CFESA Gas Certification Exam 2026/2027 |
300+ Practice Questions, Correct Answers &
Detailed Rationales
1. Natural gas is primarily composed of which gas?
A) Propane
B) Methane
C) Butane
D) Hydrogen
Answer: B
Rationale: Natural gas is mostly methane with small amounts of other hydrocarbons.
2. LP gas is primarily composed of which gas?
A) Propane
B) Methane
C) Ethane
D) Nitrogen
Answer: A
Rationale: Liquefied petroleum gas is primarily propane.
3. Which gas is heavier than air?
A) Natural gas
B) LP gas
C) Methane
D) Hydrogen
Answer: B
Rationale: LP gas settles in low areas because it is heavier than air.
,4. Which gas is lighter than air?
A) LP gas
B) Natural gas
C) Propane
D) Butane
Answer: B
Rationale: Natural gas rises and dissipates in air.
5. What is the primary purpose of combustion air?
A) Cool the burner
B) Supply oxygen for burning gas
C) Increase gas pressure
D) Clean the flue
Answer: B
Rationale: Combustion requires oxygen to burn fuel safely.
6. What is the ideal flame color for natural gas combustion?
A) Yellow
B) Blue
C) Orange
D) Red
Answer: B
Rationale: A blue flame indicates complete combustion with proper air mixture.
7. A yellow flame indicates:
A) Complete combustion
,B) Incomplete combustion
C) Too much air
D) High gas pressure
Answer: B
Rationale: Yellow flame means insufficient primary air or dirty burner.
8. A lifting flame indicates:
A) Too little air
B) Too much primary air
C) Low gas pressure
D) High gas pressure
Answer: B
Rationale: Excess air velocity lifts the flame off the burner.
9. Flashback occurs when:
A) Flame lifts off burner
B) Flame burns inside the burner tube
C) Flame is yellow
D) Flame is blue
Answer: B
Rationale: Flashback is caused by low gas pressure or wrong orifice.
10. Delayed ignition causes:
A) Smooth ignition
B) Small explosion or puff
C) No ignition
D) Yellow flame
Answer: B
, Rationale: Gas accumulates before ignition, causing a puff.
11. Rollout is defined as:
A) Normal flame
B) Flame burning outside the burner area
C) Blue flame
D) Pilot flame
Answer: B
Rationale: Rollout indicates blocked flue or combustion problem.
12. What causes rollout?
A) Too much primary air
B) Blocked flue or heat exchanger
C) Low gas pressure
D) High gas pressure
Answer: B
Rationale: Restricted flue forces flame out of the burner area.
13. What is the function of a draft hood?
A) Increase gas pressure
B) Provide draft and dilute flue gases
C) Filter gas
D) Store gas
Answer: B
Rationale: Draft hood stabilizes draft and prevents backdraft.
14. Carbon monoxide is dangerous because it is:
300+ Practice Questions, Correct Answers &
Detailed Rationales
1. Natural gas is primarily composed of which gas?
A) Propane
B) Methane
C) Butane
D) Hydrogen
Answer: B
Rationale: Natural gas is mostly methane with small amounts of other hydrocarbons.
2. LP gas is primarily composed of which gas?
A) Propane
B) Methane
C) Ethane
D) Nitrogen
Answer: A
Rationale: Liquefied petroleum gas is primarily propane.
3. Which gas is heavier than air?
A) Natural gas
B) LP gas
C) Methane
D) Hydrogen
Answer: B
Rationale: LP gas settles in low areas because it is heavier than air.
,4. Which gas is lighter than air?
A) LP gas
B) Natural gas
C) Propane
D) Butane
Answer: B
Rationale: Natural gas rises and dissipates in air.
5. What is the primary purpose of combustion air?
A) Cool the burner
B) Supply oxygen for burning gas
C) Increase gas pressure
D) Clean the flue
Answer: B
Rationale: Combustion requires oxygen to burn fuel safely.
6. What is the ideal flame color for natural gas combustion?
A) Yellow
B) Blue
C) Orange
D) Red
Answer: B
Rationale: A blue flame indicates complete combustion with proper air mixture.
7. A yellow flame indicates:
A) Complete combustion
,B) Incomplete combustion
C) Too much air
D) High gas pressure
Answer: B
Rationale: Yellow flame means insufficient primary air or dirty burner.
8. A lifting flame indicates:
A) Too little air
B) Too much primary air
C) Low gas pressure
D) High gas pressure
Answer: B
Rationale: Excess air velocity lifts the flame off the burner.
9. Flashback occurs when:
A) Flame lifts off burner
B) Flame burns inside the burner tube
C) Flame is yellow
D) Flame is blue
Answer: B
Rationale: Flashback is caused by low gas pressure or wrong orifice.
10. Delayed ignition causes:
A) Smooth ignition
B) Small explosion or puff
C) No ignition
D) Yellow flame
Answer: B
, Rationale: Gas accumulates before ignition, causing a puff.
11. Rollout is defined as:
A) Normal flame
B) Flame burning outside the burner area
C) Blue flame
D) Pilot flame
Answer: B
Rationale: Rollout indicates blocked flue or combustion problem.
12. What causes rollout?
A) Too much primary air
B) Blocked flue or heat exchanger
C) Low gas pressure
D) High gas pressure
Answer: B
Rationale: Restricted flue forces flame out of the burner area.
13. What is the function of a draft hood?
A) Increase gas pressure
B) Provide draft and dilute flue gases
C) Filter gas
D) Store gas
Answer: B
Rationale: Draft hood stabilizes draft and prevents backdraft.
14. Carbon monoxide is dangerous because it is:
