Introduction

This document is a brief summary of the Standards and the coverage requirements for protection and Fire Alarms as laid down in BS5839 (2002).

It is meant only as a guide to aid to help with the determination of coverage that a building has or will require to meet the standards. This document was produced by SbD(Fire & Security) and is not intended to be a substitute for the original.

Printed copies of our summary are available from us directly on request.

A full copy of BS 5839-1:2002 is available from the bsi-global.com. BS 5839-1:2002 is (c) 2002 by BSI.

General Need for a fire alarm

A complicated subject but in practice all but a very small relatively open plan buildings where fire will be quickly spotted by occupants will need one.

Domestic dwellings are covered by part 6 of the standard.

Categories of system

The Standard substitutes the word categories for the previous term levels.

Categories are split into L systems, where the prime aim is Life saving and P systems, where the prime aim is the protection of Property.

M or manual systems

These consist of manual call points with no automatic detection. M systems are aimed at life protection rather than property. In practice all categories will include manual call points. The only exception would be remote unmanned buildings that require automatic detection only.

 Categories Life Protection Property Protection Means of detection

M - Manual call-points only M Type systems form the basis of all L category systems

L1 P1/M -- M + detection throughout risk Generally considered to all possible areas including voids, risers and Storage areas

L2 P2/M--  M + L3 + detectors in areas of high risk Generally considered to provide detection in escape routes and rooms, voids, risers and Storage areas etc leading on to escape routes + Areas considered to be of high risk

L3 P2/M--  M + detection on escape routes and rooms off escape routes

L4 P2/M--  M + detection on escape routes and circulation areas

L5 P2/M--  M + detection in high risk areas only

Breakdown of Categories

M

This is the basic level of protection and is incorporated as part of any L or P type system i.e. L1/M BS5839 requires for the location of Manual Call Points (rule 20.2) 20.2c) Manual Call Points should be located on escape route and in particular, at all storey exits and all exist to the open (whether they are designated as a Fire Exit 20.2d) Distribution of Manual Call Points should be that no one needs to travel more than 45m (Rule 20.2e the 45m rule is reduced to 25m where a significant proportion of the occupants have limited mobility or 16m in areas of high flammable liquids or Gas) M only type systems are usually only found in building such as Schools and older office blocks which have had a fire alarm system installed prior to the requirement for Automatic Fire Alarms was made and often were installed to the requirements of CP1019 which was superseded by BS 5839 in 1980 and is only recommended where a site is fully manned at all times preferably with clear sight of all areas

L1

This is the highest level of coverage and requires for the provision of Fire Detection in all areas including. All Rooms Voids of 800mm or more including Bays within Voids (see notes for Detection Coverage) Escape routes Storage Cupboards (Greater than 1m Sq) Risers and Service Ducts Lift Shafts

L2

This is the Second Level of coverage and does not require for the provision of Fire Detection in areas apart from. Escape routes All Rooms and Storage cupboards (Greater than 1m Sq) Leading on to Escape Routes Voids of 800mm or more including Bays within Voids to areas protected by Detection (see notes for Detection Coverage) Risers and Service Ducts leading on to Escape Routes Lift Shafts Communal Areas (Circulation Areas) Areas of High Risk (i.e. areas where is considered that there is a high risk of Fire such as Gas or Liquid Fuel Storage etc.)

L3

This is similar to the L2 coverage and does not require for the provision of Fire Detection in areas apart from. Escape routes All Rooms and Storage cupboards (Greater than 1m Sq) Leading on to Escape Routes Voids of 800mm or more including Bays within Voids to areas protected by Detection (see notes for Detection Coverage) Risers and Service Ducts leading on to Escape Routes Lift Shafts Communal Areas (Circulation Areas)

L4

This requires for the provision of Fire Detection in. Escape routes Communal Areas (Circulation Areas) Voids of 800mm or more including Bays within Voids to areas protected by Detection (see notes for Detection Coverage)

L5

This requires for the provision of Fire Detection in High Risk Areas Only

Note:

all L type systems as listed above require including for an M Type system as part of the design

In L and P systems the following areas need not be covered if they are of low risk: -

Toilets, shower rooms and bathrooms, Stairway and toilet lobbies, Voids less than 800mm depth, Cupboards under 1m square,  (Risers with fire resisting floors and ceilings can be considered cupboards)

 Selection of categories.

Choice is determined by many factors such as life and business risk, legal requirements, insurers requirements, etc, between the parties to the decision.

Annex A of the Standard illustrates the typical range of current custom and practice. This is summarised below.

Type of Premises

Most offices, shops, warehouse, factories, restaurants                 M or P/2M 

Shops or resturants located  in Shopping Centres                        P1/M 

Hotels and Hostels                                                                      L2/M or L1/M

Pubs with residential areas                                                           L2/M

Pubs with no residential accommodation                                      L3/M  or M

Schools                                                                                      M or M/P2/L4          Normally based on fire risk assessment particularly arson risk. 

Hospitals                                                             L1 L1 Minor variations as per HTM1982.

Places of assembly, e.g. entertainment                                          L1/M

Transportation terminals                                                               M/L5

Covered shopping centres                                                            L3

Residential care homes                                                                 L3  (L1 in some cases)

Prisons                                                                                         M L5

Phased evacuation buildings                                                          L3

Buildings with means of escape difficulties                                      M/L5 

Insurer requirements                                                                     M/P2 M/P1 -

Audible Alarm Signals.

General sound pressure level 65dBa or 5dBa above ambient.

