Ontario Gas Technician 3 (G3) Certification
Exam With Actual Questions & Verified
Answers, Plus Explained Rationales/Expert
Verified For Guaranteed 100% Pass
2026/Latest Update/Instant Download Pdf
1. What is the primary purpose of a gas regulator?
A. Increase gas pressure
B. Reduce and maintain gas pressure
C. Measure gas flow
D. Filter impurities
Rationale: A gas regulator reduces high inlet pressure to a safe,
usable level and maintains consistent outlet pressure.
2. Which gas is most commonly used in residential heating systems
in Ontario?
A. Propane
B. Butane
C. Natural gas
D. Hydrogen
Rationale: Natural gas is the most widely used fuel for residential
heating due to its availability and cost-effectiveness.
3. What device is used to detect gas leaks?
A. Thermostat
B. Manometer
C. Gas detector
D. Flow meter
Rationale: Gas detectors are specifically designed to sense the
presence of combustible gases and alert users.
,4. What is the minimum oxygen level required for safe combustion?
A. 10%
B. 15%
C. 21%
D. 30%
Rationale: Normal atmospheric oxygen is about 21%, which is
required for proper combustion.
5. What does G3 certification allow a technician to work on?
A. All gas appliances
B. Industrial gas systems
C. Residential gas appliances under supervision
D. High-pressure pipelines
Rationale: A G3 technician can work on residential equipment
but must be supervised by a higher-level technician.
6. What is the purpose of a thermocouple?
A. Increase temperature
B. Regulate pressure
C. Sense flame presence
D. Control airflow
Rationale: A thermocouple detects heat from a pilot flame and
signals the gas valve to stay open.
7. Which instrument measures gas pressure?
A. Thermometer
B. Manometer
C. Barometer
D. Ammeter
Rationale: A manometer measures gas pressure in inches of
water column or PSI.
, 8. What is “complete combustion”?
A. Burning with excess fuel
B. Burning without flame
C. Burning with sufficient oxygen producing CO₂ and water
D. Burning at low temperature
Rationale: Complete combustion occurs when enough oxygen is
present, producing carbon dioxide and water.
9. What is a common byproduct of incomplete combustion?
A. Oxygen
B. Nitrogen
C. Carbon monoxide
D. Steam
Rationale: Incomplete combustion produces carbon monoxide, a
dangerous and toxic gas.
10. What is the main function of a gas valve?
A. Measure flow
B. Filter gas
C. Control gas flow
D. Increase pressure
Rationale: Gas valves regulate and control the flow of gas to
appliances.
11. What is the standard unit for measuring gas pressure in
residential systems?
A. PSI
B. Bar
C. Inches of water column
D. Pascals
Rationale: Low-pressure gas systems commonly use inches of
water column (in. w.c.).
Exam With Actual Questions & Verified
Answers, Plus Explained Rationales/Expert
Verified For Guaranteed 100% Pass
2026/Latest Update/Instant Download Pdf
1. What is the primary purpose of a gas regulator?
A. Increase gas pressure
B. Reduce and maintain gas pressure
C. Measure gas flow
D. Filter impurities
Rationale: A gas regulator reduces high inlet pressure to a safe,
usable level and maintains consistent outlet pressure.
2. Which gas is most commonly used in residential heating systems
in Ontario?
A. Propane
B. Butane
C. Natural gas
D. Hydrogen
Rationale: Natural gas is the most widely used fuel for residential
heating due to its availability and cost-effectiveness.
3. What device is used to detect gas leaks?
A. Thermostat
B. Manometer
C. Gas detector
D. Flow meter
Rationale: Gas detectors are specifically designed to sense the
presence of combustible gases and alert users.
,4. What is the minimum oxygen level required for safe combustion?
A. 10%
B. 15%
C. 21%
D. 30%
Rationale: Normal atmospheric oxygen is about 21%, which is
required for proper combustion.
5. What does G3 certification allow a technician to work on?
A. All gas appliances
B. Industrial gas systems
C. Residential gas appliances under supervision
D. High-pressure pipelines
Rationale: A G3 technician can work on residential equipment
but must be supervised by a higher-level technician.
6. What is the purpose of a thermocouple?
A. Increase temperature
B. Regulate pressure
C. Sense flame presence
D. Control airflow
Rationale: A thermocouple detects heat from a pilot flame and
signals the gas valve to stay open.
7. Which instrument measures gas pressure?
A. Thermometer
B. Manometer
C. Barometer
D. Ammeter
Rationale: A manometer measures gas pressure in inches of
water column or PSI.
, 8. What is “complete combustion”?
A. Burning with excess fuel
B. Burning without flame
C. Burning with sufficient oxygen producing CO₂ and water
D. Burning at low temperature
Rationale: Complete combustion occurs when enough oxygen is
present, producing carbon dioxide and water.
9. What is a common byproduct of incomplete combustion?
A. Oxygen
B. Nitrogen
C. Carbon monoxide
D. Steam
Rationale: Incomplete combustion produces carbon monoxide, a
dangerous and toxic gas.
10. What is the main function of a gas valve?
A. Measure flow
B. Filter gas
C. Control gas flow
D. Increase pressure
Rationale: Gas valves regulate and control the flow of gas to
appliances.
11. What is the standard unit for measuring gas pressure in
residential systems?
A. PSI
B. Bar
C. Inches of water column
D. Pascals
Rationale: Low-pressure gas systems commonly use inches of
water column (in. w.c.).
