Section 1 Fire alarm and fire detection systems

Fire alarm and fire detection systems

  1. Introduction
    1. Flats
      1. General
        1. Material alterations
          1. Sheltered housing
            1. Student accommodation
              1. Positioning of smoke and heat alarms
                1. Power supplies
                  1. Design and installation of systems
                    1. Buildings other than flats
                      1. General
                        1. Fire alarm systems
                        2. Warnings for people with impaired hearing
                          1. Automatic fire detection and fire alarm systems
                            1. Design and installation of systems
                              1. Interface between fire detection and fire alarm systems and other systems

                                Introduction

                                1.1Provisions are made in this section for suitable arrangements to be made in all buildings to give early warning in the event of fire.

                                Paragraphs 1.2 to 1.23 deal with flats and paragraphs 1.24 to 1.37 with buildings other than flats. Paragraph 1.38 is applicable to all uses.

                                Flats

                                1.2 Provisions are made in this section for suitable arrangements to be made in flats to give early warning in the event of fire

                                General

                                1.3 In most flats, the installation of smoke alarms or automatic fire detection and alarm systems, can significantly increase the level of safety by automatically giving an early warning of fire. The following guidance is appropriate for most flats. However, where it is known that the occupants of a proposed flat are at a special risk from fire, it may be more appropriate to provide a higher standard of protection (i.e. additional alarms).

                                1.4 All new flats should be provided with a fire detection and fire alarm system in accordance with the relevant recommendations of BS 5839- 6:2004 Code of practice for the design, installation and maintenance of fire detection and fire alarm systems in dwellings to at least a Grade D Category LD3 standard.

                                1.5 The smoke and heat alarms should be mains-operated and conform to BS 5446-1:2000 or BS 5446-2:2003 respectively: Fire detection and fire alarm devices for dwellings, Part 1 Specification for smoke alarms; or Part 2 Specification for heat alarms. They should have a standby power supply such as a battery (either rechargeable or non-rechargeable) or capacitor. More information on power supplies is given in clause 15 of BS 5839-6.

                                Notes: BS 5446-1 covers smoke alarms based on ionization chamber smoke detectors and optical (photo-electric) smoke detectors. The different types of detector respond differently to smouldering and fast-flaming fires. Either type of detector is generally suitable. However, the choice of detector type should, if possible, take into account the type of fire that might be expected and the need to avoid false alarms. Optical detectors tend to be less affected by low levels of ‘invisible’ particles, such as fumes from kitchens, that often cause false alarms. Accordingly, they are generally more suitable than ionization chamber detectors for installation in circulation spaces adjacent to kitchens.

                                Material alterations

                                1.6 Where new habitable rooms are provided above the ground floor level, or where they are provided at ground floor level and there is no final exit from the new room, a fire detection and fire alarm system should be installed. Smoke alarms should be provided in the circulation spaces of the dwelling in accordance with paragraphs 1.10 to 1.18 to ensure that any occupants of the new rooms are warned of any fire that may impede their escape.

                                Sheltered housing

                                1.7 The detection equipment in a sheltered housing scheme with a warden or supervisor should have a connection to a central monitoring point (or alarm receiving centre) so that the person in charge is aware that a fire has been detected in one of the flats and can identify the flat concerned. These provisions are not intended to be applied to the common parts of a sheltered housing development, such as communal lounges, or to sheltered accommodation in the Institutional or Other residential purpose groups. Means of warning in such facilities should be considered on a case by case basis following the general guidance for buildings other than flats given in paragraphs 1.24 to 1.38.

                                Student accommodation

                                1.8 Some student residential accommodation is constructed in the same way as a block of flats. Where groups of up to six students share a self-contained flat with its own entrance door, constructed on the compartmentation principles for flats in Section 7 (B3), it is appropriate to provide a separate automatic detection system within each flat. Where a general evacuation is required (e.g. halls of residence), the alarm system should follow the guidance for buildings other than flats given in paragraphs 1.24. to 1.38.

