Part of the Fire Alarm System

Building regulations require that due consideration must be given in buildings to:

  • the flammability of building materials
  • the duration of fire resistance of the components expressed in terms of fire resistance classifications
  • the integrity of the sealing of openings
  • the arrangement of escape routes.

 

The aim is to prevent the start and spread of a fire, stem the spread of smoke and facilitate the escape or rescue of persons and animals. In addition consideration must be given to effective extinguishing of a fire. Active and passive precautions must be taken to satisfy these requirements. Active precautions are those systems that are automatically deployed in the event of fire; passive precautions are the construction solutions in the building and its components.

Active precautions include smoke and fire alarm systems, sprinkler systems, water spray extinguisher plant, CO2 extinguishing installations, powder and foam extinguisher plant, and automatic smoke and heat venting systems. Passive precautions relate mainly to minimum structural sections, casings and coatings. In addition to these, other important measures are the layout of rising mains, installation of fire doors and fire windows, construction of supporting floors, water cooling of hollow steel profiles and the dimensioning of casings and coatings for steel profiles.

 

Fire detectors

A fire detector is a part of the fire alarm system and can trigger a transmitting device that raises the alarm in a remote control centre. There are automatic and non-automatic fire detectors. The latter are those which can be activated manually.

Automatic fire detectors are parts of the overall fire alarm system that sense changes in specific physical and/or chemical parameters (either continuously or sequentially in set time intervals) to detect a fire within the monitored area.

Automatic fire detectors must be:

  • installed in sufficient numbers and be suited to the general arrangement of the area to be monitored
  • selected according to the fire risk
  • mounted in such a way that whatever parameter change triggers the alarm can be easily sensed by the detector.

 

Smoke detectors

These are used in rooms containing materials that would give off large volumes of smoke in the event of a fire.

  • Optical smoke detectors: triggered by visible smoke.
  • Ionization smoke detectors: triggered by small amounts of smoke which have not been detected by optical means. These detectors provide earlier warning than optical smoke detectors and are suitable for houses, offices, storage and sales rooms.

 

Flame detectors

These are activated by radiation emanating from flames and are used in rooms containing materials that burn without smoke, or produce very little.

 

Heat detectors

These are useful for rooms in which smoke that could wrongly set off other early warning systems is generated under normal working conditions (e.g. in workshops where welding work is carried out).

  • Maximum detectors: triggered when a maximum temperature is exceeded (e.g. 70°C).
  • Differential detectors: triggered by a specified rise in temperature within a fixed period of time (e.g. a rise of 5°C in 1 minute).

The planning and installation of fire detection systems must be designed to suit the area to be monitored, room height and the type of ceiling and roofing.

 

Taken from: Architects’ Data by Ernst and Peter Neufert

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