Grades of Fire Alarm Systems
Part B of the Building Regulations relating to Fire Safety states that a building shall be designed and constructed so that there are appropriate provisions for the early warning of fire.
All new dwellings should be provided with a fire detection and fire alarm system in accordance with the relevant recommendations of BS 5839-6:2004 to at least Grade D Category L3.
BS 5839: Pt.6:2004 is essential to providing adequate fire protection in all dwelling types.
The Grade System
This relates to system engineering, not level of protection.
BS 5839: Pt.6 grades fire detection systems from
Grade F up to Grade A.
The greater the fire risk and the more demanding the application and the more comprehensive the system needs to be.
Battery powered smoke alarms
These are the simplest form of fire detection and alarm system. They are low cost and relatively simple to install which makes them suitable for the DIY market.
Smoke alarms to BS 5446-1 and heat alarms to BS 5446-2 give
a low battery warning which is an essential feature to maintain continuous protection.
A disadvantage of a Grade F system is that removal of the battery disables the protection.
Interlinked mains powered smoke alarms without standby battery supply.
This system may incorporate one or more heat alarms, with or without standby supplies.
The system is potentially more reliable than a
Grade F system, because it requires less attention by the user.
A disadvantage of a Grade E system is that loss of mains results in loss of protection.
Interlinked mains powered smoke alarms with with integral standby battery supply to BS5446-1:2000 or BS 5466-2:2003.
This is the minimum grade of system required by Part B of the Building Regulations.
The system may incorporate one or more mains-powered heat alarms, each with an integral standby supply.
One or more batteries or capacitors are provided to ensure protection is available under loss of mains conditions.
Mains powered detectors may be interconnected by radio links.
Detectors and sounder with a central control system linked to a main control System.
The fire detectors are supplied from a common power supply unit with central control equipment and this type of system normally incorporates a secondary rechargeable battery.
Detectors and sounder in compliance with BS5839 Pt1, with the exception of the control panel.
Fire Detection and Alarm System installed to BS 5839: Pt.1
Levels of Protection – Categories of System
This was previously referred to as ‘type’ of system.
It relates to the level of protection afforded by the system.
LD3 – A system incorporating detectors in all circulation spaces that form part of the escape routes from the dwelling
LD2 – A system incorporating detectors in all circulation spaces that form part of the escape routes from the dwelling, and in all rooms or areas that present a high risk of fire
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
Alarm System Mains Power Supply Recommendations
The batteries of smoke alarms and heat alarms should be capable of supplying the normal load, including the additional load from routine weekly testing for at least one year before the battery fault warning is given.
At the point at which the battery fault warning commences, the batteries should have sufficient capacity to give a fire alarm warning signal for at least 4 minutes or, in the absence of a fire, a battery fault warning for at least 30 days.
The mains supply to smoke and heat alarms should be a single dedicated independent circuit from the dwelling’s main consumer unit.
Smoke and heat alarms should be interconnected and must be supplied from the same circuit.
The circuit supplying the smoke and heat alarms should preferably not be protected by an RCD unless one is required for reasons of electrical safety.
The RCD should serve only the circuit supplying the smoke or heat alarms or the RCD protecting the fire alarm system should operate independently of any RCD protecting circuits supplying socket-outlets or portable equipment.
The mains supply to smoke and heat alarms should either be a single independent circuit from the dwelling’s main consumer unit or a separately electrically protected regularly used local lighting circuit.
Grade A systems should be inspected and serviced and a certificate issued at periods not exceeding six months by a competent person as in accordance with the recommendations of BS 5839.
Grade B and C systems should be serviced by a competent person every six months in accordance with the supplier’s instructions.
Grade D, E and F systems should be cleaned periodically in accordance with manufacturer’s instructions.
Where experience shows that undue deposits of dirt and dust are likely to accumulate, then more regular cleaning should take place.
Further information on Fire Alarm Installation.