Enclosure fires

7.3.2 Course of action
If smoke gases have already accumulated in the adjacent area
the situation is very diffi cult to resolve. At fi rst, it is very diffi -
cult to neutralise the effect of the gases by spraying fi ne particles
of water on them. The smoke gases may well be fairly
cool, which makes it very diffi cult to vaporise the water. The
fact is that they are still dangerous because the temperature
does not have any infl uence in this case.
If we decide to ventilate the area we must be careful not to
cause any sparks, as this is the most dangerous factor of all.
This can be diffi cult if we have to pierce a hole to let the smoke
gases out. In other cases, it is perhaps not possible to ventilate
the area easily, which means that we are facing an even more
diffi cult situation.
The overall conclusion must be, therefore, that the easiest
solution is to prevent the build-up of smoke gases through
preventive maintenance, as well as to ventilate the area at an
early stage before any smoke gases have managed to accumulate
within the fl ammability range. The prerequisite for this,
of course, is to call the fi re service early so that they can arrive
quickly at the scene.
At the scene of the fi re it may be important to get hold of
people who are familiar with the building. If we can get access
to a good plan drawing at an early stage this will facilitate our
job immensely.
Sometimes we can perhaps manage to exert pressure on
the area before smoke gases accumulate. But there needs to be
a small level of leakage, otherwise it will be diffi cult to do
this.
7.4 Summary
A smoke gas explosion occurs when a premixed gaseous mass
ignites in a room or area. This most commonly occurs in an
area in proximity to the fi re room. The smoke gases are able to
mix well here. This phenomenon is mainly controlled by
premixed fl ames. Smoke gas explosions can also occur in the
fi re room, but this is less frequent.
There are a number of factors which determine the magni-
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