ADR Hazard Diamonds & Classes

Hazardous Chemicals and Dangerous Goods are transported throughout the United Kingdom, by road and rail every day. These goods include dangerous chemicals such as:

  • Acids 
  • Toxins and carcinogenic substances 
  • Explosives 
  • Radioactive materials 
  • Inflammable liquids 
  • Volatile chemicals likely to spontaneously combust or react with air, water etc.  
  • Inflammable, poisonous or compressed gases 

Although the Health and Safety Executive is primarily responsible for enforcing the many regulations designed to ensure safety while these substances are in transit, it is the members of the emergency services who will have to deal with the consequences of any incident. 

Laid out below are the UN Hazard Classes and Danger Signs. To find out what each class number is and what each sign represents, please refer to the list at the foot of this page.  


The following are danger labels that will be displayed on vehicles, containers and packaging during the transportation of dangerous goods. 

Class 1 – Explosive substances or articles 

Class 1 – Explosive substances or articles

Class 2 – Gases 

Class 2 – Gases

Class 3 – Flammable Liquids 

Class 3 Flammable Liquids

Class 4.1 – Flammable Solids, self-reactive substances and de-sensitised explosives 

Class 4.1 Flammable Solids, self-reactive substances and de-sensitised explosives

Class 4.2– Substances liable to spontaneous combustion 

Class 4.2 Substances liable to spontaneous combustion

Class 4.3– Substances which, in contact with water, emit flammable gases 

Class 4.3 Substances which, in contact with water, emit flammable gases

Class 5.1 – Oxidising Substances 

Class 5.1 Oxidising Substances

Class 5.2 – Organic Peroxides 

Class 5.2 Organic Peroxides

Class 6.1 – Toxic Substances 

Class 6.1 Toxic Substances

Class 6.2 – Infectious Substances 

Class 6.2 Infectious Substances

Class 7 –Radioactive Material 

Class 7 Radioactive Material

Class 8 –Corrosive Substances 

Class 8 Corrosive Substances

Class 9 –Miscellaneous 

Class 9 Miscellaneous

Under the requirements of the 2019 editions of the European Agreements Concerning the International Carriage of Dangerous Goods by Rail (RID) and by Road (ADR), all goods classified as dangerous in carriage whether or not assigned to another class may need to have the Environmentally Hazardous Substance (EHS) mark displayed on their packaging if they meet the EHS criteria contained in of ADR and RID. 

The following are additional danger labels that are used

in the transportation of dangerous goods.  

Environmental Hazardous Substance mark 

Environmental Hazardous Substance mark

The following are marks that may appear on vehicles during the transportation of dangerous goods and would appear in addition to the danger labels at 1.2.1

ADR Sign


ADR Sign


ADR Sign


Class Number 

Hazard Class Information 

Class 1 



Substances with a mass explosion hazard 


Substances which present a projection hazard but no mass explosion hazard 


Substances which present both a fire hazard and a minor blast or projection hazard (or both) but not a mass explosion hazard 


No significant hazard 


Very insensitive substances with a mass explosion hazard 


Very insensitive articles with no mass explosion hazard 

Class 2 



Flammable gases 


Non-flammable, non-toxic gases 


Toxic gases 

Class 3 

Flammable liquids 

Class 4 

Flammable solids 

Class 4.1 

Flammable solids, self-reactive substances and solid desensitised explosives 

Class 4.2 

Materials liable to spontaneous combustion 

Class 4.3 

Substances which, in contact with water, release flammable gases 

Class 5 

Oxidizing substances and organic peroxides 

Class 5.1 

Oxidizing agents 

Class 5.2 

Organic peroxides 

Class 6 

Toxic and infectious substances 

Class 6.1 

Toxic substances 

Class 6.2 

Infectious substances 

Class 7 

Radioactive substances and articles 

Class 8 

Corrosive substances 

Class 9 

Miscellaneous dangerous substances and articles. Class 9 includes items such as asbestos, automotive airbags, lithium batteries and environmentally hazardous substances which don't fit into any of the other 8 classes.