ADR hazard identification panels â dangerous substances and their UN numbers
27 February '25
Reading time 9 minutes
When carrying out international transport, it is crucial to adhere to safety regulations, especially when dealing with hazardous goods.
The distinctive orange ADR hazard identification panels play a key role in the system that allows for the clear identification of such materials.
Table of contents
What is the ADR agreement and why is it important?
What does an ADR hazard identification panel look like?
Example hazardous substances by UN number
Responsibilities of carriers and drivers
Transport of hazardous goods
The transport of environmentally hazardous substances raises many concerns and questions, particularly among transport company employees and logistics professionals. This is completely understandable, as every day, vehicles transporting dangerous materials travel on public roads. In the event of unforeseen incidents, these substances can pose serious risksânot only to people nearby but also to the environment and road infrastructure.
To minimize these risks, strict regulations have been introduced to govern the transportation of hazardous goods. Compliance with these rules is not just a legal requirement but also a critical factor in ensuring transport safety.
One of the most important documents regulating this process is the ADR agreement. Want to learn more about what it covers, the key rules it establishes, and which goods are classified as hazardous?
In this article, we will answer these questions and explain how ADR regulations impact road transport safety and logistics operations.
What is the ADR agreement and why is it important?
The ADR agreement (LâAccord europĂŠen relatif au transport international des marchandises Dangereuses par Route) is an international treaty that regulates the road transport of dangerous goods.
First signed on September 30, 1957, in Geneva, it was initially adopted by just nine countries. Since then, ADR regulations have been updated every two years, ensuring their relevance and effectiveness. Over time, the number of signatory countries has significantly increased, reflecting the importance and universal adoption of these safety measures in road transport. By 2018, 50 countries had joined the agreement, and as of 2023-2025, the number has risen to 54.
The full list of ADR signatory countries is available in UNECE (United Nations Economic Commission for Europe) publications. This organization regularly updates data, ensuring access to the latest information on signatories and the international transport of hazardous materials.
What does an ADR hazard identification panel look like and what information does it provide?
ADR hazard identification panels are distinctive orange, reflective signs placed on the front and rear of vehicles transporting dangerous goods. They play a crucial role in road transport within ADR-compliant countries, providing essential information about the type and nature of hazardous substances being transported.
Each ADR hazard identification panel contains two key identification numbers:
- Hazard identification number (Kemler code): A two- or three-digit code indicating the type of hazard, e.g., “33” signifies flammable liquids.
- UN number: A four-digit number assigned to specific hazardous substances, such as toxic, corrosive, flammable, explosive, or radioactive materials.
Thanks to their simple and standardized format, these ADR panels are easily recognizable and understood by trained personnel, ensuring quick identification of hazardous goods in transport.
Colors and markings on ADR hazard identification panels
The orange color of ADR hazard identification panels is not chosen at randomâit serves as a warning signal. The black printed numbers ensure high contrast and readability, making the information easily recognizable even from a distance.
In some cases, additional pictograms are placed next to the ADR panel to indicate specific hazards, such as corrosive substances, flammable materials, or explosive risks. These symbols provide clear visual cues to emergency responders, transport operators, and law enforcement, ensuring quick hazard identification in case of an incident.
Types of hazardous substances
According to the ADR agreement, hazardous goods are materials and objects whose international road transport is either prohibited or permitted only under specific conditions outlined in Annexes A and B of the treaty.
Below is the complete classification of hazardous substances based on ADR hazard classes:
| Class | Substance Type |
|---|---|
| Class 1 | Explosive materials and substances |
| Class 2 | Gases (flammable gas, non-flammable gas, toxic gas) |
| Class 3 | Flammable liquids |
| Class 4.1 | Flammable solids, self-reactive substances |
| Class 4.2 | Spontaneously combustible substances |
| Class 4.3 | Substances that emit flammable gases when in contact with water |
| Class 5.1 | Oxidizing substances |
| Class 5.2 | Organic peroxides |
| Class 6.1 | Toxic substances |
| Class 6.2 | Infectious substances and materials |
| Class 7 | Radioactive materials |
| Class 8 | Corrosive substances |
| Class 9 | Miscellaneous dangerous substances and articles |
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What are UN numbers?
