Standardization of gas cylinders
Regulation and standardisation of transportable pressure equipment

The diversity and complexity of the characteristics of the gases and gas mixtures transported means that cylinders need to be made from materials with characteristics compatible with their contents, and therefore need to be manufactured specifically by a few highly specialized companies. These include welded steel, seamless steel, stainless steel, aluminum alloy and composite cylinders, drums, frames and battery-vehicles (figure 1 ). In addition to these cylinder manufacturers, there are also manufacturers of accessories, and in particular valves, which play an essential role in the cylinder's leak-tightness.