helium gas cylinder for balloons

Common cylinder sizes

We measure cylinder volume by the amount of free air (of standard pressure of about 1 bar) that can be compressed into the cylinder; Europe and most of the rest of the world measure the cylinder volume as the internal volume (= water capacity) and specifies the working pressure of the cylinder: e.g. United States 19 cubic feet = International 3 liter at 180 bar.^{[citation need}

The below are example cylinder sizes and do not constitute an industry standard.

Gas storage tubes

For larger volume high pressure gas storage units, known as tubes, are available. They generally have a larger diameter and length than high pressure cylinders, and usually have a tapped neck at both ends. They may be mounted alone or in groups on trailers, permanent bases, or intermodal transport frames. Due to their length, they are mounted horizontally on mobile structures. In general usage they are often manifolded together and managed as a unit.

Gas storage banks]

Hydrogen storage cylinders in a cascade filling system

Groups of similar size cylinders may be mounted together and connected to a common manifold system to provide larger storage capacity than a single standard cylinder. This is commonly called a cylinder bank or a gas storage bank. The manifold may be arranged to allow simultaneous flow from all the cylinders, or, for a cascade filling system, where gas is tapped off cylinders according to the lowest positive pressure difference between storage and destination cylinder, being a more efficient use of pressurised gas.[citation needed]

Gas storage quads

Helium quad for surface-supplied diving gas

A gas quad is a group of high pressure cylinders mounted on a transport and storage frame. There are commonly 16 cylinders, each of about 50 litres capacity mounted upright in four rows of four, on a square base with a square plan frame with lifting points on top and may have fork-lift slots in the base. The cylinders are usually interconnected as a manifold for use as a unit, but many variations in layout and structure are possible