Typical Extracts from Building Regulations and Guidelines

Typical extracts from building regulations and guidelines produced by fire and insurance specialists

Fire development
If the initial phase of a fire is likely to be of a type characterised by smouldering (i.e. considerable smoke generation, very little heat and little or no flame propagation), then smoke detectors should be used. If rapid development of fire is anticipated in the initial phase (severe heat generation, strong flame propagation and smoke development), then smoke, heat and flame detectors can be used, or combinations of the various types.

Fire detection areas
The total area to be monitored must be divided into detection areas. The establishment of these detection areas should be carried out in such a way that rapid and decisive pinpointing of the source of the fire is possible. A detection area must only extend over one floor level (the exceptions to this being stairwells, ventilation and elevator shafts and tower type structures, which must have their own detection areas). A detection area must not overlap into another fire compartment and typically should not be larger than 1600 m2.

Fire detection systems for data processing facilities
The monitoring of electronic data processing facilities places special additional requirements on the planning and execution of fire alarm systems.

 

Factors influencing detector positions and numbers

  1. Room height
  2. Monitoring areas and distribution of detectors
  3. Arrangement of detectors on ceilings with down-standing beams
  4. For spaces with multi-bay type roofs

Room height
The greater the distance between the fire source and the ceiling, the greater the zone of evenly distributed smoke concentration will be. The ceiling height effects the suitability of the various types of smoke and fire detectors. Generally, higher ceiling sections whose area is less than 100/0 of the total ceiling area are not considered, so long as these sections of ceiling are not greater in area than the maximum monitoring area of a detector.

 

Monitoring areas and distribution of the detectors
The number of fire detectors should be selected such that the recommended maximum monitoring areas for each detector are not exceeded. Some standards specify the maximum distance between detectors and the maximum distance allowed between any point on the ceiling and the nearest detector. Within certain limits there may be a departure from the ideal square grid pattern of the detectors.

 

Arrangement of detectors on ceilings with down-standing beams
Depending on the room size, beams above a specified depth must be taken into account in the arrangement of the fire detectors. Typically, if the area of ceiling between the down-standing beams is equal to or greater than 0.6 of the permissible monitoring area of the detector, then each of these soffit areas must be fitted with detectors. If the portions of soffit area are larger than the permissible monitoring area, then the individual portions of soffit must be considered as individual rooms. If the depth of the down-standing beam is greater than 800 mm, then a fire detector must be provided for each soffit area.

 

For spaces with multi-bay type roofs
Generally in this case, each bay must be provided with a row of detectors. Heat detectors are always to be fitted directly to the ceiling. In the case of smoke detectors, the distances required between the detector and the ceiling, or the roof, depend on the structure of the ceiling or roof and on the height of the rooms to be monitored. In the case of flame detectors, the distances should be determined for each individual case.

 

Taken from: Architects’ Data by Ernst and Peter Neufert

No Comments

Leave a Comment