The Guide To Fire Alarm Systems Design BS5839 PART 1: 2002

The Regulatory Reform (Fire Safety) Order (RRO) became law on 1st October 2006. Legally you must comply!

What is RRO?
Fire authorities no longer issue fire certificates and those previously in force will no longer have legal status. The Regulatory Reform (Fire Safety) Order (RRO) replaces most fire safety legislation with one new order. It means that any person who has some level of control in premises must take steps to reduce risk from fire, consider how to contain a fire should one break out and then also make sure people can safely escape if there is a fire.

• All fire alarm designs should be based on a fire risk assesment
• All fire risk assesments should be carried out by a competent person
• Fire risk assesments must be reviewed annually

What constitutes a fire risk assesment?
• Identifying fire hazards such as sources of ignition, fuel or oxygen
• Identifying all people at risk in and around the premises
• Evaluating the risk of a fire starting or the risk to people from a fire
• Removing or reducing fire hazards or risks to people from a fire
• Protecting people by providing fire precautions
• Recording any major findings
• Preparing an emergency plan
• Informing and instructing any relevant people
• Providing training for staff and guests
• Reviewing the fire risk assesment regularly and make changes where necessary
• Keeping accurate fire

Where does the order apply?
Virtually all premises and nearly every type of building, structure and open space. If you would like to find out more about the services that Eurotech can provide, please contact us on: T +44 (0) 203 141 0999

This guide is intended to be an aid to designers and installers of fire detection systems. It is not to be used as a substitute for BS5839 which should be read in full. In order to help identify the relevant sections each diagram includes a reference to BS5839 Part 1.


BS5839 Section 5


Fire alarm and detection systems are categorised in the following way:

Property protection fire systems

  • P1 AFD installed throughout all areas
  • P2 AFD installed only in defined areas
  • Life protection fire systems
  • L AFD designed to primarily protect human life
  • L1 AFD installed throughout all areas
  • L2 AFD installed only in defined areas in addition to L3
  • L3 AFD installed in escape routes and rooms opening onto these routes
  • L4 AFD installed in escape routes comprising circulation areas and spaces such as corridors and stairways
  • L5 A non-perspective system in which protected area(s) and/or the location of detectors is designed to satisfy a specific fire risk objective (other than
  • that of L1 to L4)
  • M System design to be operated manually (no AFD)

AFD Automatic Fire Detection

BS5839 Section 13.2.3



A person searching a zone for a fire in a non-addressable fire system should not have to travel for more than 60m to identify the source of a fire.

BS5839 Section 22.3

 A person searching a zone for a fire in a non-addressable fire system should not have to travel for more than 60m to identify the source of a fire.

BS5839 Section 22.3

 The sensing element of a heat detection thermistor device should not be less than 25mm below ceiling, and not greater than 150mm below ceiling.

BS5839 Section 35.2.3

 The minimum static response to heat devices should not be less than 29°C above the average ambient temperature, or less than 4°C above the highest temperature the device can expect to experience.

BS5839 Section 22.3

 When mounted on a ceiling, smoke detection devices have an individual coverage of 7.5m radius. However these radii must overlap to ensure that there are no ‘blind spots’. therefore individual coverage can be represented by a square measuring 10.6×10.6m giving an actual area coverage of 112m2 per device.

BS5839 Section 22.3

 When mounted on a ceiling, smoke detection devices have an individual coverage of 5.3m radius. However these radii must overlap to ensure that there are no ‘blind spots’. therefore individual coverage can be represented by a square measuring 7.5×7.5m giving an actual area coverage of 56.3m2 per device.

BS5839 Section 22.3

 For ceilings that feature an apex: as long as the height of the apex from the rest of the ceiling is less than 150mm for heat detectors or less than 600mm for smoke detectors, then these can be treated the same as flat ceilings. For higher apexes, a device should be installed to the highest point. The distance to adjacent devices can be increased by 1% per degree of angle of roof up to a maximum of 25%.

BS5839 Section 22.3

 Do not put detectors less than 1m from air inlets or air circulating units.

BS5839 Section 22.3

 Devices should not be mounted within 500mm of any obstruction. If the top of a solid partition is less than 300mm from the ceiling then treat it as a wall. Similarly, ceiling obstructions such as beams should be treated as walls if deeper than 10% of the ceiling height.

BS5839 Section 22.3


In corridors less than 2m wide the horizontal spacing of detectors may be increased, the areas of coverage need not overlap as in the case of a room. Any corridor over 2m wide is deemed a room and device spacing should follow the standard for rooms (see page 6).

Please note, heat detectors are not recommended for use in corridors that are escape routes.

BS5839 Section 22.3

 Never mount devices closer than twice the depth of light fittings or other obstructions on the ceiling.

BS5839 Section 22.2

 Voids less than 800mm in height need to have independent coverage, unless fire or smoke is able to spread from one area to another through the void or risk assessment shows AFD (Automatic Fire Detection) to be necessary.

BS5839 Section 22.2

 Vertical shafts like lifts and stairways should have a device mounted within 1.5m of any opening.

BS5839 Section 22.2

 Enclosed stairways should have a detector at the top of the stairway and on each main landing.

BS5839 Section 20.2

 A person should not have to travel more than 45m along an escape route to reach a manual call point (25m if disabled person to operate, or rapid fire development is likely). Manual call points should be sited at all stairwells and exits from the building.

BS5839 Section 20.2

 The centre of the frangible element of the manual call point should be positioned 1.4m (+/-200mm) from floor level (unless a wheelchair user is likely to be the first person to raise the alarm).

