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The classification of dangerous goods

Classification of dangerous substances under ADR

ADR groups hazardous substances into 9 different categories which are referred to as classes. Each class has danger sign to show it’s major hazard and some classes are then sub-divided further to identify the specific hazard.

Here is a brief overview of the 9 classes of dangerous goods under ADR:

Class 1 : Explosives

These are substances which are capable of producing gas at such a temperature, pressure and speed as to cause damage to surroundings. The explosives class is a specialist class which requires an additional training course and exam.

Class 2 : Gases

Gases are sub-divided into 2.1 Flammable gas, 2.2 Non-flammable and Non-toxic and finally 2.3 Toxic gas. In order to transport large quantities of gas economically the volume is reduced under pressure and they are usually carried in one of the following conditions, either compressed, liquefied, refrigerated or dissolved, each of which carry their own risks.

Class 3 : Flammable Liquids

These are liquids which give off flammable vapours such as petrol. The liquids themselves do not burn however the vapours that evaporate from them burn when mixed with air and ignited. The most common are fuels or solvents.

Class 4: Flammable Solids

Class 4 is sub-divided into 3 further classifications depending on the substance:

4.1 Solids which are easily ignited by sparks or flames. A good example of this is the substance that makes up the head of a match stick, which can cause or contribute to fire through friction.

4.2 Spontaneously Combustible substances which may ignite and burn upon contact with the air such as phosphorus.

4.3 Dangerous when Wet substances which will emit flammable gases on contact with water such as calcium carbide.

Class 5: Oxidising Agents

Class 5 is sub-divided into 2 classifications depending on the substance:

5.1 Oxidising agents are substances which break down easily producing oxygen and heat if contaminated. They may not burn themselves but they create an environment which supports burning.

5.2 Organic Peroxides are very unstable substances containing both fuel and oxygen which can cause fires and explosions.

Class 6: Toxic Substances

Class 6 is sub-divided into 2 classifications depending on the substance:

6.1 Toxic Substances may cause death, serious injury or harm a persons health if ingested, inhaled or absorbed through contact with the skin.

6.2 Infectious Substances can cause disease in humans and animals such as clinical waste from hospitals, vets, dental practices and other places. Infectious substances are further classified into category A, which means that the substance is carried in a form that when exposure occurs, the substance is capable of causing permanent disability, life-threatening or fatal disease to humans or animals. Category B infectious substances are those which do not meet the criteria to class as a category A infectious substance.

Class 7: Radioactives

These are substances which emit radiation at levels harmful to the body. The radioactives class is a specialist class which requires an additional training course and exam.

Class 8: Corrosives

These are substances which, through a chemical reaction, will attack and destroy goods, materials and living tissue. They are acids and alkalis and can be carried in various forms from raw liquids to prepacked containers such as batteries.

Class 9: Miscellaneous

These are substances which present a danger to people, animals and the environment and are not covered within one of the other 8 classes. The list is extensive however the most commonly recognised will be asbestos and lithium batteries.


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