Spontaneous combustion
As a self-ignition is defined as the spontaneous ignition of combustible materials. Inflammation are generally, as soon as the auto-ignition temperature is reached, but it can also be carried out catalytically.
Auto-ignition of organic material
To a self-ignition may occur if sufficiently large quantities of highly combustible organic material (eg hay, coal, flour, oil soaked rags or wood chips ) stored with adequate, but not excessive ventilation. In these materials, different processes can lead to self-ignition.
On the one hand it may lead to a sufficient temperature increase in carbohydrate-rich materials by biological oxidation ( decay ) to trigger chemical processes that lead to inflammation, if sufficient heat dissipation is guaranteed. This is explained in more detail below self-ignition of damp hay. The same mechanism applies not only for hay, but for each major sufficient moisture accumulation carbohydrate-rich material. So it may come to self-ignition even in compost heaps, under certain circumstances. Also household waste from landfills may tend to self-ignition, which is why large areas to be monitored with thermal imaging cameras here.
On the other hand, unsaturated compounds such as vegetable oils, if they are distributed over a large surface, generated by direct oxidation with atmospheric oxygen enough heat to trigger under appropriate conditions ( greater amount of loose bulk material mounted ) a smoldering fire, and finally an open fire. Oil -soaked rags must therefore be stored in tightly closed as a precaution metal vessels. In particular, hardening oils, such as linseed oil varnish, parquet floor oil that respond to rag on a large surface reaction with atmospheric oxygen.
Also threatened by spontaneous combustion are coal stockpiles and underground coal deposits ( cf. coal fire and burning heaps ), which are near the earth's surface or were exposed (eg in China). Coal stockpiles are therefore often chilled or rearranged with water.
Auto-ignition could be a cause for a smoldering anthracite deposit below the village Centralia (Pennsylvania).
An unscientific legend, however, is the spontaneous human spontaneous combustion.
ORF.at cites a documentation of Channel4 ( of November 10, 2013) based on a recent British study that when Tutankhamen an incredible chemical reaction of Balsamierungsöle to spontaneous combustion of the oils or the corpse has resulted in the sarcophagus shortly after his funeral. However, it is conceivable that textile fabric, the curing oil contains, heated at suitable environmental conditions and smoldering, glosend or begins to burn with flame and thus heats the body and this scorched to a certain degree, on or burns.
Spontaneous chemical autoignition
Some substances react even at room temperature under appearance of flames with oxygen in the air. Thus, cesium, rubidium, white phosphorus, many substituted phosphines or silanes spontaneously ignite at room temperature on contact with atmospheric oxygen; they are called pyrophoric.
Elemental lithium - in metallic form - ignites in air in the liquid state and as metal dust even at room temperature. Freshly prepared magnesium powder is heated in air up to the self-ignition.
In some cases, the heat generation speed of the end of the trigger further reaction, which is a danger exacerbated by self-ignition.
Aerosols of fine metal powder can ignite spontaneously in air also.
Spontaneous combustion in oxygen-rich atmosphere
Generally tend many substances, especially hydrocarbons, in the presence of pure oxygen for self-ignition. This is especially true in the presence of liquid oxygen.
Fittings of oxygen cylinders must therefore be free from oil and grease.