User Manual

Siemens Switzerland Ltd

Building Technologies Division

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. Obviously providing an adequate number of appropriate manual fire-

extinguishers is essential, however, one factor that is common to the vast majority of cultural heritage buildings

lost to fire is the lack of an automatic extinguishing system.

Due to the high fire load of historical buildings and the difficulties in ensuring effective compartmentalization (as

discussed earlier) if the fire is not stopped or controlled in the early stages of development it can rage through a

building very quickly. Rapid fire brigade intervention using water hoses may be able to prevent the total loss of

the building structure, but it is not uncommon to find that the consequential water damage to the contents of the

building is at least equal to that caused by smoke and fire.

Many historical buildings are not situated in urban areas and the closest municipal fire station may be some

considerable distance from the building concerned. 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 automatic extinguishing systems and basic

manual firefighting equipment (portable fire extinguishers and water hoses).