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The Flashover (German Ignition; also Flash-over, flash-over, F / O) is a phase within a fire event and describes the sudden transition of a damaging fire (e.g. room fire) from the initial phase to the full fire phase. This process usually occurs very quickly over the entire fire area.

Idealized temperature-time diagram of a room fire, according to Karlsson and Quintiere


The definition of the International Organization for Standardization for the Flashover reads: "The rapid transition of all surfaces of combustible materials in a room to a fire."

In fire protection engineering, the flashover is described as the boundary between the development phase (pre-flashover) and the full fire (post-flashover) of a room fire. The general criterion for the flashover is the rise in room temperature to 500–600 ° C, a heat flow density (of the flames and smoke) of 15 to 20 kW / m² or flames leaking out of the room openings.

The time until the flashover is strongly dependent on the factors of the size of the fire room, ventilation and fire load.


In the development phase, furnishings (e.g. sofa, table, furniture) first burn and form combustion gases and pyrolysis gases. If the smoke produced cannot be discharged through openings in the room, heat will build up on the ceiling. The heavily heated layer of smoke now radiates ever increasing thermal radiation onto all of the furnishings. At the same time, the temperature rises in the entire fire room. The surfaces of the flammable but not yet burning objects pyrolyze and then ignite suddenly at 15 to 20 kW / m² heat flow density (see also solar constant) or a flue gas temperature of 500–600 ° C without a pilot flame. The horizontal flame propagation speed in the room (ignition of further material by already burning objects) is then about 10 m / min. The result is a full fire in the room and temperatures of around 1000 ° C. Further information on the burn rate, heat release, temperature development before and after the flashover and times until a flashover occurs can be found in research reports No. 130 and 142 of the Research Center for Fire Protection Technology at the University of Karlsruhe (TH).[1]

Pre and post flashover

As Pre-flashover is the term used to describe the fire development phase before the flashover. At that time, survival for people lying on the ground and the action of a respirator is still possible. As Post flashover or full fire is the term used to describe the state after the flashover. Temperatures sometimes exceed 1000 ° C. Because of the large amounts of energy released in this phase, survival is only possible for a short time. Even modern protective clothing for a firefighter can only protect against severe burns for a few seconds at this point.


The term Flashover wrongly with the term of the flue gas ignition.rollover), or the smoke explosionbackdraft) equated. In the Flue gas ignition it is only a matter of burning pyrolysis gases from a layer of smoke Flashover around the phenomenon described above. In fire protection engineering, there is the clear definition given above.


  • Cutter: Basics of engineering methods in fire protection. Werner Verlag
  • Karlsson, Quintiere: Enclosure Fire Dynamics. Publishing house CRC Press
  • Drysdale: An Introduction to Fire Dynamics - Second Edition. Publisher John Wiley & Sons
  • Kunkelmann: Flashover / Backdraft - causes, effects, possible countermeasures; Research center for fire protection technology at the University of Karlsruhe (TH). 2003
  • Grimmwood: Tactical firefighting. 2003


  1. ↑ http: //

See also

  • Studied fire protection engineer at the University of Wuppertal
  • Trench effect

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