Recent updates to FDNY Books Haz-Mat 1 – Alternate Fuels - have detailed important changes regarding CNG vehicle fires. When arriving at a Compressed Natural Gas vehicle fire DO NOT apply water to CNG cylinders exposed to fire because this may cool the pressure relief device (PRD) resulting in it not activating. This can result in a catastrophic cylinder failure (high pressure gas rupture). Exploding cylinders can rocket.
• When a PRD activates, it will not reset/close. The gas in the cylinder will burn off. The result is often a jet fire which may go out and reignite several times.
• It may take 10-15 minutes for the high-pressure release to subside and up to 30 minutes to fully discharge, depending on the size of the tanks involved.
• Establish a minimum safe perimeter of 100-ft around the vehicle.
• PRD’s are located on both ends of the cylinder. They may be vented up and sideways. Additional PRD’s may be located in the bottom of a vehicle on the regulator. Always approach from 45° angle.
• If the CNG cylinders are not involved in the fire, proceed with normal extinguishment tactics All members are encouraged to review the video link above.
A link to the updated version of FD Books Haz-Mat 1 is also provided