Sounds unlikely to persist for more than 30 secs may be ignored.

Noise made by running water in bathrooms may be ignored.

65dBa may be reduced to 60dBa in stairways, enclosures of not more than 60m sq e.g. cellular offices, points of limited extent.

75dBa is considered necessary to rouse people from sleep. In practice this means a sounder in each bedroom.

120dBa is the maximum allowed at a particular point.

If music is being played at over 80dBa the system should automatically mute the music

These figures are arbitrary and deemed to be appropriate.

In noisy factory areas, primary sounders that meet the Standards' requirement when the machines are silent may be fitted

 In hospitals and care homes HTM82 applies.

Visual Alarm Signals.

Uses if sound levels exceed 90Dba or hearing defenders are used.

Flash range 30-130 per minute.

Fire Warning For People with Impaired Hearing.

For the profoundly deaf a portable appliance such as tactile pagers are likely to be the best solution.

 

Device Location

Manual Call Points.

Should be located on escape routes, at all storey exits and at all exits to open air whether or not they are designated as fire exits. Normally may be in stairwell or on accommodation side.

Max distance to a call point 45m travel by normal route.

At design stages if layout is unknown use 30m straight line.

In environments with a risk of rapid fire spread or where the person likely to operate the call point has limited mobility reduce distances to 25m and 16m.

High risk activities, e.g. communal kitchens or spray booths, should have call points nearby.

Normal mounting height 1.4m plus or minus 200mm. May be lower for wheelchair users. Should be located in well lit areas against a contrasting background and where they need to be viewed from the side e.g. corridors should protrude 15mm.

Spacing and Sighting of Fire Detectors.

Where and when to use detection depends on the category of design chosen and on the risk. The following recommendations clarify the position

 

Enclosed stairways	Each principle landing
Open stairways, lifts, hoists, etc	Top of the structure and within 1.5m of the penetration on each floor
Horizontal void over 800mm	(May not be required in areas concidered to be of Low Risk)
Lantern lights over 800mm in depth or if used as ventilation

The maximum distance from any point in a protected area to a detector

Smoke Detectors under a flat ceiling                            7.5m

Smoke Detector n corridors under 2m wide                15m

Heat Detectors under a flat ceiling                               5.3m

Heat Detector in corridors under 2m wide                   10.6m

On pitched roofs with detectors at or near the apex distances increase by 1% for each degree of slope to a maximum of 25%.

On apex roofs detectors should be sited in or near the apex (within 600mm of the apex).

Detectors should not be mounted within 1m of air inlets or forced ventilation and the ceiling should not be perforated for a distance of more than 600mm around the detector.

A clear space of 500mm should be maintained below each detector.

Power Supplies.

Mains.

Should be supplied by a dedicated circuit via an isolating device from the load ("dead side") of the main isolating device for the building

A means of isolation of the fire alarm during routine maintenance should be provided.

 A protective device that serves only the fire alarm and has no switch should be labelled "FIRE ALARM".

A switch that serves only the fire alarm "FIRE ALARM DO NOT SWITCH OFF".

Standby Supplies.

Comprises of a rechargeable battery and automatic charger

The battery should have an expected life of 4 years.     Car batteries are not to be used.

The batteries should be labelled with their date of installation.

Battery should charge up from its final voltage in 24Hrs.

For category M and L systems the battery should be able to support the system for 24hrs and then ring the bells for half an hour.

If a back up generator is used the battery should be able to support the system for 6hrs and then ring the bells for half an hour.

For category P the 24 hrs plus half an hour ring applies a) providing the building is manned so that staff would be aware in 6 hours of mains failure or b)

Power failures are automatically notified to a remote station and hence to the key holder.

For category P the battery should support the system for 24 hrs longer than the building is unoccupied up to 72 hrs whichever is the less, plus half an hour ringing whatever applies.

Wiring

All system cables including power supply cables now need to be fire resistant. Although not specially required metal clad cables are generally used where cables require to run below or on vertical tray etc

Recommendations

All system cables including low voltage mains supply to the panel to be fire resistant Electrical Safety. - Design should meet BS7671. -

Earthing requirements of manufacturer should be met. 

Mains and system cables should be segregated.

For circuits with removable components and exposed parts with ELV potential, e.g. detectors: - Relevant power supplies should conform to BS EN 54-4 and have safety isolating transformers conforming to BS EN 61558. -

In dry conditions detectors do not have to be locked in their bases.

In wet areas one or more of the following should apply:

Circuit voltages less than 15V ripple free dc or 6V ac rms. 

Special tool required to expose live parts.

Parts are positioned out of reach other than for maintenance personnel.

Limitation of False Alarms Categories of false alarms

The user should categorise the false alarm as one of the following:

Unwanted alarm:                                     Covers the most common caused Faulse Alarms  

Accidental damage                                  i.e unintentional activation of a call point

Equipment false alarm:                            Malfunctioning of the equipment.

If any doubt arises as to cause it should not be assumed it is the equipment and the cause should be recorded as unknown.

Malicious false alarm:                               Typically deliberate call point activation.

False alarm with good intent:                    Call point activation in the genuine belief of a fire

Unknown:                                                Cause not certain.

Acceptable rate of false alarms.

The user should initiate an investigation by a specialist if:

In systems with more than 40 detectors the rate of false alarms exceeds one false alarm per 20 detectors per annum or if one particular detector or call point gives more than one false alarm in a year.

In systems with less than 40 detectors the rate of false alarms exceed 2 false alarms per year.