Fire detection and fire alarm systems for buildings – 
Part 1: Code of practice for design, installation, 
commissioning and maintenance of systems in non -
domestic premises  BOTSWANA  STANDARD  BOS 813 -1:2023 
Edition 1.0 BOS 813 -1:2023 
BOTSWANA BUREAU OF STANDARDS   
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Copyright Protection Notice  
 
© BOBS [ 2023] – All rights reserved  
This Botswana standard is copyright -protected by BOBS. Unless otherwise specified, no part of this publication 
may be reproduced or utilized otherwise in any form or by any means, electronic or mechani cal, including 
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permission to reproduce should be addressed to BOBS at the address below.  
Botswana Bureau of Standards  
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Telephone:  +267 3903200  
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Website:  www.bobstandards.bw  
 
ICS 13.220.20 13.320  
Published in Botswana  
 
 
  BOS 813 -1:2023  
Edition 1.0 
i  
 
 
Table of Contents                  
                      Page  
Foreword  ................................ ................................ ................................ ................................ ............... iiiii 
Section 1: General  ................................ ................................ ................................ ................................ ... 1 
1 Scope  ................................ ................................ ................................ ................................ ...........  1 
2 Normative references  ................................ ................................ ................................ .................  1 
3 Terms and definitions  ................................ ................................ ................................ ................  3 
4 Need for a fire detection and fire alarm system and type of system  ................................ .... 7 
5 Categories of system  ................................ ................................ ................................ .................  8 
6 Exchange of information and definition of responsibilities  ................................ ................. 10 
7 Variations from the recommendations of this standard ................................ ....................... 12 
 
Section 2: Design considerations  ................................ ................................ ................................ ........ 14 
8 Relationship between system category a nd protected areas  ................................ .............. 14 
9 Actuation of other fire protection systems or safety facilities  ................................ ............ 16 
10 Systems ln explosive gas or dust atmosph eres ................................ ................................ ...17 
11 System components ................................ ................................ ................................ ................. 17 
12 Monitoring, integrity and reliability of circuits external to control equipment  .................. 18 
13 Detection zones  ................................ ................................ ................................ ........................ 23 
14 Alarm zones  ................................ ................................ ................................ .............................. 25 
15 Communication with the fire and rescue service  ................................ ................................ ..27 
16 Audible alarm signals ................................ ................................ ................................ ............... 30 
17 Visual alarm signals  ................................ ................................ ................................ ................. 33 
18 Fire alarm warnings for people who are Deaf and hard of hearing  ................................ .....34 
19 Staged fire alarms ................................ ................................ ................................ ..................... 37 
20 Manual call points  ................................ ................................ ................................ ..................... 39 
21 Types of fire detector and their selection  ................................ ................................ .............. 41 
22 Spacing and siting of automatic fire detectors  ................................ ................................ .....47 
23 Control and indicating equipment  ................................ ................................ .......................... 62 
24 Networked systems  ................................ ................................ ................................ .................. 65 
25 Power supplies  ................................ ................................ ................................ ......................... 66 
26 Cables, wiring and other interconnections  ................................ ................................ ............ 69 
27 Radio -linked systems  ................................ ................................ ................................ ............... 75 
28 Electromagnetic compatibility  ................................ ................................ ................................ 77 
29 Electrical earthing ................................ ................................ ................................ ..................... 78 
  BOS 813 -1:2023  
Edition 1.0 
ii  
Section 3: Limitation of false alarms and unwanted fire alarm signals  ................................ ........... 80 
30 Responsibility for limitation of false alarms and unwanted fire alarm signals  .................. 80 
31 Categories of false alarms  ................................ ................................ ................................ .......82 
32 Acceptable rate of false alarms  ................................ ................................ ............................... 82 
33 Causes of false alarms  ................................ ................................ ................................ ............. 83 
34 Design process for limitation of false alarms and unwanted fire  alarm signals ................ 84 
35 Measures to limit false alarms and prevent unwanted fire alarm signals  .......................... 85 
 
Section 4: Installation  ................................ ................................ ................................ ............................ 91 
36 Responsibility of installer  ................................ ................................ ................................ ........ 91 
37 Installation Practices and workmanship  ................................ ................................ ................ 92 
38 Commentary  ................................ ................................ ................................ .............................. 94 
 
Section 5: Commissioning and handover  ................................ ................................ ........................... 96 
39 Commissioning  ................................ ................................ ................................ ......................... 96 
40 Documentation  ................................ ................................ ................................ .......................... 98 
41 Certification  ................................ ................................ ................................ ............................... 99 
42 Acceptance  ................................ ................................ ................................ .............................. 100 
43 Verificatio n ................................ ................................ ................................ .............................. 101 
 
Section 6: Maintenance  ................................ ................................ ................................ ....................... 102 
44 Routine testing  ................................ ................................ ................................ ........................ 102 
45 Inspection an d servicing  ................................ ................................ ................................ .......103 
46 Non-routine attention  ................................ ................................ ................................ ............. 107 
Section 7: User's responsibilities  ................................ ................................ ................................ ......111 
47 Premises management  ................................ ................................ ................................ .......... 111 
48 Logbook  ................................ ................................ ................................ ................................ ...112 
 
ANNEX A (normative )  Choice of appropriate category of fire detection and fire a larm system and 
frequency of servicing fire alarm systems  ................................ ................................ .......... 113 
ANNEX B (informative)  Typical noise levels in buildings  ................................ ................................ .116 
ANNEX C (normative)  Control and transmission equipment for tactile alarm devices provided for 
people who are Deaf and hard of hearing  ................................ ................................ ............ 119 
ANNEX D (normative)   Method for calculating standby battery capaci ty ................................ .......121 
Annex E  (informative)  The Selection and Application of Fire Detectors  ................................ ......122 
ANNEX F (normative )   Model format for system logboo k ................................ ................................ 129 
Annex G  (informative)  Model certificates ................................ ................................ ......................... 132 
Bibliography  ................................ ................................ ................................ ................................ ......... 139 
 BOS 813 -1:2023  
Edition 1.0 
iii Foreword  
This Botswana standard  was approved by the Technical Advisory Committee of the Standards Council on 
2023-02-07. 
The Botswana Bureau of Standards (BOBS) was established under the Standards Act No.16 of 1995 with a 
primary responsibility of preparing Botswana Standards.  
During th e preparation of this standard, assistance was derived from the British standard, BS 5839 ‑1:2017, 
The Design, Installation, Commissioning and Maintenance of Fire Detection and Fire Alarm Systems in 
Non‑domestic Premises. Published by British standards institute  
 
During the preparation of this standard, the following organizations were directl y represented in the Technical 
Committee, MED 6 – Fire Safety:  
 
Ministry of Local Government & Rural Development  
Fire Department  Mr D Sebeso    (Chairperson)  
Botswana Bureau of Standards   Mr KJ Lekaunyane  (Technical Secretary)  
Boma Fire Protection (Pty)  Ltd Mr Z Moseki   
Botswana Energy Regulatory Authority  Mr O Moremedi   
Botswana Energy Regulatory Authority   Mr U Monyatsi   
College of Fire Safety  Mr E Muzenda   
Fire Suppression & Electrical Systems (Pty) Ltd  Mr T Taziveyi   
Hollard Insurance Botswana ( Pty) Ltd  Mr B Daniel   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
© BOBS [ 2023] – All rights reservedBOS 813 -1:2023  
Edition 1.0 
1 Fire detection and fire alarm systems for buildings – Part 1: Code of 
practice for  design, installation, commissioning and maintenance of 
systems in non -domestic premises  
Section 1: General  
1 Scope  
This standard provides  recommendations for planning , design, installation , commissionin g and maintenanc e of 
fire detection and fire alar m system s in and aroun d buildings , other than domesti c premises . It does not 
recommend whether or  not fire detection should be installed in any given premises. Recommendations for fire 
detection and fire alarms systems in domestic premises are given in BS 5839 -6. 
The term fire detection and fire alarm system, in the context of this standard , include s systems, that range from 
those comprising of only one or two call points sonders to complex networked systems that incorporate a large 
number of automatic fire detectors, manual call point s and sounders,  connected to numerous int er -
communicating control a nd indicating panels . 
The term also includes systems that are capable of providing signals to initiate the operation of  other fire 
protection systems and equipment (such as fire extinguishing systems, smoke control  systems or automatic 
door release equipme nt) or safety measures (such as shutdown of air handling  systems, closing of oil or gas 
valves or grounding of lifts). It does not apply to the other systems and  equipment themselves, or the ancillary 
circuits to interface with them. Recommendations for th e planning installation and servicing of facilities for 
operation of certain fire protection systems by the systems  addressed within this this standard  are given in  
BS 7273 (all parts)  
This standard does  not cover systems whose primary  function is to exti nguish or control fire,  such as sprinkler 
or automatic extinguishing systems, even though they might have a secondary  alarm function; it does, 
however, cover the use of a signal from an automatic extinguishing system as  one initiating element of a fire 
alarm system (e.g. by use of a pressure or flow switch).  
This standard  does not cover voice alarm systems. Recommendations for voice alarm systems  and voice 
sounders are given in BS 5839 -8, This  standard does not cover systems combining fire alarm functions w ith 
other non -fire related functions. Recommendations for such integrated systems are given in  DD CLC/TS 50398.  
This standard does not cover the  997 (or 112) public emergency call system, or manually or  mechanically  
operated sounders.  This standard does no t cover audible or visual way -guidance systems which are designed 
to complement fire alarm systems.  
Recommendations for fire detection and fire alarm systems in electronic data processing  installations and  similar 
critical electronic equipment rooms are gi ven in BS 6266, which provides  recommendations over and above 
those given in this standard . 
This standard applies to extensions and alterations to existing systems, at least in respect of  the design, 
installation, commissioning and certification of the new  work, albeit that the extended or  altered system might 
not, overall, conform to the recommendations of this standard.  
2 Normative references  
The following documents are indispensable for the application of this document. For dated references, only 
the editi on cited applies. For undated references, the latest edition of the referenced document (including any 
amendments) applies. Botswana Bureau of Standards (BOBS) maintains registers of currently valid 
documents.  
BS 476, (relevant parts), Fire tests on buildi ng materials and structures   
BS 4678 -4, Cable trunking - Part 4: Specification for cable trunking made of insulating material  
BS 5839 -6, Fire detection and fire alarm systems for buildings  BOS 813 -1:2023  
Edition 1.0 
2 BS 5839 -8, Fire detection and fire alarm systems for buildings - Part 8: Code of practice for the design, 
installation, commissioning and maintenance of voice alarm systems  
BS 5839 -9, Fire detection and alarm systems for buildings - Part 9: Code of practice for the design, installation 
commissioning and maintenance of eme rgency voice communication systems  
BS 6266, Fire Protection for Electronic Equipment Installations  
BS 7273, (all parts), Code of practice for the operation of fire protection measures  
BS 7629 -1, Electric cables - Specification for 300/500 V fire resistant screened, fixed installation cables having 
low emission of smoke and corrosive gases when affected1y fire - Part 1: Multicore cables  
BS 7671, Requirements for Electrical Installations - JET Wiring Regulations (Seventeenth edition)  
BS 7846, Electric cables - Thermosetting insulated, armoured fire -resistant cables of rated voltage 600 / 1000 
V fixed insulation, having low emission of smoke and corrosive gases when affected by fire -Specification  
BS 8434 -2, Methods of test for assessment of the fire integrity of electric cables - Part 2: Test for unprotected 
small cables for use in emergency circuits - BS EN 50200 with a 930°C flame and with water spray  
BS 8591, Remote centres receiving signals from alarm systems -Code of practice  
BS EN 54 -2:1997+A1:2006, Fire d etection and fire alarm systems - Part 2: Control and indicating equipment  
BS EN 54 -3, Fire Detection and fire alarm systems - Part 3: Fire alarm devices - Sounders  
BS EN 54 -4, Fire detection and fire alarm systems - Part 4: Power supply equipment  
BS EN 54 -5, Fire detection and fire alarm systems - Part 5: Heat detectors - Point heat detectors  
BS EN 54 -7, Fire detection and fire alarm systems - Part 7: Smoke detectors - Point detectors using scattered 
light, transmitted light or ionization  
BS EN 54 -10, Fire detection and fire alarm systems - Part 10: Flame Detectors - Point detectors  
BS EN 54 -11, Fire detection and fire alarm systems - Part 11: Manual call points  
BS EN 54 -12, Fire detection and fire alarm systems - Part 12: Smoke detectors - Line detectors usin g an 
optical beam  
BS EN 54 -13, Fire detection and fire alarm systems - Part 13: Compatibility and connectability assessment of 
system components  
BS EN 54 -20, Fire detection and fire alarm systems -Part 20: Aspirating smoke detectors  
BS EN 54 -21, Fire detect ion and fire alarm systems - Part 21: Alarm transmission and fault warning routing 
equipment  
BS EN 54 -23, Fire detection and fire alarm systems - Part 23: Fire alarm devices – Visual alarm devices  
BS EN 54 -25:2008 , Fire detection and fire alarm systems -Part 25: Components using radio links  
BS EN 54 -26, Fire detection and fire alarm systems - Part 26: Carbon monoxide detectors - Point detectors  
BS EN 54 -29, Fire detection and fire alarm systems - Part 29: Multi -sensor fire detectors - Point detectors using 
a combination of smoke and heat sensors  
BS EN 54 -30, Fire detection and fire alarm systems -Part 30: Multi -sensor fire detectors – Point detectors using 
a combination of carbon monoxide and heat sensors  BOS 813 -1:2023  
Edition 1.0 
3 BS EN 54 -31, Fire detection and fire alarm system -Part 31: Multi -sensor fire detectors – Point detectors using 
a combination of smoke, carbon monoxide and optionally heat sensors  
BS EN 50200:2015, Method of test for resistance to fire of unprotected small cables for use in emergency 
circuits  
BS EN 60079 -14, Explosive atmospheres. Electrical installations design, selection and erection  
BS EN 60079 -17, Electrical apparatus for use in the presence of combustible dust -Part 17: Inspection and 
maintenance of electrical installations hazardous areas (other than mines ) 
BS EN 60702 -1, Mineral insulated cables and their terminations with a rated voltage not exceeding 750 V - 
Part 1: Cables  
BS EN 60702 -2, IEC 60702 -2, Mineral insulated cables and their terminations with a rated voltage not 
exceeding 750 V - Part 2: Termin ations  
BS EN 61386 ( all parts), Conduit systems for cable management  
BS EN ISO 13943, Fire safety - Vocabulary  
ISO 7240 -8, Fire detection and alarm systems — Part 8: Point -type fire detectors using a carbon monoxide 
sensor in combination with a heat sensor  
ISO 7240 -15, Fire detection and alarm systems — Part 15: Point -type fire detectors using smoke and heat 
sensors  
SANS 10400 Part T,  The application of the National Building Regulations Part T: Fire protection  
3 Terms and definitions  
For the purpose of this standard  this standard,  the terms and definitions in ISO 13943  and the following 
apply.  
3.1 addressable system : system in which signals from detectors, manual call points or any other devices are 
individually identified at the control and indicating equipment.  
3.2 alarm receiving centre (ARC ): continuously manned premises, remote from those in which the fire 
detection and fire alarm system is fitted, where the information concerning the state of the fire alarm system is 
displayed and/or recorded, so that the fire and  rescue service can be summoned  
3.3 alarm zone : geographical subdivision of the protected premises, in which the fire alarm warning can be 
given separately, and independently, of a fire alarm warning in any other alarm zone  
3.4 aspirating smoke detection system : smoke detection system in which a sample of the atmosphere in 
the protected space is drawn by a fan or pump into a detector which may be remote from the protected space.  
3.5 audibility : property of a sound which allows it to be heard among other sounds  
NOTE Aud ibility depends upon the relative loudness and frequency content of the sound in comparison with other 
sounds which are present at the same time . 
3.6 automatic fire detection and fire alarm system : system (other than a single self -contained smoke or 
fire alarm ) in which an alarm of fire can be initiated automatically.  
3.7 circuit : assembly of fire alarm components supplied from the same control equipment and protected 
against overcurrent by the same protective devices) r current limitation arrangements.  
3.8 circulation  area: area (including a stairway) used mainly as a means of access between a room and an 
exit from the building or compartment.  
3.9 Coincidence : arrangement designed so that an output is obtained only when at least two independent 
input triggering signals are  present at the same time  
NOTE This is not to be mistaken for “double knock”: which ls a colloquial term often used for an arrangement whereby an 
output is given only when two successive signals are received from the same device.  BOS 813 -1:2023  
Edition 1.0 
4 3.10 combustion gas detector : automatic fire detector sensitive to gaseous products of combustion and/or 
thermal decomposition . 
3.11 commissioning : process by which it is determined that the installed system meets the defined 
requirements.  
3.12 competent  person : person with the relevant current t raining and experience, and with access to the 
requisite tools, equipment and information, and capable of carrying out a defined task.  
Note The technician shall have a qualification in Electronics and Electrical Engineering or its equivalence  
3.13 control  and i ndicating equipment (CIE): component or components of a fire detection and fire alarm 
system through which other components can be supplied with power and which:  
a) are used:  
1) to receive signals from the connected detectors, manual call points or any other dev ices (e.g.in  
put/output units);  
2) to determine whether these signals correspond to a fire alarm condition;  
3) to indicate any such fire alarm condition audibly and visually;  
4) to indicate the location of the danger; and  
5) possibly to record any of this information;  
b) are used to monitor the correct functioning of the system and give audible and visible  warning of  any 
faults (e.g. short circuit, open circuit or fault in the power supply);  
c)  if necessary , are able to pass on the fire alarms signal:  
1) to audible or visible fire alarm devices or to a voice alarm system,  
2) to the fire alarm routing function to a fire ARC;  
3) to the control function for fire protection equipment or systems; and  
4) to other systems or equipment, such as a mimic panel.  
3.14 critical signal path : components an d interconnections between every fire alarm initiation point (manual 
call point or automatic fire detector) and the input terminals on, or within, each fire alarm device and (where 
provided) transmission equipment within the premises for routing of signals  to an ARC  
designer person or organization taking responsibility for design considerations.  
3.15 Designer: person or organization taking responsibility for design considerations  
3.16 detection zone : subdivision of the protected premises such that the occurrence of a  fire within It is 
indicated by a fire detection and fire alarm system separately from an indication of fire in any other subdivision.  
NOTE A detection zone usually, consists of an area protected by several manual call points and/or detectors, and is  
separ ately indicated to assist in location of the fire, evacuation of the building and firefighting.  
3.17 Detector : part of an automatic fire detection and fire alarm system that contains at least one sensor 
which constantly, or at frequent intervals, monitors at le ast one suitable physical and/or chemical phenomenon 
associated with fire, and that provides at least one corresponding signal to the CIE  
NOTE The decision to give the alarm of fire or to operate automatic fire protection equipment might be made at the 
detector or another part of the system, for example at the CIE.  
3.18 dual path alarm transmission system : alarm transmission system consisting of one primacy alarm 
transmission system and one secondary alarm transmission system using diverse technology  
3.19 false  alarm : fire signal resulting from a cause(s) other than fire  
NOTE False alarms can be subdivided into four categories:  
a) unwanted al arms, in which a system has responded, either as designed or as the technology might reasonably  be 
expected to respond, to any of t he following:  
1) a fire-like phenomenon or environmental influence (e.g. smoke from a nearby bonfire, dust or insects,  processes 
that produce smoke or flame, or environmental effects that can render certain types of  detector unstable, such 
as rapid air flow)  
2) accidental damage;  
3)  inappropriate human action {e .9. operation of  a system for test or maintenance  purpose s without  prior 
warning to building occupants and/or an ARC);  BOS 813 -1:2023  
Edition 1.0 
5 b) equipment false alarms, in which a false alarm has resulted from a fault in the system;  
c) malicious false alarms, in which a person operates a manual call point or causes a fire detector to initiate a  fire 
signal, whilst knowing that there is no fire;  
d) false alarms with good intent, in which a person operates a manual call point or otherwise in itiates a fire  signal in the 
belief that there is a fire, when no fire actually exists.  
3.20 fire alarm  device : component of a fire detection and fire alarm system, not incorporated in the CIE, 
which is used to give a warning of fire  
NOTE For example, a sounder  or visual alarm device.  
3.21 fire alarm sounder : audible fire alarm device.  
3.22 fire engineering solut ion:  application of science and engineering to the achievement of one or more 
fire safety objectives in such a way that the objectives are achieved without follo wing, in full, prescriptive 
recommendations  of a recognized code of -practice.  
3.23 fire hazard level : likelihood of  fire occurring  
3.24 fire-resisting construction : construction that is able to satisfy for a stated period of time some or all of  
the appropriate crite ria given in the relevant parts of BS 476 (or equivalent International Standards)  
3.25 fire risk : combination of the probability of fire occurring and the magnitude of the consequences of fire.  
3.26 fire signal : signal intended to indicate the occurrence of a fire.  
3.27 flame detector : automatic fire detector which responds to the radiation emitted by the flames from a fire  
3.28 heat detector : automatic fire detector which responds to an increase in temperature.  
3.29 installation:  work of fixing and interconnecting the components a nd elements of a system  
 
