What is spontaneous combustion?

Spontaneous combustion refers to the phenomenon where materials ignite without any external flame or spark, primarily due to internal heat buildup. This internal heat can result from various factors, such as the oxidation of organic materials, biochemical activity, or the accumulation of oily rags, which generate heat as they decompose.

For instance, when materials such as hay, compost, or oily rags are piled together, can trap heat and eventually reach a temperature high enough to ignite on their own. This process doesn't require an external ignition source, which is a key characteristic that distinguishes it from other forms of combustion.

In contrast, combustion requiring an external ignition source would not qualify as spontaneous combustion, nor would controlled burns for waste disposal, which are deliberately ignited. Additionally, explosions caused by chemical reactions involve rapid expansion of gases, often characterized by a violent release of energy, and do not fit the definition of spontaneous combustion either.