ADR classes and ADR transport
blog 23/08/2022

ADR classes and ADR transport

As a transporter, we transport all kinds of goods. In most cases, these are simple pallets with customers’ products loaded on them. These may contain soft teddy bears, but not all goods are so safe and innocent. Certain types of goods carry risks. These include flammable products, explosion hazards and toxic substances. You cannot simply transport these goods. You will have to consider ADR Classes. You can read more about these ADR Classes in this blog!

ADR meaning

ADR is the abbreviation for Accord relatif au transport international de marchandises Dangereuses par Route. If you don’t speak French: simply put, it means the transport of dangerous goods. ADR is the European treaty, consisting of agreements and regulations concerning the transport of dangerous goods and substances by road. 

ADR Rules

The ADR rulebook has been compiled by the United Nations. These rules lay down everything relating to the transport of hazardous substances. For example, there are rules on how the substances must be transported, what markings are required on the truck and which substances may be transported through which tunnels. The full set of rules can be found on the UNECE website.  


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ADR classes and labels 

In total there are 9 ADR classes, with classes 2, 4, 5 and 6 further divided into several hazard classes. The description of these ADR classes and hazard classes can be found below.

Class 1: Explosive substances and objects

This class mainly includes objects such as fireworks, weapons and ammunition. The main hazard is the risk of explosion. You can recognise them by the label below: 

ADR klasse 1

Class 2: Gases

Class 2 involves different types of gases. The main hazards are flammability, suffocation, corrosive substances and toxic substances.  

Class 2.1 Flammable gas 

Flammable gases fall under class 2.1. You can recognise them by the red sign with the flame. 

ADR klasse 2.1

Class 2.2 Non-flammable, non-toxic gas 

Class 2.2 designates gases that are not flammable or toxic. It is indicated by a green label with a gas bottle on it:

ADR Klasse 2.2

Class 2.3: toxic gas

Toxic gas also has its own subclass, namely ADR Class 2.3. This is indicated by the skull on a white sign.  

ADR klasse 2.3

Class 3: Flammable liquids 

Class 3 contains liquids that can ignite under specific conditions. The risk of fire is therefore the most important. The label below identifies these flammable liquids: 

ADR klasse 3

Class 4: Flammable solids

Like class 3, ADR class 4 classifies flammable substances. In this case, it concerns flammable solids. Class 4 is divided into three hazard classes: 


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Class 4.1: Flammable solids

Highly flammable substances in granular, powder, metal or paste form. They can be recognised by their red and white striped label: 

ADR klasse 4.1

Class 4.2: Substances liable to spontaneous combustion 

These are substances that can ignite with oxygen from the air without an ignition source. They can be recognised by the red and white label: 

ADR klasse 4.2

Class 4.3: Substances emitting gas in water 

Class 4.3 contains substances that develop flammable gases when combined with water. There is a risk of gas formation and explosion. You can recognise them by the blue label:

ADR klasse 4.3

Class 5: Oxidising substances

Class 5 contains oxidising substances. This means that these substances release oxygen and can cause combustion in other substances. The substances themselves do not have to be combustible. Class 5 is also divided into two hazard classes.

Class 5.1: Oxidising substances

These are substances that are not combustible themselves, but may cause combustion of other substances. These substances have the following yellow label: 

ADR klasse 5.1

Class 5.1: Organic Peroxides

Organic peroxides are chemically unstable substances that can decompose themselves. They are mainly used as auxiliary materials for plastics. The substances can be corrosive and/or flammable. You can recognise them by the following label:  

ADR klasse 5.2

Class 6: Toxic substances

Toxic substances also have their own ADR class. This is further subdivided into classes 6.1 and 6.2.  

Class 6.1: Toxic substances

Met giftige stoffen bedoelt men stoffen die bij inademing, aanraking met de huid of inslikken de gezondheid van de mens schaden of de dood veroorzaken. Deze herken je aan het label met een doodshoofd, gelijk aan het label dat bij klasse 2.3 hoort.

ADR klasse 6

Class 6.2: Infectious substances  

Class 6.2 classifies infectious substances that can cause disease in humans and/or animals. It also has a white label, recognisable by the logo that you see in every sci-fi film:   

ADR-klasse-6.2

Class 7: Radioactive material

Class 7 includes substances that spontaneously emit energy in the form of invisible radiation, i.e. radioactive substances. You will also see this logo in a film from time to time:

ADR Klasse 7

Class 8: Corrosive substances 

Corrosive substances are chemicals that attack the skin or mucous membranes, such as hydrochloric acid and sulphuric acid. The following label shows that a corrosive substance is being transported: 

ADR klasse 8

Class 9: Miscellaneous dangerous substances and articles

Class 9 is something of an “other” category. This concerns substances which pose a hazard during transport but do not fall under the description of any of the other classes. They are labelled as follows:

ADR klasse 9

ADR numbers

To indicate certain ADR classes and dangerous goods, we use different numbers in the industry. The most important ones are listed below.

Kemler sign

The Kemler sign, also known as the UN sign, is not really a number in itself, of course. This sign serves as a warning sign on trucks to indicate the hazardous substances transported in the trailer. It is an orange sign, divided into two areas by a black line. The lower area shows the UN number. The upper area is used to indicate the GEVI number (or Kemler Code). 

Kemler bord

UN number

A UN number is the classification number of a dangerous substance, also called substance designation number. It is a four-digit number that classifies the substance according to the guidelines set by the United Nations (UN). 

The UN number is recognised worldwide and is even an obligation in most countries when transporting dangerous goods. This number must be printed on the outside of the packaging of the goods and be clearly visible.


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Some common dangerous goods and substances have their own UN number. All other types are assigned a UN number that corresponds to the umbrella category to which they belong. The latter numbers can be recognised by the words “N.E.G.” after the number. (not mentioned elsewhere) after the number. 

GEVI number

GEVI number stands for hazard identification number. Whereas the UN number indicates which substance is being transported, the GEVI number shows which specific hazard is involved. The first number in the number indicates the principal hazard. If the second number is equal to the first, this means that the primary hazard is increased.

Easy Road Transport and ADR Classes

Are you looking for a partner to transport your ADR goods? We are happy to think along with you about the best way to get your goods from A to B. Reach out, we’ll be happy to help!


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Calculate your transport costs in under 2 minutes!

Do you want to know the costs of transporting your goods from A to B? The price calculator lets you calculate your transport costs. No more surprises for you!