The UN number is a unique identification number for dangerous goods labelling. A dangerous goods number must always be specified when dangerous goods are transported. It does not matter which goods or substance groups it is. As soon as the transported goods have a potential risk, they must be marked with a UN number.
The UN number always consists of four numbers, which are uniform throughout the world. By marking dangerous goods, an accident can quickly identify which goods have been loaded and which safety measures have to be taken.
It is obligatory to label dangerous goods with a Dangerous Goods number which is consistent in each country so that relief and security forces around the world know exactly what to do in the event of an accident.