Flashover
The flashover (short F / O ) or German: Feuersprung is the English-language technical term for a phase within a fire 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 happens very quickly over the entire fire area.
The flashover is to be distinguished from the backdraft (German: backfire).
Demarcation
The terminology and definition of the International Organization for Standardization for the Flashover is: "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 duration until the flashover is heavily dependent on the factors of the size of the fire room (especially the ceiling height), ventilation (one or more openings and their arrangement in the room), fire load (and their arrangement in the room) and the arrangement of the source term (place where the fire started).
Emergence
In the development phase, furnishings (e.g. sofa, table, furniture) first burn and form combustion gases and pyrolysis gases. If the smoke that has arisen cannot be discharged through openings in the room, heat will build up on the ceiling. The heavily heated layer of smoke now sends ever increasing thermal radiation to 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 pyrolize and then ignite suddenly at 15 to 20 kW / m² heat flow density (see also solar constant ) or a flue gas temperature of 500 to 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 KIT (formerly University of Karlsruhe (TH)).
Pre and post flashover
- The fire development phase before the flashover is called pre- flashover. At that time, survival for people lying on the ground and the action of a respirator is still possible.
- The state after the flashover is called post-flashover or full fire. 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.
Mix-ups
On the Internet and in some cases also in the training of fire brigades , the term flashover incorrectly with the terms flue gas ignition (Engl. Rollover ) or Backdraft (Engl. Backdraft ) equated.
- The flue gas ignition is simply the burning of pyrolysis gases in a layer of smoke. This combustion process can take place with or without an increase in pressure.
- In the case of a smoke gas explosion, the fire gases ignite explosively due to the supply of oxygen from outside. In this respect, standard language translations are not identical to the differentiated, technical use of the terms.
literature
- Schneider: Basics of engineering methods in fire protection. Werner Verlag.
- Karlsson, Quintiere: Enclosure Fire Dynamics. Publisher 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.
See also
Web links
- Phenomena of extreme fire spread (PDF; 1.1 MB)
- Animation of a flashover
- Video of a flashover in a supermarket
- Video of a training course in a Flashover container
- Large series of pictures of a flashover