3.30 installer : person or organization having responsibility for all or part of the process of installation.  
3.31 lantern -light : construction standing above the surface of a roof and intended to admit light to the space 
below.  
3.32 line detector : detector which responds to the phenomenon sensed in the vicinity of a continuous line 
3.33 low fire risk area or room :  area or room containing little or no combustible material and no ignition 
source  in which any foreseeable fire is unlikely to spread such as  to present any significant threat to escape 
by occupants or damage to property.  
NOTE Examples of combustible materials are furniture, fittings , storage or linings.  
3.34 Maintenance : work of inspection, servicing and repair necessary in, and testing in or der to maintain the 
efficient operation of the installed system.  
3.35 manual call point : component of a fire detection and fire alarm system which is used for the manual 
initiation of an alarm.  
3.36 manual system : system containing no automatic detectors and in which an a larm of fire can only be 
initiated manually.  
3.37 maximum alarm lo ad: maximum load imposed on a fire alarm system power supply under fire 
conditions, comprising the power required for simultaneous operation of all fire alarm devices, fire signals from 
all autom atic fire detectors and manual call points in the building, any power drawn by other systems and 
equipment in the alarm condition and any power required for transmission of fire signals to an ARC (if a facility 
for this is provided).  
3.38 mimic diagram : topogra phic representation of the protected premises and their subdivisions, using 
light-emitting indicators for each subdivision such that the indications of the fire detection and fire alarm  system 
can be rapidly related to the layout of the premises.  
3.39 minimum s tatic response temperature  minimum temperature at which a heat detector would produce 
a fire alarm signal if subjected to a very small rate of rise of temperature  
3.40 multi -sensor fire detector : fire detector that monitors more than one physical and/or chemica l 
phenomenon associated with fire  
3.41 networked system : fire detection and fire alarm system in which several items of CIE are BOS 813 -1:2023  
Edition 1.0 
6 interconnected and able to exchange information.  
3.42 normal supply : supply from which the fire detection and fire alarm system is expecte d to obtain its 
power under  normal conditions.  
NOTE The normal supply is usually derived from the public electricity supply system.  
3.43 phased evacuation : system of evacuation in which different parts of the premises are evacuated.in a 
controlled sequence of p hases, those parts of the premises expected to be at greatest risk being evacuated 
first. 
NOTE A phased evacuation normally requires at least a two -stage alarm system.  
3.44 point detector : detector which responds to a phenomenon sensed in the vicinity of a fixe d point  
3.45 pre-alarm warning  early warning of conditions which might (or might not) represent a fire  but indicates 
an approaching alarm condition . 
3.46 premises management : persons having day -to-day control of the premises, the fire detection and fire 
alarm system (s) and implementation of the fire procedures  
NOTE In large premises, a single person with specialist knowledge ls often delegated the responsibility for the fire detectio n 
and fire alarm system and associated matters. In small premises, a person with spe cialist knowledge is unlikely to be 
present, be responsibility for the fire detection and fire alarm system can still be delegated to a specific person.  
3.47 Protection : presence of o ne or more automatic fire detector(s) able to initiate actions needed for the 
safety of life or property in the event of a fire.  
3.48 Purchaser : person or organization taking primary responsibility for acceptance of and payment for the 
installed system  
3.49 radio -linked system : fire detection and fire alarm system in which some or all of the interconnections 
between  components are made by radio links.  
3.50 rate of rise heat detector : automatic fire detector which initiates an alarm when the rate of change of 
the measured phenomenon with time exceeds a certain value, for a sufficient time.  
NOTE For each class in BS EN 54 -5, there are two subclasses: Rand S. So -called rate of rise heat detectors may be taken 
to correspond to R, and fixed temperature detectors to S.  
3.51 repair : non-routine work necessary to restore the efficient operation of the installed system.  
3.52 search distance : distance which has to be travelled by a searcher within a zone in order to determine 
visually the  position of a fire.  
NOTE The distance is not measured between the point of entry of the zone and the location of the fire, but only b etween 
the point of entry and the location at which a person searching for the fire would first become aware of the location of the 
fire. 
3.53 Sector : subdivision of the protected premises normally containing several zones  
NOTE A sector can cover more than one building.  
3.54 Servicing : routine process of work on the system (including cleaning. realignment, adjustment and 
replacement) carried out at predetermined intervals  
3.55 short circuit isolators : device, which can be connected into a transmission path of a fire defec tion and 
fire alarm system, to limit the consequences of low parallel resistance faults between the lines of this 
transmission path.  
NOTE A short circuit isolating device can be a physically separate device or it can be incorporated into another device 
(e.g. integrated into a smoke detector or detector base).  
3.56 Smoke : particulate and aerosol products of combustion generated  by a fire, whether this be of the  
smouldering or open flame type.  
NOTE In general, the particle diameters range from 1 nm (invisible smok e) to 10 μm (visible smoke).  
3.57 smoke detector : automatic fire detector sensitive to particulate products of combustion and/or pyrolysis 
suspended in the atmosphere (aerosols)  
3.58 soak period : period after a fire detection and fire alarm system has been commissio ned, but prior to 
handover, during which the system's performance in relation to false alarms and faults is monitored.  
3.59 staff  alarm: restricted alarm, following the operation of a manual call point or automatic fire detector; BOS 813 -1:2023  
Edition 1.0 
7 given to curtain staff in the p remises to permit investigation prior to evacuation and/ or summoning of the fire  
and rescue service  
NOTE The use of staff alarms in response to signals from manual call points is not generally acceptable (see19.2.2).  
3.60 staged fire alarm : arrangement in whic h two or more stages of alarm can be given within a given area.  
NOTE 1 Examples of staged alarm systems are a two -stage system capable of giving "alert" or “evacuate” signals, or a 
three -stage alarm system capable of giving "staff alarm: "alert" or "evacua te” signals.  
NOTE 2 The normal condition, under which no alarm is given, is not counted as a stage of alarm.  
NOTE 3 In this standard, in order to avoid confusion:  
a) the term stage" is used to describe the different stages of alarm in part, or all, of the premises;  
b) the term "phase" is used in describing the sequence of phases of evacuation from different areas of the premises.  
NOTE 4 A pre -alarm warning (see 3.45) is not a stage of alarm.  
3.61 standby supply : electricity supply, commonly from a rechargeable b attery, which is automatically 
connected to the fire alarm system when the normal supply fails.  
3.62 time-related system : system in which the response or sensitivity of automatic fire detectors is changed 
with the time of day.  
3.63 unwanted fire alarm signal UFAS : false alarm from an automatic fire detection and fire alarm system 
that has been passed on to the fire and rescue service.  
3.64 user : person or organization having control of the building (or part of the building) in which the fire 
detection and fire alarm syste m is installed.  
3.65 visual alarm device : device which generates a flashing light to signal to the occupants of a building that 
a fire condition exists.  
3.66 voice alarm system : sound distribution system that provides means for automatically broadcasting 
speech mess ages and  warning signals  
NOTE Voice alarm system commonly include a facility for transmission of live voice messages, as well as automatically 
generated messages  
3.67 voice sounder : fire alarm sounder that contains the components necessary to generate and broad cast 
digitally  recorded speech messages  
3.68 zone plan : diagrammatic representation of a building, showing specific topographic information and the 
division of the detection zones   
4 Need for a fire detection and fire alarm system and type of system  
4.1 Commentary  
The need for a fire detection and fire alarm system in any specific building is normally determined  by the 
authority responsible for enforcing fire safety legislation in that building and/or by a fire risk  assessment carried 
out by the owner, landlord, occup ier(s) or employer(s), as appropriate. In general,  it is appropriate to install 
some form of  fire detection and fire alarm system in virtually all buildings,  other than very small premises that 
are relatively open -planned, so that any fire is quickly detec ted by  occupants, who will then be able to warn 
others by word of mouth or simple mechanical devices such  as hand -operated bells or super sounders  
Manual fire detection and fire alarm systems are often sufficient to satisfy legislation in workplaces  in whi ch no 
one sleeps. Automatic fire detection is usually required by legislation to supplement the  manual system in 
premises in which people sleep. Automatic fire detection might also be necessary to  satisfy legislation under 
the following circumstances:  
a) wher e the automatic fire detection forms part of a fire engineering solution;  
b) where fire protection systems, such as door closing facilities or smoke control systems, are to be  operated 
automatically in the event of fire;  
c) where the low level of occupancy of a building, or part of a building, is such as to create the  potential for 
fire to prejudice means of escape by occupants before they are aware of the fire.  
Automatic fire detection is also commonly used to protect property by ensuring the early attendance of  the fire 
and rescue service, in response to summoning by occupants of the building orby transmission  of fire alarm BOS 813 -1:2023  
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8 signals to an ARC from where the fire and rescue service will be summoned. Automatic fire  detection and fire 
alarm systems might, therefore , be required or recommended by the property insurers.  
The early detection of fire by automatic means, and rapid summoning of the fire and rescue service in  the 
event of fire, is also important in premises in which people cannot readily be evacuated immedia tely. In certain 
premises of this type (e.g. residential care premises), it is also important to give accurate  and unambiguous 
information to staff regarding the location of  a fire. In general, this standard makes no recommendations as to 
whether systems n eed to addressable; it is possible for addressable  and non -addressable systems to satisfy 
the recommendations of Section 2. However, where accurate  and unambiguous information about the location 
of a fire is critical to the safety of life, it is sometimes  necessary to use only an addressable system.  
4.2  Recommendations  
The following recommendations are applicable.  
a) Where there is uncertainty regarding the need for a fire detection and fire alarm system, or the  category 
of system to be used (see Clause 5), the d eveloper, potential purchaser or user  should make reference to 
one or more of the following:  
1) SANS 10400 Part T;  
2) guidance documents that support fire safety legislation;  
3) any authority responsible for enforcing fire safety legislation that applies to the pre mises;  
4) the property insurer;  
5) Mandatory fire risk assessment in all commercial building  
b) The purchaser or user should ensure that the fire engineer designer or installing company of  fire alarm 
system is adequately apprised of the objectives of the system and  any relevant  requirements of enforcing 
authorities and insurers . 
Where occupants of a building are likely to need assistance from staff to evacuate the building (e.g. in 
residential care premises and hospitals), the fire detection and fire alarm system sh ould be  addressable if the 
building has facilities for more than 10 people to sleep.  
5 Categories of system  
5.1 Commentary  
5.1.1  Introduction  
Fire detection and fire alarm systems can be installed in buildings to satisfy one, or both, of two principles  
objectives, nam ely protection of life and protection of property. The objectives can differ in time or place.  Other 
possible objectives exist, such as protection against business interruption and protection of the  environment; 
these are likely to be satisfied by the reco mmendations in this standard for protection  of property.  Because of 
the great variety of applications for systems covered by this standard , systems are  divided into a number of 
different Categories, as described in 5.1.2, 5.1.3  and 5.1.4.  
5.1.2  Category M system s 
Category M systems are manual systems and, therefore, incorporate no automatic fire detectors.  
5.1.3  Category L systems  
Category L systems are automatic fire detection and fire ala rm systems intended for the protection of  life. They 
are further subdivided into : 
a) Category L1: systems installed throughout all areas of the building.  The objective of a Category L1 
system is to offer the earliest possible warning of fire, so as to  achieve the longest available time for 
escape,  
b) Category L2: systems installed only in d efined parts of the building . A Category L2 system ought to 
include the coverage necessary to satisfy the recommendations of  this standard for a Category L3 
system; the objective of a Category L 2 system is identical to that of  a Category  L3 system, with th e 
additional objective of affording early warning of fire in specified  areas of high fire hazard  level and/or 
high fire risk;  
c) Category L3: systems designed to give a warning of  fire at an early enough stage to enable all  
occupants, other than possibly thos e in the room of fire origin, to escape safely, before the escape  
routes are impassable owing to the presence of  fire, smoke or toxic gases;  BOS 813 -1:2023  
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9 NOTE 1 To achieve the above objective it is normally necessary to install detectors in rooms which open on  to 
an es cape route (see 8,2.).  
d) Category L4: systems installed within those parts of the escape routes comprising circulation areas  
and circulation spaces, such as corridors and stairways. The objective of a Category L4 system is to  
enhance the safety of occupants by providing warning of smoke within escape routes;  
NOTE 2 The installation of detectors in additional areas is not precluded, and the system could then still be  
regarded as a Category L4 system.  
e) Category L 5: systems in which the protected area(s) and/or t he location of detectors is designed  to 
satisfy a specific fire safety objective (other than that of  a Category L1, L2, L3 or L4 system).  Often, 
the design is based on a localized need for fire detection in only part of a building. Protection  might be 
provided to compensate for some departure from normal guidance elsewhere or as a part  of the 
operating system for a fire protection system. Such a system could be as simple as one that  
incorporates a single automatic fire detector in one room (in which outbrea k of fire would create  undue 
risk to occupants, either in the room or elsewhere in the building), but the system could  comprise 
comprehensive detection throughout large areas of a building in which, for example,  structural fire 
resistance is less than that  normally specified for buildings of that type.  
NOTE 3 The protection afforded by a Category L 5 system might, or might not, incorporate that provided by a  
Category L2, L3 or L4 system.  
5.1.4  Category P systems  
Category P systems are automatic fire detection and fire alarm systems intended for the protection of  property. 
They are further subdivided into:  
a) Category P 1: systems installed throughout all areas of the building.  
The objective of a Category P1  system is to offer the earliest possible warning of fire so as  to minimize 
the time between ignition and  the arrival of firefighter;  
b)  Category P2: systems installed only in defined parts of the building.  
The objective of a Category P2 system is to provide early warning of fire in areas of high fire hazard  
level, or a reas in which the risk to property or business continuity from fire is high.  
NOTE The defined parts of the building might be as few as one or more rooms, or as e xtensive as,  for example,  
complete floors of the building.  
5.1.5  Selection of category  
Even in buildi ngs with comprehensive fire detection, the provision of manual call points is still normally  of great 
value; people in the vicinity of a fire are normally aware of the fire, and able to raise the alarm  by use of a 
manual call point, before it is detected a utomatically.  
If a system is intended to fulfil the objectives of more than one category of system, then the system needs  to 
conform to the recommendations for each of the categories. For  - example, a system whose sole purpose  is 
to provide property protec tion throughout the building (a Category P 1 system) might not need to  give an alarm 
signal of sufficient audibility to rouse al l occupants who might sleep in the building. If,  however, the system 
was also installed for the purpose  of life safety (a Categor y L system), sufficient fire  alarm sounders to rouse 
sleeping  occupants would be necessary.  
This standard  does not recommend which category of system needs to be installed in any given  premises. 
The various system categories are to be regarded as a "menu ” from which purchasers, users,  specifiers, 
enforcing authorities, insurers or system fire engineer designers or servicing company can  select a suitable 
system for any  building . However, Annex A provides information on the Categories of systems that are typi cally 
installed  in various types of premises .  
Because of the wide range of systems covered by the recommendations of this standard , the specification of 
requirements for a system, by a purchaser, user, enforcing authority or insurer, or the  description of  a system  
by a fire engineer designer or servicing company by reference to this standard,  without a reference to system 
category, has little meaning.  
The category  of system to be installed always needs to be included in the specification. Similarly, the  
specification of any category of system, other than Category L 1, M P1, always needs to include details  of those 
areas of the building that are to be protected.  
In some cases, there is little distinction between, for example, a Category P 1 system with variati ons (see 
Clause 7) and a Category P2 system. In such cases, either description could be used; the designated  system BOS 813 -1:2023  
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10 category is to be regarded as a shorthand form of description, rather than a rigid form of  prescription. Where 
a choice exists, however, the  description needs to be based on the specified objective  of the system . 
5.2  Recommendations  
The following recommendations are applicable.  
a) Any statutory requirements imposed by enforcing authorities, and any requirements imposed by  
property insurers, for a fi re detection and fire alarm system should clearly state the category of  system 
required.  
b) The purchaser of the system or their agent should inform the fire engineer designer or servicing  
company as to the category of system that is required (e.g. in purchas e or tender specifications).  
c)  If the fire engineer designer or servicing company is not informed as to the category of system  
required, the fire engineer designer or servicing company should make clear, to the purchaser  or their 
agent, the category of syst em that is proposed, prior to an order for the system being  of the situations 
described in a), b) and c), the description of the system should be  further amplified by adequate 
information on the areas of the building that are to be protected,  except in the  case of a Category L1 
or P1 system, for which such further information might not  be necessary.  
d) In each  of the situations described in a), b) and c), the description of the system should be  further 
amplified by adequate information on the areas of the buil ding that are to be protected,  except in the 
case of a Category L1 or P 1 system, for which such further information might not  be necessary.  
e) Category L 1, L2, L3 and L4 systems should also satisfy the recommendations  of this standard for  a 
Category M system.  
f) Where the recommendations of this standard for a Category M system are to be satisfied in  conjunction 
with the recommendations for a Category  P1, P2 or L 5 system, the combined system  should be 
described as a Category P 1/M, P2/M or L 5/M system respectively . 
g) Where the objectives of more than one type of system  are to be satisfied, the system should be  
described as a Category X/Y system (e.g L2/P2 or L3/P2).  
h) The system design certificate (see clause 41 ) should clearly state the category of system that has  
been designed and should, except in the case of a Category M, L 1 or P1 system, provide a brief  
description of the areas of the building that are protected by automatic fire detection.  
6 Exchange of information and definition of responsibilities  
6.1 Commentary  
The p urpose of a  fire detection and fire alarm systems is to support the fire safety strategy for the  buildings. It 
is, in particular, important that fire engineer  who design s or servicing company suitably supports  the required 
fire evacuation procedures, rathe r than those procedures being designed around a  predetermined system  
design. To a large  extent , the design of the fire detection and fire alarm system  depends on the actions required 
after the alarm has been given. Particular care is necessary in the case  of a system that is capable of giving a 
two (or more) stage alarm (see Clause 19).  
If a building contains alarm systems associated with hazards other than fire, the various hazard  alarms need 
to be properly coordinated and be distinct  rom each other. In th ese buildings, the relative  priorities need to be 
carefully assessed, and the system arranged so that a higher priority alarm cannot  be prevented or obscured 
by one of a lower priority. Although, in general, fire has the highest priority,  there are buildin gs in which other 
hazards can have higher priorities than fire.  
The system requirements, including those imposed by the evacuation procedures, the configuration of  the 
building, and the use to which the building is put, need to be ascertained as accurately  as possible by  
consultation between the user or purchaser and other interested parties, such as the enforcing authority  or fire 
insurer.  
It is advisable that there also be relevant consultation between the user or purchaser and the fire  engineer 
designer or servicing company. In a small, simple building, the extent to which such  consultation is  necessary 
might be  minimal; the user or purchaser might have little knowledge of  fire safety principles, and system design  
can involve little more than determinatio n of the appropriate locations of manual call points and fire  alarm 
devices. In complex premises, there is a need for extensive consultation between the user or  purchaser, the 
enforcing authority, the fire engineer designer or installing company and, possi bly, specialist consultants.  
The design may be undertaken by the supplier, the installing company representatives of the user or  purchaser 
or by any combination of these parties. It is desirable that, at the contract stage, a single  organization takes BOS 813 -1:2023  
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11 responsibility for the design of the system, a single organization takes responsibility  for the installation work, 
including compliance with the design, and responsibility for commissioning  of the system. The two of these 
parties may take the form of one singl e organization. The responsibility  for each of these three stages needs 
to be clearly defined and documented. Experience shows that the  responsibility for provision of a zone plan 
[see 23.2.2 (e)] is often ill -defined, leading to the absence of a  suitable z one plan when an installation is handed 
over. It is important that this responsibility is defined  at an early stage of  the planning of an installation.  
It is essential that, at the design stage, avoidance of the potential for false ala rms and unwanted fire  alarm 
signals  are considered, as well as the effectiveness of the system to give a -warning in the event of  fire (see 
Section 3).  
6.2  Recommendations  
The following recommendations are applicable.  
a) The user or purchaser of the system should ensure that, to the  extent appropriate, there is  consultation 
at, or prior to, the system design stage with all relevant interested parties within the  following list:  
1) the authority responsible for enforcing fire safety legislation (e.g. the building control  authority, fire 
and rescue authority, local authority. Health and Safety Executive);  
2) the property insurer.  
NOTE 1 Where any variations from  the recommendations of this standard are  proposed, they need to  be agreed with 
the relevant interested  parties.  
NOTE 2 Some of the co nsultations may be undertaken by parties, such as the fire engineer designer or  installing 
company, acting on behalf of the user or purchasers.  
NOTE 3 Even where none of the above is considered to be an interested party, advice is available from  enforcing 
authorities and, in the case of Category P systems, installing company or risk assurer.  
b) The fire engineer designer or installing company o f the system should ensure that, to the extent 
appropriate,  there is consultation at the design stage with all relevan t interested parties within the 
following list:  
1) the user or purchaser;  
2) consultants (including architects, fire engineer, fire servicing companies, fire consultants  
c) The installing company of the system should ensure that, to the extent appropriate, there is  
consultation with all relevant interested parties. These might include the following:  
1) the fire engineer designer; fire servicing companies, fire consultants  
2) the user or purchaser;  
3) the supplier of the system;  
4) consultants (including architects, fire enginee r, fire servicing companies, fire consultants  
d) Before an order is placed for the system, the responsibility for each of the following stages  should be 
clearly defined and documented:  
1) system design;  
2) installation,  
3) commissioning.  
One of these stages should in clude the provision of a zone plan [ see 23.2. 2e)]. 
e) Where a fire detection and fire alarm system is to be integrated with a voice alarm system, one  
installing company should take responsibility for the interface connections and all necessary  
communications  between the fire detection and fire alarm system and the voice alarm system.  
f) Where a fire detection and fire alarm system is to be interfaced with another system or  facility (such 
as a fire extinguishing system, smoke control system or lift grounding faci lity and  HVAC) that is the 
responsibility of an installing organization of the fire detection and fire alarm  system, the  responsibility 
of each organization should be clearly defined and documented.  BOS 813 -1:2023  
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12 7  Variations from the recommendations of this standard  
7.1 Com mentary  
This standard  is code of practice and, as such, its contents take the form of  recommendations. The 
recommendations are primarily  based on recognized good  practice in the design,  installation, commissioning 
and maintenance off ire detection and fire  alarm systems. Accordingly, they  are likely to be suitable for the 
majority of normal applications.  
There are, however, applications in which the recommendations are unsuitable and would lead to  systems that 
would be unnecessarily expensive, incorporating  measures that could not be regarded as cost -effective, or 
that could be difficult install. In extreme cases, the recommendations might even be inadequate to provide the 
appropriate level of protection.  
In these circumstances, variations from the recommend ations might be necessary, even though, in  general, 
the user, purchaser, enforcing authority or insurer requires quite strict compliance with the  standard.  
This does not, however, imply that the fire engineer designer or installing company has freedom to  ignore the 
recommendations of this standard under circumstances in which a user, purchaser, enforcing  authority or  
insurer seeks compliance with it. Variations always need to be the subject of specific  agreement amongst    all 
interested parties and need to be clearly identified in all relevant system  documentation.  
Some variations can arise from a fire risk assessment, in which it is determined, for example, that an  area of 
the building might be unprotected by automatic fire detection, albeit that, in the ca tegory of  system  otherwise 
deemed necessary, protection is mandatory. Other variations might be  based on the  engineering judgment of 
a competent person, who might, for example, consider that the  extent of protection  disabled in the event of a 
single cable fault can slightly exceed the limitations  recommended in this standard, without any significant 
decrease in the integrity of the system.  
It also needs to be borne in mind that, while it is necessary for certain limitations or performance levels  
recommended  in this standard to be quantified, so that the relevant recommendations are expressed  
numerically, the values quoted are often arbitrary. The values are often based on well -established  and proven 
custom and practice, or on the judgment of experts. While t hey are, therefore, generally  applicable, rigid 
adherence to them might not be appropriate in every case, nor is it the case that minor  variations need 
necessarily have any significant effect.  
Examples of arbitrary values include, but are not restricted to , the following:  
• maximum zone size;  
• maximum area of protection disabled in the event of specified fault conditions;  
• maximum size of open areas in public buildings above which duplication of sounder circuits is 
recommended;  
• maximum travel distance to the ne arest manual call point;  
• maximum area of coverage of an automatic fire detector;  
• minimum sound pressure levels;  
• minimum duration of standby power supplies; and  
• performance parameters for standard and enhanced fire -resisting cables, and restrictions on the use of 
the former type of cable.  
Thus, for example, although this standard recommends that no one be required to travel further than  23 m to 
reach the nearest manual call point.  
7.2  Recommendations  
The following recommendations are applicable : 
a) Any variations from the recommendations o f this standard  incorporated within a  specification or design 
proposal should be clearly identified so that they are obvious to any party  from whom approval of the 
specification or design proposal might be sought, such as the user ; purchaser; enforcing authority or 
insurer.  
b) Any variations from the recommendations of this standard  identified or proposed during  installation or 
commissioning, but not clearly identified in the documented design, should be  documented (other  than  
in the  case of errors or "snags" for which rectification is proposed), for  subsequent approval.  BOS 813 -1:2023  
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13 NOTE This recommendation is not intended to imply that it is the responsibility of the installing company to  verify 
or certificate conformity of the system design wit h this standard. However, if variations are identified by  an 
installing  company particularly variations related to circumstances that might not have been known to the  designer 
( e.g. structural features of the building that affect detector number or siting , or conditions in the  building that might 
result in an unacceptably high rate of  false alarms), they ought to be documented for  referral to the designer, user 
or purchaser for agreement or action.  
c) All variations, whether of the type described in a) or b),  should be agreed amongst the interested  
parties (see Clause 6).  
d) All variations should be listed in the relevant system certificate (see Clause 41).  
e) Major non -compliances (see 46.2) that are agreed variations should be clearly recorded in the  logbook 
so th at they are readily available for future reference by servicing companies and any  other  interested 
parties.  BOS 813 -1:2023  
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14 Section 2: Design considerations  
8  Relationship between system category and protected areas  
8.1 Commentary  
8.1.1  General  
Before fundamental system design  can b egin, it is essential that the system category is defined, as this  governs 
the areas in which the manual call points and any automatic fire detectors are to be installed,  along with other 
design parameters. The areas that are to be protected are those whic h enable  the objective of the system to 
be satisfied (see 5.1).  
 
