Flammable solids, spontaneously combustible, dangerous when wet

Division 4.1 Flammable Solids
Examples include hexamine, solid fuel tablets for camping stoves, self-reactive substances, desensitized explosives

Division 4.2 Spontaneous Combustion
Substances susceptible to spontaneous combustion or to spontaneous generation of heat during transportation which can lead to a fire.

Examples by risk level (packing groups):

• Packing group I: pyrophoric solid organic, pyrophoric liquid inorganic, hafnium powder dry.
• Packing group II: self-heating solid organic, organic pigments self-heating, thiourea dioxide, p-nitrodosodi-methylaniline.
• Packing group III: carbon activated, copra, xanthates, zirconium powder dry.

Division 4.3 Dangerous When Wet
Substances that emit flammable gases when they come into contact with water. Examples include aluminium phosphate, calcium, calcium carbide, potassium, sodium, zinc particles, and activated carbon.