                                Positioning of smoke and heat alarms

                                1.9 Detailed guidance on the design and installation of fire detection and alarm systems in flats is given in BS 5839-6. However, the following guidance is appropriate to most common situations.

                                1.10 Smoke alarms should normally be positioned in the circulation spaces between sleeping spaces and places where fires are most likely to start (e.g. kitchens and living rooms) to pick up smoke in the early stages.

                                1.11 There should be at least one smoke alarm on every storey of a flat.

                                1.12 Where the kitchen area is not separated from the stairway or circulation space by a door, there should be a compatible interlinked heat

                                1.13 Where more than one alarm is installed they should be linked so that the detection of smoke by one unit operates the alarm signal in all of them. The manufacturers’ instructions about the maximum number of units that can be linked should be observed.

                                1.14 Smoke alarms/detectors should be sited so that:

                                • a. there is a smoke alarm in the circulation space within 7.5m of the door to every habitable room;
                                • b. they are ceiling-mounted and at least 300mm from walls and light fittings (unless in the case of light fittings there is test evidence to prove that the proximity of the light fitting will not adversely affect the efficiency of the detector). Units designed for wall-mounting may also be used provided that the units are above the level of doorways opening into the space and they are fixed in accordance with manufacturers’ instructions; and
                                • c. the sensor in ceiling-mounted devices is between 25mm and 600mm below the ceiling (25-150mm in the case of heat detectors or heat alarms).
                                  Note: This guidance applies to ceilings that are predominantly flat and horizontal.

                                 

                                1.15. It should be possible to reach the smoke alarms to carry out routine maintenance, such as testing and cleaning, easily and safely. For this reason smoke alarms should not be fixed over a stair or any other opening between floors.

                                1.16. Smoke alarms should not be fixed next to or directly above heaters or air-conditioning outlets. They should not be fixed in bathrooms, showers, cooking areas or garages, or any other place where steam, condensation or fumes could give false alarms.

                                1.17. Smoke alarms should not be fitted in places that get very hot (such as a boiler room), or very cold (such as an unheated porch). They should not be fixed to surfaces which are normally much warmer or colder than the rest of the space, because the temperature difference might create air currents which move smoke away from the unit.

                                1.18. A requirement for maintenance can not be made as a condition of passing plans by the Building Control Body. However, the attention of developers and builders is drawn to the importance of providing the occupants with information on the use of the equipment and on its maintenance (or guidance on suitable maintenance contractors). See paragraph 0.13.

                                Notes:BS 5839-1 and BS 5839-6 recommend that occupiers should receive the manufacturers’ instructions concerning the operation and maintenance of the alarm system.

                                Power supplies

                                1.19 The power supply for a smoke alarm system should be derived from the flat’s mains electricity supply. The mains supply to the smoke alarm(s) should comprise a single independent circuit at the flat’s main distribution board (consumer unit) or a single regularly used local lighting circuit. This has the advantage that the circuit is unlikely to be disconnected for any prolonged period. There should be a means of Isolating power to the smoke alarms without isolating the lighting.

                                1.20 The electrical installation should comply with Approved Document P (Electrical safety).

                                1.21 Any cable suitable for domestic wiring may be used for the power supply and interconnection to smoke alarm systems. It does not need any particular fire survival properties. Any conductors used for interconnecting alarms (signalling) should be readily distinguishable from those supplying mains power, e.g. by colour coding.

                                Notes:Mains powered smoke alarms may be interconnected using radio-links, provided that this does not reduce the lifetime or duration of any standby power supply below 72 hours. In this case, the smoke alarms may be connected to separate power circuits (see paragraph 1.19)

                                1.22 Other effective options exist and are described in BS 5839: Parts 1 and 6. For example, the mains supply may be reduced to extra low voltage in a control unit incorporating a standby trickle-charged battery, before being distributed at that voltage to the alarms.

