion condition to continue.
9. What is the purpose of the flame sensor on a direct-ignition furnace?
A. Measure flue temperature
B. Prove that the burner flame has been established
C. Measure gas pressure
D. Control blower speed
Answer: Prove that the burner flame has been established
Rationale: The flame sensor provides flame-proving feedback to the ignition
control so the gas valve can remain energized safely.
10. What electrical phenomenon is commonly used by a flame sensor to prove
flame?
A. Resistance heating
B. Flame rectification
Certification Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A Instant Download
1. What is the primary purpose of a furnace heat exchanger?
A. Increase blower speed
B. Transfer heat from combustion gases to the circulating air without mixing the
two
C. Regulate gas pressure
D. Remove moisture from indoor air
Answer: Transfer heat from combustion gases to the circulating air without
mixing the two
Rationale: The heat exchanger transfers combustion heat to the air stream while
keeping combustion products separated from indoor air.
2. Which gas is commonly used as the odorant added to natural gas?
A. Oxygen
B. Nitrogen
C. Mercaptan
D. Carbon monoxide
,Answer: Mercaptan
Rationale: Mercaptan is added to otherwise odorless natural gas so leaks can be
detected by smell.
3. What is the normal primary purpose of a furnace pressure switch?
A. Measure indoor static pressure
B. Prove proper draft or pressure conditions before allowing ignition
C. Control blower speed
D. Measure gas temperature
Answer: Prove proper draft or pressure conditions before allowing ignition
Rationale: The pressure switch verifies that the inducer and venting system are
producing the required pressure conditions for safe operation.
4. What component normally initiates the ignition sequence on a modern
induced-draft furnace?
A. Limit switch
B. Thermostat call for heat
C. Flame sensor
D. Gas valve
Answer: Thermostat call for heat
Rationale: When the thermostat calls for heat, the control board begins the
programmed ignition sequence.
5. What is the purpose of an induced-draft blower?
,A. Increase return-air temperature
B. Establish proper combustion airflow and assist in exhausting combustion
products
C. Circulate room air
D. Increase gas pressure
Answer: Establish proper combustion airflow and assist in exhausting
combustion products
Rationale: The inducer creates the draft needed for combustion and venting
before and during burner operation.
6. A furnace has a 100,000 Btu/h input rating and an 80% AFUE. Approximately
how much useful heat is delivered?
A. 20,000 Btu/h
B. 50,000 Btu/h
C. 80,000 Btu/h
D. 125,000 Btu/h
Answer: 80,000 Btu/h
Rationale: An 80% efficiency applied to a 100,000 Btu/h input gives
approximately 80,000 Btu/h of useful heat output.
7. What is the purpose of the furnace rollout switch?
A. Increase blower speed
B. Detect abnormal flame or heat rollout from the burner area
C. Control room humidity
D. Measure supply-air temperature
Answer: Detect abnormal flame or heat rollout from the burner area
, Rationale: A rollout switch is a safety device designed to shut down the furnace
if flame or excessive heat escapes from the intended combustion area.
8. What should a technician do if a manual-reset rollout switch has tripped?
A. Immediately reset it repeatedly
B. Bypass it temporarily
C. Determine and correct the cause before resetting it
D. Increase gas pressure
Answer: Determine and correct the cause before resetting it
Rationale: Repeated resetting without finding the cause can allow a dangerous
combustion condition to continue.
9. What is the purpose of the flame sensor on a direct-ignition furnace?
A. Measure flue temperature
B. Prove that the burner flame has been established
C. Measure gas pressure
D. Control blower speed
Answer: Prove that the burner flame has been established
Rationale: The flame sensor provides flame-proving feedback to the ignition
control so the gas valve can remain energized safely.
10. What electrical phenomenon is commonly used by a flame sensor to prove
flame?
A. Resistance heating
B. Flame rectification
