Which hazard designation corresponds to Spontaneously Combustible?

• A. Hazard Division 5.2
• B. Hazard Division 4.3
• C. Hazard Division 4.2
• D. Hazard Division 5.1

Answer: (C)

Self-heating leading to ignition is the behavior that defines spontaneously combustible materials within the flammable solids category. In hazard classifications, there is a specific division for substances that ignite without an external ignition source because they heat up on their own as they oxidize. That division is the one used for Spontaneously Combustible materials.

So the correct hazard designation is Division 4.2, which signals to handlers to store these materials away from heat, friction, and oxidizers and to manage them with extra care to prevent heat buildup. Other divisions cover related but distinct risks: flammable solids that ignite readily under normal conditions, solids that are dangerous when wetted, oxidizers, and organic peroxides.