Science, Tech, Math › Science UN ID Number Definition for Chemicals Share Flipboard Email Print Steve Froebe / Getty Images Science Chemistry Chemical Laws Basics Molecules Periodic Table Projects & Experiments Scientific Method Biochemistry Physical Chemistry Medical Chemistry Chemistry In Everyday Life Famous Chemists Activities for Kids Abbreviations & Acronyms Biology Physics Geology Astronomy Weather & Climate By Anne Marie Helmenstine, Ph.D. Chemistry Expert Ph.D., Biomedical Sciences, University of Tennessee at Knoxville B.A., Physics and Mathematics, Hastings College Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels. our editorial process Facebook Facebook Twitter Twitter Anne Marie Helmenstine, Ph.D. Updated February 02, 2019 A United Nations Number – also called a UN number or UN ID – is a four digit code used to identify flammable and harmful chemicals. Non-hazardous chemicals are not given UN numbers. UN numbers are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods and range from UN0001 to about UN3534. However, UN 0001, UN 0002, and UN 0003 are no longer in use. In some cases, specific chemicals are assigned a UN ID, while in other cases, a number can apply to a group of products with similar properties. If a chemical behaves differently as a liquid than as a solid, two different numbers may be assigned. For the most part, NA numbers (North America numbers) from the United States Department of Transportation are identical to UN numbers. In some cases, a NA number exists where a UN number has not been assigned.There are a few exceptions, including the identifier for asbestos and that for non-pressurized self-defense spray. Use of UN Numbers The primary purpose for the codes is to regulate modes of transport for hazardous chemicals and provide key information for emergency response teams in the event of an accident. The codes may also be used to identify storage incompatibilities. UN Number Examples UN numbers are only assigned for hazardous materials, such as explosives, oxidizers, toxins, and flammable substances. The first number in modern use is UN0004, is for ammonium picrate, present at less than 10% by mass. The UN for acrylamide is UN2074. Gunpowder is identified by UN0027. Air bag modules are indicated by UN0503.