When a gas cylinder fails, all similar canisters could be at risk—which is why the failure mechanism must be identified.

When there’s any kind of failure in a system that sees a lot of use, that failure is analyzed so that the safety and effectiveness of the overall system is not compromised.  That rule applies for all sorts of combined or distributed systems, from nuclear power plants to airport security checks.  So when a Department of Transportation-approved metal cylinder leaks, they want to figure out why.  A report from Packer Engineering describes the tests they did to determine the characteristics and cause of the fracture and leak.  To ensure the characterization of the fracture identified the relevant features, they did a good ultrasonic cleaning of the fracture surface prior to scanning electron microscopy.