Designing, Installing and Maintaining a Fire Detection and Protection System

Design planning

Design planning is very important. Many parties are likely to have an interest in the design of a fire alarm system including:

• the fire risk assessor or the individual responsible for the building’s fire strategy
• the system installer/contractor
• the local Fire and Rescue Service (fire officer)
• consulting engineers or building services engineers
• architects
• the Health and Safety Executive
• the local authority building control officer
• the building insurer

In design planning a fire alarm system you will need to consider:

• the purpose of the fire alarm system such as life or property protection
• typical attendance time for the Fire and Rescue Service
• occupant escape times
• other actions to be taken in the event of a fire such as salvaging contents
• other building occupants (particularly for multiple occupancy)
• service and maintenance requirements for the system such as replacement batteries for wireless components
• system operation requirements such as a delay before the sounders activate or a ‘double-knock’ activation system

The brief

When considering a new fire alarm project, a good starting point is to establish exactly what type of system you need after carrying out your risk assessment.

Any brief should cover:

• the type of system, whether wired, wireless, manual, property or life protection
• the detector types to be used and where
• additional equipment or services to be linked to the system
• any associated emergency lighting to highlight the escape routes as agreed with the Fire and Rescue Service
• the emergency response plan and where it is kept
• maintenance and testing regimes required
• any other requirements of the monitoring service provider and fire alarm call centre

Standards, regulations and guidance

British Standard BS 5839 Fire detection and fire alarm systems for buildings

The BS 5839 sets out recommendations for the planning, design, installation, commissioning and maintenance of fire detection and fire alarm systems for both non-domestic and domestic properties. The standard is for building professionals, installers and others responsible for implementing fire precautions in domestic premises.

BS 5839 defines the eight fire alarm system categories:

• Category M Manual fire alarm system
• Category L1 Maximum life protection automated fire alarm system
• Category L2 Additional life protection automated fire alarm system
• Category L3 Standard life protection automated fire alarm system
• Category L4 Modest life protection automated fire alarm system
• Category L5 Localised life protection automated fire alarm system
• Category P1 Maximum property protection automated fire alarm system
• Category P2 Minimum property protection automated fire alarm system

The type you need will depend upon the use of the building, the contents of the building and the level of risk.

Historic England recommends that a L1/P1 category system be installed wherever possible so that both the building and its occupants have the highest level of protection possible as fire is probably the most devastating hazard that a historic structure can face.

The Regulatory Reform (Fire Safety) Order 2005

These are the statutory regulations covering fire alarms. They set out the minimum fire safety standards in all non-domestic premises.

Building Regulations Approved Document B: Fire safety - Volume 1 Dwellings; Volume 2 Buildings other than dwellings.

Approved Document B is the statutory guidance on fire safety matters within and around buildings including the minimum grade and category of alarm system for different types of property.

Fire safety

Under the Regulatory Reform (Fire Safety) Order 2005 the 'responsible person' must carry out, and keep up to date, a risk assessment and implement appropriate measures to minimise the risk to life and property from fire. The Health & Safety Executive provide advice on general fire safety.

Fire alarm components, and choosing the appropriate detection device

It is vital that the most appropriate detection device is used for the space and that the volume of the room, its uses and evacuation distances are all considered before a final choice is made.

• Main and repeater panels: These are located at the main building access points to provide information for both the building occupants and for the Fire and Rescue Service.

• Optical smoke detectors: These are for general use in living areas, circulation areas, bedrooms, hallways and staircases where no cooking takes place.

• Ionisation smoke detectors: These will soon be phased out because of the radioactive element used in its manufacture and operation. It has similar limitations to the optical version.

• Heat detectors: These detectors are either fixed temperature or rate of rise. The former is suitable for boiler rooms and kitchens, the latter for where high heat output fires are expected such as enclosed carparks.

• Sounders: The sounder is the modern equivalent of the fire bell giving an audible warning. Sounders should be located so that the warning can be heard throughout the building, especially in areas where there is a lot of background noise.

• Xenon beacons: Xenon beacons should be used where there are, or could be, audibility issues.

• Beam detectors: A beam detector is a variation of the optical smoke detector. Beam detectors are suitable for large and unrestricted areas where point detectors are not viable.

• Aspiration smoke detection systems: This is a sophisticated and sensitive air sampling system ideally suited to large volume buildings such as cathedrals.

• Carbon monoxide (CO) detector: Toxic, colourless carbon monoxide gas is produced with the incomplete burning of fuels such as gas, oil, wood and coal used in heating appliances, car engines and produced by fires. There are two main types of detector, metal oxide and electrochemical. They sound an alarm when carbon monoxide is detected.

• Signal booster aerials: If the building structure blocks or weakens the signal strength of a wireless fire alarm system, booster aerials may be necessary ensure the system operates correctly.

• Solenoid valves: These are simple electromagnetic devices that are used to automatically shut off gas and oil supplies to equipment such as standby electrical generators and heating boilers when an alarm is detected. This prevents a dangerous build-up of gas and fumes.

• Magnetic door contacts: These keep circulation doors open via an electro-magnet contact until an alarm is activated. The fire alarm system will then cut off the power to the magnet so the doors close helping to prevent the spread of both the fire and the associated smoke and fumes. The door magnets can be overridden by a push button that should be provided adjacent to the door set. It should be noted that on some historic doors it will not be possible to fit these and specialist advice should be sought before working an any historic door or its furniture. Our joint publication with the Institution of Fire Engineers Guide to the Fire Resistance of Historic Timber Panel Doors provides further advice.

