Quote Originally Posted by Dave A View Post
When it comes to gas leaks, you don't need to "sniff it out." There's a simple pressure test where you charge the system up to ?* and lock it off for ten minutes. If the pressure doesn't drop - no leaks.
This is a standard 'drop test' and it's not an accurate test. With a large installation there could be hundreds of litres of gas in the pipework and even a small pressure drop over a few minutes could mean a very large leak.

With refrigeration a deep vacuum is pulled on the entire system and a similar test is done over time but when using a vacuum a small leak will be detectable far faster than using the pressurisation method. You can't use a vacuum with a gas installation because the pipework wall thickness is insufficient and the pipe will collapse.

Refrigeration engineers are often qualified to work with LPG if they are R600a or R290a certified. Lpg is used as a refrigerant in some domestic fridges nowadays.