Fire detector recommendations

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BS 5839-6: Changes to the recommendations for fire detectors in the principal habitable rooms of domestic premises

A revised edition of BS 5839-6, the code of practice for fire alarm systems in domestic premises came into eff ect on 31 May 2013. This 2013 edition does not constitute a full revision of BS 5839-6; however, it does supersede BS 5839-6: 2004, which has been withdrawn.

At fi rst glance it is evident that the Standard has been renamed. Compared to BS 5839-6: 2004, the title of the 2013 edition includes the addition of the words ‘commissioning’ and ‘domestic premises’, where the later replaces the word dwelling.

The full title is now ‘Fire detection and fi re alarm systems for buildings – Part 6: Code of practice for the design, installation, commissioning and maintenance of fi re detection and fi re alarm systems in domestic premises’.

The Foreword of the 2013 Standard reveals that a number of the technical changes have been introduced, and one such technical change, the subject of this article, regards the type of detector recommended for installation in the principal habitable room of domestic premises.

Other technical changes will be discussed in future Connections articles.

Defi nition given in BS 5839-6

Principal habitable room – a room that is normally the most frequently used room for general daytime living purposes.

Scope of BS 5839-6: 2013

BS 5839-6: 2013 applies to new and existing buildings used as domestic premises that are: • designed to accommodate a single family, • houses in multiple occupation that comprise a number of self-contained units, each designed to accommodate a single-family, and • sheltered housing, including both the dwelling units and common areas.

Class of buildings considered as domestic premises by BS 5839-6 include, for example, bungalows, multi-storey houses, individual fl ats and maisonettes. It should be noted that for a building containing fl ats or maisonettes BS 5839-6 does not apply to the communal areas. For a full description of the class of domestic premises covered by BS 5839-6 see clause 1 (Scope).

Changes relating to the type of detector

For protection of life in new or materially altered buildings commonly used as domestic premises the information given in Table 1 of BS 5839-6: 2013 recommends that to provide the earliest practicable warning of fi re to occupants, fi re detection and fi re alarm systems should incorporate a smoke detector installed in every principal habitable room.

This is a change to the recommendations given in Table 1 of the 2004 edition of BS 5839-6 which recommended heat detectors should be installed in every principal habitable room.

It should be noted that Table 1 of the 2013 edition still recommends heat detectors should be installed in every kitchen of new or materially altered premises.

Detectors in principal habitable rooms

As previously mentioned Table 1 now recommends smoke detectors are installed in every principal habitable room. Smoke detectors employed in domestic premises are generally of two types: optical detectors (OD) and ionization detectors (ID). Either may be used in the principal habitable room. However: • Optical detectors are less likely than ionisation detectors to respond to fumes from cooking. Thus, ODs are more suitable in rooms or areas into which kitchen cooking fumes may discharge. • Ionisation detectors are less likely than optical detectors to respond to tobacco smoke. Thus, IDs are more suitable in rooms or areas where smoking is likely.

To limit false alarms, the response of ODs and IDs should not be overlooked when designing a fi re alarm system. Unwanted alarms can have a detrimental eff ect on a fi re alarm system, such as when the frequency of unwanted alarms results in occupants ignoring the fi re alarm system signal (clause 12 (Limitation of false alarms) refers).

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Fig 1 Smoke detectors rather than heat detectors

should be used in the principal habitable room

Where the designer identifi es that ODs and IDs mounted in the principal habitable room might produce an unacceptable rate of unwanted alarms a carbon monoxide fi re detector (CMFD) may alternatively be used in such rooms (clause 10.2(g) (Recommendations) refers).

Carbon monoxide fi re detectors generally do not respond to dust, steam and cigarette smoke and, therefore, limit the production of alarm signals (compared to smoke detectors).

Carbon monoxide fi re detectors are not recommended as the sole means of fi re detection in domestic premises. Their response to fi re is generally not suffi cient to give an audible warning signal which provides adequate time for occupants to escape safely in the event of fi re. However, where appropriate, a CMFD may be incorporated within systems.

Where the designer selects to use carbon monoxide fi re detectors in the principal habitable room or other recommended areas within the premises the detector should incorporate a warning device to indicate expiry of the electrochemical cell is approaching. Such a warning device is not necessary where a CMFD is incorporated within a Grade A, B and C system that is subject to periodic maintenance not exceeding 12 months (clause 10.2(e) (Recommendations) refers).

Carbon monoxide fi re detectors should not be confused with carbon monoxide warning detectors (CMWD). The function of a CMWD is to detect levels of carbon monoxide in the air from incomplete combustion within a fuel burning appliance.

The NICEIC and ELECSA publishing team

Sue Heybourne, technical illustrator Sue joined NICEIC in 2000 and previously worked for The Electrical Safety Council before moving to Certsure in 2013. She is responsible for producing and archiving all the illustrations for publications, articles and presentations, pocket guides and books. She also helps design all certifi cates.

Derek Cooney, technical author Derek is a time-served electrician who spent many years electrical contracting on domestic, commercial and industrial installations, before becoming a college lecturer. He joined NICEIC as a technical operations engineer in 2009.

Chris Long, technical engineer Chris is a gas professional responsible for providing a technical overview of all gas-related articles and publications. He lives in Hampshire with his family and outside of work is a motorbike nut.

John Clark, senior engineer John started out by serving a fi ve-year apprenticeship before spending some time installing plant in power stations. He then took a degree in electrical and electronic engineering before becoming a lecturer. He now works as senior engineer helping to develop the learning guides.

Tim Benstead, principal technical author Tim started his career as an apprentice electrician and worked in both contracting and maintenance prior to spending some 16 years as a lecturer. He began working for the Electrical Safety Council in 2006 as a senior engineer and was part of the team responsible for the production of The Essential Guide, NICEIC publications and certifi cates.

Mike Burling, senior engineer A former JIB technician, Mike had his own NICEIC-registered electrical contracting business, before taking on a role as a college tutor and NVQ assessor. He now works as a senior engineer responsible for overseeing the technical content of all technical publications and articles.