The key entry point for the application of ADR is the classification of substances.
These are, “coded” with a UN number (followed by four digits) that uniquely characterizes them as substances, groups of substances or collective headings.
All subjects in ADR (with their UN numbers) are also divided into classes:
Class 1: Explosive substances and articles (ADR 2.2.1)
Class 2: Gases (ADR 2.2.2)
Class 3: Flammable liquids (ADR 2.2.3)
Class 4.1: Flammable solids, self-reactive substances, polymerizing substances and solid desensitized explosives (ADR 2.2.41)
Class 4.2: Substances liable to spontaneous combustion (ADR 2.2.42)
Class 4.3: Substances which, in contact with water, emit flammable gases (ADR 2.2.43)
Class 5.1: Oxidizing substances (ADR 2.2.51)
Class 5.2: Organic peroxides (ADR 2.2.52)
Class 6.1: Toxic substances (ADR 2.2.61)
Class 6.2: Infectious substances (ADR 2.2.62)
Class 7: Radioactive material (ADR 2.2.7)
Class 8: Corrosive substances (ADR 2.2.8)
Class 9: Miscellaneous dangerous substances and articles (ADR 2.2.9)
The first step in understanding what ADR requirements apply to a particular matter is to identify its corresponding UN number and class.