Ontario Gas Technician 3 (G3) Certification
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
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1. The primary responsibility of a Gas Technician 3 is to:
A. Design gas distribution systems
B. Install and service large industrial burners
C. Install, service, and maintain residential gas appliances under
supervision
D. Approve gas system designs
Answer: C
G3 technicians are qualified to work on residential appliances and
systems within defined limits and often under supervision.
2. Natural gas is primarily composed of:
A. Propane
B. Butane
C. Methane
D. Ethane
Answer: C
Methane makes up the majority of natural gas used in Ontario.
, 3. Propane is classified as:
A. Lighter than air
B. Heavier than air
C. Same density as air
D. Non-combustible
Answer: B
Propane vapour is heavier than air and can collect in low areas.
4. The chemical symbol for carbon monoxide is:
A. CO₂
B. O₂
C. CO
D. CH₄
Answer: C
Carbon monoxide consists of one carbon atom and one oxygen atom.
5. Carbon monoxide is dangerous because it:
A. Has a strong odor
B. Causes corrosion
C. Displaces oxygen in the blood
D. Irritates the skin
Answer: C
CO binds to hemoglobin, preventing oxygen transport.
, 6. The typical supply pressure of natural gas to a residence is
approximately:
A. 14 in. w.c.
B. 7 in. w.c.
C. 2 psi
D. 5 psi
Answer: B
Residential natural gas pressure is commonly around 7 inches water
column.
7. One inch of water column is approximately equal to:
A. 0.5 psi
B. 1 psi
C. 0.036 psi
D. 0.1 psi
Answer: C
27.7 inches of water column equals 1 psi.
8. The purpose of a gas regulator is to:
A. Increase gas flow
B. Store gas
C. Control and reduce gas pressure
D. Filter contaminants
Answer: C
Regulators ensure safe and consistent appliance pressure.
, 9. A manometer is used to measure:
A. Voltage
B. Temperature
C. Gas pressure
D. Gas volume
Answer: C
Manometers measure low pressures such as inches of water column.
10. When testing for gas leaks, the safest method is to use:
A. A lighter
B. A match
C. Soap and water solution
D. A torch
Answer: C
Soap solution reveals leaks through bubble formation without ignition
risk.
11. The flammable range of natural gas in air is approximately:
A. 1–3%
B. 5–15%
C. 10–25%
D. 20–40%
Answer: B
Natural gas is combustible within roughly 5% to 15% concentration.
Exam Questions And Correct Answers (Verified
Answers) Plus Rationales 2026 Q&A | Instant
Download Pdf
1. The primary responsibility of a Gas Technician 3 is to:
A. Design gas distribution systems
B. Install and service large industrial burners
C. Install, service, and maintain residential gas appliances under
supervision
D. Approve gas system designs
Answer: C
G3 technicians are qualified to work on residential appliances and
systems within defined limits and often under supervision.
2. Natural gas is primarily composed of:
A. Propane
B. Butane
C. Methane
D. Ethane
Answer: C
Methane makes up the majority of natural gas used in Ontario.
, 3. Propane is classified as:
A. Lighter than air
B. Heavier than air
C. Same density as air
D. Non-combustible
Answer: B
Propane vapour is heavier than air and can collect in low areas.
4. The chemical symbol for carbon monoxide is:
A. CO₂
B. O₂
C. CO
D. CH₄
Answer: C
Carbon monoxide consists of one carbon atom and one oxygen atom.
5. Carbon monoxide is dangerous because it:
A. Has a strong odor
B. Causes corrosion
C. Displaces oxygen in the blood
D. Irritates the skin
Answer: C
CO binds to hemoglobin, preventing oxygen transport.
, 6. The typical supply pressure of natural gas to a residence is
approximately:
A. 14 in. w.c.
B. 7 in. w.c.
C. 2 psi
D. 5 psi
Answer: B
Residential natural gas pressure is commonly around 7 inches water
column.
7. One inch of water column is approximately equal to:
A. 0.5 psi
B. 1 psi
C. 0.036 psi
D. 0.1 psi
Answer: C
27.7 inches of water column equals 1 psi.
8. The purpose of a gas regulator is to:
A. Increase gas flow
B. Store gas
C. Control and reduce gas pressure
D. Filter contaminants
Answer: C
Regulators ensure safe and consistent appliance pressure.
, 9. A manometer is used to measure:
A. Voltage
B. Temperature
C. Gas pressure
D. Gas volume
Answer: C
Manometers measure low pressures such as inches of water column.
10. When testing for gas leaks, the safest method is to use:
A. A lighter
B. A match
C. Soap and water solution
D. A torch
Answer: C
Soap solution reveals leaks through bubble formation without ignition
risk.
11. The flammable range of natural gas in air is approximately:
A. 1–3%
B. 5–15%
C. 10–25%
D. 20–40%
Answer: B
Natural gas is combustible within roughly 5% to 15% concentration.
