Emergency Procedures and Response Flashcards

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

Answer: Vent gas to prevent cylinder rupture from excessive heat or pressure

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

In the context of CNG emergencies, BLEVE stands for:

Answer: Boiling Liquid Expanding Vapor Explosion

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

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

Answer: 300 feet

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

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

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

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

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

Answer: Shut off the fuel system and exit the vehicle

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

Which condition requires a CNG cylinder to be immediately removed from service?

Answer: Visible bulging, deep denting, or evidence of fire/heat damage

Physical deformation, deep denting, bulging, or thermal damage compromises the structural integrity of a CNG cylinder, making it unsafe to use.

When first responders arrive at a CNG vehicle accident, their FIRST priority should be:

Answer: Securing the scene and identifying CNG system components

Scene security and identification of CNG system components allow responders to assess fire and explosion risks before taking further action.