Fire Alarm Systems Explained: BS 5839 Part 6 – 2013

BS 5839-6 is the key standard for fire detection in domestic premises. It is written to assist the non-specialist in compliance and will help make installations easier to audit. The standard is used by enforcing authorities and contractors, and applies to domestic premises accommodating single families, houses in multiple occupation (HMOs) and sheltered housing (housing and common areas). It applies both to new and existing housing.
BS 5839-6 is not intended for householders themselves, but to provide guidance and recommendations for architects and other building professionals, enforcing authorities, contractors and others responsible for implementing fire precautions in buildings. Householders should refer to the government guidelines.

It is also pointed out that compliance with a British Standard cannot automatically confer legal immunity. However, for a landlord or installer, compliance with the latest Code is obviously the best line of defence in any claim made against them.


The Scope of BS 5839-6
This Code of Practice covers fire alarm systems starting from a simple self-contained battery smoke alarm right through to major systems with central panel(s) in accordance to BS 5839-pt1.

It covers the following domestic building types:
Multi-storey houses
Individual flats
Individual maisonettes
Mobile homes
Individual sheltered accommodation as well as their common parts
Houses in multiple occupation (HMOs)
Certain NHS housing in the community
Shared houses
Houses divided into several self-contained single-family dwelling units

Not included are hostels, caravans, boats (other than permanently moored) and communal parts of blocks or flats or maisonettes.

BS 5839-6 is primarily concerned with saving lives and reducing injuries. However, it does contain within it recommendations for helping to reduce property damage too. Good fire safety practice and adherence to the Code can give the best possible early warning of fire and so reduce the financial impact as well as human suffering.


The Grade System
Relates to system engineering, not level of protection.

BS 5839-6 grades fire detection systems from Grade F up to Grade A. Generally speaking, the greater the fire risk and the more demanding the application, the more comprehensive the system needs to be.

Grade F – System of one or more battery powered smoke alarms (and heat alarms if required)

Grade E – System of interlinked mains powered smoke alarms (and heat alarms if required) with NO stand-by supply. The interlink can be hardwired or radio-interlinked.

Grade D – System incorporating one or more interlinked mains powered smoke alarms (and heat alarms if required), each with an integral stand-by supply. The interlink can be hardwired or radio-interlinked.

Grade C – System consisting of fire detectors and alarm sounders (which may be smoke alarms) connected to a common power supply, comprising normal mains and stand-by supply, with central control equipment

Grade B – Fire detection and alarm system comprising fire detectors (other than smoke alarms), fire alarm sounders and control and indicating equipment to either BS EN 54-2 (and power supply to BS EN 54-4), or to BS 5839-6

Grade A – Fire detection system incorporating control and indicating equipment to BS EN 54-2, and power supply to BS EN 54-4, installed to BS 5839-1 with some very minor exceptions

As the overwhelming number of residential applications in the UK will fall into the D to F categories, this is the area on which this guide will naturally focus. If you are particularly interested in unusual grades of protection, you are invited to look further at the relevant clauses of the Code.

Of course, installers may install a system with greater safety features than laid down in the letter of the Code. For example, rather than a Grade E system landlords might consider it prudent to install a Grade D system instead. This is especially true considering the many restrictions that apply to the use of Grade E systems.


Battery Powered Smoke Alarms – Grade F

BS 5839-6 acknowledges the advantages of the single, battery powered smoke alarm. They are simple to install and offer protection at very low cost. Battery powered smoke alarms conforming to BS EN 14604:2005 are recommended. Battery powered smoke alarms are typically suitable for owner-occupied buildings (existing buildings) with up to two storeys. Please note: if your property has multiple levels, it is recommended to have interlinked alarms. This is to ensure you receive the earliest possible warning of fire.
Single story tenanted properties were allowed in the last version (2004) of this standard to be fitted with Grade F alarms. This has now been changed to a grade D requirement. As an aside, landlords have now been found liable in cases where tenants themselves have disabled an alarm. For this

reason, it is unlikely that landlords will be able to trust tenants to adequately look after a smoke alarm. The Code highlights the fact that battery powered smoke alarms are also only suitable for owner-occupied properties if the likelihood is, that batteries will be replaced within five days of a low battery signal.

