Fat fire

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Fat explosion of approx. One liter of burning edible fat, which was carried out by the fire brigade for demonstration purposes at an event.

Fat fires are fires caused by edible fats or oils that are heated above their focal point , typically occurring in the kitchen area. Fat fires are particularly problematic because attempts to extinguish the fire with water can lead to a fat explosion .

Fat fire

Fire brigade simulates fat fire / fat explosion to demonstrate the danger. Length of the sequence 2.4 seconds. 1 kg of deep-frying fat and 1 liter of water were used.
Demonstration of a fat explosion by introducing water into burning oil

Grease fires used to belong to fire class B, but since January 2005 they have been classified in the specially created fire class F due to their special dangers and peculiarities.

Fats and oils can self-ignite when they are very hot - a clear difference between them and the flammable liquids classified in fire class B, which generally require an ignition source for ignition.

Fat explosion

The fat explosion belongs to the physical explosions in the phase of water evaporation, since the energy for evaporating the water comes from the heat of the fat. The subsequent explosive (exothermic) combustion of the fine droplets drives the explosion further and leads to a chemical explosion.

Since burning fat or oil is already several hundred degrees Celsius hot when it ignites and thus hotter than boiling water, added water evaporates suddenly. This tears the burning fat out of the container with the water vapor and comes into contact with the oxygen in the air, more or less finely distributed. While the liquid surface of the burning fat is still relatively small, it is torn open by the resulting water vapor and atomized into very fine droplets. Similar to combustion in a diesel engine, the smallest droplets ignite first, heat their surroundings and neighboring fat droplets and rise with the air they heat. This creates a characteristic pillar of fire above the place of fire, which forms a mushroom when it unfolds freely.

The phenomenon of a fat explosion can also occur with other substances, e.g. B. with heated wax or the like occur.

A fat explosion may occur when incorrectly trying to make a grease fire with water to or high water content fluids (drinks etc.) delete .

  • Schematic representation

  • The excessive heating of the oil leads to spontaneous combustion .

  • Water is poured into the burning container.

  • Since the density of water is higher than that of oil, it sinks to the bottom of the container. As a result of the great heat of the oil and the soil, the water evaporates immediately.

  • Due to evaporation, the volume of the water expands very quickly and the burning oil is thrown out of the container. This increases the surface of the oil and increases the rate of fire.

Web links

Commons : Grease Fires  - Collection of pictures, videos and audio files