Extinguishing systems such as water mist and gas suppression

Fire alarm systems can include extinguishing systems such as water mist and gas suppression for large areas like roof spaces or specialist rooms such as libraries that require additional protection.

Water mist systems cool the fire down and stop the chemical reaction leading to combustion. They are normally activated via a temperature sensitive glass bulb in the nozzle head. Water mist systems use very little water compared to a sprinkler system. The major problem with the system compared to heat/smoke detection heads is that it involves the use of pipework. This will require a designed route through the space which in turn might entail loss of historic fabric. There will be situations where the extent of loss of fabric makes using such a system unviable.

Gas suppression systems are often used in situations where water cannot be used either for safety reasons, such as in an electrical switch room, or in a library housing historic books and manuscripts.

Gas suppression systems extinguish fires by removing the oxygen content to below 15% where most materials do not burn. They are activated by a smoke detector system. Various gases are used in these systems including:

• Novec 1230 (clean agent)
• Inergen (Inert gas IG541), a blend of nitrogen, argon and carbon dioxide (CO₂)
• Argonite (inert gas IG55), a blend of argon and nitrogen

Where a space is normally unoccupied but contains vulnerable materials such as a library or archive, there are nitrogen systems on the market that are designed to prevent fires by feeding a controlled supply of the gas into the protected area to keep the oxygen concentration levels consistently below the ignition threshold of the combustible materials inside.

Cabling and power supplies

There are certain types of cables that are specifically designed for fire alarms. They do not have to be red but the same colour should be used throughout the installation. All cabling should have low smoke and fume (LSF) outer sheath. This sheath can be colour matched to the building surface to help with disguising the cable’s presence. You should use the building’s detailing and structure to camouflage the wiring route wherever possible.

The type of cable should also ensure that staining cannot occur from the use of bare metal types such as mineral insulated copper cable (MICC).

The most commonly used types of cabling are:

• Mineral insulated copper cable with sheath (MICV): This dresses very tightly around building features and so is very easy to disguise but it requires training to be able to terminate and can be heavy and awkward to work with.

• FP200 Gold: This is a 'standard' fire resistant cable as defined by British Standards and the original alternative to mineral insulated cable. It is a tough, durable and dressable fire resistant cable which is easy to install and terminate.

Cabling should not be installed in PVC trunking or left unclipped. However, all clips and fixings must be carefully located to avoid permanent damage to, or loss of, historic fabric. It is best to agree the cabling route before any work starts on site.

The power supply for a fire alarm panel, and any repeater panels, should be via an unswitched, suitably fused connection unit (FCU) possibly with a neon ‘healthy supply’ indicator. It is also advisable to have the FCU labelled as to its function and that it should not be isolated.

The fire alarm panel should also have its own separate supply from a dedicated miniature circuit breaker (MCB) which in turn ought to be red in colour and if possible lockable to ensure the mains supply cannot be accidently switched off.

Fire stopping

As well as ensuring that all ‘back of house’ areas like plantrooms and service risers are provided with automatic fire detection, it is crucial that appropriate fire stopping is installed between levels and fire compartments. This will stop any voids or risers providing a route for the fire, or like a chimney draw the fire into other areas. Separate fire zones will also require fire resistant compartmentalisation.

Fire stopping measures include:

• fire resistant doors and furniture
• fire shutters and curtains
• fire compartment walls and floors
• fire stopping seals to services such as drainage, pipes and cables
• cavity barriers to fill concealed internal gaps within walls, ceilings and other parts of a building
• automatic smoke dampers in ventilation ductwork where it passes through a fire-resistant wall to resist the passage of smoke, toxic gases and air

Materials used for fire stopping purposes include:

• cement mortar
• gypsum-based plaster
• cement or gypsum-based vermiculite mixes
• intumescent mastics

Testing and maintenance

The time between inspections by your chosen fire alarm company can vary depending upon the level of risk. However, they should be carried out every 6-12 months and always by a suitably trained contractor. The inspection should include checks and testing of:

• the fire alarm panel visual display
• all heat/smoke detectors to prove they are connected, can detect heat/smoke and produce a fire alarm signal
• beam detectors, and their lenses should be cleaned
• analogue levels of each detector and appropriate action taken
• cable fixings
• wireless signal strengths
• wireless system batteries and replaced as necessary
• standby power supplies
• any other checks recommended by the manufacturer carried out

Any outstanding defects should be reported to the building owner/occupier. The system logbook must be completed, and a service certificate issued.

Weekly tests must be carried out too. These are not maintenance checks, and you may need several people trained and assigned to do the tests. Always remember to put the system into test mode if you have an alarm monitoring system.

These weekly tests include:

• a rotational test of individual break glass units and check that the fire alarm system panel registers the correct fire zone for the activate unit
• recording the test results and actions in the fire alarm logbook along with the date and time, and keep the logbook in a fire-proof box or other container
• reporting any problems immediately to your fire alarm maintenance contractor

It is best to conduct these during normal operating/work hours to ensure that staff are familiar with the alarm tone and that the panel and sounders are operating correctly. However, do not mix your weekly fire alarm tests with fire drills for staff.

Planning permissions and other consents

Fire alarm schemes for listed and scheduled buildings are likely to require planning permission and heritage consents. You should involve the local planning authority and stakeholders early on in developing the fire alarm design.

Learn more

Watch the video of our webinar ‘Fire Alarm Systems in Historic Buildings: Installation and Design’.