Spontaneous Combustion
Spontaneous combustion is the onset of fire through an exothermic oxidation or decomposition reaction occurring within a material itself, which builds up to ignition temperature without any external ignition source.
Hazard picture
Certain materials continuously release heat as they chemically decompose or oxidise; if this heat is not carried away by air movement, the temperature inside the material gradually rises until it reaches ignition temperature – without any spark, open flame or other external ignition source. Typical risk materials include oil- or varnish-soaked rags, hay and other agricultural produce, coal, oil-bearing oilseeds, and certain chemicals and waste materials; large, densely stored piles act like insulation that promotes self-heating.
Protection measures
The most effective measure is consistent operational hygiene: soaked rags and similar waste belong in closed, non-combustible containers and must be removed from the premises regularly, at least daily. Larger quantities of self-heating-prone bulk materials require limiting pile size, adequate ventilation and regular temperature monitoring, particularly for materials classified under transport regulations as Class 4.2 substances liable to spontaneous combustion. Separating such materials from other fire loads also limits the consequences should ignition nevertheless occur.
Insurance relevance
Spontaneous combustion fires often start outside operating hours and are detected late, since no external ignition source precedes them to signal a hazard. Property insurers therefore specifically assess waste and storage hygiene, along with compliance with pile-size and ventilation requirements, as an indicator of a systematically managed risk at facilities handling such materials.