Dangerous goods are classified into 9 different classes, based on the dangerous properies of the goods or substance. If the goods have multiple dangerous propreties, the most dominant one determines the class to which it shall belong.
The classes are part of the United Nations-based system of identifying dangerous goods, and are used within many different subsystems such as the ADR, RID, IMDG and DGR for classifying dangerous goods and hazardous materials.
Class 1 Explosive substances and articles
Class 1 contains substances and articles which pose a hazard due to explosion. Items in Class 1 are further divided into divisions 1.1 - 1.6 depending on the nature of the explosion hazard and the sensitivity of the item. A compatibility group, consisting of a single letter, is also assigned to each item. The compatibility group letter indicates which items can be transported together.
See also: List of all items in class 1
Class 2 Gases
Class 2 contains potentially dangerous gases.
Gases in class 2 are assigned one or more groups, representing their dangerous properties.
|Toxic, Flammable, Corrosive
|Toxic, Oxidizing, Corrosize
In some regulations, gases in class 2 are divided into divisions 2.1 - 2.3 depending on their primary hazard.
|Non-flammable, non toxic gases
See also: List of all items in class 2
Class 3 Flammable liquids
Class 3 covers flammable liquids, which includes some molten solid substances and liquid desensitized explosives. Substances are divided into different packing groups according to the degree of danger they present to transportation.
|Initial boiling point
|≥ 23°C ≤ 60°C
See also: List of all items in class 3
Class 4 Flammable solids
Class 4, like class 5 and 6, is actually an umbrella term, where all substances belong to one of the subclasses.
|Flammable solids, self-reactive substances, polymerizing substances and solid desensitized explosives
|Substances liable to spontaneous combustion
|Substances which, in contact with water, emit flammable gases
They all have in common that they are flammable under certain conditions. For instance, strike-anywhere-matches (UN 1331) would be classified as a Class 4.1 substance.
See also: List of all items in class 4
Class 5 Oxidizing substances and organic peroxides
Class 5.1, oxidizing substances, are substances that may decompose quickly, releasing oxygen or other oxidizing substances. This can cause a fire to accelerate quickly, or to start due to the heat given off in the oxidation process.
Class 5.2, organic peroxides, may also decompose at a high rate and give off oxygen or flammable gases, as well as heat. They can be very unstable and extremely flammable under certain circumstances such as heat, friction, mechanical shock, or when they come into contact with other substances.
See also: List of all items in class 5
Class 6 Toxic and infectious substances
Class 6.1, toxic substances, is used to classify substances that - in relatively small amounts and in a short duration - can cause serious injury or death to humans if swallowed, inhaled or with by absorption through skin contact.
Class 6.2, infectious substances, covers substances which are known or are reasonably expected to contain pathogens, i.e. microorganisms (including bacteria, viruses, parasites and fungi) and other agents which can cause disease in humans or animals.
See also: List of all items in class 6
Class 7 Radioactive material
Class 7 contains substances and articles that are radioactive, meaning that they contain radionuclides where both the activity concentration and the total activity exceed certain threshold values defined in the regulations.
For some (Type A) materials and packages, a transport index is calculated on the basis of the maximum dose rate on the external surface of the packaging, and different labels and regulations apply depening on this index.
|Maximum dose rate on external surface
|>0.005 <0.5 mSv/h
|>0.5 <2 mSv/h
Other regulations and labels apply to radioactive waste and materials exceeding the limits for Type A packages.
See also: List of all items in class 7
Class 8 Corrosive substances
Class 8 covers substances that can cause a chemical reaction that can potentially destroy living tissue or other goods. This includes substances which only form a corrosive substance in the presence of water, or produce corrosive vapour in the presence of moisture in the air.
|Other corrosive substances
|Corrosive substances, flammable
|Corrosive substances, self-heating
|Corrosive substances which, in contact with water, emit flammable gases
|Corrosive substances, oxidizing
|Corrosive substances, toxic and articles containing such substances
|Corrosive substances, flammable, liquid, toxic
|Corrosive substances, oxidizing, toxic
See also: List of all items in class 8
Class 9 Miscellaneous dangerous substances and articles
Substances and articles which, during carraige, present a danger not covered by any of the other classes fall under class 9.
|Substances which, on inhalation as fine dust, may endanger health
|Substances and articles which, in the event of fire, may form dioxins
|Substances evolving flammable vapour
|M6 - M8
|Environmentally hazardous substances:
M6: Pollutant to the aquatic environment, liquid
M7: Pollutant to the aquatic environment, solid
M8: Genetically modified microorganisms and organisms
|M9 - M10
|Elevated temperature substances:
|Other substances and articles presenting a danger during carriage, but not meeting the definitions of another class.
See also: List of all items in class 9