Enclosure fires

Fires in enclosed spaced with
minimal ventilation
Figure 105. Backdraught
warning signs.
The smoke gases’
colour is not a
defi nite warning
signal.
138
Bränder
ventilatio
Oily deposits on window panes
Oljiga avlagringar på fönste
Hot doors and windows
Varma dörrar och fönster
Pulsating smoke gases from small openings
Pulserande brandgaser från
Whistling sound
Visslande ljud
an imminent backdraught. It is simply not enough at all to
consider the smoke gases’ colour as the only warning signal.
Before a fi refi ghter opens the door to the fi re room, the following
points need to be taken into consideration:
• Fires in enclosed spaces with minimal ventilation, for
instance, closed rooms or spaces under the roof.
• Oily deposits on window panes, which is a sign that
pyrolysis products have condensed on cold surfaces. A
sign of an under-ventilated fi re.
• Hot doors and windows, indicating that the fi re has been
burning a while, perhaps with limited ventilation.
• Pulsating smoke gases from small openings in the room,
which are a sign of under-ventilated conditions. When
the air enters the room combustion takes place, which
means that the oxygen runs out as the temperature rises.
Then the temperature falls slowly and when the pressure
has dropped slightly the air can be sucked into the room.
• A whistling sound in openings, which may be related to
the fi re pulsating.
In those cases where the decision is made to enter, the fi refi
ghter must be on the lookout for the following signs, particularly
at the moment when he has opened the door to the
fi re room and looks into the room. These signs, along with the
others, can provide warning signs for an imminent backdraught.