of a CNG Facility Exam Practice

FDNY C99 Supervision and Maintenance of a CNG Facility Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• Which of the following is the primary hazard associated with

compressed natural gas (CNG)?

• Electrical shock
• Explosion
• Radiation
• Corrosion

Rationale: CNG is highly flammable and under high pressure, making

explosion the primary hazard.

• What is the standard pressure range for CNG storage cylinders in most

fueling stations? 1 / 4

• 1,000–2,000 psi
• 2,000–2,500 psi
• 3,000–3,600 psi
• 4,000–5,000 psi

Rationale: CNG is typically stored in cylinders at pressures of 3,000–3,600

psi.

• Which type of detector is most commonly used to identify natural gas

leaks at a CNG facility?

• Carbon monoxide detector
• Oxygen sensor
• Methane detector
• Smoke detector

Rationale: Methane is the primary component of CNG; detectors

specifically sense methane for leak detection.

• When conducting a visual inspection of CNG cylinders, which of the

following indicates that a cylinder should be removed from service?

• Minor scratches
• Faded paint
• Cracks or bulges
• Slight surface rust

Rationale: Cracks, bulges, or deep corrosion compromise cylinder integrity

and pose safety risks. 2 / 4

• The primary purpose of a pressure relief device (PRD) on a CNG

cylinder is to:

• Increase cylinder pressure
• Reduce maintenance requirements
• Prevent over-pressurization
• Indicate gas purity

Rationale: PRDs prevent cylinders from exceeding safe pressure limits and

reduce the risk of rupture or explosion.

• How often must CNG cylinders undergo hydrostatic testing?
• Every 2 years
• Every 3–5 years
• Every 10 years
• Only when damaged

Rationale: Hydrostatic testing is mandated every 3–5 years depending on

cylinder type and regulatory standards.

• Which NFPA standard governs CNG fueling station design and

operation?

A) NFPA 30

B) NFPA 70

C) NFPA 1

D) NFPA 52 3 / 4

Rationale: NFPA 52 specifically addresses vehicular natural gas systems

and fueling stations.

• Which valve is used to isolate the CNG supply from the dispenser

during maintenance?

• Check valve
• Shutoff valve
• Pressure relief valve
• Flow control valve

Rationale: Shutoff valves allow safe isolation of the gas supply for

maintenance or emergency purposes.

• What is the maximum allowable leak rate for a CNG system under

NFPA 52 guidelines?

• 0.5% of system volume per day
• 1% of system volume per day
• 2% of system volume per day
• 5% of system volume per day

Rationale: NFPA 52 limits leaks to 2% of system volume per day to ensure

operational safety.

• Which of the following is considered a primary component of a

CNG fueling station?

• Diesel fuel tank
• Cooling tower
• / 4