What do gas cylinder colours mean?

At a glance

Europe and UK

EN 1089-3:2011 — shoulder colour by hazard or specific gas

Medical

ISO 32:1977, where adopted

United States

No legal colour code — read the label

Where the colour is

The shoulder (top), not the body

Why the shoulder

The shoulder is the part of a cylinder you see first when cylinders stand in a row or a cage, and it stays visible when the body is hidden by a trolley or other cylinders. By putting the code there, EN 1089-3 frees the body colour for the gas supplier's branding or for historical national colours. That is also its weakness: a cylinder painted in a supplier's corporate colour can look alarming or reassuring for reasons that have nothing to do with the gas. The shoulder, and above all the label, are the parts that mean something.

Hazard colours and named-gas colours

The code works at two levels. For most gases, the shoulder shows the primary hazard: toxic or corrosive, flammable, oxidising, or inert. Mixtures with two hazards show both colours in bands or quarters. For a handful of very common gases the code assigns a specific colour instead, so that the most frequently handled cylinders are recognisable at once: oxygen white, acetylene maroon, argon dark green, nitrogen black, carbon dioxide grey, helium brown, nitrous oxide blue, hydrogen red and chlorine yellow. Some of these match the hazard rule (hydrogen is flammable, so red) and some deliberately do not (oxygen is oxidising but white rather than light blue).

UK oxygen cylinders were once black and nitrogen grey. The move to the European code swapped the meanings of familiar colours for a generation of users, which is why cylinders from the transition period were marked to show they followed the new scheme.

Medical gases and diving

Medical gas cylinders are covered by ISO 32, which dates from 1977 and is not adopted everywhere. Its white-for-oxygen convention is shared by the European industrial code, but other countries, notably the United States, use green for medical oxygen by long practice. Diving cylinders are another exception: they are often bright yellow or left as bare aluminium for visibility and durability, and breathing-gas mixtures are shown by shoulder quarters in white, black and brown. A yellow diving cylinder is not a toxic-gas cylinder, which is exactly the kind of cross-context confusion colour codes cannot prevent.

What colour does not tell you

A colour cannot state pressure, purity, grade, or whether the cylinder is full or empty. Paint fades, chips and is sometimes renewed in the wrong colour, and a cylinder may have been refilled with a different product by an operator who did not repaint it. In the United States, where colour coding is not regulated by law, the same gas can come in different colours from different suppliers. Industry and regulators are consistent: the label identifies the contents; colour is a quick visual prompt. This page explains the code and is not gas-safety advice.

The data

What goes wrong, and what to do

How to check it yourself

1. Look at the shoulder, not the body.
2. Read the product label and any hazard diamond on it.
3. If the shoulder colour and label disagree, the cylinder should not be used until the supplier confirms the contents.

What the evidence says

Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.

• FactModerate evidence

  EN 1089-3, the European standard for colour coding of transportable gas cylinders (excluding LPG), is current in its 2011 edition.

  Source: European Standards online catalogue (EN, ISO, IEC, BSI, ASTM listings)

• StandardModerate evidence

  Under EN 1089-3 the shoulder colour shows the primary hazard — yellow toxic or corrosive, red flammable, light blue oxidising, bright green inert — and applies to the shoulder only.

  Caveat: Summarised from a secondary source and not yet checked against the standard itself; confirm with the standard before relying on it.

  Source: Bottled gas — colour coding (Wikipedia)

• FactModerate evidence

  In the United States gas cylinder colour coding is not regulated by law, and users are told to identify contents from the label rather than the colour.

  Caveat: Summarised from a secondary source and not yet checked against the standard itself; confirm with the standard before relying on it.

  Source: Bottled gas — colour coding (Wikipedia)

• FactStrong evidence

  ISO 32, covering colour marking of medical gas cylinders, dates from 1977 and remains the listed edition.

  Source: International Organization for Standardization (ISO) catalogue; European Standards online catalogue (EN, ISO, IEC, BSI, ASTM listings)

Related questions

What colour is an oxygen cylinder?

Under the European code, a white shoulder. In the United States medical oxygen is commonly green by long practice, and industrial oxygen varies by supplier — the label decides.

Why does an acetylene cylinder have a maroon top?

Acetylene is one of the gases EN 1089-3 gives its own colour rather than the general red for flammables, so welders can pick it out immediately from other fuel gases.

Does a cylinder's body colour mean anything?

Not under EN 1089-3, which codes the shoulder only. Body colours are often supplier branding or older national practice.

Related topics

Go further

Sources

• European Standards online catalogue (EN, ISO, IEC, BSI, ASTM listings) — European Standards s.r.o. (Reference work)
• Bottled gas — colour coding (Wikipedia) — Wikipedia (Reference work)
• International Organization for Standardization (ISO) catalogue — ISO (Standards body)

Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.