Ventilating a fire compartment during operational fire
fighting procedures may have unpredictable consequences.
In some cases the ventilation is advantageous: the hot
gases are removed from the fire enclosure, the visibility
improves and the enclosure cools down. In some cases the
opposite happens: with the accelerated burning rate, more
smoke is spread around, and the temperatures rise. The
most dramatic consequence is the initiation of a
backdraft, where the pyrolyzed gases ignite
instantaneously, in the worst case causing a severe
The effect of ventilating the fire compartment was
studied systematically by quarter scale laboratory tests.
The fire was initiated in a one-storey three-room
compartment subject to different horizontal ventilation
conditions. Both natural and positive pressure
ventilation (PPV) were applied. The tests revealed many
critical factors affecting the success of the attack.
When properly used, PPV clearly improves the survival
probability in the compartment: the visibility
dramatically improves, and the temperatures are low
everywhere outside the fire room.
A fire spread zone model code (BRI2T) was applied to a
few principal test scenarios. The model simulates well
scenarios with no vigorous turbulent mixing of the gas
layers, but predicting dependences between different
parameters is tedious because the model (like all zone
models) does not contain a feedback between varying
ventilation conditions and the heat release rate. Due to
these limitations, the available zone models are not
suitable for PPV applications.
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||54|
|Publication status||Published - 1997|
|MoE publication type||Not Eligible|
- fire fighting
- fire tests