spontaneous combustion

spontaneous combustion phenomenon in which a substance unexpectedly bursts into flame without apparent cause. In ordinary combustion , a substance is deliberately heated to its ignition point to make it burn. Many substances undergo a slow oxidation that, like the rapid oxidation of burning, releases heat. If the heat so released cannot escape the substance, the temperature of the substance rises until ignition takes place. Spontaneous combustion often occurs in piles of oily rags, green hay, leaves, or coal; it can constitute a serious fire hazard.

spontaneous combustion Outbreak of fire without external application of heat. Phosphorous, for example, ignites spontaneously in air. When combustible material, such as damp hay, paper or rags, is slowly oxidized by bacteria or air, the temperature may rise to the ignition point.

spon·ta·ne·ous com·bus·tion • n. the ignition of organic matter (e.g., hay or coal) without apparent cause, typically through heat generated internally by rapid oxidation.