When a cylinder is manufactured, it is stamped with its specifications. These include the manufacturer, working pressure, test pressure, date of manufacture, capacity, and weight. The requirement to test a cylinder is dictated by the type of gas traffic which is being used in it.
Transportable pressure vessels for high-pressure gases need to be routinely inspected and tested as part of the manufacturing process. Evidence of passing the test is recorded, either individually or as part of a batch (some tests are destructive), and certified as meeting the standard of manufacture by the authorised testing agency. This process makes the transportable pressure vessels legal for import and sales.