System category is simply a shorthand means of describing whether the system is manual or automatic,  and, 
in the case of automatic systems, the object of the automatic fire detection  and fire  alarm system.  The 
appropriate extent of automatic fire detection is normally determined by a fire risk assessment,  rather than a 
rigid application of system category to every building of a specific type or occupancy.  
8.1.2  Protection of life  
If the objective of  the system is to protect the occupants off building in which no one sleeps, and fire  is likely 
to be detected by people before smoke serious ly reduces visibility in escape routes, automatic  fire detection 
might not be necessary: a Category M system might suffice. Whether there is a need for  automatic fire 
detection and, if so, the extent to which  it needs to be provided is often determined by a  fire risk assessment 
carried out on behalf of the user; such a fire risk assessment is mandatory in this  standard  (see4.2 a .) 
If there is significant probability that a fire in the building, or part of the building, could threaten escape  by 
occupants before it is detected by people in the building, a Category M system is unlikely  to be adequate, and 
the provision of automatic fire detection will be necessary. This could arise from the  likelihood of the presence 
of occupants at special risk (including sleeping occupants), inadequate  structural fire protection or the 
probability of very rapid -fire development . 
In some buildings,  a fire risk assessment might determine that unacceptable risk to occupants can be  reduced 
by the installation  of fire detectors in all rooms or areas in the building.  
If there is a need for a reliable means of warning of the presence of smoke in escape routes, a Category  L4 
system, in -which  smoke detectors are installed in escape routes, such as corridors and stairways,  might be 
appropriate. For example, this can arise from the presence of lone workers in a large, generally  unoccupied 
area of a bu ilding in which the fire hazard level is assessed to be relatively high.  
In buildings in which people sleep within rooms accessed by corridors, other than short lengths of  corridor, 
research has shown that passage of hot fire gases through a door crack can  produce smoke  sufficiently dense 
and cool for a corridor to become smoke -logged before adequate warning can be  given by detectors in the 
corridor. In this case, a Category L3 system, in which detectors are installed in  rooms that open onto the 
escape rout es, as well as within the escape routes themselves, is likely  to be appropriate. The purpose of the 
detectors in these rooms is to give an early enough warning to  occupants, other than,  possibly, the person in 
the room of  fire origin, such that they have a dequate time  to escape before their escape route is impassable 
as a result of smoke. Accordingly, within the rooms,  the use of one or more of the following types of detectors 
is satisfactory: heat, smoke, combustion gas or  multi -sensor detectors.  
In some c ircumstances, even a Category L3 system might not be sufficient to achieve the life safety  objective. 
A fire risk assessment might determine that, in addition to the protection afforded by a  Category L3 system, 
fire detectors need to be installed in rooms or areas that would not be protected in  a Category L3 system. The 
resulting system would then be a Category L2 system. A Category L2 system  would be  appropriate if a risk 
assessment determines that the fire risk associated with rooms other than  those openi ng onto escape routes 
is unacceptable. Alternatively, there might be a need to give enhanced  early warning to occupants of certain 
rooms, such as disabled people, of a fire in their own room. In this  case, smoke or  combustion gas detectors 
within the rooms  in question are necessary; heat detectors will  not respond quickly enough.  
The highest possible enhancement of life safety is provided by a Category L1 system. In a Category L1 system, 
all areas of the building are protected by automatic fire detectors. l n rooms or areas in which  there is a need  
for automatic detection of  fire in order to protect the occupants of these rooms or  areas, smoke or  combustion 
gas detectors need to be provided. In other rooms, heat detectors might be  acceptable. An L 1 system mig ht 
be appropriate in buildings in which there is a significant number of  occupants at special risk in the event of  
fire (e.g. hospitals and certain residential care premises), or in  which, throughout the building, structural fire 
precautions are not of as high standard as normally specified for buildings of that type.  BOS 813 -1:2023  
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15 A Category M system, in which there is no automatic fire detection and fire alarm system, is only likely  to 
sufficient  if no one sleeps  in the building and fire is likely to be detected by peo ple before smoke seriously 
reduces visibility in the escape routes.  
8.1.3  Protection of property  
If the objective of the system is property protection, there needs to be sufficient provision of automatic  fire 
detectors to ensure that fire is detected at an early  stage, that an effective warning is given in time  for 
firefighters to take action before unacceptable damage to property occurs and that an indication of  the location 
of the fire is given to those responding to the alarm signal .  The value of the system d epends  on a combination 
of the speed of  detection, the delay before firefighters are summoned, the attendance  time of trained  
firefighters, and the probable rate of  fire spread. If the attendance time of the fire  and rescue service (whether 
private or loca l authority) is incompatible with the probable rate of  fire spread, adequate property protection 
might not be achieved purely by automatic fire detection, even if  a Category P 1 system is installed . The system 
might, however, form one component of a "packag e" of fire protection measures, such  as compartmentation 
(to limit the extent of  fire spread prior to the arrival  of the fire and rescue service) or an automatic fire 
suppression system (to control or extinguish the fire  prior to the arrival of the fire an d rescue service).  
The highest  standard of property protection is provided by a Category P1 system. ln a Category P 1 system, 
automatic fire detectors are installed in all areas of the building ng. This category of syste m might  be appropriate 
if the system i s intended to satisfy the requirements off ire insurers, if the building or its  contents are of high 
value, or if the facilities provided within the building are critical to the operations of  an organization.  
A lower, but often adequate, standard of proper ty protection is provided by a Category P2 system. In  a 
Category P2 system, automatic fire detectors are provided only in specified rooms or areas of the  building . 
The protected areas are usually those in which the fire hazard level is high, or from which  there is significant 
potential for fire to spread and cause damage to contents of high value. Since the  determination of these  
factors depends on a fire risk assessment, it is important that whoever specifies a Category P2 system qualifies 
this description  with details of the rooms or areas that are to be protected.  
8.2 Recommendations  
The following recommendations are applicable : 
a) System documentation, including any purchase specification, tender document design  proposal,  
submission to enforcing authorities or insurers for approval and the certificate  issued by the designers 
(see Clause  41), should clearly identify the system category as well  as, where  appropriate, the areas 
to be protected and any specific proposals for the type(s ) of detector to be used.  
b) Any s pecification or proposal for a Category L 5 system should clearly identify the rooms or areas  that 
are to be protected by automatic fire detectors.  
NOTE 1 There might also be benefit in giving  a simple description of the objective of the protection proposed , 
particularly in submissions to enforcing authorities.  
NOTE 2 The standard of protection (extent ofc overage) of a Category L5 system might be lower or higher than 
that afforded by Category L2, L3 or L4 systems.  
c) In Category L3 and L4 systems, smoke detect ors, multi -sensor detectors conforming to the fire  
sensitivity requirements of BS EN 54 -7 or a mixture of smoke and combustion gas detectors,  should 
be provided in the following:  
1) all escape stairways;  
2) all corridors; and  
3) any other areas that form part of th e common e scape routes.  
NOTE 3 Main access and egress stairways normally form part of escape routes, and ought to be treated as  
escape stairways . 
d) In Category L3 systems, heat, smoke, combustion gas or multi -sensor detectors should be  installed 
in all rooms  that open onto the escape routes described in c), except that rooms  opening onto corridors 
of less than 4 m in length need not be protected, provided fire  resisting  construction  including, doors , 
separates these corridors from any other section of the  escape routes.  
NOTE 4 For recommendations on the siting of these detectors, see 22.3e ). 
NOTE 5  An open-plan area of accommodation, in which occupants quickly become aware of  fire, need not be  
protected in a Category L3 or L4 system, even though occupants with in the area clearly need to pass through  the 
area in the first stage of escape, unless it forms part of the escape route from other areas. However, in a  Category BOS 813 -1:2023  
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16 L3 system a heat, smoke, combustion gas detector or multi -sensor detector ought to be installe d on the 
accommodation side of any door that opens into an escape stairway, a corridor of more than 4 m in  length or, 
alternatively, where stairways are approached through low fire risk lobbies, any door that opens  onto the lobby.  
e)  In a Category L2 system,  the rooms or areas protected should conform to the recommendations  in c) 
and d) for a Category L3 system, but, in addition, automatic fire detectors should  be installed in rooms 
in which the fire risk (see 3 .25) is high enough to warrant  individual protec tion. 
NOTE 6 Any reference to a Category L2 system (e.g. in a specification, proposal or submission to an enforcing 
authority needs to clearly identify the rooms or areas in which these additional detectors are to be installed and 
identify the type of dete ctor (e .g. heat, smoke or combustion gas) required.  
NOTE 7 The first step in designing a Category L2 system Is to design a Category L3 system. Thereafter a decision 
is taken as to which unprotected rooms or spaces warrant further detection, or the detector  type or siting needs 
to be modified.  
f)  In a Category L1 or P1 system, automatic fire detectors should be installed in all rooms and areas of 
the building, but the following rooms or areas need not be protected if they are of low fire risk (see 
3.33):  
1) toilets, shower rooms and bathrooms;  
NOTE 8 In some public buildings, such as hospitals and shopping centres, toilets might not be of low fire risk, 
owing to the potential for malicious ignition.  
2) stairway lobbies and toilet lobbies;  
3) small cupboards (typically, less than 1 m2); and 
NOTE 9 A riser in which there is a fire -resisting floor and ceiling may be treated as a cupboard.  
NOTE 10 If detection can be excluded from any room or area in a Category Lt system, it can also be excluded 
from such rooms or areas in a  Category L2, L3 or L4 system.  
4)  some shallow voids (less than 800 mm in depth) [see 22.2d)].  
g) In a Category L 1 system, the detectors within escape routes should be smoke detectors, multi -sensor  
detectors conforming to the fire sensitivity requirements of BS  EN 54 -7 or a mixture of  smoke and 
combustion gas detectors.  
NOTE 11 Some smoke and multi -sensor detectors can be programmed such that they would not then 
meet the fire sensitivity tests of BS EN 54 -7; in that operating mode, the detectors would not satisf y 
the recommendations of 8.2c) and g).  
h)  In a Category P2 system, the rooms or areas to be protected by automatic fire detectors should  be 
clearly identified in the specification or proposal. There should  be physical barriers between  protected 
and unprotect ed areas to limit the spread of smoke and hot gases in, at least, the early  stages of fire.  
NOTE 12 It is not necessarily the case that these physical barriers have a recognized period of fire resistance.  
NOTE 13 The physical barriers described in h) might  be unnecessary where detectors are installed to detect fires 
in specific equipment.  
9 Actuation of other fire protection systems or safety facilities  
9.1  Commentary  
Any of the system categories defined in 5.1 may be used to actuate other fire protection syst ems or trigger 
safety facilities, whether for the purpose of life safety, property protection or a  combination of the two.  
If the system is to be used for the actuation of other fire protection systems or safety facilities,  the, 
recommendations  of this standard  might, or might not, be necessary or sufficient . The system might have 
special requirements in respect of the number, zoning and siting of detectors,  provision of power supplies, 
control, indication or other facilities, or monitoring and fire resista nce of  interconnecting wiring.  
It needs to be ensured that the interconnection of other systems or equipment with the fire detection and  fire 
alarm system does not prejudice the reliability of the fire detection and fire alarm system.  
9.2  Recommendations  
The following recommendations are applicable in the case of systems intended to actuate other  fire protection 
systems or safety facilities (e.g. by triggering an automatic fire extinguishing system,  closing fire -resisting 
doors, shutting down an air handling s ystem or grounding lifts).  
a) The system should conform to the recommendations of any applicable part of BS 7273.  BOS 813 -1:2023  
Edition 1.0 
17 b) if no part of BS 7273 is applicable, any special requirements for system design should be  identified in 
the purchase specification or design prop osals.  
c) if operation of the fire detection and fire alarm system during routine testing would have an  undesirable 
effect on other systems or equipment, means should be provided for disabling the  automatic actuation 
of the system or equipment. The facility f or disablement, and the indication  of disablement, should 
conform to BS EN 54 -2. 
d) The other equipment or systems should not draw power from the fire detection and fire alarm  system 
in the non -fire state, other than for indicators and interface devices (e.g.  relays).  The power 
consumption of any such indicators and interface devices should be taken into account in  the 
calculation of battery capacity (see 25.4). 
10 Systems ln explosive gas or dust atmospheres  
10.1 Commentary  
If it is necessary to install fire alarm eq uipment or wiring in are  as where an explosive atmosphere could  result 
from the presence of  flammable gases, vapours or mists, or the presence of combustible dusts,  special 
protection measures are essential to ensure that the potential/or ignition of the a tmosphere by  the fire alarm 
equipment or wiring is minimized.  
10.2 Recommendations  
The following recommendations are applicable.  
a)  Any system (or part of a system) protecting an area, or with cables passing through an area,  in which 
there might be an explosive g as, vapour or mist atmosphere should conform to  BS EN 60079 -14. 
b) Any system (or part of a system) protecting an area, or with cables passing through an area, in  which 
there might be an explosive dust atmosphere should conform to BS EN 60079 -14 and  BS EN 600 79-
17. 
11  System components  
11.1 Commentary  
The reliability of the system to perform its functions on demand is, to a significant degree, governed by  the 
reliability of individual components. Components , such as manual call points, detectors, CIE and  fire alarm 
devices, are required to  conform to relevant standards, and need to have undergone type testing to these  
standards. It is advisable to use components having certification under a recognized product  certification 
scheme [comprisi.ng third -party certification  of product conformity against a relevant  standard, based on 
testing and continuing surveillance, together with assessment of the manufacturer's  quality assurance systems 
against BOS ISO 900 1). 
Where there is no relevant Botswana or international Standard,  it is advisable that care is taken to  ensure, as 
far as possible, that the components are fit for their purpose. Third -party approval against an  appropriate test 
standard can provide assurance of this.  
Conformity of an individual component to a recognized  standard does not necessarily ensure that it will  operate 
satisfactorily in conjunction with another component that conforms to the relevant standard  for that  component 
It is essential that compatibility between components is taken into account by the  designer of the system. BS 
EN 54 -13 can be used to confirm system compatibility.  
11.2  Recommendations  
The following recommendations are applicable.  
a)  Manual call points should conform to the requirements of BS EN 54 -11 for Type A ("single  action")  
manual call poin ts. 
NOTE 1 This standard  recommends that a protective cover is fitted to a type A manual call  point, see 20.2b ). 
b)  Point heat detectors should conform to the requirements of BS EN 54 -5 for Class A 1or A2  detectors, 
unless the foreseeable maximum ambient temp erature in the protected area is  40 °C or above, in  
which case a Class B -G detector should be used as appropriate (see section  3 of this standard).  
c) Point smoke detectors should conform to BS EN 54 -7. 
d) Flame detectors should conform to BS EN 54 -10. BOS 813 -1:2023  
Edition 1.0 
18 e) Optical b eam smoke detectors should conform to BS EN 54 -12. 
f) Aspirating smoke detectors should conform to BS EN 54 -20. 
g) Components and systems using radio links should conform to BS EN 54 -25. 
h) Multi -sensor, optical and heat detectors should conform to either:  
1) ISO 7240 -15; 
2) BS EN 54-29; or 
3) BS EN 54-5 and BS EN 54 -7. 
i) Multi -sensor, carbon monoxide and heat detectors should conform to ISO 7240 -8 or BS EN 54 -30. 
