STANDARDS AND REGULATIONS CONTINUE TO VARY STIPULATING JUST HOW MANY SMOKE AND HEAT ALARMS ARE NEEDED IN HOMES, AND WHERE BEST TO LOCATE THEM. AND NEW ELECTRICAL WIRING REGULATIONS PROVIDE RATIONALISATION OF SMOKE, HEAT AND CO ALARM SYSTEM DESIGN AND WIRING IN HOUSING.

The current Code of Practice for domestic fire alarm systems is BS 5839-6:2004, wellrecognised as the authoritative guide for both new and existing dwellings. Firstly, it considers ‘Grades’ - effectively the reliability of a system in terms of its power sources. For new - and many existing - dwellings Grade D is the minimum standard, comprising interlinked mains alarms with backup, a requirement matched in all the national building regulation guidelines applying to new-build. The Code of Practice then goes on to define ‘Categories’, effectively in which areas smoke and/or heat alarms are required. The Code of Practice recommends Category LD2 for new – and many existing - dwellings as a minimum.

CONFLICTING REQUIREMENTS
This means smoke or heat alarms in Living Rooms and a heat alarm in every Kitchen, as well as the usual smoke alarms in circulation areas. This approach has been embraced in both the Northern Ireland and Eire building regulations. But, in stark contrast, Scotland’s ‘Domestic Technical Handbook’ just calls for smoke alarms in circulation areas and there are no provisions for heat alarms in kitchens at all. This poor level of protection is considered completely unsuitable for new homes in the Code of Practice. The situation is not much better in England and Wales, where the current Building Regulations ‘Approved Document B’ effectively requires only smoke alarms in corridors with heat alarms in some kitchens only.

Whilst this conflict remains in place, the safe route is to simply implement the BS 5839- 6:2004 Code of Practice in both new and existing homes.

DECENT HOUSING
Other steps are also being taken to require hard-wired alarms with backup power in existing homes. For example, this is a requirement of the Housing (Scotland) Act 2006, while the Housing Health and Safety Rating System, which defines the ‘Decent Homes’ standard and applies to England and Wales, considers mains powered smoke alarms with backup to be the ‘ideal’.

This is particularly important for rented properties where landlords have a duty of care to their tenants and where battery failure or removal results in non-functioning alarms – sometimes with fatal consequences. So, hardwired smoke and heat alarms will become a more common feature of refurbishment and rewiring programmes

Applying to both new and existing housing, the latest IEE 17th Edition BS 7671:2008 Wiring Regulations stipulate that smoke, heat and CO alarms should be served by an independent circuit so that they are unaffected by, for example, “tripping-out” of lighting circuits – an increased possibility with the expanded 17th Edition requirements for RCD circuit breakers. This means that individual smoke and heat alarms can no longer be powered from lighting circuits – currently a common practice endorsed in both Building Regulations and BS 5839-6:2004. There is another good reason for this separate circuit requirement, as devices on the lighting circuit – such as LV lighting transformers, CFL lamps and dimmers – are often identified as causes of electromagnetic interference (EMI). Anyway, the requirement is easily and inexpensively met using “three core and earth” cable, where the third cable simply provides the interconnect signal to trigger all alarm sounders. This is set to become the normal method for connecting hardwired alarms, heralding a new system approach.

SILENT KILLER
We are also seeing a growing use of CO alarms in both new and existing homes. Again, landlords have a legal duty to protect their tenants against carbon monoxide poisoning and the same failure problems can be encountered with stand-alone battery alarms. The simple “three core and earth” approach can simply be extended to CO alarms as well, on the same circuit as smoke and heat alarms. Some manufacturers also offer special facilities enabling their CO alarms to interconnect with their smoke and heat alarms. It is important to have different, distinct alarm sounder patterns for carbon monoxide and fire – preferably supported by different digital display messages - as totally different actions are required with a CO event compared with fire.

More information is available via www.smoke-alarms.co.uk

Visit Building Specification.com for the latest Building News, Product Features and Articles