Classes 1-9 of dangerous goods explained


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.

Example of label for class 1

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.

Groups of class 2
GroupProperty
AAsphyxiant
OOxidizing
FFlammable
TToxic
TFToxic, Flammable
TCToxic, Corrosive
TOToxic, Oxidizing
TFCToxic, Flammable, Corrosive
TOCToxic, Oxidizing, Corrosize

In some regulations, gases in class 2 are divided into divisions 2.1 - 2.3 depending on their primary hazard.

Divisions of class 2
DivisionPrimary hazardLabel
2.1Flammable gasesLabel for class 2.1
2.2Non-flammable, non toxic gasesLabel for class 2.2
2.3Toxic gasesLabel for class 2.3

Labels for class 2.1, flammable gases Labels for class 2.2, non-flammable, non-toxic gases Labels for class 2.3, 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.

Packing groups for class 3
Packing groupFlash pointInitial boiling point
I-≤ 35°C
II< 23°C> 35°C
III≥ 23°C ≤ 60°C> 35°C
Label for class 3

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.

Class 4 consists of the following subclasses
ClassPrimary hazardLabel
4.1Flammable solids, self-reactive substances, polymerizing substances and solid desensitized explosivesLabel for class 4.1
4.2Substances liable to spontaneous combustionLabel for class 4.2
4.3Substances which, in contact with water, emit flammable gasesLabel for class 4.3

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.

Label for class 4.1, flammable solids, self-reactive substances, polymerizing substances and solid desensitized explosives Label for class 4.2, substances liable to spontaneous combustion Label for class 4.3, substances which, in contact with water, emit flammable gases

See also: List of all items in class 4

Class 5 Oxidizing substances and organic peroxides

Class 5 consists of the following classes
ClassPrimary hazardLabel
5.1Oxidizing substancesLabel for class 5.1
5.2Organic peroxidesLabel for class 5.2

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.

Label for class 5.1, oxidizing substances Label for class 5.2, organic peroxides

See also: List of all items in class 5

Class 6 Toxic and infectious substances

Class 6 consists of the following classes
ClassPrimary hazardLabel
6.1Toxic substancesLabel for class 6.1, toxic substances
6.2Infectious substancesLabel for class 6.2, 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.

Label for class 6.1, toxic substances Label for class 6.2, infectious substances

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.

Transport indexes, dose rates and labels of class 7
Maximum dose rate on external surfaceTransport indexLabel
<0.005 mSv/h0Label for class 7, transport index 0
>0.005 <0.5 mSv/h0-1Label for class 7, transport index 0-1
>0.5 <2 mSv/h1-10Label for class 7, transport index 1-10

Other regulations and labels apply to radioactive waste and materials exceeding the limits for Type A packages.

Label for class 7, transport index 0 Label for class 7, transport index 0-1 Label for class 7, transport index 1-10 Label for class 7, fissile materials Placard for class 7

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.

Subcategories of class 8
CategoryProperties
C1-C4Acid substances
C5-C8Basic substances
C9-C10Other corrosive substances
C11Corrosive articles
CFCorrosive substances, flammable
CSCorrosive substances, self-heating
CWCorrosive substances which, in contact with water, emit flammable gases
COCorrosive substances, oxidizing
CTCorrosive substances, toxic and articles containing such substances
CFTCorrosive substances, flammable, liquid, toxic
COTCorrosive substances, oxidizing, toxic
Label for class 8, corrosive substances

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.

Subcategories of class 9
CategoryProperties
M1Substances which, on inhalation as fine dust, may endanger health
M2Substances and articles which, in the event of fire, may form dioxins
M3Substances evolving flammable vapour
M4Lithium batteries
M5Life-saving appliances
M6 - M8Environmentally hazardous substances:
  M6: Pollutant to the aquatic environment, liquid
  M7: Pollutant to the aquatic environment, solid
  M8: Genetically modified microorganisms and organisms
M9 - M10Elevated temperature substances:
  M9: Liquid
  M10: Solid
M11Other substances and articles presenting a danger during carriage, but not meeting the definitions of another class.
Label for class 9, miscellaneous dangerous substances and articles Label for class 9, lithium batteries

See also: List of all items in class 9