j) Multi -sensor detectors combining smoke, carbon dioxide and heat sensors should conform to BS  EN 
54-31. 
k) If there is  a facility in a multi -sensor detector to disable sensors leaving a single active sensor, the  
multi -sensor detector should also meet the performance requirements of the appropriate part of  BS 
EN 54 relevant to that single active sensor.  
l) Carbon monoxide fir e detectors should conform to BS EN 54 -26. 
m) ClE should conform to BS EN 54 -2. 
NOTE 2  BS EN  54-2 contains optional performance characteristics which are not necessarily provided in  all 
CIE, even if third -party certificated against BS EN 54 -2. It needs to be  ensured that the CIE provided has  
appropriate facilities to enable conformity to all the recommendations of this Botswana Standard and the  project 
specification.  
n) Audible fire alarm devices should conform to BS EN 54 -3. 
o)  Visual alarm devices should conform  to BS EN 54 -23. 
NOTE 3  Wireless audible and visual alarm devices are outside the scope of BS EN 54 -3 and BS EN 54 -23 
respectively, but this does not preclude their use in a system that conforms to this standard , provided the  devices 
satisfy the relevant performance requirements of these standards.  
p) Power supply equipment should conform to BS EN 54 -4. 
q) Cables should conform to the recommendations of Clause 26.  
r) Those functions of the system that are recommended in this standard , for which the  storage of 
progr ams and data are necessary to control the fire detection and fire alarm system,  should  conform 
to the additional design requirements for software -controlled  CIE in BS EN 54 -2. 
s) Where a PC or similar IT equipment is used as a user interface, e.g. in networke d systems, it  should 
be considered as a supplementary interface and there should be CIE conforming to  BS EN 54 -2 
mounted nearby, as it is unlikely that a PC would conform to BS EN 54 -2. 
t)  Radiopaging transmitters and receiver s should conform to the relevan t Botswana or  harmonized 
European Standards applicable.  
u)  Alarm transmission and fault warning routing equipment should conform to the product  requirements 
(but not the installation requirements) specified in BS EN 54 -21. 
NOTE 4 Some elements of a) to  r) ma y be combined to form a single device  
12  Monitoring, integrity and reliability of circuits external to control equipment  
12.1 Commentary  
External circuits need to be arranged such that the probability of faults that could prevent the system  from 
giving a fire war ning is minimized. However, such faults occur occasionally. Work on the system, for  the 
purpose of modification, repair or routine attention, can a lso cause an impairment of the system to  operate as 
designed in the event of fire . 
Measures are incorporated within this standard to limit the probability of impairments, whether as  a result of 
faults or work on the system, and to limit the duration of any impairment. The wiring of  all critical signal paths 
is protected against mechanical damage and damage by fir e. Critical signal  paths are monitored, so that faults 
are identified quickly. Compliance to maintenance these systems  shall ensures that any such fault is quickly 
repaired. The probability that a  fault would exist at the time of a fire is, therefore, cons idered to be extreme ly BOS 813 -1:2023  
Edition 1.0 
19 low. In the event of  fire, fire damage to wiring during the period required for evacuation is unlikely to occur in 
view of the  recommendations of this standard for the fire resistance of cables . 
As a result of the above consideration s, duplication of, or redundancy in, external circuits is not normally  
necessary. However, in the case of circuits serving fire alarm devices, special measures need to be  taken to 
ensure that, during, or following, evacuation, damage to any wiring, with re sultant loss of the  evacuation signal, 
does not imply to occupants of the building that it is safe to remain in, or reoccupy,  the building.  
This can achieved by ensuring that, in the event of a short circuit developing on any fire alarm device  circuit 
during a fire (e .g. at a cable termination), a minimum of one audible  fire alarm device continues  to sound as a 
reminder that the system has not been silenced or reset. Normally, this sounder is located  close to the CIE as 
this equipment is sited in a suitabl e area (e.g. a reception area, security control room  or main entrance foyer) 
at which the reminder needs to be given.  
Note that duplication of sounder circuits throughout a building is not generally necessary and can even  fail to 
achieve the objective outl ined above. In this case, if fire damages one circuit, it is also likely to  damage any 
other circuit in the same area. However, in a large building with multiple sounder circuits,  each serving a 
different area of the building, the above objective is satisf ied. In a smaller building, which  could be served by 
a single sounder circuit, additional measures are necessary to ensure that, if this single circuit fails during a 
fire, at least one sounder (e.g. on a second circuit) continues to operate.  
However, in b uildings designed to accommodate the general public in large numbers, typically within  a single 
space, the threat to life in the event of a fire might be such that additional fire alarm device  circuits, over and 
above those described above, is justified; t his then addresses the remote possibility of  failure or impairment of 
a single circuit serving a large public space at the time of a fire. Frequently,  such buildings are served by a 
voice alarm system. In the case of such systems, BS 5839 -8 recommends  additional loudspeaker circuits in 
large, uncompartmented  public spaces of public buildings such as  transport terminals, shopping malls, places 
of entertainment, large department stores and leisure  centres. The size of the uncompartmented  public space 
above wh ich additional loudspeaker circuits  are recommended by BS 5839 -8 is entirely arbitrary but, for 
consistency, if such a large public space is  protected by audible fire alarm devices, duplicated and evenly 
distributed fire alarm device circuits  need to be in stalled within the space. Such duplication is, however, not 
necessary in other parts of  the building.  
System design needs to be arranged to limit the extent of impairments, whether as a result of faults or  work  
on the system. A fault but not fire  signal  needs to be given at the CIE in the event of any failure in  the critical 
signal path (see 3.14).  
Care needs to be taken in the use of multicore cable for the wiring of more than one circuit. It needs to be  
assumed that any fault that affects a multi core cab le affects all conductors of the cable; this precludes  the use 
of multicore cable for certain applications in which the failure of more than one circuit as a  result of a single 
fault is precluded by the recommendations of this standard.  
12.2 Recommendations  
12.2.1  Fault monitoring  
The following recommendations are applicable.  
a) A fault indication should be given at the CIE within 100 s of the occurrence of any of the  following 
conditions:  
1)  short circuit or open circuit in any circuits servicing manual  call points or fire  detectors;  
2) the removal of a manual call point or a fire detector that is designed to be detachable;  
3) short circuit or open circuit of any circuits serving fire alarm devices;  
4) short circuit or open circuit of any wiring between any power supply that is in a  separate  
enclosure and the equipment to which it supplies power;  
5) any earth fault that is capable  of preventing the system from performing in accordance with  the 
recommendations this  standard  
6) the rupture of any fuse, or the operation of any other protectiv e device, that affects the  ability of 
the system to perform as recommended i n this this standard ; 
7) a short circuit or open circuit in the wiring between separate control and/or indicating  equipment 
that is provided in order to satisfy the recommendations o f this standard  
8)  a short circuit or open circuit in the wiring between  main and any repeat control and/or  indicating 
equipment (such as a mimic diagram) that is provided in order to satisfy the  recommendations of BOS 813 -1:2023  
Edition 1.0 
20 this standard  
9) a short circuit or open circu it in the wiring between control equipment and any separate  
enclosure of equipment used for transmission of alarm signals to an ARC [ see 15. 2l); 
10) removal from its circuit of a fire alarm device that is designed to be detachable.  
b) A fault indication should b e given, within the times indicated below, in the event of any of  the 
following:  
1) failure of the main power supply to any part of the system (within 30 min of occurrence);  
2) failure of the standby power supply (within 15 min of occurrence);  
3) failure  of the bat tery charger (within 30 min of occurrence);  
4) reduction  of the battery voltage to  less than the voltage specified in BS EN 54 -4 at which a  fault 
warning should be given (within 30 min of occurrence).  
c) Visual indications of the faults identified in a)3) and a) 9) should continue to be given at the  CIE 
during a fire alarm condition. Other fault indications may be suppressed during the fire  alarm 
condition . 
NOTE The recommendations of a), b) and c) can be satisfied by the use of CIE and power supply equipment  
conforming to BS EN 54 -2 and BS EN 54 -4, respectively, provided the system installation complies with the  
recommendations of the manufacturer, on which conformity with BS EN 54 -2 and BS EN 54·4 might be reliant,  
d) Where any standby power supply comprises a numbe r of batteries connected in parallel, a fault  
indication should be given in the event of disconnection of any one battery (within 15 min of  
occurrence).  
e) If the system incorporates a separate voice alarm system or fire warning system for people  who are 
Deaf  and hard of hearing. any short circuit or disconnection of the communicating link  between the fire 
detection and fire alarm system and the other system , should be indicated at the  fire detection and fire 
alarm system CIE within 100 s.  
f) If the system is use d to actuate other fire protection systems or safety facilities (see  reference should 
be made to BS 72 73 (all parts) or other applicable codes of practice  for recommendations on 
monitoring connections between the fire detection and fire alarm  system and th e other systems or 
equipment . 
g) Where tactile fire alarm devices provided for people who are Deaf and hard of hearing are  installed, 
the system should conform to Annex C and indicate the failure to receive a monitoring  signal correctly 
[see 18.2.lb)].  
12.2.2  System  integrity  
The following recommendations are applicable.  
a) A fault on one circuit containing manual call points, fire detectors or fire alarm devices, or a  combination 
of them, should not affect any other circuit.  
b) A single short circuit or open circuit fault  on an automatic fire detector circuit should neither  disable 
protection within an area of more than 2 000 m2, nor on more than one floor of the  building plus a 
maximum of five devices (automatic detection, manual call points, sounders or a  combination of these) 
on the floor immediately above and five devices on the floor immediately  below that floor.  
c) Two simultaneous faults on a manual call point or fire detector circuit should not disable  protection 
within an area greater than 10 000 m2 
NOTE 1 The areas q uoted in b) and c) are relatively arbitrary; in the case of  b), the  recommendation is based  on 
custom and practice in non -addressable fire detection and fire alarm systems over many years. Engineering  
judgement might determine that, in a given system, mino r increases in the areas quoted do not significantly  
impede the system integrity, but this ought then to be regarded as a variation from the recommendations of  this 
standard.  
d) For software -controlled  CIE that has more than 512 detectors and/or manual call p oints  connected, 
reference should be made to the manufacturer's instructions regarding the means by  which conformity 
with BS EN 54 -2 is to be achieved.  
e) Where detectors are designed to be detachable from their bases for the purpose of routine  
maintenance of  the system:  
1) removal of any detector(s) from the circuit should not affect the operation of any manual  call point 
regardless of whether locking devices are used to secure the detectors within  their bases;  BOS 813 -1:2023  
Edition 1.0 
21 NOTE 2 This recommendation applies even if all fire  detectors in the system are removed from circuit.  
2) during the design stage, the possibility of malicious removal of detectors should be taken  into 
account If malicious removal is considered likely, detectors of a type that can be  removed only by 
the use of  a special tool or special technique should be used.  
NOTE 3 A special tool in this context is a tool not likely to be carried by a member of the general  public.  Slot-
headed screws would not be acceptable, since various articles can be used as screwdrivers.  
f) Any facility specifically provided for deliberate disablement of manual call point or detector  circuits 
should be such that it is possible to disable  protection throughout one zone of the system  without 
disabling protection in other zones. Use of such fac ilities should not prevent evacuation  of the building 
by use of an evacuate control on, or close to, the CIE.  
g)  Removal of any manual call point or detector from its circuit should not - affect the ability of any  fire 
alarm device to respond to an alarm sign al other than in the case of fire alarm devices and  detectors 
that are combined at a single fixing position.  
h) Fire alarm devices should be capable of being removed only  by the use of a special tool.  
i) In the event of a single open circuit or short circuit fau lt on any circuit that serves fire alarm  sounders, 
at least one single fire alarm sounder, normally located in the vicinity of the ClE,  should still sound 
correctly if a fire alarm condition occurs anywhere within the building. This  fire alarm sounder shou ld 
have an identical sound to the general fire alarm sounders in the  building [see also 15.2c)].  
NOTE 4 It is possible to comply wit h this recommendation by at least the following  two arrangements although 
are not precluded:  
• wiring all fire alarm sounders within the building on a single  sounder circuit, with the additional provision  of a 
second, independent sounder r circuit, to which only a  single sounder, located in the vicinity of the CIE is  
connected {see Figure  1a)]; 
• wiring al/fire alarm sounders on a r ing circuit capable of transmitting signals in either direction; the first (or  
last) three devices  on the circuit would then comprise a short circuit isolator, capable of isolating the circuit 
in the event of detection of a short circuit, a sounder and a f urther short circuit isolator {see Figure 2 b)]. 
NOTE  5 The sounder that continues to operate normally comprises one of the general alarm sounders in  the area 
in which the CIE is housed. In a building without phased evacuation, the alarm sounder gives an  "Evacuate" signal 
until silenced. In a building with multiphase evacuation, the sounder may give an "Evacuate"  signal  or "Alert" 
signal until silenced, according to the location(s) from which the fire alarm signal originates  and the phase of the 
evacuation at the time in question.  
j) In buildings designed to accommodate the general public in large numbers (e.g. transport  terminals, 
shopping centres, places of public entertainment, department stores and leisure  centres), at least two 
sounder circuits should be p rovided in every uncompartmented  public  space if the space is either:  
1) greater than 4 000 m2 in area; or  
2) is designed to accommodate more than 500 members of the public.  
This should be achieved either:  
i) by means of at least two sounder circuits, which are eve nly distributed and interleaved  such that 
adjacent sounders are on different circuits; or  
ii) by means (e.g. a protected loop circuit) such that not more than 50% of sounders in  that area are 
lost in the event of a single open or short circuit fault.  
NOTE 6 Th e figures of 4 000 m2 and 500 members of the public are arbitrary , but are the criteria for  duplication 
of loudspeaker circuits of voice alarm systems conforming to BS 5839 -8. Engineering judgement  might determine 
that, in a given system, a single sounder circuit can be used to protect a public space that  slightly exceeds these 
criteria without undue increase in risk to occupants. This would then be regarded as a  variation  from the 
recommendations of this standard.  
NOTE 7 It is not intended that this recomm endation would be applied to small cellular spaces or non -public  areas 
of the buildings in question,  
k) Where two (or more) sounder circuits are necessary in order to satisfy the recommendations  of i) or 
j), the circuits should not be contained within a commo n cable sheath. For example, two  circuits 
intended to satisfy these recommendations should not be served by a common four core  cable, as this 
would not adequately protect against the simultaneous loss of both circuits.  
NOTE 8 This recommendation does not a pply to those sounder circuits that  need not be independent to  satisfy 
the recommendations of this standard (e.g. that are provided purely as a result of electrical engineering  
considerations).  BOS 813 -1:2023  
Edition 1.0 
22 l) If the CIE is supplied with power from power supply: equipment  contained in a separate  enclosure, the 
cables between the equipment should be duplicated such that a single open or  short circuit in the 
connections does not completely remove power from the ClE. The duplicate  cables should be 
separated by at least 300 mm  where practical.  
Where a power supply unit or a standby battery(ies) is housed in a separate enclosure from  the CIE,  
any cable between that enclosure and the CIE should be suitably protected against  overcurrent in 
accordance with BS 7671.  
NOTE 9 Where the  enclosure is located immediately adjacent to, and in contact with, the C IE, such that cables  
run directly between the enclosure and the ClE, the enclosure  need not be regarded as separate from the CIE;  
the recommendations of 12.2.2 l) do not then apply.  
 
