CNG Emergency Procedures and Response 3

Question 1

What is the function of a pressure relief device (PRD) on a CNG cylinder?

Accepted Answer

Vent gas to prevent cylinder rupture from excessive heat or pressure

Answer

PRDs are thermally and/or pressure-activated safety devices that release gas to prevent catastrophic cylinder failure under abnormal conditions.

Question 2

In the context of CNG emergencies, BLEVE stands for:

Accepted Answer

Boiling Liquid Expanding Vapor Explosion

Answer

A BLEVE occurs when a pressurized container fails catastrophically, releasing a rapidly expanding vapor cloud that can ignite explosively.

Question 3

What is the recommended minimum safe distance for first responders from a CNG vehicle fully engulfed in fire?

Accepted Answer

300 feet

Answer

A 300-foot safety perimeter is recommended for CNG vehicle fires due to the risk of PRD venting, cylinder rupture, and projectile hazards.

Question 4

Why should water be continuously applied to CNG cylinders during a vehicle fire?

Accepted Answer

To cool cylinders and delay or prevent PRD activation or structural failure

Answer

Cooling cylinders with water reduces heat buildup that would otherwise trigger PRD venting or compromise cylinder structural integrity.

Question 5

After a CNG vehicle is involved in a collision, the driver should immediately:

Accepted Answer

Shut off the fuel system and exit the vehicle

Answer

Shutting off the CNG fuel system after a collision eliminates the gas supply and significantly reduces fire and explosion risk.

(CNG) Compressed Natural Gas Practice Test