                                Design and installation of systems

                                1.23 It is essential that fire detection and fire alarm systems are properly designed, installed and maintained. Where a fire alarm system is installed, an installation and commissioning certificate should be provided. Third party certification schemes for fire protection products and related services are an effective means of providing the fullest possible assurances, offering a level of quality, reliability and safety.

                                Buildings other than flats

                                General

                                1.24To select the appropriate type of fire alarm/ detection system that should be installed into a particular building, the type of occupancy and means of escape strategy (e.g. simultaneous, phased or progressive horizontal evacuation) must be determined.

                                1.25For example, if occupants normally sleep on the premises e.g. residential accommodation, the threat posed by a fire is much greater than that in premises where the occupants are normally alert. Where the means of escape is based on simultaneous evacuation, operation of a manual call point or fire detector should give an almost instantaneous warning from all the fire alarm sounders. However, where the means of escape is based on phased evacuation, then a staged alarm system is appropriate. Such a system enables two or more stages of alarm to be given within a particular area, e.g. “alert” or “evacuate” signals.

                                Notes:the term fire detection system is used here to describe any type of automatic sensor network and associated control and indicating equipment. Sensors may be sensitive to smoke, heat, gaseous combustion products or radiation. Normally the control and indicating equipment operates a fire alarm system and it may perform other signalling or control functions as well. Automatic sprinkler systems can also be used to operate a fire alarm system.

                                1.26The factors which have to be considered when assessing what standard of fire alarm or automatic fire detection system is to be provided will vary widely from one set of premises to another. Therefore the appropriate standard will need to be considered on a case by case basis.

                                Notes:General guidance on the standard of automatic fire detection that may need to be provided within a building can be found in Table A1 of BS 5839-1:2002.

                                Fire alarm systems

                                1.27All buildings should have arrangements for detecting fire. In most buildings fires are detected by people, either through observation or smell and therefore often nothing more will be needed.

                                1.28In small buildings/premises the means of raising the alarm may be simple. For instance, where all occupants are near to each other a shouted warning “FIRE” by the person discovering the fire may be all that is needed. In assessing the situation, it must be determined that the warning can be heard and understood throughout the premises, including for example the toilet areas. In other circumstances, manually operated sounders (such as rotary gongs or handbells) may be used. Alternatively a simple manual call point combined with a bell, battery and charger may be suitable.

                                1.29In all other cases, the building should be provided with a suitable electrically operated fire warning system with manual call points sited adjacent to exit doors and sufficient sounders to be clearly audible throughout the building.

                                1.30An electrically operated fire alarm system should comply with BS 5839-1:2002 Fire detection and alarm systems for buildings, Code of practice for system design, installation commissioning and maintenance.

                                BS 5839-1 specifies three categories of system, i.e. category L for the protection of life; category M manual alarm systems; category P for property protection. Category L systems are sub-divided into:

                                • L1systems installed throughout the protected building;
                                • L2systems installed only in defined parts of the protected building (a category L2 system should normally include the coverage required of a category L3 system);
                                • L3systems designed to give a warning of fire at an early enough stage to enable all occupants, other than possibly those in the room of fire origin, to escape safely, before the escape routes are impassable owing to the presence of fire, smoke or toxic gases;
                                • L4systems installed within those parts of the escape routes comprising circulation areas and circulation spaces, such as corridors and stairways; and
                                • L5systems in which the protected area(s) and/or the location of detectors is designed to satisfy a specific fire safety objective (other than that of a category L1, L2, L3 or L4 system).

                                Type P systems are sub-divided into P1 – systems installed throughout the protected building and P2 – systems installed only in defined parts of the protected building.

                                1.31Call points for electrical alarm systems should comply with BS 5839-2:1983, or Type A of BS EN 54-11:2001 and these should be installed in accordance with BS 5839-1. Type B call points should only be used with the approval of the Building Control Body.

