Licensing Exam Class B Practice Exam

Gas Fitter Residential/Commercial Licensing Exam Class B Practice Exam 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 fuel system?

a) Increase gas pressure

b) Filter impurities

c) Reduce and control gas pressure

d) Detect gas leaks

Rationale: Regulators lower incoming pressure to a safe, usable level

for appliances.

• Which type of piping material is commonly allowed for natural gas in

commercial buildings?

a) Copper type M

b) Steel Schedule 40 1 / 3

c) PVC

d) CPVC

Rationale: Schedule 40 steel is standard for gas distribution due to

strength and code compliance.

3. Propane is heavier than air and will:

a) Rise and disperse

b) Collect in low areas

c) Vaporize quickly upward

d) Not pose an accumulation hazard

Rationale: Propane sinks, risking pooling and explosion hazards.

• The maximum gas pressure allowed inside most residential appliances

is:

• 14" w.c.
• ½ psi
• 3 psi
• 10 psi

Rationale: Residential appliances typically operate at low pressure

not exceeding ½ psi.

5. The primary component of natural gas is:

a) Propane

b) Methane

c) Butane 2 / 3

d) Ethane

Rationale: Natural gas is primarily methane (CH₄).

6. A shutoff valve must be located:

a) Anywhere in the gas line

b) Within 6 ft of the appliance

c) Outdoors only

d) Next to the meter only

Rationale: It must be accessible and near the connected appliance

per code.

• What is the typical pressure drop allowed in residential gas piping?
• 0 psi
• 0.5" w.c.
• 5 psi
• 10 psi

Rationale: Codes allow ~0.5" w.c. pressure drop for correct sizing.

8. Combustion air must be provided to prevent:

a) Carbon dioxide removal

b) Heat loss

c) Incomplete combustion

d) Excess humidity

Rationale: Lack of oxygen causes incomplete combustion and CO

formation.

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