UN numbers (United Nations Numbers) are four-digit international codes established by the United Nations (UN) to uniquely identify hazardous materials and substances transported internationally.
These numbers are widely used in the ADR system and play a key role in ensuring safety when handling and transporting dangerous goods.
UN numbers â examples of classification for transported substances
Each UN number is assigned to a specific substance or a group of substances with similar chemical properties and hazards. These UN identifiers are complemented by ADR hazard classes, providing a clearer assessment of potential risks.
The full list of UN numbers can be found in official documents, such as Annex I of the Dangerous Goods List included in the ADR agreement.
| UN Number | Material / Substance |
|---|---|
| UN Number 1033 | Dimethyl Ether |
| UN Number 1049 | Compressed, Hydrogen |
| UN Number 1092 | Acrolein, Stabilized |
| UN Number 1104 | Amyl Acetates |
| UN Number 1123 | Butyl Acetates |
| UN Number 1129 | Butyraldehyde |
| UN Number 1173 | Ethyl Acetate |
| UN Number 1202 | Gas Oil or Diesel Fuel (flash-point not more than 60 °C) |
| UN Number 1203 | Gasoline |
| UN Number 1243 | Methyl formate |
| UN Number 1263 | Paint related material (incl. paint thinning, drying, removing, reducing compound) |
| UN Number 1300 | Turpentine Substitute |
| UN Number 1594 | Diethyl Sulphate |
| UN Number 1595 | Dimethyl Sulphate |
| UN Number 1648 | Acetonitrile |
| UN Number 1715 | Acetic Anhydride |
| UN Number 1727 | Ammonium Hydrogendifluoride |
| UN Number 1813 | Potassium hydroxide, Solid |
| UN Number 1823 | Sodium Hydroxide, Solid |
| UN Number 1831 | Sulphuric Acid, Fuming |
| UN Number 1832 | Sulphuric Acid, Spent |
| UN Number 1990 | Benzaldehyde |
| UN Number 2014 | Hydrogen Peroxide |
| UN Number 2031 | Nitric Acid |
| UN Number 2032 | Nitric Acid, Red Fuming |
| UN Number 2353 | Butyryl Chloride |
| UN Number 2426 | Ammonium Nitrate, Liquid |
| UN Number 2800 | Batteries, Wet, Non-Spillable |
| UN Number 2809 | Mercury |
Responsibilities of carriers and drivers
Transporting goods with hazardous properties is a major responsibility that requires not only a thorough understanding of ADR regulations but also strict compliance with them. Both carriers and drivers play a crucial role in ensuring safety during the transportation of ADR-classified substances.
Below is a detailed breakdown of their key responsibilities.
Proper vehicle marking
Any vehicles (road and rail vehicles) carrying dangerous goods must be equipped with ADR hazard identification panelsârectangular, orange reflective plates. These mandatory signs must be clearly displayed at both the front and rear of the vehicle.
The ADR panels must be clearly visible, durable, and in perfect condition to eliminate any doubts regarding the nature of the transported materials. Missing, damaged, or incorrectly placed panels can result in serious legal consequences and pose safety risks on the road.
Transport documentation
Transporting hazardous substances requires detailed transport documentation. The carrier is responsible for providing the driver with the necessary documents, which must include information such as the type of transported substances, their ADR classification, UN numbers, quantity of transported materials, hazard type, and recommended safety measures.
Additionally, the driver must carry a transport document, driver qualification certificate, vehicle approval certificate for hazardous goods transport, and an ADR training completion certificate.
ADR training for drivers
Every driver transporting dangerous goods must complete ADR training. After successful completion, the driver receives a certificate confirming knowledge of ADR regulations, safety procedures, and emergency response protocols.
