For these gasses its 10 years, however there is a caveat that the filler / supplier must be able to prove the prevention of moisture entering the cylinder.

Phil

Hi Helton81, I work for one of the main compressed gas cylinder suppliers in the UK and though I dont know who supplies your cylinders it is very unlikely that they are not inspecting and testing their cylinders. The supplier will be inspected and monitored and have to provide records of cylinder testing and inspection. The cylinder test dates may be stamped on the cylinder or there may be plastic month/year test rings where the valve attaches to the cylinder. This will indicate when the next test is due, Usually a ten year period. If the date is lets say 2016, that means the cylinder cannot be refilled by your supplier without a full test. However the cylinder can be used well beyond this test date without any risk to the user. However with dispensing gases I would expect cylinders to be turned over frequently and not sitting in a cellar for years. The risk of a cylinder failing is very, very remote. The greatest risks to you are from handling cylinders and the risk of a leaking cylinder valve which could lead to an oxygen deficient atmosphere, especially in a small cellar. Having said all that any supplier worth their salt should be able to satisfy you that their procedures for cylinder testing and for ensuring gas quality are robust. If they can't then it might be time to change supplier