User Manual

30
5 Extinguishing
5.1 Introduction
Although preventing the outbreak of fire is the highest
priority, the possibility of a fire occurring will always
remain present. An automatic fire detection system, as
discussed in Section 3 must also be supplemented by an
effective fire extinguishing infrastructure. In many
countries the installation of a sprinkler system is being
made mandatory in new school buildings and providing
an adequate number of appropriate manual fire-
extinguishers is essential. Many country schools may be
some distance from the closest municipal fire station. The
time that the fire brigade may take to arrive at the scene
of a fire is a factor that should be taken into consideration
when assessing what fire suppression infrastructure
should be provided locally. Similarly any vehicular access
difficulties (e.g. narrow or low bridges, winter access,
etc.) or lack of extinguishing water should also be borne
in mind.
5.2 Principles
For a fire to exist, three elements need to be present:
 Heat to raise the material to its ignition temperature
 Fuel to support combustion
 Oxygen to sustain combustion
Extinguishing a fire implies interfering with the
combustion process in such a way that the preconditions
to maintain combustion are no longer present. This can
be achieved by removing any one of these three elements
or by interfering directly with the combustion process.
This results in the four basic extinguishing mechanisms:
 Reducing the temperature of the inflammable
materials or the flames (cooling)
 Cutting off the supply of oxygen
(smothering, inerting)
 Physically separating the inflammable materials from
the flames (starvation)
 Use of chemicals to inhibit the combustion process
An appropriate fire suppression infrastructure may include
both automated extinguishing systems and basic manual
firefighting equipment (portable fire extinguishers and
water hoses).
For a fire to exist, three elements need to be present:
heat, fuel and oxygen
5.3 Extinguishing systems
The most appropriate automated extinguishing systems
for education facilities depend to a large extent on the
application.
In general areas:
 Sprinkler systems
 Water mist systems
In electrical plant rooms, server rooms or archives:
 Gas extinguishing systems
 Extinguishing systems using gas/water-combined
technology
5.3.1 Sprinkler systems
These automatic systems use water as the extinguishing
agent and provide a very effective protection both for
property and human life. The advantages of sprinkler
systems are their high reliability and wide application
spectrum in the protection of people and material assets.
Not only do they stand out due to their relatively simple
and robust technology, there is generally a plentiful
supply of the extinguishing agent – water. Very often the
primary fire protection provision is the water sprinkler
system, either wet pipe or pre-action arrangements. Such
systems are intended to protect the integrity of the
building structures and prevent their collapse. In effect,
the purpose of sprinkler systems is to control the fire and
to cool the building infrastructure in order to allow
firefighters to reach the fire location and to perform their
duty. Sprinkler systems are becoming common in modern
purpose-built schools and are required by local building
regulations in many countries. The advantages are
considerable as sprinklers are very effective in preventing
a fire from spreading to other areas of a building. It is a
common misconception that all sprinkler heads are
activated simultaneously and not just the one(s) in the
immediate vicinity of the fire. Any water damage caused
by a sprinkler system is very limited, as over 80% of all
fires can be controlled by only 1 or 2 sprinklers. This is in
stark contrast to water damage that can be caused by fire
brigade water hoses. Although accidental activation of
a sprinkler is often quoted as an additional and
unwarranted risk, this is a very rare occurrence
(statistically shown to be in the million-to-one region).
Sprinkler systems consist of a network of water pipes with
sprinkler heads positioned in such a way that (in case of
fire) all areas to be protected would be reached by the
extinguishing water spray. The sprinkler heads react
individually to heat, opening to discharge a pressurized
water spray when the temperature is sufficiently high.
In this way an incipient stage fire can be suppressed at its
source as only those sprinklers in the immediate vicinity
of the fire will be activated, minimizing any unnecessary
water damage.
Wet-pipe systems
Since colleges and universities are not generally subject to
freezing or overheating (+95 °C) during the year, the most
appropriate type of sprinkler is the wet-pipe system. Such
systems are permanently filled with water, which is
maintained under pressure so that in case of fire the
water can be immediately discharged from the sprinklers.