ABSTRACT
Certain materials have the characteristics to get self-heated on interacting with the environment. If the heat so liberated is faster than the rate it is lost to the surrounding, it may culminate to the eruption of fire—known as Spontaneous Combustion or Endogenous Fire. Unlike the piloted ignition or exogenous fires that require external energy input for ignition, spontaneous fires are not instantaneous. The interaction of oxygen with coal, like all oxidation reactions, is exothermic. The contribution of heating due to the action of bacteria cannot be completely ruled out. In fact, spontaneous heating observed in haystacks and in wood are known to be mainly due to bacterial action, at least upto 70 °C beyond which chemical reaction takes over. Heating due to oxidation of pyrites has been known to be a common phenomenon in pyrite mines.
