What defines spontaneous combustion?

Spontaneous combustion is defined as a fire that occurs without an external heat source. This phenomenon happens when a material undergoes a chemical reaction that generates heat faster than it can dissipate, leading to an increase in temperature and ultimately igniting the material. Common examples include oily rags that can heat up due to the oxidation of oils, compost piles that can internalize heat from microbial activity, or various chemicals that may react with each other under certain conditions.

The characteristics of spontaneous combustion set it apart from fires that are ignited by external sources, such as matches, lighters, or electrical faults. External ignition sources involve an intentional or unintentional application of heat or flame to ignite a material, which is not the case with spontaneous combustion, thereby highlighting the unique nature of this type of fire. In contrast, fires resulting from electrical faults typically occur when faulty wiring or equipment creates a spark or excessive heat, which again distinguishes them from spontaneous combustion scenarios.