Selvantænding

Selvantænding refers to the spontaneous combustion of a substance without an external source of ignition, such as a spark or flame. This phenomenon occurs when a material undergoes slow oxidation or decomposition, generating heat. If this heat cannot dissipate into the surrounding environment quickly enough, the material's temperature will rise. Eventually, it can reach its ignition point, leading to self-ignition and fire.

Several factors contribute to selvantænding. The type of material is crucial; many organic substances, such as oily rags, hay, sawdust, and coal, are prone to this. Their chemical structure allows for exothermic reactions at relatively low temperatures. The presence of moisture can also play a role, as it can accelerate the decomposition process or facilitate certain chemical reactions. Poor ventilation is another significant factor. When flammable materials are piled up or stored in confined spaces, heat becomes trapped, preventing adequate cooling. This creates a positive feedback loop where increasing temperature leads to increased reaction rates, further increasing temperature.

Common examples of materials susceptible to selvantænding include oily rags used in workshops or garages. Linseed oil, for instance, oxidizes and generates heat. If these rags are crumpled and left in a pile, the heat can accumulate, leading to ignition. Similarly, improperly stored hay or compost piles can generate enough heat from microbial activity to self-ignite, especially if they are damp. Understanding these conditions is important for preventing fires in domestic, industrial, and agricultural settings.