Editing UN number

{{Short description|United Nations code for dangerous substances}}{{Multiple issues|
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[[File:Placard 1814.jpg|200px|thumb|A United States [[Placard#United States Department of Transportation|placard]] showing the UN number 1814, indicating [[potassium hydroxide]] solution, on a railroad tank car.]]
A '''UN number''' ([[United Nations]] number) is a four-digit number that identifies [[hazardous materials]], and articles (such as [[explosive]]s, [[flammable liquid]]s, [[oxidizer]]s, [[toxic]] liquids, etc.) in the framework of [[international trade]] and [[transport]]. Some [[hazardous substances]] have their own UN numbers (e.g. [[acrylamide]] has UN 2074), while sometimes groups of [[Chemical substance|chemicals]] or products with similar properties receive a common UN number (e.g. flammable liquids, not otherwise specified, have UN 1993). A chemical in its [[solid]] state may receive a different UN number than the liquid phase if its hazardous properties differ significantly; substances with different levels of purity (or [[concentration]] in solution) may also receive different UN number

==Hazard identifiers==
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.

==Range==
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 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.

==Non-UN identifiers==
An '''NA number''' ([[North America]] number) is issued by the [[United 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 all [[asbestos]] with UN 2212 limited to [[asbestos]], [[amphibole]] amosite, [[tremolite]], [[actinolite]], [[anthophyllite]], or [[crocidolite]]. Another exception, NA 3334, is self-defense spray, non-pressurized while UN 3334 is [[aviation]]-regulated liquid, not otherwise specified. For the complete list, see [[NA/UN exceptions]].

An '''ID number''' is a third type of identification number used for hazardous substances being offered for [[Aviation|air transport]]. Substances with an ID number are associated with proper [[Freight transport|shipping]] names recognized by the [[ICAO]] Technical Instructions.<ref>{{cite web|url=https://www.ecfr.gov/current/title-49/subtitle-B/chapter-I/subchapter-C/part-172/subpart-B/section-172.101|title=Title 49 - Part 173 - Subtitle B - Chapter I - Subchapter C - Part 172 - Subpart B|website=eCFR - Code of Federal Regulations|publisher=U.S. Government Publishing Office|access-date=2023-11-13}}</ref> ID 8000, Consumer commodity does not have a UN or NA number, and is classed as a [[HAZMAT Class 9 Miscellaneous|Class 9]] hazardous material. 

==See also==
* [[Globally Harmonized System of Classification and Labelling of Chemicals]]
* [[Lists of UN numbers]]
* [[Dangerous goods]]
* [[CAS registry number]]
* [[List of NA numbers]]

==References==
{{reflist}}

==External links==
* [http://www.unece.org/trans/danger/danger.html United Nations Committee of Experts on the Transport of Dangerous Goods]
* [http://www.unece.org/trans/danger/publi/unrec/12_e.html UN Recommendations on the Transport of Dangerous Goods.]  Part 2 defines the hazard classes and their divisions and Part 3 contains a complete list of all UN numbers and their hazard identifiers.
* The [https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/docs/ERG2016.pdf Emergency Response Guidebook] from the U.S. Department of Transportation contains a list of all assigned NA numbers along with recommended emergency procedures.

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[[Category:Chemical numbering schemes]]
[[Category:Lists of UN numbers| ]]