<P> The fundamental difference between smouldering and flaming combustion is that smouldering occurs on the surface of the solid rather than in the gas phase . Smouldering is a surface phenomenon but can propagate to the interior of a porous fuel if it is permeable to flow . The characteristic temperature and heat released during smouldering are low compared to those in the flaming combustion (i.e., ~ 600 ° C (1,112 ° F) vs. ~ 1,500 ° C (2,730 ° F)). Smouldering propagates in a creeping fashion, around 0.1 mm / s (0.0039 in / s), which is about ten times slower than flames spread over a solid . In spite of its weak combustion characteristics, smouldering is a significant fire hazard . Smouldering emits toxic gases (e.g., carbon monoxide) at a higher yield than flaming fires and leaves behind a significant amount of solid residue . The emitted gases are flammable and could later be ignited in the gas phase, triggering the transition to flaming combustion . </P> <P> Many materials can sustain a smouldering reaction, including coal, tobacco, decaying wood and sawdust, biomass fuels on the forest surface (duff) and subsurface (peat), cotton clothing and string, and polymeric foams (e.g., upholstery and bedding materials). Smouldering fuels are generally porous, permeable to flow and formed by aggregates (particulates, grains, fibres or of cellular structure). These aggregates facilitate the surface reaction with oxygen by allowing gas flow through the fuel and providing a large surface area per unit volume . They also act as thermal insulation, reducing heat losses . The most studied materials to date are cellulose and polyurethane foams . </P> <Table> <Tr> <Td> </Td> <Td> This article is in a list format that may be better presented using prose . You can help by converting this article to prose, if appropriate . Editing help is available . (February 2009) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article is in a list format that may be better presented using prose . You can help by converting this article to prose, if appropriate . Editing help is available . (February 2009) </Td> </Tr>

What sort of temper is a smouldering temper