UN number UN numbers or UN IDs are four-digit numbers that identify hazardous substances and products (such as explosives and poisonous materials) of commercial importance. This numbering scheme is widely used in international commerce, for instance to label the contents of shipping containers. Some chemical compounds have their own UN numbers (e.g. acrylamide has UN2074), while sometimes groups of chemicals or products with similar properties receive a common UN number (e.g. cigarette lighters with flammable gas have UN1057). 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 may also receive different UN numbers. UN numbers range from UN1001 to about UN3500 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 typically adopted by the member states. NA numbers (North America), also known as DOT numbers 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 NA8000 - NA9999. 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). For instance, the hazard identifier of acrylamide is 6.1 and the one of cigarette lighters is 2.1. If a substances 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. The hazard classes and their divisions are: Class 1: Explosives Division 1.1: Substances and articles which have a mass explosion hazard Division 1.2: Substances and articles which have a projection hazard but not a mass explosion hazard Division 1.3: Substances and articles which have a fire hazard and either a minor blast hazard or a minor projection hazard or both, but not a mass explosion hazard Division 1.4: Substances and articles which present no significant hazard Division 1.5: Very insensitive substances which have a mass explosion hazard Division 1.6: Extremely insensitive articles which do not have a mass explosion hazard Class 2: Gases Division 2.1: Flammable gases Division 2.2: Non-flammable, non-toxic gases Division 2.3: Toxic gases Class 3: Flammable liquids Class 4: Flammable solids; substances liable to spontaneous combustion; substances which, on contact with water, emit flammable gases Division 4.1: Flammable solids, self-reactive substances and solid desensitised explosives Division 4.2: Substances liable to spontaneous combustion Division 4.3: Substances which in contact with water emit flammable gases Class 5: Oxidizing substances and organic peroxides Division 5.1: Oxidizing substances Division 5.2: Organic peroxides Class 6: Toxic and infectious substances Division 6.1: Toxic substances Division 6.2: Infectious substances Class 7: Radioactive material Class 8: Corrosive substances Class 9: Miscellaneous dangerous substances and articles External References 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 Emergency Response Guidebook from the U.S. Department of Transportation contains a list of all assigned NA numbers along with recommended emergency procedures. FAVORITE ARTICLES: History of the World    History of the United States    History of Europe    Ancient History    History    Military History    World War I    Bombing of Dresden    California    US Constitution    Frank Sinatra    Boston    Marbury v. Madison This article is licensed under the GNU Free Documentation License at http://www.gnu.org/copyleft/fdl.html You may copy and modify it as long as the entire work (including additions) remains under this license. You must provide a link to http://www.gnu.org/copyleft/fdl.html To view or edit this article at Wikipedia go to http://www.wikipedia.org/wiki/UN_number