ADR Hazardous Materials Classification: The 9 Classes Explained for Shippers
Hazard class, UN number, packaging group, additional hazards: ADR classification determines every aspect of your shipment. Here’s a reliable method to master it and ensure the safety of your road freight operations.
The ADR classification of hazardous materials is the first—and most critical—step in any shipment of chemicals, batteries, aerosols, or spirits. An incorrectly identified class, an approximate UN number, or a missing packaging group can bring the entire process to a standstill: from refusal to load to detention at customs.
This guide reviews the nine ADR hazard classes, their divisions, the associated packaging and labeling requirements, and the most common classification errors. The goal is to provide you with a reliable method for ensuring the safety of your road shipments, both in France and internationally.
What is the ADR classification of hazardous materials?
Definition and Role of the ADR
The ADR, the Agreement on the International Carriage of Dangerous Goods by Road, is the reference document published by the UNECE, the United Nations Economic Commission for Europe. It establishes the rules governing the classification, packaging, labeling, documentation, loading, and road transport of dangerous goods.
The ADR 2025 edition has been in effect since January 1, 2025, and remains the working version for European shippers. In France, the Ministry of Ecological Transition describes the ADR as one of the major regulatory frameworks governing the transport of dangerous goods, including for many domestic routes.
What are the 9 classes in the ADR classification of dangerous goods?
The ADR classifies dangerous goods into nine main classes, several of which are subdivided: Class 1 has six divisions, Classes 4 and 2 have three each, and Classes 5 and 6 have two each. Below is a table of the classes, including specific examples and the most common points of caution for shippers.
Classes 1 through 4: Explosives, gases, flammable liquids, and flammable solids
| ADR Class | Nature of the hazard | Product Examples | Point to Watch For |
|---|---|---|---|
| 1 | Explosive substances and objects | Fireworks, ammunition, recreational fireworks | Six divisions, ranging from 1.1 to 1.6, and compatibility groups that must be observed when loading |
| 2 | Compressed, liquefied, and dissolved gases | Aerosols, gas cylinders, cartridges | Distinguish between 2.1 flammable gases, 2.2 non-flammable, non-toxic gases, and 2.3 toxic gases |
| 3 | Flammable liquids | Gasoline, solvents, alcohol-based fragrances, high-proof spirits | The flash point is the key criterion, which must be verified precisely on the safety data sheet |
| 4.1 | Flammable solids, self-reactive substances, desensitized solid explosives | Matches, sulfur, certain self-reactive substances | Check thermal stability and control temperatures |
| 4.2 | Materials Prone to Spontaneous Combustion | Impregnated rags, certain pyrophoric metals | Protection Against Air Exposure and Monitoring of Temperature Rises |
| 4.3 | Substances that release flammable gases when in contact with water | Calcium carbide, metallic sodium | Complete waterproofing and protection against moisture |
Class 5 distinguishes oxidizing agents from organic peroxides; Class 6 distinguishes toxicity from infectiousness; and Classes 7 through 9 cover more specific hazards: radioactivity, corrosion, or miscellaneous hazards.
Grades 5 through 9: Oxidizing, Toxic, Radioactive, Corrosive, and Miscellaneous Substances
| ADR Class | Nature of the hazard | Product Examples | Point to Watch For |
|---|---|---|---|
| 5.1 | Oxidizing substances | Nitrates, chlorates, concentrated hydrogen peroxide | They are not combustible in and of themselves, but they fuel a fire |
| 5.2 | Organic peroxides | Peroxides Used in Cosmetics and Plastics Manufacturing | Exothermic decomposition, often carried out under controlled temperature conditions |
| 6.1 | Toxic Substances | Pesticides, certain laboratory reagents | Toxicity from ingestion, inhalation, or skin contact |
| 6.2 | Infectious materials | Biological samples, medical waste | Triple packaging and specific documentation |
| 7 | Radioactive Materials | Sealed sources, radiopharmaceuticals | Classification by activity, radionuclide, and package type |
| 8 | Corrosive substances | Acids, lye, battery electrolytes | Chemical compatibility between the product and the packaging |
| 9 | Miscellaneous Hazardous Materials and Objects | Lithium batteries, aquatic pollutants, products transported at high temperatures | Residual class, often underestimated by shippers |
Categories and Associated Risks: Why a Product May Pose Multiple Hazards
The divisions within the ADR classes reflect distinct physical behaviors. A solid that burns rapidly, a solid that self-heats, and a solid that reacts with water require very different measures—hence the distinction between 4.1, 4.2, and 4.3. The same logic applies to Class 5, where oxidizing substances (5.1) are distinguished from organic peroxides (5.2), as the latter can decompose exothermically and cause a fire or explosion.
