2.15 Automatic fire suppression systems
Automatic fire suppression systems installed in domestic premises are primarily designed for life safety purposes. Successful activation can provide occupants, including vulnerable occupants, with additional time to escape following the outbreak of fire. The added benefit of automatic fire suppression in domestic buildings means that the damage and disruption caused by fire is greatly reduced.
Automatic suppression systems react to heat therefore, the greatest protection is afforded to those occupants outwith the room of fire origin. Automatic suppression may provide some benefit to occupants in the room of fire origin where for example the fire growth is fast and the temperatures allow the sprinkler system (normally 1 or 2 heads) to open early in the development phase of the fire. The spray pattern delivered from the sprinkler heads should control fire spread. Whilst the effect of sprinkler spray will increase the smoke volume and could obscure exits, smoke temperatures and toxicity will be greatly reduced. In some cases, the fire might be extinguished if the fire is not shielded from the sprinkler spray.
Automatic life safety fire suppression systems are required in 2 categories of domestic building:
The term automatic life safety fire suppression system includes sprinkler systems but provides the opportunity for designers to propose other systems which may be just as effective. The key characteristics of the system are:
it must be automatic and not require people to initiate its activation
it must be designed primarily to protect lives, rather than property, which means it should be fitted with faster responding sprinkler heads, and
it must be a fire suppression system, one designed specifically to deal with fires rather than other hazards.
Concealed or recessed pattern sprinkler heads may be used in the system design. However there is a risk that the heads are rendered ineffective or operate less efficiently by the application of any decorative ceiling finish. Therefore, consideration should be given to labelling of the heads with words to the effect of 'DO NOT PAINT'.
Alternative suppression systems - there are many alternative or innovative fire suppression systems available including systems utilising domestic plumbing and water-mist systems. Verifiers should satisfy themselves that such systems have been designed and tested for use in domestic buildings and are fit for their intended purpose (see Section 0).
Alternative approaches in a particular case may or may not be compensated by an automatic fire suppression system.
A sheltered housing complex is a purpose built complex comprising of 2 or more dwellings e.g. houses, flats and maisonettes, where the occupants are likely to receive a support service due to the nature of their vulnerability or need e.g. age, infirmity, disability, illness, mental disorder or are dependant on alcohol or drugs. Such occupants are likely to react slowly to the fire alarm (see Standard 2.11) and the suppression system may provide the additional time necessary to make a safe escape.
Therefore, a sheltered housing complex should have an automatic life safety fire suppression system designed and installed in accordance with BS 9251: 2005. For the purposes of satisfying Standard 2.15, a sheltered housing complex should be regarded as a ‘residential occupancy’ as defined in BS 9251: 2005 and the limit on the scope of BS 9251: 2005 to buildings below 20m in height can be ignored.
Where the sheltered housing complex is designed as individual dwellings (for example, terraced houses) served by individual sprinkler systems, the sheltered housing complex may be regarded as a ‘domestic occupancy’ as defined in BS 9251: 2005.
Occupants are at greater risk from fire if they are located on a floor high above the ground. Wind effects might also have an influence on the speed, intensity and direction of fire development within the dwelling or other ancillary room or space of fire origin.
Therefore, in order to help contain the fire and to protect occupants in high rise domestic buildings, every flat or maisonette including all ancillary rooms and spaces throughout the building should be provided with an automatic life safety fire suppression system designed and installed in accordance with BS 9251: 2005. For the purposes of satisfying Standard 2.15, a high rise domestic building should be regarded as a ‘residential occupancy’ as defined in BS 9251: 2005 and the limit on the scope of BS 9251: 2005 to buildings below 20m in height can be ignored.
For a suppression system to be effective it is essential that there is an appropriate water supply. Therefore, designers need to discuss with Scottish Water what supply is likely to be available and what pressure can be expected. It is recognised that pressures will vary during the day, over the year and perhaps in future years. Therefore it is imperative that the system is designed on the basis of what the minimum pressure and flow is likely to be. If there is any doubt, a tank and pump arrangement should be used.