Figur e 1a ― Radial Sounder Circuit  
BOS 813 -1:2023  
Edition 1.0 
23  
13 Detection zones  
13.1 Commentary  
In order to direct those responding to  a fire alarm signal particularly the fire and rescue service , to the area  of 
a fire, all buildings, other than very small buildings, need to be divided into detection zones  {see 3.16). 
Detection zones need to be small enough for a fire to be located quickly.  
Even if the system is addressable {see 3.1),  detection zone indication needs to be provided, as this  often 
provides a quicker, albeit less specific, indication of the location of a fir e than typical addressable  text displays. 
Zone indicators also provide a simple "at a glance" overview of the extent of  fire or  smoke spread.  
If the alarm is raised by a manual call point, as opposed to an automatic detector, detection zone  indication 
migh t be misleading; on discovery of a fire a person might operate a manual call point that is  a considerable 
distance from the fire. The benefits of zoning in a Category M system are, therefore, less  significant.  
If a detector is concealed in a relatively ina ccessible area (such as a floor or ceiling void), it is normally  desirable 
to provide a remote indication of its operation. In an addressable system, the provision of an  individual remote 
indicator might not be necessary provided that the location of each fire detector is  clearly indicated at the CIE.  
Figure 1 b ― Ring Sounder Circuit  
BOS 813 -1:2023  
Edition 1.0 
24 13.2 Recommendations  
13.2.1  Recommendations applicable to all detection zones  
The following recommendations are applicable.  
a) If manual call points are located on the landings of an enclosed stairway [ see 20.2d ), the manual  call 
point on each level, other than a final exit level from the stairway, should be incorporated  within the 
zone that serves the adjacent accommodation on that level. A manual call point  located within  the 
stairwell at a final exit to open air may be inc orporated within the detection  zone serving the stairwell l 
[see 13.2.3c)].  
b) If the total floor area of the building is greater than 300 m2 each zone should be restricted to a  single 
storey.  
c) If the total floor area of the building is less than 300 m2 a zone  may cover more than a  single storey.  
d) For voids above or below the floor area of a room, these may be included  within the same zone of  the 
room, provided that the voids and the room constitute a single fire compartment.  
13.2.2  Additional recommendations applicabl e to detection  zones that  contain only  manual call  points  
The floor area of a single zone should not exceed 2 000 m2 other than in the case of a zone  comprising  mainly 
a single, open -plan area (e.g. an compartmented  warehouse), which should not  exceed 10 0 00 m2 in area.  
13.2.3  Additional recommendations applicable to detection zones that contain non -addressable  
automatic fire detectors  
The following recommendations are applicable : 
a) The floor area of a single zone  should not exceed 2 000 m 
b) The search distance (see 3 .5.2.) should not exceed 60 m.  
NOTE 1 Having entered the zone, the person responding to the alarm signa  need not reach the seat of the  fire 
within the recommended search distance; it is only necessary to become aware of the location of the fire.  
NOTE 2 In measuring search distance, the worst case, in which the fire is located at the furthest concealed  area 
from any likely point of entry to the zone, ought to be considered (see Figure 2).  
c) Automatic fire detectors within any enclosed stairwell, lift well or o ther enclosed flue -like structure 
should be considered as a separate detection zone. Manual call points located at final  exits to open 
air from stairwells may be incorporated within these detection zones [but may,  alternatively, be  
incorporated within the detection zone described in 13.2. 1a)]. 
13.2.4  Additional recommendations applicable to detection zones containing addressable  automatic 
fire detectors  
The following recommendations are applicable.  
a) Zone indication should be given at the CIE even if addressable tex t information is also available  
b) The recommendations of .13.2.3. apply, except that 13.2.3b) does not apply if:  
1. clear addressable text display of the location of, at least, the first detector to respond to a  fire is 
available at the CIE, without manual inte rvention; and  
2. the display , if necessary in conjunction with other information on, or adjacent to, the CIE,  would 
enable firefighters, unfamiliar with the building, to proceed to the location of the fire.  
NOTE For example, the CIE might provide a text indic ation of room number, and a plan adjacent to the CIE  might 
show the location of the room . 
13.2.5  Remote indication of detector operation  
Any remote indicators should be clearly labelled to indicate their function. They should be sited and/  or labelled 
in such a w ay as to assist in determining the location of the detector that they serve.  
Any cable between a detector and a remote indicator required for conformity to this standard should conform 
to, and be installed in accordance with, the recommendations of 26.2 
NOTE Remote indicators might be required in a specification for areas such as inaccessible voids or locked rooms.  See 
also 40.2. for the as -fitted drawing.  BOS 813 -1:2023  
Edition 1.0 
25  
14 Alarm zones  
14.1 Commentary  
In many buildings, the evacuation strategy is very simple; on operation of a ny manual call point, or  detection 
of fire by an automatic fire detector, fire alarm sounders operate throughout the building to  indicate the need 
for evacuation of the entire building.  
In larger, more complex buildings, the "Evacuate" signal might, in the  first instance, be restricted in  extent (e.g. 
to a single floor, a limited number of floors or a limited area of the building). In other areas,  an "Alert" signal 
might be given to warn occupants of the alarm si9nal, without any requirement for  those occup ants to evacuate . 
In order to support such arrangements, it is necessary for the building  to be divided into a number  of individual 
alarm zones, such that the operating state of fire alarm sounders in any alarm one  is independent of the 
operating state of fire alarm sounders in all other alarm zones. The fire  alarm sounders in the building are thus 
grouped, so that, at any point in time, all alarm sounders  within any given alarm zone are in the same state 
(i.e. silent, giving an “Alert" signal or giving an  "Evacuate ” signal).  
The need for subdivision of a building into discrete alarm zones might arise for a number of  reasons, including:  
• the use of phased evacuation (see Clause 19);  
• to avoid unnecessary disruption when false alarms occur (see Section 3); and   
• any other circumstances in which a two -stage alarm arrangement applies,  
Since it is the case that, when occupants of one alarm zone are required to evacuate, occupants of one  or 
more alarm zones above, below or adjacent to that zone will be expected to re main in the building,  every alarm 
zone needs to be separated  from all other alarm zones by fire -resisting construction. (In  some complex public 
Figure 2 ― Examples of search distances in an open area [see 13.2.3b)]  BOS 813 -1:2023  
Edition 1.0 
26 buildings, such as shopping centres, alarm zones are designed to coincide with  smoke control zones, which 
are se parated from each other by smoke curtains, rather than fire -resisting  construction. However, in this case, 
the audible signal is normally given by a voice message, rather than  audible fire alarm devices.)  
As the subdivision of a building into alarm zones i mplies that, in the early stages of a fire, occupants in  certain  
areas will not b e expected to evacuate, the configuration of alarm zones might require approval  by the authority 
responsible  for the enforcement of fire safety legislation in the building  
14.2 Recommenda tions 
The following recommendations are applicable.  
a) The boundaries of every alarm zone (other than external walls) should comprise fire -resisting  
construction.  
b) The extent of any overlap of signals between alarm zones should not be sufficient to resu lt in confusion 
of occupants in any area of the building.  
c) A common signal should be used throughout all alarm zones to convey the need for evacuation,  and 
a (different) common signal should be used throughout all alarm zones for any alert signal  that can b e 
given by the system.  
d) While an alarm zone may incorporate more than one detection zone (but not vice versa), the  
boundaries of alarm zones should coincide with the boundaries of the relevant detection zones  (see 
Figure 3).  
e) The user or purchaser should ens ure that, where appropriate, the configuration of alarm zones is  
approved by the relevant enforcing authority or authorities.  
 BOS 813 -1:2023  
Edition 1.0 
27  
15 Communication with the fire and rescue service  
15.1 Commentary  
For a fire alarm and fire detection system to give the maximum benefi t, the fire and rescue service needs  to 
be summoned as quickly as possible on every occasion that it operates in the event of a fire, unless,  in order  
to avoid false alarms being passed to the fire and rescue service, filtering arrangements are  appropriate  (see 
35.2.7).  
In occupied buildings, the primary means for summoning the fire and rescue service needs to comprise  a call 
to the fire and rescue service by occupants, using the 997. This is the case even if there is a means  for 
automatic transmission of a larms to an ARC, as any  automatic system can fail at the time it is required to 
operate. It needs to be ensured that the fire alarm  sounders cannot interfere with any emergency call to the 
fire and rescue service.  
In the case of manual fire alarm systems, automatic transmission to an ARC is usually unnecessary.  When 
the building is unoccupied, the system does not respond to fire; when the building is  occupied,  the call to the 
fire and rescue service from occupants suffices. Automatic means for transmission is only likely to be of benefit, 
Figure 3―All Zones [see 14. 2d] BOS 813 -1:2023  
Edition 1.0 
28 as a secondary means of summoning the fire and rescue service, if factors  such as the size or complexity of 
the building, or low level of occupancy, could result in a significant  delay between discovery of fire and 
summonin g of the fire and rescue service, thereby warranting the  duplication of the call to the fire and rescue 
service (i.e. with calls made manually from the premises and  automatically via an ARC).  
Since the objective of a Category L system is evacuation of occu pants, rather than protection of property,  
manual summoning of the fire and rescue service by occupants might, again, suffice. However, if the  early 
attendance of the fire and rescue service is likely to be essential to life safety in the event of fire  (e.g. in 
hospitals and residential care homes), a secondary, automatic means of transmission might  be warranted, 
unless there are adequate arrangements to ensure that there is no delay at any time in  manual summoning of 
the fire and rescue service by occupant s. In practice, automatic transmission of  fire alarm signals is considered 
necessary in the case of residential care premises.  
Even in a Category L system, if the premises are unoccupied at certain times and the system incorporates  
automatic fire detection  throughout a significant proportion of the pre mise , it can represent a missed  
opportunity, in respect of property protection, if no means of automatic transmission of alarm signals  is 
provided.  
In a Category P system, unless the premises are continuously occupied at all times, the objective of  property 
protection is unlikely to be satisfied unless the system  incorporates means for automatic  transmission of alarm 
signals to an ARC. Even in a Category P2 system, unless the extent of the  automatic fire detect ion is minimal, 
in premises that are not continuously occupied, the absence of an  automatic means of transmission of fire 
signals to an ARC is likely to be false economy.  
In premises in multiple occupation, the responsibility for summoning the fire and res cue service on operation 
of the fire alarm system always needs to be clearly defined, particularly in the case of  Category L or Category 
P systems.   
If a Category L or Category P  system is installed in non -domestic premises in multiple occupation,  there mi ght 
be a need for automatic transmission of alarm signals to an ARC. The primary means of  summoning the fire 
and rescue service still needs, if practicable, to comprise a call to the fire and rescue  service from persons on 
the premises. However, in some pr emises in multiple occupation, the reliability  of this arrangement can be 
insufficient, and a secondary means of summoning the fire and rescue  service via an ARC might be warranted.  
The reliability of the means for summoning the fire and rescue service, wh ether by manual or  automatic means, 
always needs to be subject to consideration. Various methods of automatic alarm  transmission system to an 
ARC are available.  
Their performance, reliability and security  characteristics vary, depending upon the type of t echnology used. 
BS EN 50136 -1 defines ten  categories of alarm transmission system (ATS): SP1 to SP6 are based on a single 
alarm transmission  path. DP1 to DP4 add resilience by requiring a dual transmission path.  
Alarm transmission systems that incorporate reporting of an alarm transmission path (ATP} failure are 
preferred. The reporting time period varies with the ATS category selected (32 days to 90  seconds). BS EN 
50136 -1 shows these performance criteria together with alarm transmission times  and the ATS and ATP 
availability  in any 7 -day period.  
PD 6669 gives guidance that is additional to BS EN 50136 -1, with particular reference to dual path  alarm 
transmission systems.  
Regardless of whether the arrangement for summoning the fire and rescue service is manu al or automatic, 
the effect of  fire on the reliability of the arrangement needs to be considered (e.g. the effect  of fire on persons 
tasked with summoning the fire and rescue services and on communication lines  and equipment).  
If the services of a commerci ally operated ARC are used, it needs to be ensured that the alarm receiving  centre 
has a formal arrangement with the fire and rescue authority  in whose area the protected  premises are situated 
for rapid communication with the fire and rescue service by rel iable means.  
If provision is made for automatic transmission  of fire signals to an ARC, it is often quite simple to  arrange for 
fault signals on the fire alarm system to be transmitted as a separately identifiable signal;  this has the benefit 
of ensuring t hat faults on the fire alarm system receive attention when the premises  are unoccupied.  
It is now common practice for the transmission of  fire alarm signals to an ARC to be routed via the  alarm 
routing equipment of an intruder alarm system. Notwithstanding  that the mains power supplies,  cable types 
and cable routing for this alarm routing equipment might not necessarily conform to  the recommendations of 
this standard , this practice is regarded as acceptable and need not  be regarded as a variation f rom the 
recommendations of this standard. However, standby battery  capacity and any cable between the CIE and the 
alarm routing equipment needs  to conform to the  recommendations of this standard.  BOS 813 -1:2023  
Edition 1.0 
29 15.2 Recommendations  
The following recommendations are applicable : 
a) The use r should ensure that there are suitable arrangements for summoning the fire and rescue  
service when the fire detection and fire alarm system operates. The arrangements should be  such as 
to minimize the risk to any person responsible for summoning the fire and rescue  service. Systems 
that automatically transmit a pre -recorded message direct to the fire and rescue  service, via the public 
emergency  call system, should not be used.  
b) In occupied buildings, the primary means of summoning the fire and rescue servic e should  always 
comprise a call to the fire and rescue service by occupants, using the public emergency  call system.  
c) In any area specifically designated as that from which the fire and rescue service is to be  summoned 
in the event of fire, the fire alarm s ignal should not be so loud as to interfere with  telephone speech.  
NOTE 1 Cases have been reported in which the frequency of the alarm sounders has been such as to corrupt  
tone dialling systems, leading to failure of the emergency call.  
d) The designer should  determine from the purchaser or user whether automatic means of  transmission 
of alarm signals to an ARC is required by the user.  
e) If the early summoning of the fire and rescue service is considered critical to the safety of  occupants 
(e.g. on the basis of a fire risk assessment), facilities should be provided for automatic  transmission of 
alarm signals to an ARC , unless there are reliable arrangements for summoning  the fire and rescue 
service by persons in the building  
f)  In residential care premises, facilit ies should be provided for automatic transmission of alarm  signals 
to an ARC.  
g) Except in the case of continuously occupied premises, Category P systems should incorporate a  
means for automatic transmission of fire signals to an ARC.  
h) In non -domestic premises  in multiple occupation, Category L systems should incorporate an  automatic 
means for transmission of alarm signals to an ARC, unless there are arrangements in  place for 
summoning the fire and rescue service by occupants of the building, at all times that the premises are 
occupied (or partly occupied).  
i)  Any ARC to which fire alarm signals are relayed should conform to the recommendations of BS 8591 
and have in place an agreement with the appropriate fire and rescue service to pass on  fire signals 
from fire alarm systems at the monitored property.  
NOTE 2 An ARC that conforms to the recommendations of BS 5979 (withdrawn, superseded by BS 8591) in  
respect of monitoring of  fire alarm  signals is acceptable.  
NOTES 3 Schemes exist for third -party certification of A RC' s to BS 8591 and BS 5979 (withdrawn, superseded  
by BS 8591). However, transmission off ire alarm signals (a s opposed to intruder alarm signals) is not always  
within the scope of the ARC'  s certification; if reliance is placed on third -party certificat ion, it needs to be  confirmed 
that monitoring of  fire alarm signals is within the scope of certification.  
j)  If a Category L or Category P system incorporates facilities for automatic transmission of fire  signals 
to an ARC, any telephone switch room or frame  room  on which automatic transmission  depends 
should be protected by automatic fire detection or an automatic fire extinguishing  system. As far as 
reasonably practicable, any cables within the building (including telephone  lines) on which 
communication dep ends should be:  
1) routed through areas of  low fire risk; or  
2) routed through areas protected by automatic fire detection or an automatic fire  extinguishing 
system; or ;  
3) cables of standard or enhanced fire resistance (see Clause 26).  
k) Automatic transmission of a larm signals should not be prevented by the act of silencing fire  alarm 
sounders, nor should it depend on the state of any silencing switch . 
NOTE 4 Although  any ARC to which fire signals are relayed is normally operated on a commercial basis, the  
function could, for example , be fulfilled by a fire and rescue service control room or a continuously manned  
security control room on the same site as the protected premises.  
l) Where an alarm transmission device is mounted in an enclosure separate from that of the fi re alarm 
CIE, the connection from the CIE to the alarm transmission device should be monitored  and comprise 
cables of standard fire resistance. The CIE should conform to BS EN 54 -2. BOS 813 -1:2023  
Edition 1.0 
30 NOTE 5 Monitoring may be performed by the alarm routing equipment. For exa mple, the connection between  the 
CIE and the alarm routing equipment may comprise a cable from an input in the alarm routing equipment  to the 
common fire relay in the C IE, such that an open circuit fault in the cable results in transmission of a fault  signal to 
the ARC.  
m) Power supplies for any facility used for the transmission of fire alarm signals to an ARC should  conform 
to Clause 25.  
NOTE 6 15.2m)  does not apply to the mains power supplies for an intruder alarm system, to which  15.2n) applies.  
n) Where fire  alarm signals are routed via the routing equipment of an intruder alarm  system, the standby 
power supplies for the routing equipment should conform to the  recommendations in 25.4 
o) If it is intended for the CIE to signal a fault from the fire alarm system t o an ARC, the CIE should  have 
a suitably monitored means of interfacing with the relevant fault routing equipment.  
NOTE 7 Monitoring may be performed by the fault routing equipment. For example, the connection between  the 
CIE and the fault routing equipmen t may comprise a cable from an input in the fault routing equipment to  the 
common fault relay in the CIE, such that an open circuit fault in the cable results in transmission of a fault  signal 
to the ARC.  
NOTE 8 It is common for the alarm routing  equipment  and the fault routing equipment to comprise a  single device.  
p) Faults in either the alarm transmission equipment or in the alarm transmission path should be  
displayed at the CIE.  
NOTE 9 It is recognized that temporary loss of service in the alarm transmissi on path or service provision  might 
occur. The risk associated with loss of communications can be mitigated by use of a dual path  alarm transmission 
system where primary and secondary signal paths are provided. For dual path alarm  transmission systems, loss  
of both si9nal paths is indicated as a fault at the CIE. However, it is not necessary to  indicate loss of a single  
transmission path at the CIE. 
q)  Where the alarm transmission path relies upon a physical TCP /IP or similar data connection, the  
following re commendations apply.  
1) Final connections to the alarm routing equipment should be secured against unauthorized  
disconnection.  
2) Power supplies for routing equipment  within the premises on which alarm transmission  depends 
should conform to the recommendations o f 25.4e).  
NOTE 1 0 Where there is a dual path alarm transmission system, the recommendations contained in 15. 2q)2) 
need on ly be applied to one of the transmission systems.  
3)  The physical data network cable used for ala rm transmission within the building shou ld be  
differentiated from other services by colour.  
NOTE 11 Where the n etwork cable cannot conform to the recommendations of 15.2q)3), or where local data  
network reliability fs a concern, a dual path alarm transmission system would be beneficial.  
16 Audible alarm signals  
16.1 Commentary  
In practice, a Category P system is usually combined with a Category M system, in which case the  
considerations applicable to the Category M system take precedence as these are more onerous.  In those 
areas in which audible alarm signals  are intended to alert occupants, the sound pressure level  and frequency 
of alarm signals need to be adequate to provide unambiguous warning of fire. Particular  care needs to be 
taken to ensure adequate sound pressure levels in small cellular spaces, such as cellular  offices, toilets and 
plant rooms. if the alarm signal comprises a speech message, it is also necessary to  ensure that the 
message(s) is intelligible.  
Traditionally, a sound pressure level of 65 dB(A) has been regarded as the minimum accept able sound  
pressure level for fire alarm signals. However, a sound pressure level difference of 2 dB to 3 dB is only  just 
perceptible to the human ear: It is, therefore, unnecessary to install additional fire alarm sounders  if, in open 
areas, 65 dB(A) is g enerally achieved. If, at specific points of limited extent within any area, a sound pressure 
level of at least 60 dB(A) is achieved this is considered acceptable. It is also acceptable for the sound pressure 
level to be as low as 60 dB(A) in small enclose d spaces, such as cellular offices , and in stairways.  
In order to prevent excessive sound pressure levels, which can cause disorientation or even damage to  
hearing, a larger number of quieter sounders is preferable to a few very loud sounders . BOS 813 -1:2023  
Edition 1.0 
31 Once started , alarm signals generally need to continue until manually silenced by use of a silencing  control. In 
large sites comprising many buildings in single ownership (e.g. industrial sites), an external  fire alarm device 
can be of value in directing firefighters to the correct building ; an external fire alarm  device can also be useful 
in directing firefighters to the correct entrance of a large building with many  entrances. It is not necessary for 
an external fire alarm sounder  to sound for a prolonged  period; for  it to do so is unlikely to be acceptable 
because of disturbance in neighbouring properties, particularly if false  alarms occur when the protected 
premises are unoccupied   
In rad io linked systems, in which the power supply for sounders may comprise batteri es, prolonged  operation 
of sounders (e.g. as a result of a false alarm  when the premises are unoccupied) can exhaust  the batteries, 
leaving the premises w ithout an operational fire alarm system when they are subsequently  reoccupied. Since 
this creates grea ter risk than that associated with automatic silencing of alarm  signals, the alarm signal may 
be automatica lly silenced in certain radio -linked systems, subject to the  agreement of the enforcing authority  
16.2 Recommendations  
16.2.1   Recommendations  applicable to Cate gory M and L systems (other than in hospitals and  
residential care premises)  
The following recommendations are applicable.  
a) The sound pressure level of alarm signals should be:  
1) throughout all accessible areas of the building [other than as described in 15.2c) and in  enclosures 
of less than 1 m2], not less than 65 dB(A) but, as shown in Figure 4. this may be  reduced to 60 
dB(A) in:  
i) stairways;  
ii) enclosures of not more than approximately 60 m2 in area (e.g. cellular offices); and  
iii) specific points of limited extent ; 
2) where the sound pressure level of background noise is greater than 60 dB(A), the sound  pressure 
level of the fire alarm signal should be 5 dB above the sound pressure level of the  background 
noise;  
NOTE 1 Background noise that is unlikely to persist for longer than 30 s may be ignored . 
NOTE 2 This recommendation does not apply to noise created by running water in bathrooms and  shower 
rooms.  
NOTE 3 Typical noise levels in buildings are given in Annex 8.  
3) not less than 75 dB(A) at the bedhead within rooms in  which the fire detection and fire  alarm 
system is intended to rouse people from sleep;  
NOTE 4 Experience has shown that this normally  necessitates the provision of a fire alarm sounder  within 
the room in question.  
4)  not greater than 120 dB(A) at any normal ly accessible point.  
NOTE 5 All these figures are arbitrary but  are judged to  be generally appropriate.  
NOTE 6 In carrying  out measurements to verify compliance with these recommendations, other than  in the 
case of 16.Z.1a)3), account need not be taken of sound pressure levels within 500 mm of any walls  or 
partitions.  
NOTE 7 Measurements need to be made with all doors shut,  
NOTE 8 An instrument conforming to BS EN 61672 -1, set to slow response and A  weighting, is suitable  for 
measuring the sound pressure le vel of the alarm signal.  
NOTE 9 It is often necessary to measure the sound pressure level of the fire alarm signal in the presence  of 
background noise. The sound pressure level of the fire alarm signal (in isolation) can be deemed to be 5  dB 
above backgrou nd noise if, when the background noise is present, a sound pressure level increase of  6 dB 
occurs on operation of the fire alarm system.  
b) The fundamental frequency(ies) produced by fire alarm sounders should lie in the range of 500  Hz to 
1 000 Hz, unless th e frequency of background noise is such as to mask these frequencies, in  which 
case the use of sounder frequency  outside this range is acceptable. The sounders should  produce a 
continuous output, although the frequency and amplitude might vary (e.g. as in a warbling note), to 
indicate the need for evacuation or other immediate response.  
c) All fire alarm sounder  within a  building should have similar sound characteristics, unless  particular 
conditions, such as an area of high background noise, make this impract icable. The  sounders should BOS 813 -1:2023  
Edition 1.0 
32 be distinctive in sound from the sounds of other alarm systems in the building.  The fire alarm sounders 
should be distinctive in sound.  
NOTE 10 On a site where occupants move regularly between buildings , there is a benefit to adopting  fire alarm 
signal that has similar sound characteristics throughout all buildings on the site.  
d) In premises designed for public entertainment, retail and similar premises, in which the  sound pressure 
level of music is likely to be greater than 80 dB( A), the music should be muted  automatically when a 
fire alarm signal is given.  
NOTE 11 In premises with two (or more) sta ge alarm systems, consideration ou ght to be given as to  whether  the 
music is to be muted at the "Alert" or the "Evacuate" stage.  
NOTE 1 2 Where the sound pressure level of the music is likely to be between 60 dB(A ) and 80 dB(A), the  
recommendation of16.2.1a )2) applies.  
e) In parts of a building with noisy machines, in order to achieve 5 dB(A) above background  noise, the 
fire ala rm sounders (" primary sounders") may be supplemented by mains powered  sounders, without 
a standby supply ("secondary sounders"), operated from the same final  circuit(s) as the noisy 
machines, so that failure of the supply to the secondary sounders also  results in silenc ing of the noisy 
machines. The primary sounders should still be sufficient to  satisfy the recommendations of  16.2.1a) 1) 
when the machines are silent . 
f) In large sites with many buildings, or in the case of large buildings with many entrances, an  external 
sounder(s) and/or visual alarm devices may be provided to direct firefighters to the  building or 
appropriate entrance to the building. Where the provision of such sounders and/or  visual alarm devices 
is considered, there should be consultation with the fire a nd rescue service  to confirm the need of, or 
benefit from, their provision. The sounder(s) and/or visual alarm  device(s) should be clearly marked 
with the words "FIRE ALARM".  
g) A facility should be provided to enable silencing of alarm signals. The operation  of the  facility should:  
1) require a manual operation;  
2) not cancel any visual signal of the ala rn at the control equipment;  
3) sound any fire alarm sounders configured to that zone if, following silencing of fire alarm  sounders, 
a new zone goes into alarm, and n ormally should also resound those fire alarm . sounders which 
were previously sounding;  
4) not prevent the correct operation of any control for starting or restarting the alarm  sounders [see 
23.2.3b)];  
5)  not prevent the transmission of an ala rm to an ARC.  
h) Alarm  signals should not silence automatically (i.e. after a predetermined time period), other  than in 
the following circumstances:  
1) any external fire alarm sounders [see 16.2. 1f)] in Category Land P systems should silence  
automatically after 30 min, unless the premises are continuously occupied so enabling  manual 
silencing by occupants, After silencing. the sounders might (or might not) restart if,  before the 
system is reset, a further alarm condition occurs . 
2) where a radio -linked Category L  or P system incorpora tes battery powered fire alarm  sounders, 
the sounders should silence automatically after 30 min, unless the premises are  continuously 
occupied so enabling manual silencing by occupants. The sounders should  restart if, before the 
system is reset, a further alarm condition occurs. Where a period longer  than 30 min Is required, 
e.g, for phased evacuation, the 30 min period may be extended to  meet the requirements of the 
system specification.  
3) in a two (or more) stage alarm system, alert signals may be silenced automatically after a  
predetermined period, subject to compliance with 19. 2.3d). 
i)  The system should Incorporate at least two fire alarm sounders, even if the recommended sound  
pressure levels could be achieved with one sounder. At least one sounder should be provided in  each 
fire compartment.  
j) If audible alarms comprise speech messages generated by a voice alarm system, the relevant  
recommendations of  BS 5839 -8 should be followed in respect of message content, sound  pressure 
levels and speech Intelligibility . If voice sounders (see 3.61) are used, reference should  be made to 
BS 5839 -8, as well as complying with the recommendations of this standard.  BOS 813 -1:2023  
Edition 1.0 
33 k) Fire alarm sounders should not be used for purposes other than warning of  fire, unless the  response 
required is identical to that required in the event of fire ( i.e. immediate evacuation  by use of all escape 
routes). However, as an established exception, the fire alarm signal may be  used in schools to indicate 
start or finish of predetermined periods. The duration o f such signals  should not exceed 5 s.  
 
