# ISO 32: colour coding of medical gas cylinders

ISO 32:1977 is the ISO standard that sets a marking system and a series of colours for identifying the contents of medical gas cylinders; ISO still lists its first edition, from May 1977, as in force, confirmed at its latest systematic review.

## 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](https://library.ultracontrolo.com/standards/iso-7396-1/) requires non-interchangeability between components of different gas and vacuum systems, and [ISO 9170-1](https://library.ultracontrolo.com/standards/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](https://library.ultracontrolo.com/standards/iso-10524/).

### Does ISO 32 apply to pipeline outlets?

No. ISO 32 concerns the marking and colours of medical gas cylinders; pipeline terminal units are covered by ISO 9170-1.

### Is colour the main way to identify what is in a cylinder?

Not under EN 1089-3, which treats colour as a secondary method; the label required by the RID/ADR transport regulations is the primary one.

## Sources

- [ISO 32:1977, Gas cylinders for medical use: Marking for identification of content (iso.org)](https://www.iso.org/standard/3659.html)
- [DIN EN 1089-3:2011-10, Transportable gas cylinders, Gas cylinder identification (excluding LPG), Part 3: Colour coding (DIN Media)](https://www.dinmedia.de/en/standard/din-en-1089-3/137561856)
- [ISO 7396-1:2016, Medical gas pipeline systems, Part 1 (iso.org)](https://www.iso.org/standard/60061.html)
- [ISO 9170-1:2017, Terminal units, Part 1 (iso.org)](https://www.iso.org/standard/67451.html)
- [ISO 21969:2009, High-pressure flexible connections (iso.org)](https://www.iso.org/standard/52967.html)
- [ISO 10524-3:2019, Pressure regulators integrated with cylinder valves (iso.org)](https://www.iso.org/standard/66691.html)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/standards/iso-32-cylinder-colours/