                                BS EN 54-11 covers two types of call points, Type A (direct operation) in which the change to the alarm condition is automatic (i.e. without the need for further manual action) when the frangible element is broken or displaced; and Type B (indirect operation) in which the change to the alarm condition requires a separate manual operation of the operating element by the user after the frangible element is broken or displaced.

                                1.32If it is considered that people might not respond quickly to a fire warning, or where people are unfamiliar with the fire warning arrangements, consideration may be given to installing a voice alarm system. Such a system could form part of a public address system and give both an audible signal and verbal instructions in the event of fire.

                                The fire warning signal should be distinct from other signals which may be in general use and be accompanied by clear verbal instructions. If a voice alarm system is to be installed, it should comply with BS 5839-8:1998 Code of practice for the design, installation and servicing of voice alarm systems.

                                1.33In certain premises, e.g. large shops and places of assembly, an initial general alarm may be undesirable because of the number of members of the public present. The need for fully trained staff to effect pre-planned procedures for safe evacuation will therefore be essential. Actuation of the fire alarm system will cause staff to be alerted, e.g. by discreet sounders, personal paging systems etc. Provision will normally be made for full evacuation of the premises by sounders or a message broadcast over the public address system. In all other respects, any staff alarm system should comply with BS 5839-1.

                                Warnings for people with impaired hearing

                                1.34A suitable method of warning (e.g. a visual and audible fire alarm signal) should be provided in buildings where it is anticipated that one or more persons with impaired hearing may be in relative isolation (e.g. hotel bedrooms and sanitary accomodation) and where there is no other suitable method of alerting them.

                                In buildings such as schools, colleges and offices where the population is controlled, a vibrating paging system may be more appropriate. This could also be used for alerting people with other disablilities.

                                Clause 18 of BS 5839-1:2002 provides detailed guidance on the design and selection of fire alarm warnings for people with impaired hearing.

                                Automatic fire detection and fire alarm systems

                                1.35Automatic fire detection and alarms in accordance with BS 5839-1 should be provided in Institutional and Other residential occupancies.

                                1.36 Automatic fire detection systems are not normally needed in non-residential occupancies. However, there are often circumstances where a fire detection system in accordance with BS 5839-1 may be needed. For example:

                                • ato compensate for some departure from the guidance elsewhere in this document;
                                • bas part of the operating system for some fire protection systems, such as pressure differential systems or automatic door releases;
                                • cwhere a fire could break out in an unoccupied part of the premises (e.g. a storage area or basement that is not visited on a regular basis, or a part of the building that has been temporarily vacated) and prejudice the means of escape from any occupied part(s) of the premises.

                                Notes:Guidance on the provision of automatic fire detection within a building which is designed for phased evacuation can be found in paragraph 4.29.
                                Where an atrium building is designed in accordance BS 5588-7:1997, then the relevant recommendations in that code for the installation of fire alarm/fire detection systems for the design option(s) selected should be followed.

                                Design and installation of systems

                                1.37It is essential that fire detection and fire warning systems are properly designed, installed and maintained. Where a fire alarm system is installed, an installation and commissioning certificate should be provided. Third party certification schemes for fire protection products and related services are an effective means of providing the fullest possible assurances, offering a level of quality, reliability and safety (see paragraph 0.15).

                                Interface between fire detection and fire alarm systems and other systems

                                1.38Fire detection and fire alarm systems are sometimes used to initiate the operation, or change of state, of other systems, such as smoke control systems, fire extinguishing systems, release arrangements for electrically held-open fire doors and electronically locked exit doors. It is essential that the interface between the fire detection and fire alarm system and any other system required for compliance with the Building Regulations is designed to achieve a high degree of reliability. Particular care should be taken if the interface is facilitated via another system, such as an access control system. Where any part of BS 7273 applies to actuation of other systems, the recommendations of that standard should be followed.