UN number

UN numbers (United Nations numbers) are four-digit numbers that identify hazardous materials, and articles (such as explosives, Flammable Liquids to oxidizing solid or toxic liquids, etc.) in the framework of international transport. Some hazardous substances have their own UN numbers (e.g. acrylamide has UN 2074), while sometimes groups of chemicals or products with similar properties receive a common UN number (e.g. flammable liquids, not otherwise specified, have UN1993). A chemical in its solid state may receive a different UN number than the liquid phase if their hazardous properties differ significantly; substances with different levels of purity (or concentration in solution) may also receive different UN numbers.

UN numbers range from (UN 0001 - UN 0003 no longer exist) UN 0004 to about UN 3534 and are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. They are published as part of their Recommendations on the Transport of Dangerous Goods, also known as the Orange Book. These recommendations are adopted by the regulatory organization responsible for the different modes of transport.

There is no UN number allocated to non-hazardous substances. These will simply not have a UN number.

For more details, see Lists of UN numbers.

NA numbers (North America), are issued by the United States Department of Transportation and are identical to UN numbers, except that some substances without a UN number may have an NA number. These additional NA numbers use the range NA 8000 - NA 9279. There are two exceptions NA 2212 is all asbestos with UN 2212 limited to Asbestos, amphibole amosite, tremolite, actinolite, anthophyllite, or crocidolite. The second exception is NA 3334 is self-defense spray, non-pressurized with UN 3334 being aviation regulated liquid, not otherwise specified. here are more exceptions: NA/UN exceptions

For more details see List of NA numbers.

Associated with each UN number is a hazard identifier, which encodes the general hazard class and subdivision (and, in the case of explosives, their compatibility group). If a substance poses several dangers, then subsidiary risk identifiers may be specified. It is not possible to deduce the hazard class(es) of a substance from its UN number: they have to be looked up in a table.

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