Organic materials, self-heating

Processes which generate heat in organic materials are reviewed. At ordinary temperatures, respiration of living cells and particularly the metabolism of microorganisms may cause self-heating, while at elevated temperatures pyrolysis, abiotic oxidation, and adsorption of various gases by charred materials drive temperatures up whenever the released heat is unable to dissipate out of the material. The crucial rate of pyrolytic heat release depends on exothermicity and rates of the pyrolysis process. 

Many scenarios involving spontaneous combustion involve a combination of materials exposed to sufficient air, often in an insulating situation that prevents heat from a slow oxidation reaction to dissipate and thus results in a self-heating situation. Examples include activated carbon exposed to a high concentration of organic vapors and cotton or cellulose materials contaminated with oil. These combination scenarios can be... 

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