The UN numbers range from UN0001 to about UN3600 and are assigned by the United Nations Committee of Experts on the Transport of Dangerous Goods.
A UN number is a four-digit number that identifies hazardous materials, and articles in the framework of international trade and transport. Some hazardous substances have their own UN numbers, while sometimes groups of chemicals or products with similar properties receive a common UN number. 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 may also receive different UN numbers.
Dangerous goods, abbreviated DG, are substances that when transported are a risk to health, safety, property or the environment. Certain dangerous goods that pose risks even when not being transported are known as hazardous materials. An example for dangerous goods is hazardous waste which is waste that has substantial or potential threats to public health or the environment.