Explosives shipping classification system
The Explosive Shipping Classification System exists as part of the United Nations Recommendations on the Transport of Dangerous Good: Model Regulations. The system describes the classification of explosives, divisions within that class that describe the type of hazard they present and compatibility groups that identify the specific type of explosive substance, and what articles are compatible for transport and storage.
Source: Wikipedia — Explosives shipping classification system (CC BY-SA 4.0)