High pressure gas cylinders are made from steel or aluminium alloys fitted with valves. The contents are identified by adhesive labels, stencilling and a system of color coding.

The following information is marked on each cylinder by permanent stamping :

• Cylinder Markings
• Filling pressure
• Test pressure
• Manufacturer and country of origin
• Serial number
• Stamp of official authority
• Date of previous pressure tests and/or inspections with the stamps of the testing/inspection authorities.
• Cold Rolled sheets, strips and coils

These marks must never be removed or defaced. Cylinders can only be filled if they carry the correct identification.