Smoke explosion
A smoke gas explosion or a backdraft is an explosion-like ignition of smoke gases .
If there is a fire in a closed room , which, however, soon goes out again due to a lack of oxygen (possibly via the "intermediate station" smoldering fire ), flammable gases and vapors remain due to the previous pyrolysis . As the room cools down slowly, these gases lose volume, creating a negative pressure . This leads to the impressive effect that fire smoke through gaps from z. B. doors or gates emerges and a short time later is sucked back into the fire room. If the door is now opened, the negative pressure means that fresh air is "sucked in" from outside and the mixture is then ignitable. If there is still an ignition source (e.g. embers), the mixture will explode, with potentially devastating effects.
The resulting underpressure, the (almost) extinguishing of the actual fire and the stronger explosion are clear criteria for differentiating from the “normal” smoke ignition (rollover) or the so-called flash-over .
properties
In the event of a flue gas explosion, after the supply of oxygen, a flame roller develops at a speed of up to 20 m / s and a temperature of a maximum of 850 ° C. Even good protective clothing made of Nomex cannot cope with such high temperatures . The simplest protection against a smoke gas explosion is to fall on the floor, where the temperature is much lower. For this reason, doors should always be opened from "cover".
The dangerous thing about the preliminary stage of the smoke gas explosion is that you can neither see, hear nor in any way notice the smoldering fire in a room, which often leads to deaths.
Literature and film
The biblical story in the book of Daniel about the three young men in the fiery furnace (approx. 600 BC) probably contains the first literary description of a smoke gas explosion ( Dan 3.22 EU ).
Flue gas explosions were also the basis for the film Backdraft - Men Who Go Through Fire with Kurt Russell and Robert De Niro .
See also
Web links
- A backdraft (pictures and video) Swedish text
- Animation of a smoke gas explosion
- More pictures on the subject of flue gas explosion with experience reports
- Karlsruhe Institute of Technology (KIT) - Research center for fire protection technology: Investigations into flashover, backdraft, rollover, pressure vessel bang