ISO 32: colour coding of medical gas cylinders

What the standard covers

ISO 32, Gas cylinders for medical use: Marking for identification of content, establishes a system of marking and a set of colours so that the content of a medical gas cylinder can be identified. It concerns the cylinders themselves. Pipeline outlets, hoses and connectors are covered by other standards.

Edition in force and status

There is one edition, the first, published in May 1977. On 22 October 2026 ISO lists ISO 32:1977 as confirmed (stage 90.93) at its latest systematic review. The colour assigned to each gas is in the paid text of the standard and is not reproduced here; check it against the standard and against the national rules that apply where the cylinders are used.

Colour coding in Europe: EN 1089-3

In Europe, the colour coding of transportable gas cylinders for industrial gases, breathing gases and gases for medical use is specified in EN 1089-3:2011. DIN Media lists its German edition, DIN EN 1089-3:2011-10, as current; it replaced the 2004 edition. EN 1089-3 treats colour as a secondary means of identification: the labelling required by the RID/ADR transport regulations is the primary way of indicating the dangers of the contents, and colour helps people recognise the contents from a distance, for example in a fire.

What it means for a hospital or designer

• Read the label first. Colour helps staff recognise a cylinder at a glance, but under EN 1089-3 the transport label is the primary identification of the contents.
• Colour does not stop a wrong connection; gas-specific connections do. On the pipeline side, ISO 7396-1 requires non-interchangeability between components of different gas and vacuum systems, and ISO 9170-1 terminal units are designed to prevent interchange between gases.
• Cylinders feeding a manifold connect through high-pressure flexible connections covered by ISO 21969, for nominal filling pressures up to 25 000 kPa at 15 °C.
• Cylinder valves with an integrated pressure regulator (VIPRs) are covered by ISO 10524-3.