Page 1 of 123
JOURNEYMAN PLUMBER Restricted
Appliance Exam Questions And Correct
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Explanation 2026 Q&A | Instant
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Q1. What two elements are essential for complete combustion of
natural gas (methane)?
A) Carbon and oxygen
B) Methane and oxygen
C) Hydrogen and oxygen
D) Carbon monoxide and oxygen
Answer: B
Rationale: Complete combustion requires methane (CH₄) and
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sufficient oxygen (air). Products are carbon dioxide and water
vapour.
Q2. Incomplete combustion produces which dangerous gas?
A) Carbon dioxide (CO₂)
B) Carbon monoxide (CO)
C) Nitrogen dioxide (NO₂)
D) Sulfur dioxide (SO₂)
Answer: B
Rationale: Incomplete combustion due to insufficient oxygen
creates carbon monoxide, a colorless, odorless, highly toxic gas.
Q3. The ideal air-to-fuel ratio for natural gas is approximately:
A) 5:1
B) 10:1
C) 20:1 (about 10 parts air to 1 part gas by volume? Actually
10:1 air:gas by volume is typical)
D) 30:1
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Answer: B
Rationale: Stoichiometric air-to-gas ratio for natural gas is
roughly 10:1 by volume (approximately 9.6:1). For propane it is
about 24:1.
Q4. What is the primary purpose of an appliance draft hood?
A) Increase efficiency
B) Prevent downdrafts from extinguishing the burner and ensure
proper venting
C) Reduce gas consumption
D) Filter combustion air
Answer: B
Rationale: A draft hood allows room air to mix with flue gases,
cools them, and provides a draft diverter to prevent wind from
blowing out the burner.
Q5. The heating value of natural gas is typically measured in:
A) BTU per cubic foot (BTU/ft³)
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B) BTU per pound
C) Therms per gallon
D) Joules per kilogram
Answer: A
Rationale: Natural gas heating value is typically 950–1050 BTU
per cubic foot (approx 1000 BTU/ft³). Propane is about 2500
BTU/ft³.
Q6. What is the specific gravity of natural gas relative to air?
A) 0.6 (lighter than air)
B) 1.0 (same as air)
C) 1.5 (heavier than air)
D) 2.0
Answer: A
Rationale: Natural gas (methane) has a specific gravity of
approximately 0.6, meaning it rises and dissipates upward in the
event of a leak.
JOURNEYMAN PLUMBER Restricted
Appliance Exam Questions And Correct
Answers (Verified Answers) Plus
Explanation 2026 Q&A | Instant
Download Pdf
Q1. What two elements are essential for complete combustion of
natural gas (methane)?
A) Carbon and oxygen
B) Methane and oxygen
C) Hydrogen and oxygen
D) Carbon monoxide and oxygen
Answer: B
Rationale: Complete combustion requires methane (CH₄) and
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sufficient oxygen (air). Products are carbon dioxide and water
vapour.
Q2. Incomplete combustion produces which dangerous gas?
A) Carbon dioxide (CO₂)
B) Carbon monoxide (CO)
C) Nitrogen dioxide (NO₂)
D) Sulfur dioxide (SO₂)
Answer: B
Rationale: Incomplete combustion due to insufficient oxygen
creates carbon monoxide, a colorless, odorless, highly toxic gas.
Q3. The ideal air-to-fuel ratio for natural gas is approximately:
A) 5:1
B) 10:1
C) 20:1 (about 10 parts air to 1 part gas by volume? Actually
10:1 air:gas by volume is typical)
D) 30:1
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Answer: B
Rationale: Stoichiometric air-to-gas ratio for natural gas is
roughly 10:1 by volume (approximately 9.6:1). For propane it is
about 24:1.
Q4. What is the primary purpose of an appliance draft hood?
A) Increase efficiency
B) Prevent downdrafts from extinguishing the burner and ensure
proper venting
C) Reduce gas consumption
D) Filter combustion air
Answer: B
Rationale: A draft hood allows room air to mix with flue gases,
cools them, and provides a draft diverter to prevent wind from
blowing out the burner.
Q5. The heating value of natural gas is typically measured in:
A) BTU per cubic foot (BTU/ft³)
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B) BTU per pound
C) Therms per gallon
D) Joules per kilogram
Answer: A
Rationale: Natural gas heating value is typically 950–1050 BTU
per cubic foot (approx 1000 BTU/ft³). Propane is about 2500
BTU/ft³.
Q6. What is the specific gravity of natural gas relative to air?
A) 0.6 (lighter than air)
B) 1.0 (same as air)
C) 1.5 (heavier than air)
D) 2.0
Answer: A
Rationale: Natural gas (methane) has a specific gravity of
approximately 0.6, meaning it rises and dissipates upward in the
event of a leak.
