NATE Gas Heating Furnace Specialty
Certification Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a gas furnace
heat exchanger?
A. To regulate indoor airflow
B. To burn fuel efficiently
C. To transfer heat from combustion gases to the air without
mixing the gases with indoor air
D. To filter impurities from the air
Answer: C
Rationale: The heat exchanger in a gas furnace transfers heat from
the combustion gases to the air that circulates in the home while
preventing the harmful combustion gases from entering the indoor air.
, 2. What type of ignition system is commonly used in modern gas
furnaces?
A. Standing pilot
B. Intermittent pilot or electronic ignition
C. Manual match lighting
D. Flame rectification
Answer: B
Rationale: Modern furnaces use electronic ignition or intermittent
pilot systems to ignite the gas only when needed, improving safety
and energy efficiency compared to standing pilots.
3. A high-limit switch in a gas furnace is designed to:
A. Control the thermostat
B. Prevent overheating by shutting down the furnace if
temperatures exceed safe levels
C. Regulate gas pressure
D. Control blower speed
Answer: B
Rationale: The high-limit switch acts as a safety device, shutting down
the furnace if the heat exchanger or surrounding air becomes too hot.
4. Which venting method uses natural convection to exhaust
combustion gases?
, A. Power venting
B. Atmospheric venting
C. Direct venting
D. Induced draft venting
Answer: B
Rationale: Atmospheric venting relies on the natural buoyancy of hot
combustion gases to rise through a vertical vent pipe.
5. What is the main purpose of a draft inducer motor in a modern
furnace?
A. To increase airflow across the heat exchanger
B. To ensure proper venting of combustion gases before ignition
C. To control fan speed
D. To regulate thermostat signals
Answer: B
Rationale: The draft inducer motor creates a negative pressure in the
furnace vent to ensure safe and complete combustion gas venting
before ignition.
6. Which gas pressure is typically considered safe for natural gas
furnaces?
A. 1–3 psi
B. 3–5 psi
, C. 3.5–7 inches water column
D. 1–2 atmospheres
Answer: C
Rationale: Residential natural gas furnaces operate with gas pressures
typically around 3.5–7 inches of water column (in. w.c.), measured at
the inlet to the gas valve.
7. A furnace has a cracked heat exchanger. What is the safest course
of action?
A. Patch the crack with high-temperature sealant
B. Continue operating until repair parts arrive
C. Shut down the furnace and replace the heat exchanger
D. Adjust the thermostat to limit temperature
Answer: C
Rationale: A cracked heat exchanger can allow carbon monoxide to
enter the home, posing a serious health risk. Replacement is the only
safe solution.
8. In a sealed combustion furnace, the combustion air is:
A. Drawn from the living space
B. Drawn directly from outside through a dedicated vent
C. Mixed with return air
D. Not required
Certification Exam Questions And Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which of the following is the primary purpose of a gas furnace
heat exchanger?
A. To regulate indoor airflow
B. To burn fuel efficiently
C. To transfer heat from combustion gases to the air without
mixing the gases with indoor air
D. To filter impurities from the air
Answer: C
Rationale: The heat exchanger in a gas furnace transfers heat from
the combustion gases to the air that circulates in the home while
preventing the harmful combustion gases from entering the indoor air.
, 2. What type of ignition system is commonly used in modern gas
furnaces?
A. Standing pilot
B. Intermittent pilot or electronic ignition
C. Manual match lighting
D. Flame rectification
Answer: B
Rationale: Modern furnaces use electronic ignition or intermittent
pilot systems to ignite the gas only when needed, improving safety
and energy efficiency compared to standing pilots.
3. A high-limit switch in a gas furnace is designed to:
A. Control the thermostat
B. Prevent overheating by shutting down the furnace if
temperatures exceed safe levels
C. Regulate gas pressure
D. Control blower speed
Answer: B
Rationale: The high-limit switch acts as a safety device, shutting down
the furnace if the heat exchanger or surrounding air becomes too hot.
4. Which venting method uses natural convection to exhaust
combustion gases?
, A. Power venting
B. Atmospheric venting
C. Direct venting
D. Induced draft venting
Answer: B
Rationale: Atmospheric venting relies on the natural buoyancy of hot
combustion gases to rise through a vertical vent pipe.
5. What is the main purpose of a draft inducer motor in a modern
furnace?
A. To increase airflow across the heat exchanger
B. To ensure proper venting of combustion gases before ignition
C. To control fan speed
D. To regulate thermostat signals
Answer: B
Rationale: The draft inducer motor creates a negative pressure in the
furnace vent to ensure safe and complete combustion gas venting
before ignition.
6. Which gas pressure is typically considered safe for natural gas
furnaces?
A. 1–3 psi
B. 3–5 psi
, C. 3.5–7 inches water column
D. 1–2 atmospheres
Answer: C
Rationale: Residential natural gas furnaces operate with gas pressures
typically around 3.5–7 inches of water column (in. w.c.), measured at
the inlet to the gas valve.
7. A furnace has a cracked heat exchanger. What is the safest course
of action?
A. Patch the crack with high-temperature sealant
B. Continue operating until repair parts arrive
C. Shut down the furnace and replace the heat exchanger
D. Adjust the thermostat to limit temperature
Answer: C
Rationale: A cracked heat exchanger can allow carbon monoxide to
enter the home, posing a serious health risk. Replacement is the only
safe solution.
8. In a sealed combustion furnace, the combustion air is:
A. Drawn from the living space
B. Drawn directly from outside through a dedicated vent
C. Mixed with return air
D. Not required
