The nine hazard classes
Dangerous goods are grouped into nine classes by their main hazard. Several classes are split further into divisions, written as a decimal: 2.1 is the first division of Class 2.
Class 1: Explosives
Class 1 covers explosive substances and articles, from blasting explosives to fireworks and ammunition. It's split into six divisions by how the material behaves in a fire or accident, from 1.1 (mass explosion hazard) to 1.6 (extremely insensitive articles). Explosives also carry a compatibility group letter, such as 1.4S, which governs which explosives can be transported together.
- 1.1 Explosives
- 1.2 Explosives
- 1.3 Explosives
- 1.4 Explosives
- 1.5 Explosives
- 1.6 Explosives
Class 2: Gases
Class 2 covers gases, whether compressed, liquefied, dissolved under pressure or refrigerated. Division 2.1 is flammable gases such as propane, 2.2 is non-flammable, non-toxic gases such as nitrogen, and 2.3 is toxic gases such as chlorine.
- 2.1 Flammable gases
- 2.2 Non-flammable, non-toxic gases
- 2.3 Toxic gases
Class 3: Flammable liquids
Class 3 covers flammable liquids such as gasoline, diesel, solvents, paints and alcohols. In the United States, some liquids with higher flash points can also be shipped as combustible liquids under the same class.
Class 4: Flammable solids
Class 4 covers flammable solids and other substances that can catch fire. Division 4.1 is flammable solids and self-reactive substances, 4.2 is substances that can spontaneously combust in air, and 4.3 is substances that give off flammable gas when wet.
- 4.1 Flammable solids
- 4.2 Spontaneously combustible
- 4.3 Dangerous when wet
Class 5: Oxidizers and organic peroxides
Class 5 covers substances that supply oxygen or otherwise intensify a fire. Division 5.1 is oxidizers such as ammonium nitrate and hydrogen peroxide; 5.2 is organic peroxides, which may also be thermally unstable.
- 5.1 Oxidizing substances
- 5.2 Organic peroxides
Class 6: Toxic and infectious substances
Class 6 covers poisons and infectious material. Division 6.1 is toxic substances that harm people if swallowed, inhaled or absorbed through the skin; 6.2 is infectious substances such as cultures and medical waste.
- 6.1 Toxic substances
- 6.2 Infectious substances
Class 7: Radioactive material
Class 7 covers radioactive material, from medical isotopes to nuclear fuel. Packages are labelled by radiation level at the surface and the type of packaging used.
Class 8: Corrosives
Class 8 covers corrosive substances such as acids, alkalis and battery fluid, which can destroy skin or corrode metal on contact.
Class 9: Miscellaneous dangerous goods
Class 9 covers dangerous goods that don't fit any other class, including lithium batteries, dry ice, environmentally hazardous substances, elevated-temperature materials and magnetized material.