 
16.2.2  Recommendations applicable to Category P systems  
The recommendations of apply in respect of those areas where audible alarm signals  are required.  
16.2.3  Recommendations applicable to hospitals and residential care premise s 
The following recommendations are applicable.  
a) Audible alarms  in hospitals should conform to the recommendations of the Department of Health  
Publications . 
b)  Audible alarms in residential care premises should conform to.16.2.1, except that, if  the alarm sig nal 
is not intended to rouse occupants of some or all rooms from sleep, 16.2.1a)3)  does not apply.  
17 Visual alarm signals  
17.1 Commentary  
Visual alarm signals need to be used to supplement audible alarm signals in situations in which the  latter are 
likely to be i neffective, but normally ought not to be used on their own. Their use is principally  in areas with 
high ambient sound levels, where hearing protection is likely to be worn. However, they are  sometimes used, 
as the sole initial warning to staff, in situatio ns in which the disturbance of an audible  warning is undesirable 
(e.g. television and radio studios, cinemas, theatres and hospital operating  theatres). Visual alarm signals can 
also be used as a means of giving warning of  fire to people who are  deaf and h ard of hearing (see Clause 18).  
Where visual alarm signals are used, consideration might need to be given to the potential effects on  people 
with photosensitive epilepsy . 
Figure 4―Sound pressure levels [see 16.1a]  
BOS 813 -1:2023  
Edition 1.0 
34 For more information, see the Joint LPCB/FIA document CoP 0001, Code of Practice for visual alarm  devices 
used for fire warning [1].  
Visual alarm devices recommended in this standard are intended to apply to circumstances in which the  visual 
alarm is a primary warning o f fire, but not to situations in which the visual alarm provides on ly supplementary 
information, such as those recommended in BS 7273 -1 for areas protected by a gaseous  fire suppression 
system.  
17.2 Recommendations  
The following recommendations are applicable.  
a) Visual alarm signals should be provided in areas where ambient noise le vels exceed 90 dB(A)  and in 
other areas where hearing protection is likely to be used under normal circumstances.  
b) Visual alarm devices should be sufficient in number and distribution to be readily visible from  all 
normally accessible locations, throughout the area in which they are provided, under normal  ambient 
lighting levels.  
c) The visual alarm signal should flash at a rate within the range of 30 to 120 flashes per minute.  
d) The visual alarm signal should be clearly distinguishable from any other visual sign al used in the  
premises. Visual alarm signals should be white or red, or both white and red, in colour, unless  use of 
another colour is necessary to distinguish the signals from other visual signals.  
NOTE 1 Labelling the visual alarm device with the word ''FIRE” such that it would be legible from a position  
standing on the floor might be adequate to distinguish it from other visual signals.  
NOTE 2 Care needs to be taken to ensure , as far, as reasonably practicable, that visual alarm  signals do not  
cause epi leptic seizures in people with photo  sensitive  epilepsy. In this connection, a flash rate of 3 Hz or less  
(from a single visual alarm device) ls unlikely to result in seizures, but care is necessary to ensure that, in open  
areas, the field of view from any  point is not such that multiple, unsynchronized visual signals can result in  an 
apparent flash rate of a greater frequency; to avoid this, synchronization of visual alarm devices might be  
necessary. It is important to note that red flashing light is more likely to result in seizures than white (or other  
coloured) flashin g light. Particular care is necessary in, for example, certain health care premises in which a  
number of people with photosensitive epilepsy might congregate.  
e) The intensity M  output of visu al alarm devices should be sufficient to attract attention, but not so  high 
as to cause difficulty with vision due to glare.  
Note  3 Guidance on the use and siting of visual alarm devices conforming to BS EN 54 -23 is given in LPCB/ FIA 
CoP 0001  [1] This perm its two alternative approaches: an en9i11eered, applicatio11 -specific solution for  relatively 
complex situations and a “predetermined approach ” or rooms of simple geometry, specified size and  frequently 
encountered levels of ambient illumination.  
f) Visual al arms should be securely fixed in accordance with the mounting position (ceiling  or wall) and 
orientation specified by the manufacturer. The mounting height should not be  less than 2.1 m . 
18 Fire alarm warnings for people who are Deaf and hard of hearing  
18.1 Comme ntary  
Impairment of hearing does not mean that a person is completely insensitive to sound. Many people with  
severe impairment have sufficiently clear perception of some types of conventional audible alarm signals  to 
require no special provision for warnin g of fire. There will be, in some situations, other people present  who can 
alert people who are Deaf and hard of hearing to the need for evacuation, and in this case,  it might be 
necessary to put procedures in place that rely upon others to provide the nec essary warning.  
However, in circumstances, such as buildings with a significant number of people who are Deaf an d hard of 
hearing, buildings in which one or more people who are Deaf or hard of hearing Work in relative  isolation, and 
buildings in which one or more people who are Deaf or hard of hearing tend to move  around the building to a 
significant extent (including into toilet areas), additional means of giving  warning to these people might be 
appropriate. If the occupants in question tend to be located for a large  proportion of their time within a limited 
area of the building, visual alarm signals might be appropriate  in that area (and associated toilets). If they sleep 
in the building, tactile devices, with or without  associated visual alarm devices, mi ght need to be considered 
{e.g. for compliance with the accessibility  requirement imposed under Building Regulations . These devices, 
which can, for example, be  placed under pillows or mattresses, may be wired into fire alarm device circuits or 
be triggered  by radio signals.  
Alarm devices for people who are Deaf and hard of hearing can be fixed, movable or portable.  BOS 813 -1:2023  
Edition 1.0 
35 Fixed equipment is equipment fastened to a supp ly; or otherwise secured in a specific location, or  equipment 
not provided with a carrying handle  and having such a mass that it cannot easily be moved  ( e.g. a fire alarm 
system control  panel screwed, to  the wall).  
Moveable equipment is equipment  which is not fixed equipment and which is not normally in operation  while 
the location is changed (e g. a  local unit or controller which is placed on a table top and operates a  vibrating 
pad in a bed ). 
Portable equipment is equipment designed to be in operation while being carried (e.g. radio pager or  other  
system using radio communication). For the purposes of this clause, portable alarm devices are:  
• intended for, carrying by people who are Deaf and hard of hearing;  
• capable of giving visual and/or tactile signals;  
• normally radio controlled but other methods are not excluded; and  
• normally require control equip ment for transmission of signals to the portable devices,  interfaced to the fire 
detection and fire alarm control equipment  
Wherever possible, the recommendations of this clause  ought to be followed and any variations ought to be 
subject to a risk assessme nt to ensure that no  person who is Deaf or hard of hearing is exposed to undue risk.  
It is important to note that all radio paging systems used with fire detection and fire alarm systems need  to be 
licensed with relevant authority.  There are three types of  licence currently available:  
• the short -range  business paging (SRBP) licence which gives no protection from interference from  other 
authorized or unauthorized users of the same radio frequency;  
• the self select licence which offers some protection from inte rference by unauthorized use of the  frequency;  
• the manual frequency coordinated licence which ensures the elimination of Interference from  both 
authorized and unauthorized users of the assigned radio frequency.  
18.2 Recommendations  
18.2.1  General  
The following recomme ndations are applicable.  
a) Visual alarm signals provided for people who are Deaf and hard of hearing should conform to  Clause 
17. The visual alarm devices should be regarded as fire alarm devices for the purpose of  this standard 
and, for example, circuits se rving the devices should be monitored and protected  against fire 
accordingly.  
b) Tactile alarm devices provided for people who are Deaf and hard of hearing may be fixed,  moveable 
or portable. Fixed or moveable tactile devices should be regarded as fire alarm devices  for the purpose 
of this standard. For example, circuits serving the devices should be monitored  and flexible cables 
attached to devices should be protected against fire if they are greater than 3  m in length.  
c) The intensity of output of tactile alar m devices should be sufficient  to attract attention.  
d) Advice should be sought from relevant authority  as to the conformity  with regulatory requirements for 
any system using radio signals.  
e)  Where tactile devices are provided, control and transmission equipme nt should conform to the  
recommendations of Annex C.  
18.2.2  Portable alarm devices  
Portable alarm devices to supplement: the primary means of giving an alarm of fire, if activated by  radio 
signals, should conform  to the following recommendations.  
a) The alarm should  be given at the portable alarm device within 5 s of the generation of the alarm  signal 
at the fire detection and fire alarm CIE.  
b) The alarm signal emitted by the portable alarm device should continue for at least 60 s after  reception 
of eve ry alarm transmi ssion or until it is acknowledged at the portable alarm device.  This emitted alarm 
signal may be intermittent.  
c) In a fire condition the transmission equipment should continue transmitting the alarm signal  to the 
portable alarm devices until the alarm is can celled by a signal from the fire alarm control  equipment. 
If the transmission equipment does not send the alarm signal continuously, it is  acceptable for the 
transmission equipment to send the alarm signal repeatedly at periods not  exceeding 10 s.  BOS 813 -1:2023  
Edition 1.0 
36 NOTE 1 T he purpose of this recommendation is to ensure that, in the event of  fire, the portable alarm device  
continues to emit a signal until the fire alarm control equipment is silenced or reset  
NOTE 2 The recommendations in 18. 2.2b) and 18. 2.2c) are intended to ensure that, in the event fire, each  
portable alarm device emits an alarm signal continuously, until the fire alarm CIE is silenced or reset . 
NOTE 3 In the context of 18.2.2c), cancellation of the alarm signal from the fire alarm control equipment  might, 
Jar example, constitute the resetting of a relay at the fire alarm control equipment.  
d)  Where the portable alarm device is also used for other purposes (e.g. general paging), the  recipient 
should, by means of the cadence pattern, be able to tell the differen ce between a signal of fire and a 
signal for other non -emergency purposes.  
NOTE 4 It is acceptable to use the fire signal cadence pattern for other emergencies that require a similar urgency 
of response to afire (e.9. a bomb warning).  
NOTE 5 The manufactu rer's, or supplier's, instructions for users are likely to stress the importance of not using 
the fire signal cadence pattern for non -emergency purposes.  
NOTE 6 While virtually all radio -paging systems have fire as their highest level of priority, it might  be that in some 
special cases there could be a higher level of priority eg). a security attack alarm. In these rare cases, it might be 
deemed that the fire signal does not have priority over any other signal. Such a decision ought to  result from an 
adequa te risk assessment and be agreed with relevant parties.  
e) Where the portable alarm device is also used for other purposes (e.g. general paging), the fire  signal 
should have priority over any other signal so that 18.2.2a) is satisfied  regardless of the  occurr ence of 
other system activity ( e.g. transmission of general paging messages).  
f) A failure of the interconnection (e .g. radio transmission) between  the transmission equipment  and the 
portable ala m device should be identified at the portable alarm device by a  visual  and tactile signal 
within five minutes of the failure. The visual indication should remain until  the interconnection is 
reconstituted or the portable alarm device is switched off. The tactile  indication may be cancelled by 
operation of a manual con trol, provided that, at intervals not  exceeding 15 min, it is then repeated for 
a duration of at least  0.5s, unless the portable alarm  device is switched off.  
g) Portable alarm devices may be operated from a single power source (e.g. battery). A low power  source 
voltage should be identified at the portable alarm device by a visual and tactile signal.  If the tactile 
signal is given continuously until manually acknowledged, the signal should,  after acknowledgement, 
be repeated for at least 3 s at intervals not e xceeding 15 min until  the capacity of the battery can no 
longer support the tactile signal. If the battery low signal  automatically stops after a predetermined 
period, the signal should be repeated at intervals not  exceeding 15 min until the capacity of th e battery 
can no longer support the tactile signal. In any  case, a text or other. Visual  indication should be given 
continuously and remain until either the  battery is replaced or the battery can no longer support the 
display, unless overridden by a fire  signal or other message.  
h) If a portable alarm device is fitted with an off switch, or a switch disabling the alarm signal, the  design 
of the switch should be such as to avoid inadvertent operation.  
i) All faults identified at the control equipment for the porta ble ala m system should result, in, at  least, a 
common fault warning at the fire detection and fire alarm system CIE within 100 s of  the fault being 
identified at the portable alarm control equipment. Any cable used in a circuit  provided in order to 
satisfy  this recommendation should be monitored, so that an open or short  circuit fault in the cable is 
indicated at the fire detection and fire alarm system CIE. However, it is  not necessary for this cable to 
be fire -resisting.  
NOTE 7 The audible and visual faul t indication may be given by equipment separate from the fire detection  and 
fire alarm CIE, provided the audible and visual indications conform to the requirements of BS EN 54 -2 for fault 
signals.  
j) The system should conform to the recommendations of the fol lowing clauses and subclauses of  this 
standard  
• 12.2.1a) 4)     • 12.2,1e)     • 23.2. 1e)   • 27.2g)1)  
• 12.2.1a)5)     • 12.2. 1g)    • 23.2. 1f)    • 27.2g)2)  
• 12.5.1a)6)     • 12.2.21 )    • 25    • 27.2g)3)  
• 12.2.1a)7)     • 23.2.lb)     • 26     • 29.2e)  
• 12.2. 1b)     • 23.Z.lc)     • 27.2c)    • Annex C  
• 12.2. 1d)     • 23.2. 1d)    • 27.2d)  BOS 813 -1:2023  
Edition 1.0 
37 19 Staged fire alarms  
19.1 Commentary  
In simple buildings of limited size, a single stage fire alarm arrangement is likely to be sufficient . In such  a 
system, on operation of  any manual calf point or automatic fire detector, a single, common fire alarm  signal is 
given throughout the premises as a signal to all occupants to evacuate immediately  (i.e. there is  a "single 
phase" evacuation).  
In certain large and/or high -rise build ings, a staged fire alarm arrangement might be more appropriate.  In a 
staged fire detection and fire alarm system, the initial warning of  fire is given in a restricted area,  or is restricted 
to key personnel, but can be extended in further stages to warn, ultimate , all occupants  of the premises. The 
arrangement might apply regardless of whether the  alarm is triggered by a manual  call point or an automatic 
fire detector, or it might apply only to alarm signals triggered by automatic  fire detectors.  
There are  various circumstances in which a staged fire a larm arrangement might be appropriate. These  
include, but are not restricted to, the following.  
a) In certain large or high -rise buildings, it might be desirable to evacuate first those areas closest  to the 
fire and immediately above  'it: other areas are evacuated thereafter. A particular example  of this 
arrangement, commonly used in high -rise buildings, is known as phased evacuation.  This 
arrangement enables the number and/or widths of stairways to be reduced; un der these  
circumstances, is important that no control is provided to evacuate the entire building in a single  phase, 
as there w ill be insufficient stairway capacity for simultaneous evacuation of all occupants.  
b) Phased evacuation is also sometimes used in o ther types of building, irrespective of whether there  
are reduced stairway capacities (e.g. leisure complexes, shopping centres and transportation  
terminals). In these  cases, the initial phase of evacuation might be horizontal, into a place of  relative 
safety within the building.  
c) In hospitals, a system of  "progressive horizontal evacuation" is used, in which patients closest  to a fire 
are moved horizontally to an adjacent fire compartment. ln a large hospital, further  evacuation might, 
again, involve only h orizontal movement, without the need for more difficult  vertical evacuation.  
d) To minimize disruption from false alarms, signals triggered by automatic fire detectors might be  
restricted in the first instance to staff, who investigate before any general evac uation signal is given  
and/or the fire and rescue service is summoned; alternatively, the area of initial evacuation might  be 
restricted in extent (see Section 3). ln residential care premises, where early extinguishing action  by 
the fire and rescue servic e is critical to life safety, it is not appropriate to delay the summoning of  the 
fire and rescue service when the fire alarm system operates.  
e) In certain public buildings, such as places of public entertainment, an initial warning of  fire is  sometimes 
restricted to staff in order to avoid incorrect reaction by members of the public; staff are  then 
responsible for controlling the evacuation, often by use of a voice alarm system.  
f) In a widely spread range of low rise buildings, such as an industrial complex, t here might be no  need 
for evacuation of occupants in one area of the complex, even in the event of a confirmed fire of  limited 
size some considerable distance from those occupants.  
In all of the above cases, the evacuation strategy described normally requi res the support of a staged  alarm 
system, which is capable of giving two or more stages of alarm within any area. In a two -stage  alarm, the 
system might be capable of giving an ''Alert" signal in those areas not immediately affected,  as a warning of  
impend ing evacuation, and an "Evacuate" signal in those areas in which immediate  evacuation is required.  
Another form of two -stage alarm is one in which the initial alarm is restricted  to staff, usually by means of 
paging or a coded voice alarm message (a "staff  alarm,  with the  subsequent stage taking the form of an 
"Evacuate" signal throughout all or part of the premises. In a  three -stage alarm system, the system might be 
capable of giving a staff alarm, an ''Alert" signal and an  "Evacuate" signal.  
The purpose o f the fire detection and fire alarm system is to support the required fire and evacuation  
procedures. Since various arrangements are possible, it is absolutely vital that, other than in small,  simple 
buildings, the fire procedures and evacuation strategy a re formulated before final design of the  fire detection 
and fire alarm system is completed. The "cause and effect" logic of the system, the control  facilities provided,  
and the configuration of fire alarm device circuits are governed by the procedures  the system is intended to 
support. For example, to facilitate a staged alarm arrangement in which  "Alert" and "Evacuate" signals can be 
given, it is necessary to divide the building into alarm zones  (see Clause 14).  
The use of staged alarm systems can necessit ate the provision of additional facilities, such as a  voice alarm 
system and/or an emergency voice communication system to control evacuation.  Recommendations for the BOS 813 -1:2023  
Edition 1.0 
38 design of voice alarm systems are given in BS 5839 -8. Recommendations for  the design of e mergency voice 
communication systems are given in BS 5839 -9. 
In buildings with inner rooms from which escape is possible only by passing through another ( ‘’access ’’ room, 
it is common practice for a smoke detector to be installed in the access room unless there is  adequate vision  
between the inner room and the access room. The purpose of this smoke detector  is to give early warning to 
occupants of the inner room before fire in the access room prevents their  means of escape.  
19.2 Recommendations  
19.2.1  Recommendations  applicable to all staged alarm systems  
In multi -storey buildings with phased evacuation, if stairway capacity is inadequate to support a simultaneous 
evacuation of all floors, no single control should cause an "Evacuate" signal to be given throughout the bu ilding; 
a separate "Evacuate" control should be provided for each alarm zone.  
NOTE In some buildings, a two -phase evacuation arrangement is used; the area of fire origin is evacuated first and the 
remainder of the building is evacuated simultaneously as a second phase.19.,2.1 does not apply to such situations, as 
adequate stairway capacity exists to evacuate the entire building in one phase . 
19.2.2  Recommendations applicable to staff alarms  
The following recommendations are applicable.  
a) Staff alarms should be used only where staff, including any night staff, are sufficient in number  and 
fully trained in the action they are to take in the event of fire.  
b) In residential care premises, a staff alarm should not incorporate any delay in summoning of  the fire 
and rescue se rvice when the fire alarm system operates, but there may be a delay in the  general alarm 
signal, provided all staff are made aware of the fire alarm signal [see also 15. 2f)]. 
c) Staff alarms should normally be generated only in response to signals from automa tic fire  detectors, 
but not in response to signals from manual call points, heat detectors or sprinkler  systems. However, 
in premises, other than residential care homes, that generate a high  number of unwanted fire alarm 
signals, automatic transmission of a signal to an ARC might be  delayed pending investigation of alarm 
signals from these devices. Any proposal to use a staff  alarm as the initial response to a signal from a 
manual call point should be subject to special  consideration. In such special circum stances, there 
should be adequate arrangements to ensure  that a person operating a manual call point is not left in 
doubt as to the success of the operation  ( e.g. by means of visual indication at the call point that the 
signal has been correctly received at the control equipment and a suitable warning that operation of 
the manual call point will not  result in an immediate audible fire warning).  
NOTE 1 It is common practice for both manual call points and automatic detectors in large places of public  
entert ainment to initiate only a staff alarm, so that staff can be prepared to assist in an orderly evacuation,  which 
is then initiated by a voice alarm message. Such arrangements necessitate a high level of training and  awareness 
on the part of staff and might not be appropriate in other premises.  
 
