ADR Dangerous Goods Transport: UN Numbers, Classes and Packing Groups — Guide 2026

What is ADR?

ADR (Accord européen relatif au transport international des marchandises Dangereuses par Route) is the European Agreement concerning the International Carriage of Dangerous Goods by Road. It was concluded in Geneva in 1957 under the auspices of the UNECE (United Nations Economic Commission for Europe) and is updated every two years — the current edition is ADR 2025.

ADR applies in all EU Member States as well as in numerous other European countries (over 50 contracting parties in total). It is the binding framework for anyone transporting dangerous goods by road in Europe.

For the chemical trade, ADR compliance is not optional — it is mandatory: every shipment of dangerous goods by road must comply with ADR requirements, from classification through packaging to documentation.

UN Numbers — The Identity of Dangerous Goods

Every dangerous substance or article is assigned a four-digit UN number (United Nations Number) that uniquely identifies it worldwide. Examples from the OYSI product portfolio:

• UN 1789: Hydrochloric acid
• UN 1830: Sulphuric acid with more than 51% acid
• UN 1824: Sodium hydroxide solution (caustic soda)
• UN 1170: Ethanol (ethyl alcohol)
• UN 1090: Acetone
• UN 2031: Nitric acid
• UN 3264: Corrosive liquid, acidic, inorganic, n.o.s.

The UN number appears on the transport document, on the orange-coloured plate on the vehicle, and on the packages. It is the key to all dangerous goods communication.

ADR Hazard Classes

ADR divides dangerous goods into 13 classes, organised by the nature of the hazard:

• Class 1: Explosive substances and articles
• Class 2: Gases (2.1 flammable, 2.2 non-flammable/non-toxic, 2.3 toxic)
• Class 3: Flammable liquids
• Class 4.1: Flammable solids
• Class 4.2: Substances liable to spontaneous combustion
• Class 4.3: Substances which, in contact with water, emit flammable gases
• Class 5.1: Oxidising substances
• Class 5.2: Organic peroxides
• Class 6.1: Toxic substances
• Class 6.2: Infectious substances
• Class 7: Radioactive material
• Class 8: Corrosive substances
• Class 9: Miscellaneous dangerous substances and articles

For the chemical trade, Classes 3, 5.1, 6.1 and 8 are particularly relevant — they cover the majority of commercially available industrial chemicals.

Packing Groups

Within the hazard classes, substances are divided into three packing groups according to the degree of danger:

• PG I: Substances presenting high danger — e.g. concentrated sulphuric acid >51%
• PG II: Substances presenting medium danger — e.g. hydrochloric acid 25–37%, acetone
• PG III: Substances presenting low danger — e.g. diluted acids, acetic acid ≤25%

The packing group directly determines the packaging requirements: the higher the group, the more stringent the testing requirements for drums, jerrycans and IBCs.

The Transport Document

Every dangerous goods transport by road requires a transport document containing the following mandatory information:

1. UN number preceded by the letters "UN"
2. Proper shipping name
3. Label numbers (class + subsidiary hazards if applicable)
4. Packing group (I, II or III)
5. Tunnel restriction code
6. Consignor and consignee
7. Total quantity of dangerous goods

Example for hydrochloric acid: UN 1789 HYDROCHLORIC ACID, 8, II, (E)

Exemptions and Limited Quantities

Not every transport needs full ADR compliance. ADR provides important facilitations:

• Excepted quantities (EQ): Very small quantities in special packaging — greatly simplified requirements
• Limited quantities (LQ): Consumer-sized packaging below certain thresholds — no labels on packages, but marked with LQ diamond
• 1,000-point rule (1.1.3.6): Calculation using multiplication factors — below the threshold, simplified requirements for vehicle equipment, training and documentation apply

ADR and the Digital Product Passport

ADR transport data is an integral part of the Digital Product Passport (DPP). In the OYSI DPP, the following ADR-relevant information is provided automatically:

• UN number and proper shipping name
• ADR class and classification code
• Packing group
• Hazard labels (primary hazard + subsidiary risks)
• Tunnel restriction code
• Special provisions (where applicable)
• Link to the SDS — Section 14 contains the full transport data

This gives carriers, warehouse operators and dangerous goods safety advisers instant access to all transport-relevant information via a QR code scan.

OYSI Logistics Compliance

As a chemical distributor with in-house shipping, OYSI GmbH ensures full ADR compliance:

• Tested packaging: UN-approved drums, jerrycans and IBCs to ADR specifications
• Correct labeling: Hazard labels, UN marking and orientation arrows on every package
• Transport documents: Automatically generated with all mandatory ADR information
• Dangerous Goods Safety Adviser (DGSA): Qualified adviser supervises all shipping processes
• Training: All staff involved in shipping are trained per ADR 1.3
• DPP integration: Transport data on the Digital Product Passport — scannable via QR code