What describes the process of Spontaneous Combustion accurately?

Spontaneous combustion refers to a phenomenon where a material ignites without an external ignition source, primarily due to the heat generated from its own chemical processes. This typically occurs when a chemical reaction, often oxidation, takes place in such a way that it produces heat faster than it can be dissipated.

In a confined space, the heat can accumulate, creating a situation where the temperature rises sufficiently to ignite the material. This is particularly relevant for substances like oily rags, compost piles, or certain chemicals that can generate heat during decomposition or oxidation.

While the statement regarding the necessity of an external ignition source would suggest the opposite of spontaneous combustion, many materials can undergo this self-heating phenomenon, not just those classified as highly flammable. Therefore, the correct response encompasses the idea of a chemical reaction in a confined environment that leads to ignition due to heat build-up.