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

Name marking under OSHA; FDA shoulder colours for medical gases only

Where the colour is

The shoulder (top); the body too for medical gases and acetylene

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 leaves the body to a scheme chosen by the gas company, provided it does not conflict with the shoulder. 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. There are three exceptions in UK practice, where the body is coloured too: medical gas cylinders have white bodies, acetylene cylinders are maroon on body and shoulder, and hydrogen cylinders are by custom red all over. No other cylinder may have a white or maroon body. 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. A gas with two such properties shows both colours, as two bands or as quarters around the shoulder. 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, nitrous oxide blue, argon dark green, nitrogen black, carbon dioxide grey and helium brown. These deliberately depart from the hazard rule: oxygen is oxidising but white rather than light blue, and nitrogen and argon are inert but black and dark green rather than bright green. Other gases simply carry their hazard colour, so hydrogen and methane are red and chlorine and ammonia yellow.

Maroon is not quite one colour. UK law requires acetylene cylinders to be a particular maroon on body and shoulder, while the European standard designates a slightly different one, so acetylene cylinders from the Continent can look subtly different. A stencilled letter N, used elsewhere to show that a cylinder follows the European code, is not needed in the UK.

Medical gases and diving

Medical gas cylinders are covered by ISO 32, which dates from 1977 and is not adopted everywhere. In the UK the medical colours are consistent with it and with the industrial code: a white body, with white for oxygen and blue for nitrous oxide on the shoulder. The United States does it differently. An FDA rule requires each high-pressure medical gas cylinder to be coloured on the shoulder, and its list makes oxygen green and medical air yellow, while agreeing with Europe on blue for nitrous oxide, grey for carbon dioxide, brown for helium and black for nitrogen. So a green shoulder means an inert gas in Europe and medical oxygen in America, and a yellow one means toxic or corrosive in Europe and medical air in America. Breathing mixtures are shown by combining colours: in the UK, white with black for air and white with brown for helium and oxygen, and bundles for offshore diving follow a separate industry scheme. These are exactly the cross-context confusions a colour code 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 for gas mixtures the European standard gives no specific guidance, so suppliers may use their own schemes. In the United States, OSHA's rule for welding gases does not mention colour at all: it requires the cylinder to be legibly marked with the chemical or trade name of the gas. The British gases industry says the same thing from the other direction: colours are not mandatory, and the label is the primary means of identifying the contents. 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)

• StandardStrong evidence

  Under BS EN 1089-3 the shoulder colour shows a gas's hazard property — yellow toxic or corrosive, red flammable, light blue oxidising, bright green inert — unless the gas has a specific colour, and the code applies to the shoulder only, except for medical gases (white body), acetylene (maroon body and shoulder) and, by UK custom, hydrogen (red body and shoulder).

  Caveat: Checked against the British Compressed Gases Association's own summary of the standard, TIS 6 Revision 3 (2018). Revision 4 (2023) could not be consulted and EN 1089-3 itself was not read.

  Source: BCGA Technical Information Sheet 6: Gas cylinder identification — label and colour code requirements (Revision 3, 11 April 2018)

• StandardStrong evidence

  US federal rules treat cylinder colour in two ways: OSHA's rule for welding gases requires a cylinder to be marked with the chemical or trade name of the gas and assigns no colours, while an FDA rule requires high-pressure medical gas cylinders to be coloured on the shoulder — green for oxygen, blue for nitrous oxide, yellow for medical air.

  Caveat: Only these two federal rules were read. Industry codes for industrial cylinder colours in the United States, and state rules, were not checked.

  Source: 29 CFR 1910.253 — Oxygen-fuel gas welding and cutting; 21 CFR 201.328 — Labeling of medical gas containers

• FactStrong evidence

  The British Compressed Gases Association states that the colours applied to cylinders are not mandatory and that the label is the primary method of identifying a cylinder's contents.

  Source: BCGA Technical Information Sheet 6: Gas cylinder identification — label and colour code requirements (Revision 3, 11 April 2018)

• 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 an FDA rule makes green the shoulder colour for medical oxygen, and OSHA's rule for industrial welding gases sets no colour at all — 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. In the UK the acetylene safety regulations go further and require both the body and the shoulder to be maroon.

Does a cylinder's body colour mean anything?

Usually not: EN 1089-3 codes the shoulder, and the body follows the gas company's own scheme. The exceptions are white bodies for medical gases, maroon for acetylene and, by UK custom, red for hydrogen.

Related topics

Go further

Sources

• European Standards online catalogue (EN, ISO, IEC, BSI, ASTM listings) — European Standards s.r.o. (Reference work)
• BCGA Technical Information Sheet 6: Gas cylinder identification — label and colour code requirements (Revision 3, 11 April 2018) — British Compressed Gases Association (Standards body)
• 29 CFR 1910.253 — Oxygen-fuel gas welding and cutting — US Occupational Safety and Health Administration (Official standard or government)
• 21 CFR 201.328 — Labeling of medical gas containers — US Electronic Code of Federal Regulations (Food and Drug Administration rule) (Official standard or government)
• International Organization for Standardization (ISO) catalogue — ISO (Standards body)

Reviewed 1 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.