d) Staff alarm signals comprising visual fire alarm devices should conform to Clause 17.  
e) In premises with a staff alarm system, there should always be provision, throughout all areas  of the 
building, for sounding an audi ble fire warning conforming to Clause 16. Facilities  should be provided 
at the CIE, and at additional locations if appropriate, to change the stage  of alarm from a staff alarm 
stage to an "Evacuate" stage. Since operation of a manual call point  should not normally result in a 
staff alarm [see 19.2.2c)], it should normally also be possible  for those responding to a staff alarm 
signal to change the stage of the alarm by operation of a  manual call point.  
f) A staff alarm signal should automatically change to an a udible fire warning in at least the  relevant 
alarm zone after a preset period, unless manual intervention to stop the associated  timer occurs at the 
control equipment. The period for the staff to investigate should not normally  exceed six minutes.  
g)  A staff  alarm signal should automatically change to an audible fire warning in at least the  relevant 
alarm zone if a second detector operates before the system is reset. (This is known as  "coincidence 
detection").  
NOTE 2 Coincidence may be arranged such that a fu ll alarm is given only if the second detector is in the same  
defined area as the first detector or if a second detector anywhere in the building operates.  
NOTE 3 A typical staff alarm arrangement is shown in Figure 5 . 
h) In buildings with a staff alarm, smoke  detectors in access rooms that form the only means of  escape 
from inner rooms should give an immediate local warning of fire to occupants of the  inner rooms, even 
though the alarm signal might be delayed elsewhere in the building, unless  there is adequate  vision BOS 813 -1:2023  
Edition 1.0 
39 between the inner room and the access room.  
 
