What the standard defines
ISO 12402 is a family of parts, not a single document. Each part covers one class of device, and the class is stated on the label as a number in newtons together with the part number. The corpus prints one of them directly: an automatic jacket marked « 165N, ISO 12402-3 ».
What the class describes is the buoyancy the device provides and the way it is designed to support a person in water. The lower classes are buoyancy aids — swimming assistance for someone conscious and able. The higher ones are lifejackets, designed to support a person who may be unable to help themselves.
The European adoption, EN ISO 12402, is what makes the class part of the CE marking on a garment sold in the EU. That marking is the maker’s declaration, and the standard is what it declares against.
What it does not promise
It does not promise that a garment will work if it has not been serviced. An automatic jacket carries a cylinder and a water-soluble trigger, and both have a replacement date the maker sets.
It does not promise fit. A device outside the weight range printed on it is the wrong device, and the corpus shows makers stating those ranges plainly — one listing gives two bands for the same model.
It does not promise anyone will be turned face-up. That behaviour belongs to specific classes, and reading it into a lower one is the most expensive mistake available on this shelf.
And it does not address the water. The flow, the temperature, the boat and the decisions taken on it are outside any standard, and this site says nothing about them.
Where it shows up on this site
On the buoyancy aid shelf, where the class in newtons is the first figure of every listing and the only one that separates two garments at the same price. It is read alongside the weight range the maker prints, the presence of a crotch strap, and whether the device is foam or automatic — because a foam aid works unserviced and an automatic one does not.
It is also worth reading before a bait boat or a boat rod is bought, for the plain reason that both put somebody on or beside deeper water than a bank.
How to read a label that cites it
Two things, in this order. The part number — the digits after the dash — which says which class of device you are holding. Then the newton figure, which says how much buoyancy it provides. A listing that gives one without the other has given you half of the designation, and this site records that as a gap rather than filling it in.
Where a maker also cites the PPE Regulation or a CE mark, both are its own declaration against the standard. Neither is a test result, and neither is a substitute for the instructions in the box.
The questions that keep coming back
Is a buoyancy aid a lifejacket?
No, and ISO 12402 is where the difference is written down. They sit in different parts of the standard and undertake different things: one is designed to help a conscious person who can swim, the other to support a person who may not be able to help themselves. A listing that uses the two words interchangeably has told you nothing.
Which part applies to what I am buying?
Read the number after the dash and the class in newtons beside it. Both appear on the label, and both appear in several listings in this corpus. This site prints what the maker printed and does not translate one part into another.
Does a higher class make a product better?
It makes it a different product for a different use, and heavier and bulkier with it. A garment designed for offshore work is not an upgrade for a float tube; it is the wrong tool, and it is the reason the standard has parts at all.
Does the standard cover the inflation mechanism?
The standard addresses the device and its components, and a separate part deals with test methods. What matters in practice is that an automatic jacket depends on a gas cylinder and a trigger, both of which carry a replacement date set by the maker — and that date is in the maker’s instructions, not in the price.
Last reviewed 22 September 2026