A fire detection and alarm system can significantly improve the safety of occupants in dwellings by operating automatically and alerting occupants, especially those asleep, to the outbreak of fire. For these reasons, requirements for the provision of systems to provide early warning of fire are incorporated into UK building regulations.
Fig 1 Example of a Grade D, LD2 installed in a typical two-storey dwelling.
Whilst the particular requirements may vary in different parts of the UK and will be dependent on a number of factors such as the nature of the occupants, and the size, construction and layout of the building. Where a fire detection and alarm system is installed in domestic premises it should be designed, installed and commissioned in accordance with BS 5839-6: 2013 Code of practice for the design installation, commissioning and maintenance of fire detection and fire alarm systems within domestic premises.
For the purpose of life protection, Table 1 of BS 5839-6 recommends that at least a Grade D system, Category LD2 standard is installed in all new or materially altered single-family dwellings of typical construction. (Typically, a dwelling three-story or less with no floor area greater than 200 m2.)
As shown in Fig 1, the fire system should be comprised of at least:
· One smoke alarm located in every circulation space (hallway/landing) on each storey,
· One alarm (smoke or carbon monoxide) in the principal habitable room, and
· One heat alarm in the kitchen.
Note: A principal habitable room is a room that is used frequently by the occupants of a dwelling for general daytime living purposes.
In accordance with clause 15.5 fire detectors (smoke alarms and heat detectors) should be permanently connected to a circuit; either an independent circuit as shown in Fig 1 or a regularly used local lighting circuit, and all detectors should be interconnected so that the operation of any one of them causes operation of the alarm signal in all of them.
Any cable suitable for domestic wiring may be used for the power supply and the interconnections. However, to avoid the possibility of confusion, interlinking conductors operating at extra-low voltage should be readily distinguishable from those, such as power supplies, operating at 230 V AC.
The type of detector chosen should take into account the risk of unwanted (false) alarms. Table 1 provides a brief summary of the main types of detector appropriate for dwellings, detailed guidance on detectors is contained in Section 10 of BS 5839-6.
A heat alarm is not designed to provide warning of the presence of smoke and so should not be used instead of a smoke alarm to prevent unwanted alarm. A multi-sensor fire detector combines the characteristics of different types of detector and as such can help to minimise the risk of false alarms.
Smoke alarms should be located in circulation spaces not more than:
· 3 m from every bedroom door, and
· In circulation spaces more than 7.5 m long, no point within the circulation space should be more than 7.5 m from the nearest smoke alarm.
All detectors should be installed in accordance with the manufacturer’s instructions. Ceiling mounted detectors should be sited at least 300 mm from any wall or light fittings, but not directly above heaters or air-conditioning vents. If ceiling mounting is impracticable, wall mounting may be possible but the bottom of the detection element must be above the level of any door opening.
All detectors should be positioned so that they are accessible for maintenance and testing purposes, and should not be sited above staircases or in any other location that may be difficult or unsafe to access.
The installation of a Grade D fire detection and fire alarm system forms part of the fixed electrical installation so the installation of the wiring and fixed equipment must be inspected tested and certificated in accordance with BS 7671. Where appropriate a minor works electrical installation certificate may be used.
In addition to the electrical certification, a certificate appropriate for the type of building and grade of fire alarm system should also be issued to confirm that the fire detection and alarm system has been designed, installed and commissioned in accordance with BS 5839-6. As shown in Fig 2, for such purposes, the NICEIC Certificate of Design, Installation and Commissioning of a Fire Detection and Alarm System of Grade B, C, D, E, or F in Domestic Premises may be used.
The updated NICEIC and ELECSA publication, snags and solutions Part 5: Domestic Fire Detection and Fire Alarm Systems to BS 5839 (3rd Edition), provides guidance on the design, installation, inspection, testing, commissioning and maintenance of fire alarm systems within domestic and similar premises.