BS5839 Section 16.2.1

 The minimum sound level should be 65dB(A) or 5dB(A) above a background noise which is louder than 60dB(A) (if lasting more than 30 seconds) and at a frequency of between 500Hz and 1000 Hz. The maximum sound level should not be greater than 120dB(A) at any normal accessible point. May be reduced to 60dB(A) in stairways, enclosures up to 60m2 and specific points of limited extent.

BS5839 Section 16.2.1

 Sounder device cabling should be arranged so that in the event of a fault at least one sounder will remain operational during a fire condition.

BS5839 Section 16.2.1

 For areas where people are sleeping, sounder devices should produce a minimum 75dB(A) at the bed-head with all doors shut. in buildings providing sleeping accommodation for a significant number of people, all bedrooms should have both audible and visual alarms.

BS5839 Section 16.2.1

 Decibel loss occurs through doors: approximately – 20dB(A) through a normal door and approximately -30dB(A) through a fire door. Unless a sounder is installed in a bedroom, it is unlikely that 75dB(A) will be achieved.

BS5839 Section 17

 Visual alarms such as beacons should always be mounted at a minimum height of 2.1m from floor level.

BS5839 Section 26.2

 Unless MICC cable is used, all cabling should be mechanically protected from floor level up to a height of 2m.

BS5839 Section 26

 Fire resistant cabling is now required within the whole fire alarm system including the mains supply cables. The use of non-fire resisting cables whether mechanically protected by fire resisting construction or not, will no longer comply with BS5839 Part 1.

BS5839 Section 12.2.2

 Short circuit isolators limit the effect of one fault to a maximum of 2000m2. ‘2 simultaneous faults on a circuit should not disable protection within an area greater than 10,000m2.

 The EURB-4 standard conventional base from Eurotech should be wired as above.

 The EURB=4-EV standard intelligent base from Eurotech should be wired as above.

 A battery powered, intelligent programming tool is available. The Eurotech EV-AD2 hand held programmer is light, robust and easy to operate and is used for address programming and functional testing.

 Intelligent manual call points and modules are generally addressed by the use of a simple 8 bit DIL switch allowing upto a combination of 254 different addresses. The following diagram indicates an address setting for a manual call point with a device address setting of 90.

Installation considerations and key points

• All fire alarm designs should be based on a fire risk assesment
• All mains supply isolators must be double pole and suitably marked (25.2c&f)
• All cables to be fire resisting with a minimum cross-sectional area of 1mm2 (26.2J)
• All joints to be fire resisting, junction boxes to be labelled “FIRE ALARM’ (26.2)
• Enhanced cable to used where more than 4 zones of phased evacuation required, or multi storey systems. (Un-sprinklered over 30m) or risk assessment requires enhanced cable (26.2)
• Cable using trunking as a means of containment must be clipped using fire resistant supports within the trunking (26.2)
• Fire alarm control panel(s) are installed at a location appropriate for staff and fire-fighters (23.2)
• Call points are required at all exits to open air – whether or not the exits are specifically designed to be fire exits
• CO fire detectors should be spaced as per smoke detectors, but cannot be used without smoke detectors on escape routes (28.1.8)
• Multi sensors, if used as combined type, space as smoke detectors, if used at any time as a heat only then space as per heat detectors (26.1.6)
• Linear heat detection cable space as heat detectors (22.3)
• Unusual ceilings: Cellular ceiling, perforated ceilings or ceilings with closely spaced beams have special spacing and installation requirements, refer to section (22.3 & tables 1 & 2)
• Bells & electronic sounders cannot be mixed (16.2.1c)
• Sound levels can be reduced to 60dB(A) in stairs, small cellular offices or enclosures of no more than approximately 60 sq m, bedhead levels remain 75dB(A) (16.2.1)
• If the ambient background noise is above 90 dB visual alarms (beacons) are required (17.2a)
• Disabled toilets should be fitted with sounders and beacons (18.1)
• A minimum of one sounder is required in each fire compartment (16.2.1i)
• Full documentation required, test results as fitted drawings etc (Section 40)
• An installation certificate will be required (41.2)

Installation and handover checklist

1 The system complies with original specification / design
2 Any changes to original specification / design have been referred to the system designer for approval
3 System has been installed to meet the requirements of category L1, L2, L3, L4, L5, P1, P2, M, other
4 Variations to the defined category have been identified and the schedule of variations agreed with the client
5 Cables meet requirements for standard / enhanced / mixed
6 Cables are segregated as required and suitably supported (no plastic clips, cable ties or trunking used as sole means of support)
7 Cables are mechanically protected as required
8 Junction boxes are correctly labelled and identified on drawings. Connector boxes are fire resistant.
9 All cable insulation and continuity resistance measurements are logged
10 All cable penetrations are sleeved and fire stopped
11 Mains supply is dedicated, non-switched, correctly used and labelled
12 Mains supply is correctly identified at all distribution boards
13 Standby battery
14 All batteries are clearly marked and labelled with date of installation
15 Field wiring is labelled and correctly terminated in all and ancillary equipment
16 Isolators are fitted as appropriate, operate correctly and are marked on drawings
17 There are a minimum of two sounder circuits installed
18 Sound pressure levels have been checked and recorded and meet the minimum requirements
19 Detector type and spacing as appropriate to the system category
20 MCPs are located correctly and travel distance is appropriate to the system category
21 Remote signalling has been checked for correct operation to alarm receiving centre
22 Zone charts have been fitted in all appropriate locations (adjacent to control equipment and repeaters)
23 As fitted drawings are complete and have been updated where required, including cable size and routing
24 Log book and operating instructions have been issued to the responsible person
25 The responsible person has been adequately trained in the use of the fire alarm system