I actually was sent to a class and certified to do the annual inspections for the CNG tanks we use here at work. It'* funny because the instructor said there hasn't been a CNG tank explosion that he knows of but there has been many unintended sudden releases of gas with no actual fire. Every failure he knows of has been something to do with the integerty of the tank. Case in point. The dude is lucky the bottle didn't take his head off.