2.15 Automatic fire suppression systems
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Automatic fire suppression systems help control the intensity and size of a fire, suppress it and in some cases may even extinguish it. It can provide occupants, including vulnerable occupants, with the additional time necessary to escape following the outbreak of fire. The primary role of the suppression system may be for life safety or property protection.
Life safety - automatic fire 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 to open early in the development phase of the fire. The spray pattern delivered from the heads should control fire spread, reduce temperatures and dilute the smoke. In some cases, the fire might be extinguished if the fire is not shielded from the sprinkler spray. A smaller fire means that the fire and rescue service will be able to bring the fire under control and extinguish it much more quickly.
Property protection - concerns about fire have traditionally centred on life protection rather than asset protection. A primary objective of the building standards system however is to ‘further the achievement of sustainable development’. The sustainability of communities could be served by the protection against both deliberate and accidental fires in buildings such as schools that serve as social assets and components of the local economic network. There is on average 152 fires in Scottish schools each year that result in significant costs in terms of the damage and disruption they cause.
For the purposes of this standard a school is a building in which primary and or secondary education is given.
Annexes - due to the special fire precautions within residential care buildings, hospitals, and enclosed shopping centres, additional guidance is grouped in the annexes. However it is important to remember that the guidance in the annexes is in addition and supplementary to the guidance to Standard 2.1 to 2.15. For additional guidance on:
residential care buildings, see annex 2.A
hospitals, see annex 2.B
enclosed shopping centres, see annex 2.C.
Conversions - in the case of conversions, as specified in regulation 4, the building as converted shall meet the requirement of this standard (regulation 12, schedule 6).
The term automatic 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 should be automatic and not require people to initiate its activation
it should be a fire suppression system, one designed specifically to deal with fires rather than other hazards.
Life safety systems - where a system is installed for life safety purposes (other than in residential care buildings) as well as property protection, the additional recommendations for a life safety system are contained in the LPC Rules for Automatic Sprinkler Installations 2009 incorporating BS EN 12845: 2015. The suppression system should cover the entire building including roof voids where necessary.
Compensatory feature - automatic fire suppression may also be chosen by the designer as part of the escape strategy or as a compensatory feature where the recommendations in this handbook have been varied in some way. Where a system is installed as a compensatory feature the additional recommendations for a life safety system contained in the LPC Rules for Automatic Sprinkler Installations should be applied.
Alternative suppression systems - there are many alternative or innovative fire suppression systems available, including systems utilising gaseous, mist or fog systems. Verifiers should satisfy themselves that such systems have been designed and tested for use in non-domestic buildings and are fit for their intended purpose (see Section 0).
2.15.2 Residential care buildings
A residential care building should have an automatic life safety fire suppression system designed and installed in accordance BS 9251: 2014.
2.15.3 Hospitals
Due to the unique operational requirements of hospitals certain departments and high risk areas should have an automatic life safety fire suppression system designed and installed in accordance with guidance set out in clause 2.1.2.
An enclosed shopping centre should have an automatic life safety fire suppression system designed and installed in accordance with guidance set out in annex 2.C.
A school building should have an automatic fire suppression system installed for asset protection to further the achievement of sustainable development.
A fire risk assessment should be carried out to identify all the fire hazards that may be present. This will determine the appropriate hazard classification and form the basis of the automatic fire suppression system design. The hazard classification dictates the performance criteria for the suppression system, the water supply arrangements, components, design of pipework and cost.
The hazard classification for schools is normally Ordinary Hazard Group 1 (OH1). In some cases Light Hazard (LH) classification may be used where the building or compartment is not more than 126m2. See BS EN 12845: 2015 for more detailed information. It is important to recognise that clients or insurers may specify a different hazard classification, depending on the outcome of the fire risk assessment.
BS EN 12845: 2015 gives guidance on special hazards such as:
aerosol storage
flammable liquids storage
polypropylene or polyethylene storage bins
computer areas
theatres
drying ovens
areas where corrosive atmospheres may exist.
Design criteria - to ensure the suppression system is robust, the automatic fire suppression system should be designed, installed and maintained in accordance with the LPC Rules for Automatic Sprinkler Installation. These rules contain the text of BS EN 12845: 2015 together with a series of Technical Bulletins which complement the recommendations (e.g. Technical Bulletin 221, Sprinkler protection of schools). The suppression system should cover the entire building including roof voids where necessary.
Guidance on the key issues to be considered in sprinkler system design can also be found in the BAFSA ‘Code of Practice on Sprinklers in Schools’.
Existing schools - where additional accommodation is provided to an existing school by either extending the school or constructing another school building on the existing school grounds, the automatic fire suppression system should be extended into the extension or new building.
Where an existing school does not have an automatic fire suppression system, a system should still be considered for the additional accommodation.
There may be smaller school buildings on existing school grounds where it is not reasonably practicable to install an automatic fire suppression system. This would be where the benefits of a system are clearly outweighed by the costs. However, the designer should check whether an automatic fire suppression system is required to satisfy any school client or insurer requirements.
In determining whether it is not reasonably practicable to install an automatic fire suppression system all relevant factors should be taken into account. The primary consideration is likely to be the building size and proportionate cost of the fire suppression system in relation to the overall project cost. The expected life of the building is also an important factor as some buildings may only be needed for a short time. For example temporary classrooms needed for school refurbishments or other construction.
Secondary considerations include the risk of deliberate or wilful fire-raising in the immediate geographic area, for which advice could be sought from the local fire and rescue service. There is also the potential impact of any damage or disruption caused by fire.
Where an existing school is being altered, there is no need to install an automatic fire suppression system. In the case of an existing school building which has an automatic fire suppression system installed, it is important that the system’s operation is not compromised by any building work.
2.15.6 Compartmentation
There is recognition within the guidance given under Standard 2.1 that automatic fire suppression can have a role to play in limiting potential fire growth. It is possible therefore to increase the compartmentation area/size in certain building types. These building types are identified in the tables to clause 2.1.1; the intention is to allow design flexibility.
Tall buildings take longer to evacuate and where the building is at a height of more than 25m it is beyond the reach capability at which the Fire and Rescue Service can effect external rescue. Therefore, when phased evacuation is adopted in buildings, additional active and passive fire protection measures will be necessary. As part of the package of fire safety measures an automatic life safety fire suppression system should be provided on every storey.
Fire suppression should be appropriate to the occupancy and should be determined on the basis of a risk assessment. Where provided, an automatic life safety sprinkler system should be designed and installed in accordance with the LPC Rules for Automatic Sprinkler Installations 2009, Incorporating BS EN 12845: 2015 including life safety recommendations.
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 may vary throughout the day and night, 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.