Smouldering (or smoldering in American spelling) combustion is a flameless form of combustion, deriving its heat from oxidations occurring on the surface of a solid fuel.
Common examples are the initiation of fires on upholstered furniture by weak heat sources (e.g. a cigarette, a short-circuited wire), and the persistent combustion of biomass behind the flaming front of wildland fires.
Many materials can sustain a smouldering reaction, including coal, tobacco, wood, biomass fuels on the forest surface (duff) and subsurface (peat), cotton clothing and string, and polymeric foams (e.g. upholstery and bedding materials).
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