Many goods actually pose multiple hazards. The primary hazard determines the class. The others are considered secondary hazards, which require additional hazard labels and, in some cases, restrictions on mixed loading.
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How do you classify dangerous goods for road transport?
The ADR classification method used by shippers follows a logical sequence. It begins with the product’s actual properties—not its trade name—and concludes with the verification of shipping documents. Here are the steps to follow for each product.
Compile the safety data sheet
Use an up-to-date version and refer to Section 14, which contains information regarding transportation.
Confirm the UN number
Check the current ADR list of dangerous goods, for example, UN 1203 for an entry corresponding to a specific fuel.
Note the information in this section
Record the exact official shipping name, class, any subsidiary risks, and the packing group, if applicable.
Check the special provisions
As part of this section, they may waive, restrict, or tighten the shipping terms.
Choosing Packaging and Labeling
Select approved packaging that is compatible with the material, and then apply markings, hazard labels, and vehicle signage.
Prepare the shipping document
Review the required labeling information and verify the rules for separating materials that are shipped together.
The packaging group: a level of risk that should not be overlooked
The packaging group applies to certain substances in Classes 3, 4, 5, 6, 8, and 9. It indicates the level of hazard: I for high hazard, II for moderate hazard, and III for low hazard. It determines the performance requirements for the packaging and certain transportation conditions.
A single product family can thus be reclassified from one group to another based on its concentration or flash point.
ADR Classification and CLP Regulations: Two Different Approaches That Should Not Be Confused
The CLP (Classification, Labeling, and Packaging) Regulation governs the classification and labeling of substances and mixtures placed on the market. The ADR regulates hazards during transport. The two systems are related, but they do not use the same criteria or address the same exposure scenarios. The INRS reminds users that a CLP pictogram on a product’s label is never sufficient to determine its ADR class.
| CLP Regulations | ADR | |
|---|---|---|
| Subject | Classification and Labeling of Substances and Mixtures Placed on the Market | Hazards Associated with Road Transport |
| Pivot point | Hazard symbols and warnings | Class, UN number, packing group |
| Limit | A pictogram does not indicate ADR Class | A product may be subject to the ADR even without a clearly visible pictogram |
In practice, a product may bear a CLP pictogram without being subject to the ADR. Conversely, a seemingly ordinary product may be subject to the ADR because of its potential to pollute the aquatic environment. The safety data sheet is a good starting point, but it must be cross-referenced with the applicable ADR text and the actual packaging used for shipment.
Limited quantities, exempt quantities, and exemptions: What do they change?
Simplified Procedures and Conditions for Application
The ADR provides for simplified procedures, including limited quantities and exempted quantities, as well as exemptions based on the nature of the transport or on quantity thresholds per transport unit. These procedures reduce certain packaging, marking, or documentation requirements, subject to strict conditions.
What ADR 2025 Changes for Shippers
The ADR 2025 edition updates several sections, official designations, special provisions, and packing instructions. Among the changes noted is the introduction of UN Number 3551 for certain sodium-ion batteries with organic electrolytes, a new development directly linked to the growth of energy storage technologies. Revisions have also been made to the description of substances that emit flammable gases when in contact with water.
