UN Bottles are plastic bottles that are compliant with UN Packaging Regulations.  Packaging containing dangerous goods must meet or exceed minimum performance standards as described in chapter 6.1 of the UN Bottles model regulations. These are the laboratories that are currently authorised in the UK to carry out the UN tests.  When a container is certified, it will be assigned a unique code as well as being allowed to use the UN symbol.  The tests are rigorous, but the UN Specification guide is quite straightforward once you understand how it is made up. The UN symbol means that the container has been tested at an approved testing station and has passed all the tests required by United Nations. This is a quick breakdown of how the code is made up.