Spontaneous combustion is ignition resulting from internal heating which takes place due to chemical reaction to certain substances when stocked or stored in bulk. Heat is generated by combination of the substances with atmosphere oxygen (e.g., vegetable oils, coal) or by the action of micro-organization (e.g., hay) or by the reaction with water or some substance other than oxygen or by decomposition.
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UK: Self-ignition of combustible material by the internal development of heat. The standard fire policy excludes damage to property by its own spontaneous combustion but damage caused in any resultant fire spread is covered.