Glossary / Identifiers
UN number
A UN number is a four-digit code, assigned under the United Nations recommendations on the transport of dangerous goods, that identifies a particular hazardous substance or a group of similar ones. It appears on shipping papers, packages, placards, and in emergency response guides.
Explanation
The UN number links a shipment to a standardized description. Responders can look up the number and quickly learn the likely hazard and the first actions to take, even when the cargo name is unfamiliar or the markings are in another language.
UN numbers are used in the US DOT hazardous materials regulations (49 CFR Parts 171-180), in international sea, air, and rail codes, and in the Emergency Response Guidebook, where the number points to a numbered guide page.
A UN number may be tied to one specific substance or to a broad entry covering many, such as a not otherwise specified listing for a hazard type. Several entries may share a hazard class but differ in their packing groups or required packaging.
On a package or placard, the UN number is shown in the format the regulations require, usually together with the proper shipping name. It is separate from the CAS number, which identifies a chemical rather than a transport entry.
Not every chemical has a UN number. Only materials regulated as dangerous goods in transport do, and a material that is hazardous in the workplace may not be regulated in shipping.
What to do and watch for
- Copy the UN number exactly onto shipping papers and markings.
- Use the number to find the right ERG guide in an emergency.
- Do not use a CAS number where a UN number is required, or the reverse.
Where it appears on an SDS
- Section 14: Transport information. The transport section gives the UN number, proper shipping name, hazard class, and packing group for each mode where the material is regulated.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.