Without this certification, a driver is not legally permitted to transport ADR-classified hazardous goods. ADR training includes both theoretical education on material identification and practical exercises, such as handling protective equipment and responding to hazardous incidents.
Vehicle equipment
Vehicles carrying packages with hazardous substances must be properly equipped to handle potential emergency situations. Essential onboard equipment includes:
- Fire extinguishers â The number and capacity must match the vehicle size and hazard class of the cargo.
- Personal protective equipment (PPE) â Includes protective gloves, respirator masks, safety goggles, and chemical-resistant clothing.
- Emergency signage and warning markers â For marking accident sites in case of an emergency.
- Safety instructions â Emergency procedures must be available in the driver’s language and any additional languages required by ADR regulations.
Compliance with safety standards
Every stage of transport â loading, transit, and unloading â must comply with strict safety standards. Both the carrier and driver must ensure that the cargo is properly packed, secured against movement, and marked in accordance with ADR requirements.
Strict adherence to ADR regulations is essential to reduce risks, ensure public safety, and avoid legal penalties for non-compliance.
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Summary
ADR is much more than just an orange reflective hazard identification panel. The responsibilities of carriers and drivers in ADR transport are clearly defined, leaving no room for errors or oversights. Every step â from proper vehicle marking and documentation preparation to training and equipping the vehicle â plays a crucial role in ensuring the safe transport of hazardous goods.
Compliance with ADR regulations and ensuring that hazard identification numbers are clearly visible is not just a legal requirement but also a moral obligation for everyone involved in the transport of such high-risk cargo.
Frequently asked questions (FAQ)
What do the numbers on an ADR hazard identification panel mean?
The numbers displayed on an ADR hazard identification panel provide critical information about the hazardous substance being transported. The panel is divided into two sections:
The upper number (Hazard Identification Number, Kemler Code) indicates the type of hazard associated with the substance:
- “33” â Highly flammable liquid
- “80” â Corrosive substance
- “263” â Toxic and flammable gas
- “539” â Flammable organic peroxide
The lower number (UN Number) identifies the specific hazardous material being transported. Examples include:
- “1203” â Gasoline
- “1830” â Sulfuric acid
- “1017” â Chlorine
These numbers are crucial for emergency responders, drivers, and transport operators, allowing them to quickly identify the level of risk and take appropriate safety measures.
What does 33 mean on an ADR hazard identification panel?
The number 33 on an ADR hazard identification panel, located in the upper section (Kemler Code), indicates a highly flammable liquid.
- The first digit “3” signifies the hazard category, which in this case is flammable material.
- The second “3” further emphasizes the intensity of the flammability risk associated with the substance.
Examples of substances labeled with 33 on an ADR panel:
- Gasoline (UN 1203)
- Acetone (UN 1090)
- Ethanol (UN 1170)
Transporting materials classified under hazard identification number 33 requires extreme caution, as these substances can ignite easily upon contact with fire, sparks, or even high temperatures. Strict safety procedures must be followed to minimize risks during transport.
What does 23 mean on an ADR hazard identification panel?
The number 23 on an ADR hazard identification panel, displayed in the upper section (Kemler Code), indicates a flammable gas.
- The first digit “2” signifies the gas hazard category.
- The second digit “3” designates the flammability of the gas.
Examples of gases labeled with 23 on an ADR panel:
- Propane (UN 1978)
- Butane (UN 1011)
Substances classified under hazard identification number 23 are highly dangerous due to their flammability and explosion risk when exposed to fire, sparks, or ignition sources.
In hazardous materials transport, strict safety measures must be implemented, including the use of specialized tanks and compliance with ADR regulations.
For smaller quantities of hazardous substances, proper package labeling (e.g., on drums or cylinders) is essential. In the event of an accident, it is critical to quickly mark the danger zone and immediately notify emergency services.
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