Class 4: Flammable Solids

Hazardous Materials Class 4.1: Flammable Solids 4.1 Flammable Solids: Solid substances that are easily ignited and readily combustible (nitrocellulose, magnesium, safety or strike-anywhere matches).

Hazardous Materials Class 4.2: Spontaneously Combustible Solids 4.2 Spontaneously Combustible: Solid substances that ignite spontaneously (aluminium alkyls, white phosphorus).

Hazardous Materials Class 4.3: Dangerous when Wet 4.3 Dangerous when Wet: Solid substances that emit a flammable gas when wet or react violently with water (sodium, calcium, potassium, calcium carbide).