Licensing Exam Class A Practice Exam

Gas Fitter Residential/Commercial Licensing Exam Class A Practice Exam 100 Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a gas regulator in a piping system?
• Increase gas pressure
• Maintain constant downstream pressure
• Filter gas supply
• Measure gas volume

Rationale: Regulators reduce and control incoming pressure to deliver

consistent downstream pressure to appliances.

• The typical pressure for natural gas supplied to residential customers in

North America is: 1 / 4

• 10–15 psi
• 7–14 inches water column
• 2–5 psi
• 1–2 inches water column

Rationale: Most residential distribution uses low-pressure gas around 7–

14” WC.

3. Propane vapor pressure depends mainly on:

• Pipe diameter
• Temperature
• Regulator spring tension
• Odorant level

Rationale: Propane vapor pressure varies strongly with temperature

changes.

• Which gas is heavier than air?
• Natural gas
• Hydrogen
• Propane
• Carbon monoxide

Rationale: Propane has a higher vapor density and sinks to low areas.

• The minimum clearance from combustible materials for a Category I gas

appliance vent connector is usually: 2 / 4

• 0 inches
• 6 inches
• 12 inches
• 18 inches

Rationale: Clearance for single-wall vent connectors is typically 6” unless

reduced by shielding.

6. Manometers measure:

• Temperature
• Flow rate
• Gas pressure
• Combustion air

Rationale: Manometers compare pressures, commonly inches of water

column in gas work.

7. Threaded steel gas piping should be joined using:

• Solder
• Pipe thread sealant or Teflon tape approved for gas
• Brazing
• Welding

Rationale: Threaded steel joints require sealing compounds rated for fuel

gas.

8. A yellow gas flame with soot indicates: 3 / 4

• Proper combustion
• Incomplete combustion
• Excess primary air
• Excess secondary air

Rationale: Yellow/sooty flame means insufficient air or blockage causing

incomplete combustion.

9. The main component of natural gas is:

• Butane
• Propane
• Methane
• Ethane

Rationale: Natural gas consists mostly of methane (about 90%+).

10. Carbon monoxide is dangerous because:

• It smells like rotten eggs
• It is lighter than air
• It enhances combustion
• It binds to hemoglobin more strongly than oxygen

Rationale: CO reduces blood’s oxygen-carrying capacity leading to

poisoning.

11. A drip leg is installed to:

• Prevent gas leaks
• Collect moisture and sediment
• / 4