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AUN number (United Nations number) is a four-digit number that identifieshazardous materials, and articles (such asexplosives,flammable liquids,oxidizers,toxic liquids, etc.) in the framework ofinternational trade andtransport. Somehazardous substances have their own UN numbers (e.g.acrylamide has UN 2074), while sometimes groups ofchemicals or products with similar properties receive a common UN number (e.g. flammable liquids, not otherwise specified, have UN 1993). A chemical in itssolid state may receive a different UN number than the liquid phase if its hazardous properties differ significantly; substances with different levels of purity (orconcentration in solution) may also receive different UN number
Associated with each UN number is ahazard 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 subsidiaryrisk 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.
UN numbers range from UN 0004 to about UN 3550 (UN 0001 – UN 0003 are no longer in use) and are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods. They are published as part of theirRecommendations on the Transport of Dangerous Goods, also known as theOrange Book. These recommendations are adopted by the regulatory organization responsible for the different modes of transport. There is no UN number allocated to non-dangerous substances.
AnNA number (North America number) is issued by theUnited States Department of Transportation and is 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 9000 - NA 9279. There are some exceptions, for example, NA 2212 is allasbestos with UN 2212 limited toasbestos,amphibole amosite,tremolite,actinolite,anthophyllite, orcrocidolite. Another exception, NA 3334, is self-defense spray, non-pressurized while UN 3334 isaviation-regulated liquid, not otherwise specified. For the complete list, seeNA/UN exceptions.
AnID number is a third type of identification number used for hazardous substances being offered forair transport. Substances with an ID number are associated with propershipping names recognized by theICAO Technical Instructions.[1] ID 8000, Consumer commodity does not have a UN or NA number, and is classed as aClass 9 hazardous material.
