Domestic Fire Alarms FAQ
This FAQ is designed to aid you in making the best choice in selecting a fire alarm, whether it is a new
or an exsisting bilding
What are the fire alarm requirements of New - Build Properties?
BS 5839: Pt.6: 2004 recommends that a new-build property consisting
of no more than 3 floors (less than 200sqm per floor)) should be
fitted with a Grade D, LD2 system
Building Regulations in England,Wales & Scotland recommend that
BS 5839: Pt.6 should be followed, but as a minimum a
Grade D, LD3 system should be installed.
Building Regulations in Northern Ireland require a Grade D, LD2
system to be installed, with smoke alarms fitted in the escape routes
and the main living room and a heat alarm in the kitchen.
What are various Grade systems?
The BS 5839: Pt.6 standard places different alarm types into Grades,
simply described as follows:
- Grade A – a system of detectors and sounders with control and
indicating equipment (a panel & perhaps call points)
- Grade B – a similar system to Grade A with some minor
amendments.
- Grade C – detectors and sounders, or smoke alarms, with some
control features.
- Grade D – mains smoke & heat alarms with a battery
back-up supply.
- Grade E – mains only smoke & heat alarms
- Grade F – battery only smoke & heat alarms
For Domestic fire alarm system the minimum grade is D and therefore all new-builds will require
smoke and heat alarms with a battery back up whether its a alkaline or lithium
What Does LD2 Require?
LD2 refers to the level of coverage supplied by the system to be
installed. Simply put, the number of alarms to fit in the property. LD2 is one of 3 categories outlined by
BS5839: Part 6. The categories are listed below
LD1 – alarms fitted in all rooms or areas where a fire may start.
LD2 – alarms fitted in escape routes and high fire risk areas e.g hall,
landing/s plus kitchen and main living room.
LD3 – alarms fitted in escape routes only e.g hallway and landing/s.
For a domestic system in England, Wales and Scotland as a minimum need to have alarms fitted in escape routes
(LD3), however it is recommended to install them in high fire risk areas(LD2).
What are the requirements for exsisting properties?
Building Regulations do not cover existing properties (unless material
alterations are taking place e.g an extension). In this type of property
BS 5839: Pt.6 should be followed. The minimum requirement for a 2
storey rented property would be Grade D, LD3, but the standard does
recommend that a Fire Risk Assessment should be conducted to
correctly determine what system should be installed.
What type of sensors are available and what are differences?
Smoke alarms either contain an Ionisation or an Optical sensor. Each type of alarm senses fire in a
different and are better suited for different situations.
Ionisation Alarms
Ionisation Smoke Alarms contain a small sealed ionising source which causes a small electrical current to
flow through the air in the smoke chamber. Smoke particles entering the chamber reduce the current,
this is sensed by the electronics and when a pre-set threshold level is reached the alarm will sound.
These alarms are best suited for detecting fast flaming fires and are better suited in rooms where there is a
high risk of fire (except the kitchen). Ionisation alarms are more prone to false alarms due to their
sensitivity and therefore ideal locations for these alarms are living room and bedrooms.
Optical Alarms
Optical Smoke Alarms send a pulsed beam of infra red light through the smoke chamber periodically. If
visible smoke is present, it scatters the light on to the photodiode light receiver and this is detected by
the electronics causing the alarm to sound. These alarms are better on escape routes and designed to detect smouldering fires. This type of detector is
less prone to false alarms.
Heat Alarms
A Range of heat alarms are also available to incorporate in to fire alarm system. As the name implies heat alarms
only detect heat and not smoke. There are two types of heat alarm fixed and rate of rise. A Fixed heat alarm
detects when the temprature reaches a ceratin level and then sounds off, but a rate of rise alarm detects a
rapid rise in heat between 2 tempratures i.e. 58 degrees to 69 degrees. Heat alarms are the ideal solution
for kitchen as they are not set often by cooking fumes unlike smoke detectors.
Below is rough guide to what detectors are best suited for each room
What are the ideal locations for Fire Alarms
They should be sited on the ceiling, close enough to a potential
source of fire so they can respond quickly.
The Building Regulations requires that the installation of self-contained mains powered with
battery back-up Smoke Alarms in all new and refurbished dwellinghouses should, at least, meet the following
requirements:
Within 7.5m of any door to a room where a fire is likely to start.
On each storey of a multi-storey dwelling.
All Smoke and Heat Alarms in the dwelling should be interconnected.
BS 5839: Pt6 broadly supports these recommendations for alarm
systems in existing dwellings, adding that alarms should be sited no
more than 3m from bedroom doors so that they can be more easily
heard if a fire should occur during the night.
How many Detectors will I need?
The amount of detectors required depends on the size of the property, and how many areas are considered
to be a high risk of fire. The minimum recomendation is that an alarm is fitted in the hallway and the landings
of any subsequent floors. For the best protection and for the earlist warnings of fires within the property, it
is recommended that every habital room be covered with a smoke alarm and a heat alarm in the kitchen.
I currently have an exsisting alarm I want to replace can I take down the old one and put up the new one?
Depending on the model, Yes! The majority of detectors should fit on existing bases within your property provided they are the same brand and with in the same category model. Below is a list of detectors that have been superseded and the detectors that fit on the existing bases:
BRK 2002RACEN and the 86RACE - Replaced with 86RACEN
BRK 2002RACHE10N - Replaced with 86RACHE10N
Dicon 650, 670, 680MBL - Replaced with 650,670, 680MRL
Dicon 650, 670, 680MB - Replaced with 650, 670, 680MBX
Dicon 350, 370, 380MBX - Replaced with 650, 670 , 680MBX
To view our range of Domestic Fire Alarms visit our Domestic Fire Alarm Section
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