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 — Table
Every dangerous substance or article is assigned a four-digit UN number (United Nations Number) that uniquely identifies it worldwide. The following table shows common UN numbers from the OYSI chemical portfolio, with ADR class and packing group:
| UN Number | Substance | Class | PG |
|---|---|---|---|
| UN 1789 | Hydrochloric acid | 8 | II / III |
| UN 1830 | Sulphuric acid >51% | 8 | II |
| UN 1824 | Sodium hydroxide solution | 8 | II / III |
| UN 1170 | Ethanol | 3 | II / III |
| UN 1090 | Acetone | 3 | II |
| UN 2031 | Nitric acid | 8 | II |
| UN 1791 | Hypochlorite solution | 8 | II / III |
| UN 1805 | Phosphoric acid solution | 8 | III |
| UN 3264 | Corrosive acidic inorganic liquid, n.o.s. | 8 | I / II / III |
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 — Table
ADR divides dangerous goods into 9 main classes with 13 sub-classes in total, organised by the nature of the hazard. The following table shows all ADR classes with their description and a typical example substance:
| Class | Description | Example (UN number) |
|---|---|---|
| 1 | Explosives | UN 0335 fireworks |
| 2.1 | Flammable gases | UN 1965 hydrocarbon gas |
| 2.2 | Non-flammable, non-toxic gases | UN 1066 nitrogen, compressed |
| 2.3 | Toxic gases | UN 1017 chlorine |
| 3 | Flammable liquids | UN 1170 ethanol, UN 1090 acetone |
| 4.1 | Flammable solids, self-reactive substances | UN 1350 sulphur |
| 4.2 | Substances liable to spontaneous combustion | UN 1381 phosphorus, white |
| 4.3 | Substances which, in contact with water, emit flammable gases | UN 1428 sodium |
| 5.1 | Oxidising substances | UN 2014 hydrogen peroxide |
| 5.2 | Organic peroxides | UN 3105 organic peroxide type D |
| 6.1 | Toxic substances | UN 1230 methanol |
| 6.2 | Infectious substances | UN 2814 |
| 7 | Radioactive material | UN 2910 |
| 8 | Corrosive substances | UN 1789 hydrochloric acid, UN 1824 sodium hydroxide |
| 9 | Miscellaneous dangerous substances and articles | UN 3082 environmentally hazardous |
For the chemical trade, Classes 3, 5.1, 6.1 and 8 are particularly relevant — they cover the majority of commercially available industrial chemicals. The associated hazard labels correspond to the GHS pictograms: Class 3 
, Class 5.1 
, Class 6.1 
and Class 8 
.
Packing Groups (PG I, II, III) — Table
Within the hazard classes, substances are divided into three packing groups according to the degree of danger. The packing group is set out in ADR Table A (Chapter 3.2, column 4) for each UN number:
| Packing Group | Degree of danger | Packaging code | Examples |
|---|---|---|---|
| PG I | High | X (also valid for II and III) | Concentrated sulphuric acid >51%, nitric acid |
| PG II | Medium | Y (also valid for III) | Hydrochloric acid 25–37%, acetone, ethanol |
| PG III | Low | Z | Diluted acids, acetic acid ≤25%, sodium hydroxide ≤25% |
The packaging code (X, Y, Z) appears on every UN-approved package. A package tested to X may be used for all three groups, one tested to Z only for PG III. The packing group directly determines the testing requirements for drums, jerrycans and IBCs: the higher the danger (PG I), the more stringent the drop, leakproofness and internal pressure tests.
Important: The packing group must not be confused with the transport category — the latter (0–4) governs the 1,000-point calculation (see below), the former governs packaging quality.
The Transport Document
Every dangerous goods transport by road requires a transport document containing the following mandatory information:
- UN number preceded by the letters "UN"
- Proper shipping name
- Label numbers (class + subsidiary hazards if applicable)
- Packing group (I, II or III)
- Tunnel restriction code
- Consignor and consignee
- 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
The 1000-point rule in detail (1.1.3.6)
Each transport category (0 to 4) is assigned a factor. The quantity transported per category is multiplied by the factor; the sum must not exceed 1000:
| Transport category | Factor | Max quantity per unit |
|---|---|---|
| 0 | — (no exemption possible) | 0 |
| 1 | × 50 | 20 kg/l |
| 2 | × 3 | 333 kg/l |
| 3 | × 1 | 1000 kg/l |
| 4 | unlimited | unlimited |
Worked example: 100 l acetone (UN 1090, category 2, factor × 3) + 15 l hydrochloric acid 30% (UN 1789, category 3, factor × 1) = (100 × 3) + (15 × 1) = 315 points. Since 315 < 1000, the 1.1.3.6 exemption applies: reduced vehicle equipment, no vehicle ADR certificate required. Still mandatory: transport document, correct packaging/marking, and basic training per ADR 1.3.
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
Author
Olivier Höfer
Managing Director, OYSI GmbH
OYSI GmbH
Frequently Asked Questions
What does ADR mean for dangerous goods?
ADR is the European Agreement concerning the International Carriage of Dangerous Goods by Road. It defines classification, packaging, marking and documentation for road transport and applies in more than 50 contracting states.
How many ADR dangerous goods classes are there?
There are 9 main classes with 13 sub-classes in total (e.g. 2.1/2.2/2.3, 4.1/4.2/4.3, 5.1/5.2, 6.1/6.2). Classes 3 (flammable liquids), 5.1 (oxidising), 6.1 (toxic) and 8 (corrosive) cover most common industrial chemicals.
What is a UN number?
The UN number is a four-digit code that uniquely identifies each dangerous substance worldwide — e.g. UN 1789 for hydrochloric acid or UN 1170 for ethanol. It appears on the transport document, the orange plate and the packages.
What is the difference between packing groups I, II and III?
The packing group indicates the degree of danger within a class: PG I = high, PG II = medium, PG III = low danger. It is listed in ADR Table A (Chapter 3.2, column 4) and determines packaging test requirements (codes X, Y, Z).
What is the 1000-point rule?
Under ADR 1.1.3.6 the quantity carried per transport category is multiplied by a factor (category 1 × 50, 2 × 3, 3 × 1). If the sum stays below 1000 points, exemptions apply for vehicle equipment and training. The transport document, correct packaging and basic training remain mandatory.
What must a transport document contain?
Mandatory entries are: UN number, proper shipping name, hazard label numbers, packing group, tunnel restriction code, plus consignor, consignee and total quantity. Example: 'UN 1789 HYDROCHLORIC ACID, 8, II, (E)'.