"RonB" wrote in message

This has gone a little OT, but Oldun makes a damned good point. An air
compressor or an air bubble can do a very good imitation of a bomb.


Our (commercial) tanks must be inspected every two years. They used to peek
inside, tap on the wall and say "OK". No more. Now they use ultrasound to
check. The good thing is that we don't even have to shut down to do it.