By packing group in ADR refers to the degree of hazard substances (for packing):
- I Packing Group - a substance with a high degree of risk.
- II Packing group - substances presenting medium danger.
- III Packing group - substances presenting low danger.
This is a very important characteristic. It affects and requirements for transportation, and the need for special measures, including a special permit for transportation. Based on the properties, the same UN number may have different packing group numbers; Packing group indicated in column 4 of Table A of Chapter 3.2 of ADR.
Packing group is not assigned to the following classes:
Class 1 "Explosives"
Class 2 "Gases"
Class 4.1 "Flammable solids, self-reactive substances and solid desensitized explosives" - for solid desensitized explosives
Class 5.2 "Organic peroxides"
class 6.2 "Infectious substances"
Class 7 "Radioactive Materials"