Fire ventilation

A small fi re in a large
room causes the smoke
to have a low temperature
and therefore it
can be diffi cult to vent,
both with and
without fans.
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relatively cold and diluted. Because of the size of the room
the fi re will be fuel controlled for a long period, and may
not become ventilation controlled at all.
The risks associated with fi re ventilation are very small
in this situation.
It is also conceivable that a similar situation will occur in
the case of apartment fi res. The interior ceiling and walls
may be incombustible (e.g. plasterboard) and if the interior
furnishings (furniture etc.) are placed in such way that a
fi re in an individual object does not spread to other objects,
the fi re can remain fuel controlled during the entire fi re
scenario. It may self-extinguish when the fuel is used up.
The risks associated with fi re ventilation in these situations
are also very small.
Small fi res can, however, develop quickly and powerfully
during fi re ventilation if they are located in double fl ooring,
ceilings, under fl oor areas, or confi ned in other ways
in what is otherwise a large room. This sets extensive tactical
requirements, above all in the form of the build-up of
resources. Even if the room is well ventilated there can be
concealed areas that are poorly ventilated.
Since the fi re gases has a relatively low temperature and very
limited buoyancy force, an opening for an outlet should be
made as high up as possible, preferably in the roof. Supply air
should be taken from the lowest possible point, and mechanical
ventilation should be carried out. Negative pressure ventilation
can as a result of practical problems be diffi cult to implement,
especially if the room is very large. It may also be diffi cult