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Gas Fitter Class C Licensing Exam Practice Test Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf
(All subjects covered: safety, tools, codes, combustion, appliances, piping,
ventilation, propane & NG fundamentals, etc.)
- What is the primary hazard associated with natural gas leaks?
a) Frostbite
b) Noise
c) Fire or explosion
d) Electrical shock
Rationale: Gas mixed with air can ignite violently, creating fire or
explosion hazards.
- What is the approximate specific gravity of natural gas relative to air?
- 1.53 1 / 3
- 0.25
- 0.6
- 1.0
Rationale: Natural gas is lighter than air (approx. 0.6 SG), so it rises
and disperses.
- In propane systems, where should leak testing occur before placing
into service?
a) Meter only
b) At the vent termination
c) Entire system at working pressure
d) At appliance valve only
Rationale: The entire piping system must be verified leak-free before
use.
- Which tool is used to thread steel pipe?
a) Tubing cutter
b) Pipe die
c) Flaring tool
d) Crimping pliers
Rationale: Pipe dies cut threads on steel gas piping.
- A Class C Gas Fitter is typically authorized to work on what
equipment?
a) Industrial boilers
b) High-pressure gas transmission lines 2 / 3
c) Small appliances under supervision
d) All gas appliances
Rationale: Class C is an entry-level trainee license working under
supervision.
- What chemical is added to natural gas to give it odor?
a) Benzene
b) Mercaptan
c) Ethanol
d) Nitrogen
Rationale: Mercaptan provides strong sulfur odor for leak detection.
- When should soap solution be used?
a) To clean burners
b) To test regulator outlet pressure
c) To test suspected gas leaks
d) To lubricate joints
Rationale: Soap solution bubbles if gas leakage is present.
- What is the primary byproduct of complete combustion of natural
gas?
a) Soot
b) Carbon monoxide
c) Carbon dioxide
d) Nitrogen
Rationale: Complete combustion produces CO₂ and water vapor.
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