Which label describes a material that may ignite without an external ignition source?

• A. Explosive
• B. Non-flammable compressed gas
• C. Spontaneously Combustible
• D. Radioactive substance

Answer: (C)

Spontaneous combustion describes a material that can ignite on its own, without any external ignition source like a flame or spark. This happens when internal heat from chemical or biological processes builds up faster than it can escape, eventually reaching the material’s ignition temperature. The label for this risk highlights the need to control heat buildup and keep such substances cool and well-ventilated, away from oxidizers or coverings that trap heat.

So why this label fits best here? It specifically flags a material that may ignite without an external spark or flame, which is exactly what spontaneous combustion describes. The other options point to different hazards: an explosive is about a violent energy release, often triggered, not simply self-ignition; a non-flammable compressed gas does not burn under normal conditions; a radioactive substance involves radiation hazards rather than ignition risk.