Class 4

Class 4 - Flammable solids; substances liable to spontaneous combustion; substances which, in contact with water, emit flammable gases includes solid materials that may ignite or combust, such as matches, and solids that may react with water, such as sodium and potassium.

Class 4 dangerous goods are subdivided into one of three divisions:

• Division 4.1 - Flammable solids; self-reactive substances; and solid desensitized explosives includes solid material that is readily combustible or that may cause or contribute to a fire through friction. This division also includes self-reactive substances that are liable to undergo a strongly exothermic, or heat-producing, reaction and desensitized explosives that can explode if not sufficiently diluted. Examples of Division 4.1 dangerous goods include matches, straw, and sulfur.
• Division 4.2 - Substances liable to spontaneous combustion includes those substances that are liable to spontaneous heating under normal conditions of transport, or those substances that heat up on contact with air and have a potential to catch fire. These substances are classified as either pyrophoric substances or self-heating substances. Examples of Division 4.2 dangerous goods include activated carbon, oily rags, and seed cake.
• Division 4.3 - Substances which, in contact with water, emit flammable gases is for substances that are dangerous when wet. When these substances interact with water, they are liable to become spontaneously flammable or to give off flammable gas in dangerous quantities. Examples of Division 4.3 dangerous goods include calcium carbide, sodium, and alkaline earth metal alloys.

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