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VENTILATION AT FIRE

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DEFINITION
It is the art of inducing heat and smoke
to leave a building as quickly as
possible causing the minimum damage.
NEED OF VENTILATION
To prevent or reduce damage from smoke and
heat.
To prevent the spread of fire by a build-up of
heat.
To enable fire rescuer to enter, find and
extinguish the fire quickly without suffering
excessive punishment from heat and smoke.
WHAT IS SMOKE
Smoke is generally a mixture of fine
solid particles, droplets of water and other
liquids, and products given off by the
materials involved in the fire.
BEHAVIOUR OF SMOKE
The fire will heat the surrounding air and
since hot air is lighter, it will tend to rise
very rapidly and with great force. The
smoke will be carried with it.
SMOKE EXPLOSIONS
When flammable smoke and vapours collect in
an enclosed space, mixed with air
This can ignite suddenly, causing a dramatic rise
in pressure like a blast wave.
This risk of explosion is liable to arise
e.g. foamed rubber, smoldering in an enclosed
space.
VALUE OF VENTILATION
Preventing and reducing damage
Preventing fire spread
Assisting firemen
PREVENTING AND REDUCING
DAMAGE
The constituents of smoke can be
Corrosive, oily or other wise injurious.
If it is not controlled, smoke can
Cause damage to parts of the
Structure / building, which the fire
Itself does not reach.
PREVENTING AND REDUCING
DAMAGE
If a building is not ventilated or a
fire is large it becomes partially
starved of oxygen.
Unburned flammable gases may
collect beneath ceilings and roofs.
These may subsequently ignite and
lead to further, unnecessary, fire
damage.
PREVENTING FIRE SPREAD
Hot gases will rise via lift shafts,
staircases, and any other pathway
available carrying with them smoke,
flame and burning materials.
If they cannot escape by way of a
vent, they will mushroom out under
the ceilings and roofs that confine them.
PREVENTING FIRE SPREAD
In this way the fire may spread to other,
unaffected areas.
Mushrooming is in fact one of the most
common causes of fire spread though roof
spaces or from floor to floor.
Ventilation can prevent or hinder fire spread
by convection.
ASSISTING FIREMEN
Heavy smoke with its irritating properties
and reduced oxygen.
Reducing visibility.
It can also hinder the speedy location of
the seat of a fire and assessment.
Advantages of Ventilation
By ventilation firemen will face less
difficulty and danger.
When a compartment or buildings is
completely on fire, ventilation will
enable firemen to enter.
It can help by ensuring that flames and
hot gases flow out only through vents.
WHEN TO VENTILATE
little effect on the rate of burning of a
fire in a large building in its initial stages.
Incorrectly ventilation can lead to the
rapid spread of the fire within the
building.
Firemen should not start ventilation until
they are sure it is safe, subject to the
necessary precautions.
PRINCIPLE OF VENTILATION
Basic principle is that hot gases rise.
Ventilation employs this principle to
achieve the results. By removing heat and
smoke through openings in the structure.
PRINCIPLE OF VENTILATION
Firemen may create such openings
themselves or through doors, windows and
other openings.
Types of Ventilation
Natural fire ventilation.
Mechanical fire ventilation system.
VENTILATION FROM THE TOP
Firemen should start their ventilation at
the highest points they can reach, such
as staircases or lift shafts.
VENTILATION FROM THE SIDE
Top ventilations will not always be practical
for various reason.
Location
the physical properties of the building and
its contents.
VENTILATION FROM THE SIDE
The extent of the fire.
The accessibility of point for ventilation
etc.
In such case, fire rescuer should ventilate
from the side.
FACTORS FOR SIDE VENTILATION
The direction and force of the wind.
Which is the windward side of the building.
The humidity and temperature.
HOW TO VENTILATE
Correct ventilation technique is very
important and when necessary one or
more crews should be specifically
assigned to this work.
Mechanical ventilation systems
Usually work automatically with manual
over-ride.
firemen require the special operation they
should if possible consult the engineer
responsible,
As incorrect use could result in spreading
the fire.
Mechanical ventilation systems
THANKS
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