NATE Gas Heating Furnace Specialty
Certification Exam With Actual
Questions & Verified Answers, Plus
Explained Rationales/Expert Verified
For Guaranteed Pass 2026/Latest
Updated/Instant Download Pdf
1. What is the primary function of a gas furnace heat exchanger?
A) To circulate air through the ductwork
B) To transfer heat from combustion gases to the air
C) To ignite the gas
D) To remove humidity from the air
B) To transfer heat from combustion gases to the air
The heat exchanger allows combustion gases to transfer their heat to
the air circulating through the furnace while keeping the gases
separate from the indoor air.
2. Which of the following is the most common type of gas used in
residential furnaces?
A) Propane
B) Natural Gas
C) Butane
D) Hydrogen
,B) Natural Gas
Natural gas is widely used due to its availability, cost-effectiveness,
and efficiency for residential heating.
3. What is the purpose of a draft inducer in a gas furnace?
A) To ignite the burners
B) To increase air circulation in the home
C) To ensure proper venting of combustion gases
D) To regulate gas pressure
C) To ensure proper venting of combustion gases
The draft inducer motor creates a negative pressure that safely
removes combustion gases through the vent system.
4. A furnace is producing yellow flames instead of blue. What is the
most likely cause?
A) High gas pressure
B) Incomplete combustion
C) Clean burners
D) High air flow
B) Incomplete combustion
Yellow flames indicate incomplete combustion, which can produce
carbon monoxide and reduce furnace efficiency.
5. Which component controls the ignition sequence in a gas
furnace?
A) Limit switch
B) Gas valve
C) Furnace control board
D) Draft inducer
,C) Furnace control board
The control board coordinates ignition, blower operation, and safety
sequences.
6. What safety device shuts off the gas supply if the flame goes out?
A) Thermostat
B) Rollout switch
C) Flame sensor
D) Pressure switch
C) Flame sensor
The flame sensor detects the presence of a flame and signals the gas
valve to close if the flame is not present.
7. Which of the following is a common cause of a furnace not
igniting?
A) Dirty air filter
B) Faulty ignition control or igniter
C) High furnace temperature
D) Open return air vent
B) Faulty ignition control or igniter
If the igniter or ignition control fails, the furnace cannot light the
burners.
8. What is the function of the limit switch?
A) To regulate indoor air temperature
B) To protect the furnace from overheating
C) To maintain gas pressure
D) To measure outdoor temperature
B) To protect the furnace from overheating
The limit switch turns off the burners if the furnace temperature
exceeds a safe limit.
, 9. A furnace has insufficient airflow. Which of these is a likely cause?
A) Dirty filter or blocked ductwork
B) High gas pressure
C) Low gas pressure
D) Open vent hood
A) Dirty filter or blocked ductwork
Restricted airflow reduces heat transfer and can cause the furnace to
overheat.
10. What does AFUE stand for in gas furnace efficiency ratings?
A) Annual Fuel Utilization Efficiency
B) Air Flow Unit Efficiency
C) Actual Furnace Usage Efficiency
D) Automatic Fuel Utilization Evaluation
A) Annual Fuel Utilization Efficiency
AFUE measures the percentage of fuel converted into heat over a
year.
11. Which of the following is a high-efficiency furnace feature?
A) Standing pilot
B) Sealed combustion chamber
C) Atmospheric burner
D) Open vent system
B) Sealed combustion chamber
Sealed combustion prevents combustion gases from mixing with
indoor air and improves efficiency.
12. What is the typical operating temperature range for a
residential gas furnace heat exchanger?
A) 100–150°F
B) 180–250°F
Certification Exam With Actual
Questions & Verified Answers, Plus
Explained Rationales/Expert Verified
For Guaranteed Pass 2026/Latest
Updated/Instant Download Pdf
1. What is the primary function of a gas furnace heat exchanger?
A) To circulate air through the ductwork
B) To transfer heat from combustion gases to the air
C) To ignite the gas
D) To remove humidity from the air
B) To transfer heat from combustion gases to the air
The heat exchanger allows combustion gases to transfer their heat to
the air circulating through the furnace while keeping the gases
separate from the indoor air.
2. Which of the following is the most common type of gas used in
residential furnaces?
A) Propane
B) Natural Gas
C) Butane
D) Hydrogen
,B) Natural Gas
Natural gas is widely used due to its availability, cost-effectiveness,
and efficiency for residential heating.
3. What is the purpose of a draft inducer in a gas furnace?
A) To ignite the burners
B) To increase air circulation in the home
C) To ensure proper venting of combustion gases
D) To regulate gas pressure
C) To ensure proper venting of combustion gases
The draft inducer motor creates a negative pressure that safely
removes combustion gases through the vent system.
4. A furnace is producing yellow flames instead of blue. What is the
most likely cause?
A) High gas pressure
B) Incomplete combustion
C) Clean burners
D) High air flow
B) Incomplete combustion
Yellow flames indicate incomplete combustion, which can produce
carbon monoxide and reduce furnace efficiency.
5. Which component controls the ignition sequence in a gas
furnace?
A) Limit switch
B) Gas valve
C) Furnace control board
D) Draft inducer
,C) Furnace control board
The control board coordinates ignition, blower operation, and safety
sequences.
6. What safety device shuts off the gas supply if the flame goes out?
A) Thermostat
B) Rollout switch
C) Flame sensor
D) Pressure switch
C) Flame sensor
The flame sensor detects the presence of a flame and signals the gas
valve to close if the flame is not present.
7. Which of the following is a common cause of a furnace not
igniting?
A) Dirty air filter
B) Faulty ignition control or igniter
C) High furnace temperature
D) Open return air vent
B) Faulty ignition control or igniter
If the igniter or ignition control fails, the furnace cannot light the
burners.
8. What is the function of the limit switch?
A) To regulate indoor air temperature
B) To protect the furnace from overheating
C) To maintain gas pressure
D) To measure outdoor temperature
B) To protect the furnace from overheating
The limit switch turns off the burners if the furnace temperature
exceeds a safe limit.
, 9. A furnace has insufficient airflow. Which of these is a likely cause?
A) Dirty filter or blocked ductwork
B) High gas pressure
C) Low gas pressure
D) Open vent hood
A) Dirty filter or blocked ductwork
Restricted airflow reduces heat transfer and can cause the furnace to
overheat.
10. What does AFUE stand for in gas furnace efficiency ratings?
A) Annual Fuel Utilization Efficiency
B) Air Flow Unit Efficiency
C) Actual Furnace Usage Efficiency
D) Automatic Fuel Utilization Evaluation
A) Annual Fuel Utilization Efficiency
AFUE measures the percentage of fuel converted into heat over a
year.
11. Which of the following is a high-efficiency furnace feature?
A) Standing pilot
B) Sealed combustion chamber
C) Atmospheric burner
D) Open vent system
B) Sealed combustion chamber
Sealed combustion prevents combustion gases from mixing with
indoor air and improves efficiency.
12. What is the typical operating temperature range for a
residential gas furnace heat exchanger?
A) 100–150°F
B) 180–250°F
