Fire ventilation

an extinguishing operation, are in this case positive, since
the operation can be implemented with only a limited
spread of fi re gases to the stairwell. This requires, however,
making an opening in the apartment on fi re (outlet).
To take into consideration at stairwells containing
cold fi re gases:
• If an apartment door in the upper part of the
stair well is opened by evacuating people, fi re gases
can quickly spread to this apartment. The fi re gases
will, however, be cold and diluted, which means
that people in other apartments will be less
exposed to risk. If an apartment door is opened
this will also lead to a pressure drop in the
stairwell, and both the outlet through the roof of
the stairwell and any positive pressure ventilation
will be less effective.
• During the summer problems can arise if it is
warmer outside than inside the stairwell, even if
the stairwell is fi lled with fi re gases. It is then
conceivable that fi re gases will collect in the
bottom of the stairwell, especially in very high
buildings.
The stairwell is full of
cold smoke, which can
be diffi cult to vent out.
115