Gas cylinder colour coding: how not to mix up CO₂, nitrogen, oxygen and argon
Two marking systems still coexist on Ukrainian sites: the European shoulder colours and the old all-over paint. A table of both, plus what the neck stamp tells you.
Colour on a cylinder is not decoration — it is the fastest way to tell what is inside from across a yard. The catch in Ukraine is that two systems are in service at the same time: cylinders marked to EN 1089-3 and older ones painted in full according to Soviet-era standards.
Two systems, side by side
EN 1089-3 (adopted as ДСТУ EN 1089-3) colours only the shoulder of the cylinder. The body can be any colour the owner likes, which is why you see grey, black and green bodies with the same shoulder. The old system painted the whole cylinder and relied on the lettering and stripes.
| Gas | Shoulder, EN 1089-3 | Legacy marking | Lettering |
|---|---|---|---|
| Carbon dioxide CO₂ | grey, RAL 7037 | black body | yellow «CO₂» |
| Nitrogen N₂ | black, RAL 9005 | black body, brown stripe | yellow «Nitrogen» |
| Oxygen O₂ | white, RAL 9010 | blue body | black «Oxygen» |
| Argon Ar | dark green, RAL 6001 | grey body, green stripe | green «Argon» |
| Acetylene C₂H₂ | maroon, RAL 3009 | white body | red «Acetylene» |
| Ar/CO₂ welding mix | bright green, RAL 6018 | — | «Mixture» and composition |
Colour is a hint, never a document. The binding identification is the label on the shoulder and the stamp on the neck ring. If the label is missing or unreadable, the cylinder goes back to the supplier — it is not identified by guesswork.
What the neck stamp says
- Manufacturer and serial number.
- Water capacity in litres and the empty (tare) mass in kilograms.
- Working and test pressure.
- Date of manufacture and the date of the last periodic inspection.
The tare mass matters in daily work: weigh a cylinder, subtract the tare, and you know exactly how much product is left. That is a far more reliable reading than a pressure gauge, because a liquefied gas keeps almost constant pressure until it is nearly empty.
Periodic inspection for cylinders with non-corrosive gases is normally every five years. Check the current interval against the safety rules in force before you accept a delivery — an out-of-date cylinder is a finding waiting to happen during an inspection.
Three mistakes that cost real money
- Filling a cylinder with the wrong gas. Oxygen fittings must stay free of oil and grease; a cylinder that has held a hydrocarbon and is then filled with oxygen is a fire waiting for a spark.
- Adapters between different threads. The connections for oxygen, carbon dioxide and fuel gases differ on purpose, precisely so that incompatible things cannot be joined. An adapter defeats the one safeguard that works without human attention.
- Repainting a cylinder in house. Colour is applied by the filler, who is responsible for the identification. A repainted cylinder loses its traceability and will be rejected at the filling station.
When cylinders stop being the right answer
Colour coding is a cylinder problem. Once the consumption grows past a tonne or so a month, the whole cylinder fleet — with its colours, stamps, deposits and swaps — is replaced by one stationary tank with a nameplate and a passport. How to work out where that point is, we covered in a separate article on cylinder capacity and the break-even volume.
Frequently asked questions
A black cylinder — is that nitrogen or carbon dioxide?
Under the legacy scheme both are black, and the difference is in the lettering and the brown stripe that nitrogen carries. Under EN 1089-3 the shoulder settles it: black shoulder is nitrogen, grey is carbon dioxide. When the two systems meet in one yard, read the label rather than the paint.
How do we check how much gas is left in a cylinder?
Weigh it and subtract the tare mass stamped on the neck. For liquefied gases such as CO₂ this is the only accurate method: pressure stays almost constant while liquid remains, so the gauge shows a comfortable reading right up to the moment the cylinder runs dry.
You may also need
Cryogenic cylinders for liquid nitrogen (LIN, N₂)
Cryogenic cylinder for liquid nitrogen
Model: CC-N2
Portable vacuum-insulated cylinder for storing liquid nitrogen (LIN, N₂) with gas or liquid withdrawal. Volume, working pressure and configuration are selected for your process.
Price on request
On request
Cryogenic tanks for liquid CO₂ (carbon dioxide) 10–100 m³
Cryogenic tank for liquid CO₂ 10 m³
Model: CT-CO2-10
Stationary vacuum-insulated cryogenic tank for storing liquid CO₂ (carbon dioxide), geometric volume 10 m³. Supplied with valves, pressure control, vaporizers and a pressure-reducing unit; turnkey installation available.
Price on request
Made to order
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