The leak test may be quite simple and even using a spray of soapy water and looking for the bubbles can be acceptable.
Under the Fluorinated Greenhouse Gases Regs 2015, you must carry out a leak test at intervals dependant upon:
- The global warming potential (GWP) of the gas, and
- The amount stored in your system.
It is obvious that this interval is based on the risk. For most companies reading this, the interval is every year.
These two articles give you guidance on leak testing. Although the second one is from the USA, it is still relevant.