Boilover

Grease fires or fires of oil heated above their focus edible fats, typically occurring mostly in the kitchen area. Particularly problematic are fat fires because extinguishing tests can lead to a fat explosion with water.

Grease fire

Formerly belonged to grease fires of class B, but they are out because of their special dangers and peculiarities since January 2005 in the new, specially created fire class F.

Fats and oils may spontaneously ignite in the highly heated state - a distinct characteristic to the eingruppierten in fire class B flammable liquids, which require a source of ignition to ignite in the rule.

Fat explosion

A fat explosion occurs when incorrectly trying to extinguish a grease fire with water or high water content fluids ( drinks, etc. ).

Since burning fat or oil is several hundred degrees Celsius and thus hotter than boiling water during its inflammation, added water evaporates abruptly. This fat burning is torn with the water vapor from the container and comes more or less finely dispersed with oxygen in the air in contact. While the liquid surface of the burning fat is still relatively low, it is torn by the resulting water vapor and atomized into fine droplets. Similarly, the combustion in a diesel engine ignite the smallest droplets first heat their surroundings and adjacent fat droplets and rise with the heat through them for improvement. This produces a characteristic column above the fire, which forms into a fungus with free development.

The phenomenon of fat explosion can also be fitted with other materials, for example in heated wax or the like, occur.

The fat is one explosion of the water phase to the physical evaporations explosions since the energy for evaporating the water from the heat of the fat originates. By the subsequent explosion (exothermic ) combustion of the fine droplets of the explosion is further driven, and a chemical explosion.

• Schematic representation of

Water is poured into the burning container.

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

Through evaporation, the volume of water expands very strong and fast, the burning oil is thrown out of the container. The surface of the oil is greater and increases the fire rate.

Grease fire extinguishing agents

The easiest way to extinguish a grease fire, is the laying of a dry cover which smothers the fire.

Powder and CO2 extinguishers can not be applied sense, since after removal of the extinguishing agent concentration the burning material usually catches fire again. If you use a powder fire extinguisher you must also take into account the damage caused by the powder extinguishing agent.

For fat explosion occurs when a liquid aqueous extinguishing agent is introduced into the hot fat and can fall into the latter. Therefore, prohibit water and even normal foam extinguisher, since there exists a significant part of the extinguishing agent is mostly liquid. With solid fire this may be positive, in burning liquids it is very dangerous may - at burning fat is a high risk of burn injuries.

According to recent findings are fire blankets to extinguish grease fires - that they were often held in the past in kitchens - only partially suitable. The professional association of food and hospitality industry has made ​​attempts to extinguish grease fires. It was found that fire blankets made ​​of wool, cotton, glass, Nomex and Kevlar are only suitable because they can burn out. Probably condensed hot grease vapors into the ceiling and provided for their inflammation ( wicking ). In these experiments it was found that other, often proposed in the past for grease fires extinguishing agents, such as chemical or carbon dioxide, are only partially or not at all suitable.

The extinguishing agents contained in grease fire extinguishers the burning liquid is by saponification deleted and formed a barrier layer over the oil or fat, thus the absorption of oxygen is inhibited at the same time, the extinguishing agent cools the burning liquid below the auto-ignition temperature down, thus preventing the reoccurrence of the fire. [ evidence ?]

The suitability for the deletion of edible oil and cooking fat fires is indicated on the extinguisher ( fire class " A F " because it is an aqueous solution is in accordance with EN 3).