The UN Recommendations on the Transport of Dangerous Goods are contained in the UN Model Regulations prepared by the Subcommittee of Experts on the Transport of Dangerous Goods of the United Nations Economic and Social Council (ECOSOC). They cover the transport of dangerous goods by all modes of transport except by bulk tanker. They are not obligatory or legally binding on individual countries, but have gained a wide degree of international acceptance: they form the basis of several international agreements and many national laws.
"Dangerous goods" (also known as "hazardous materials" or "HAZMAT" in the United States) may be a pure chemical substance (e.g. TNT, nitroglycerin), mixtures (e.g. dynamite, gunpowder) or manufactured articles (e.g. ammunition, fireworks). The transport hazards that they pose are grouped into nine classes, which may be subdivided into divisions and/or packing groups. The most common dangerous goods are assigned a UN number, a four digit code which identifies it internationally. Less common substances are transported under generic codes such as "UN1993: flammable liquid, not otherwise specified".
The UN Recommendations do not cover the manufacturing, use or disposal of dangerous goods.