For a shipper, the practical implication is simple: product data sheets, item master files, and shipping document templates must be reviewed with each new edition. An obsolete UN number or description in an ERP system leads to a series of non-conformities that are difficult to correct once the pallets have been assembled.
Who is responsible for ADR classification in the supply chain?
Responsibility is shared, but the primary responsibility for classification lies with the shipper. The shipper is the one who knows the product’s composition, has the safety data sheet, and declares the goods. No party can rely on another.
Sender
Classifies the merchandise, maintains the safety data sheet, and reports the product.
Carrier
Check the shipping conditions, documents, and equipment.
Loader and Packer
Apply the rules for packaging and securing cargo.
Driver
Must have the appropriate training and documentation.
Recipient
Oversees receiving and unloading.
Our Approach at D&fi Group
At D&fi Groupe, we operate as a freight forwarder and an authorized economic operator. This enables us to ensure consistency between the product declaration, the choice of transport mode (road, air, or sea), and the associated customs formalities.
Our teams assist you with document verification and tracking for every shipment, from pickup to delivery, including sensitive shipments such as cosmetics, aerosols, spirits, and spare parts.
What are the most common classification errors?
There are three errors that keep cropping up in shipping records.
- Copying a classification found on an old purchase order without verifying which version of the ADR is currently in effect.
- Ignoring a secondary hazard that is nevertheless listed in the safety data sheet, which results in inaccurate labeling and incorrect rules for mixed loading.
- Using non-approved packages, or approved packaging for a packaging group lower than the required level.
Added to this are inaccuracies regarding the official transport designation—which is often replaced by a trade name—and persistent confusion between CLP and ADR classifications. These errors come at a high cost: refusal to load, delivery delays, and penalties in the event of a roadside inspection.
Securing Your Shipments: ADR Classification as the Foundation for Compliance
The ADR classification of hazardous materials is not merely an administrative formality. It is the technical foundation of your compliance and the safety of your teams. Nine classes, divisions, a UN number, an official designation, subsidiary risks, a packing group, and special provisions: each parameter has a direct impact on packaging, labeling, and documentation.
- The hazard class is the starting point, not the end point.
- The UN number, the official designation, and the packing group must be consistent with one another.
- CLP and ADR are based on different principles.
- Product data sheets and ERP systems must be updated with each new edition of the ADR.
- The shipper bears primary responsibility for classification.
If you regularly ship products subject to the ADR, have your product listings and processes audited before the next peak in activity. You can discuss your needs with us or request a quote. Depending on the product, air or ocean freight may also be an option: see our air and ocean freight services. To learn more about the regulatory framework, read our article on the transport of hazardous materials.
Frequently Asked Questions
Is hazardous waste subject to the ADR in the same way as a new product?
Yes. As long as a waste item meets the classification criteria for one of the nine classes, it must be classified, packaged, and labeled in accordance with the ADR. The labeling rules apply in full to packages containing hazardous waste.
Can goods of different classes be transported together?
Not always. Some substances are incompatible with one another, and the ADR establishes rules for mixed loading. These rules are particularly strict for Class 1, where compatibility groups govern which combinations are permitted. This verification is performed before the pallets are assembled.
Is the ADR classification valid for air or ocean shipments?
No, each mode of transport has its own set of regulations (for example, the IMDG Code for maritime transport and the technical instructions of the ICAO or IATA for air transport), with its own specific criteria and limitations. A product that is acceptable for ground transport may be prohibited or subject to much lower quantity limits for air transport. This is why it is important to determine the mode of transport as early as the classification phase.
What should I do if none of the ADR categories exactly match my product?
In such cases, you should use the generic categories—known as “not otherwise specified”—and select the one that most accurately describes the primary hazard. It is advisable to have this approach reviewed by your safety advisor.
Should we keep a record of the classification that was chosen?
Yes, and it is strongly recommended. Keeping a record of the safety data sheet used, the version of the ADR consulted, and the reasoning behind your decision will allow you to justify your choice in the event of an inspection or a dispute with a carrier.
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