"Tim Downie" wrote in message
...
I was recently told when a plumber cut off a dead leg in our gas pipework
that we had a small (but allowable) leak in our system.

Clearly he wasn't wild about chasing the leak but I'd rather there wasn't
one. Before I start hunting, what's the acceptable leak level in
mbar/min?

Zero!
Unless you know the gas is being vented to the outside air how do you know
it will not go *BANG*?
It may take weeks or months to build to an explosive mixture but how do you
know it hasn't?