CNG - Compressed Natural Gas Emergency Procedures and Response Questions and Answers

Question 1

A CNG vehicle is involved in a fire, and flames are impinging on the fuel cylinders.
According to standard emergency response guidelines, what is the correct action to take regarding the application of water?

Accepted Answer

Do not apply water to the CNG cylinders, as it can prevent the PRDs from activating.

Answer

Apply a fog stream to the top of the cylinders to keep the PRDs cool.

Answer

Direct a straight stream of water at the base of the fire to suppress it.

Answer

Apply water to the vehicle body to cool it and prevent fire spread to the cylinders.

Question 2

A technician needs to perform maintenance that requires depressurizing the low-pressure side of a CNG fuel system. After closing the manual cylinder valves, what is the next critical step in the procedure?

Accepted Answer

Start and run the engine until it stalls from lack of fuel.

Answer

Immediately open the bleed valve at the regulator.

Answer

Disconnect the fuel line at the engine.

Answer

Use a sniffer to check for leaks around the cylinder valves.

Question 3

A driver reports a strong 'rotten egg' smell inside the cab of a CNG vehicle while it is parked indoors. Which of the following actions should be taken IMMEDIATELY?

Accepted Answer

Ventilate the area, eliminate ignition sources, and move the vehicle outdoors if safe to do so.

Answer

Start the engine to burn off any excess gas.

Answer

Turn on the ventilation fans to clear the air.

Answer

Use a spray bottle with soapy water to find the source of the leak.

Question 4

During a post-accident inspection, a technician finds that a thermally-activated PRD has vented, which is evident by a missing fusible plug and soot around the vent line. What is the correct service procedure?

Accepted Answer

Replace the entire PRD assembly with a new, approved unit.

Answer

Clean the valve and reinstall a new fusible plug.

Answer

Test the PRD valve for leaks and reuse it if it seals properly.

Answer

Cap the vent line and repressurize the system to check for other leaks.

Question 5

A CNG vehicle has been partially submerged in flood water, with the water level reaching the bottom of the fuel cylinders. After retrieving the vehicle, which of the following is a mandatory first step before attempting to start or service the fuel system?

Accepted Answer

Disconnect the battery and perform a detailed inspection of the entire fuel system.

Answer

Start the engine briefly to see if it runs.

Answer

Pressurize the system at the fueling station to check for water intrusion.

Answer

Drain the engine oil and check for water contamination.

Question 6

When responding to a CNG leak in an open-air environment like a parking lot, which factor is most critical for establishing a safe perimeter?

Accepted Answer

The direction of the wind.

Answer

The current pressure reading on the fuel gauge.

Answer

The type of CNG cylinder (Type 1-4).

Answer

The time of day.