Mains Powered Smoke Alarms without Back-up Battery – Grade E

The Code does not recommend an application for alarms without back-up power source any longer. Grade E systems have serious drawbacks: power cuts or the termination of supply for whatever reason disables them totally. They can also be rendered useless by the tripping of a protective device, or even – in some cases – by the fire itself. Householders may also disable them at the mains all too easily if false alarms are a problem. Cannon Fire & Security is therefore only offering mains powered smoke alarms WITH back-up battery.

Mains Powered Smoke Alarms with Back-up Battery – Grade D

The problems outlined above can be overcome by using mains powered alarms that incorporate, within each alarm, a stand-by supply such as a primary or rechargeable battery. The alarms have to be interconnected either through wiring or radio-interlink. The mains power supply can come from a dedicated power supply directly from the fuse box or from the nearest permanently powered light fitting, as long as the smoke alarm heads can be removed without removing the base as well.

Grade D is required for new, owner-occupied buildings of up to three storeys, two storey rented properties and existing, owner-occupied buildings of more than two storeys. Very large storeys (>200m2) might require Grade B alarm system.

A question remains for landlords – can they be sure that their tenants are paying their electricity bills? Given that many tenants may have low incomes (in many local authorities, 70% or more of all tenants are on subsidised incomes), they may well experience periods of disconnection – and yet the landlord could well be liable if the alarm fails to sound because the tenant has not paid his or her bills! Unfair or not, as the law stands, it obviously makes good commercial sense to ensure that a reliable, ideally re-chargeable and sealed-in backup battery is in place.

The minimum back-up duration recommended is 72 hours, and the Code acknowledges that there could well be circumstances where a longer stand-by period is justified e.g. tenants’ inability to pay their electricity bill.

Fire Detectors supplied with Power from a common Power Supply Unit – Grade A, B, C

More expensive high specification systems can offer connection of all fire detection devices to a common power supply via low voltage transformers, or interlinked fire and security systems. Again, a minimum 72 hour back-up is recommended by the Code. Due to the complexity of A, B and C Grades, we have omitted the descriptions from this short guide.


Levels of Protection – Categories of System
This relates to the level of protection afforded by the system.

Within the A – F grades defined earlier, the standard identifies three different categories of protection:
LD1 – A system installed throughout the dwelling, incorporating detectors in all circulation spaces that form part of the escape routes from the dwelling, and in all rooms and areas in which fire might start, other than toilets, bathrooms and shower rooms
LD2 – A system incorporating detectors in all circulation spaces that form part of the escape routes from the premises, and in all rooms or areas that present a high risk of fire to occupants
LD3 – A system incorporating detectors in all circulation spaces that form part of the escape routes from the premises
It is noted that an LD3 type system is intended to protect escape routes for those not directly involved in the fire and may not save the life of anyone in the immediate vicinity of the fire.

Only by quoting Grade and Category can a meaningful and effective alarm system be specified, e.g. Grade D, Category LD2.


History of BS 5839-6

When first introduced in 1995, the BS 5839-6 Code of Practice became the most important set of recommendations ever made on fire safety in the home.

It had an immediate impact on architects, system designers, installers and landlords in the private or public sector, all of whom were required to familiarise themselves with these important recommendations. Landlords in particular needed to abide by these recommendations, as legal liability with regard to ‘duty of care’ would undoubtedly become a serious issue should a fire occur in an inadequately protected property.

In short, BS 5839-6 became the essential guide to providing adequate fire protection in all dwelling types.

In September 2004, the Code of Practice was extensively revised and updated by the publication of BS 5839-6: 2004 which superseded BS 5839-6: 1995, which is now withdrawn. The changes therein are important and need to be fully understood and appreciated by all those with responsibility for fire safety in domestic dwellings.

An updated standard came out in 2013 and included for the first time common areas in sheltered housing. Carbon monoxide detectors were also permitted as fire alarm sensors and the requirement for rented accommodations were tightened.


Information in this guide is given in good faith, but Cannon Fire and Security cannot be held responsible for any omissions or errors. The company reserves the right to change specifications of products at any time and without prior notice
For more information please visit, call 0117 974 8999 or email

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