UN numbers of hazardous substances and goods

UN numbers, or UN-IDs, are four-digit numbers representing hazardous substances and goods (such as explosives, flammable substances, toxic substances etc.) used to identify international transport. Some hazardous substances carry their own UN numbers (e.g. acrylamide carries UN2074), while certain groups of chemical substances or products with similar characteristics share a common UN number (e.g. flammable substances, not mentioned elsewhere, carry UN1993). If their hazardous properties differ significantly, a chemical substance in solid form can carry a different UN number than its liquid form. Furthermore, substances with different purity levels (or concentration levels in solutions) can also carry different UN numbers.

UN numbers vary from UN0001 to about UN3500 and are allocated by the UN 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 approved by the regulatory body responsible for the different modes of transport.