 
19.2.3  Recommendations applicable to audible ‘’Alert’’ signals  
The following recommendations are applicable.  
a) The audible alert signal should be intermittent (1 ±0.5) s on and (1 ±0.5) s off.  
b) Signals  from dif ferent fire alarm devices should be synchronized.  
NOTE 1 Synchronization ought to be sufficient to ensure that the ''Alert" signal cannot be confused with a 
continuous "Evacuate" signal.  
c) Provision should be made for manually changing the ''Alert" signal to  the "Evacuation" signal  in any 
area.  
NOTE 2 Provision may also be made for automatically changing from the ''Alert" signal to the  "Evacuate" signal.  
d) Provision may be made for the ''Alert" signal to cease automatically after 30 s, provided that, at  periods  
not exceeding three minutes, the signal is restored for a period of at least 10 s until it is  manually 
silenced.  
20  Manual call points  
20.1 Commentary  
Manual call points (MCPs) need to be prominently sited, readily distinguishable from non -fire alarm call  points  
and need to be distributed such that,  from any point in the building, it is impossible to leave the  storey or the 
building  without passing a manual call point.   
Sufficient call points need to be provided to minimize, to a reasonable extent, the delay betw een discovery of 
a fire and the sounding of the alarm. Where the fire hazard level is high and rapid -fire development is 
anticipated, this delay needs to be commensurately shorter.  
MCPs can, if present in unsupervised areas, be subject to malicious operati on. For this reason, they are  not 
normally provided in, for example, public common areas of shopping complexes and certain public  houses. In 
public car parks within a building, use of an emergency voice communication system could be  considered 
instead of M CPs.  
Stop timer  
Clear Alerts  
Signal  
Investigate cause  
Record Findings  
Avoid recurrence  
Figure 5 Typical  stall alarm arrangement  BOS 813 -1:2023  
Edition 1.0 
40 In the event of an evacuation signal, people evacuate the building via an exit that leads to a place of  ultimate 
safety, that is, a place in which there is no immediate or future danger from fire. To  conform to this standard , 
MCPs are sited  adjacent t o all storey exits and exits to open air that lead to a  place of ultimate safety.  
Therefore, if, for example, a door leads to an enclosed courtyard that is in the open air but has no exit to  a 
place of ultimate safety, this door would not need to be provid ed with an MCP as the provision of an  MCP at 
this point could infer  that the door leads to a place of safety. Moreover, to escape, people would  need to re -
enter the building and would therefore be afforded an opportunity to operate the fire alarm  system on  their 
route to a suitable exit. Similarly, the same would apply to a door leading to a flat -roofed  area from which there 
is no suitable means of escape (e.g. external escape stairway).  
Some openings in the building envelope (such as a roller shutter door)  are not normally considered as a  
pedestrian exit, but in an emergency are likely to be used as such. It might, therefore, be appropriate to  
consider them as an exit and provide an MCP at the opening. If openings cannot be used as a means of  safe 
egress fr om the premises to a place of  ultimate safety, MCPs might not need to be provided.  
20.2 Recommendations  
The following recommendations are applicable.  
a) The method of operation of all MCPs in a system should be that of type A as specified in  BS EN 54 -
11. All call points should be identical unless there is a special reason for differentiation.  
NOTE 1 The Type A manual call point is defined in BS EN 54 -11 as follows. "Type A Direct operation. A manual  
call point in which the change to the alarm condition is automatic  (i.e. without  the need for further manual  action) 
when the frangible element is broken or displaced."  
NOTE 2 The fitting of a protective cover to the type A manual call point is not deemed to conflict  with 20.2a).  
b) All MCPs should be fitted with a protecti ve cover; which is moved to gain access to the  frangible 
element.  
c) The delay between operation of an MCP and the giving of an "Evacuate" signal in, at least, the  alarm 
zone within which the call point is located should not exceed 3 s.  
NOTE 3 BS EN 54 -2 perm its a delay of up to 10 s in the response of control equipment;  accordingly, a delay of  
10 s might be acceptable, subject to the agreement of the relevant enforcing authority and the recording of the  
delay as a variation on the completion certificate.  
d) MCPs  should be located on escape routes and, in particular, at all storey exits and all exits to open  air 
that lead to an ultimate place of safety (whether or not the exits are specifically designated as  fire 
exits).  
Those located at storey exits may be sited within the accommodation or on the landing of a  stairway 
to which the storey exit gives access (see Figure 6). In multi -storey buildings with  phased evacuation, 
in which only a limited number of floors are evacuated at one time, only  the former option appl ies; 
under these circumstances, MCPs should not be located on stairway  landings, as persons travelling 
down the stairway might operate an MCP several floors below that  on which a fire is located, resulting 
in evacuation of inappropriate areas.  
e) Distribution  of MCPs should be such that no one need travel more than 23 m [ except where  20.2f)  
applies] to reach the nearest MCP, measured along the route that a person would actually  follow taking 
into account the layout of walls, partitions and fittings. If, at th e design stage, the  final layout of the 
premises is unknown, the maximum straight line distance between any  point  in the building and the 
nearest MCP should not exceed 15 m [except where 20.2 f) applies]; final fit out of the premises, the 
limit of 23 m sho uld still then apply.  
f) The figures of 23 m and 15 m recommended in e) should be reduced to 15 m and 10 m,  respectively, 
in the following circumstances:  
1) where a significant proportion of occupants have limited mobility and it can reasonable  
anticipated that one of these occupants will be the appropriate person to first operate  fire alarm 
system in the event of fire; or  
2)  where processes in the area result in the likelihood of rapid fire development (e.g. whe re there 
is use, or processing, of highly flammable l iquids or flammable gases).  
g) Where specific equipment or activities result in a high fire hazard level (e.g. kitchens or cell paint 
spraying), a MCP should be sited in close proximity.  
NOTE 5 In both examples given in g) other considerations also apply. Kit chens or food  preparation area might 
require the use of a non -glass frangible element to avoid the possibility of food contamination glass fragments. BOS 813 -1:2023  
Edition 1.0 
41 The spraying area might require the use of equipment certified for use in potentially  atmospheres (see Cla use 
10). 
h) In buildings with phased evacuation, additional MCPs are necessary to ensure that a MCP is  located 
at every designated exit from an alarm zone.  
i) MCPs should be fixed at a height of 1.4 m above finished floor level, at easily accessible, well  
illumi nated and conspicuous positions free from potential obstruction. They should be site d against a 
contrasting background to assist in easy recognition. A lower mounting height is  acceptable in 
circumstances where there is a high likelihood that the first per son to raise an  alarm of fire will be a 
wheelchair user.  
NOTE 6 The measurement ought to be made between the finished floor level and the centre  point of frangible 
element.  
NOTE 7 The figure of 1.4 m is arbitrary but  reflects long established custom and pr actice. A minor differs (e.g. 
less than 300 mm) in mounting height (e.g. to align with the mounting height of light switches) nee d be regarded 
as significant, nor need it be recorded as a variation.  
j) MCPs may be flush mounted  in locations where they will be  seen readily, but, where they  will be 
viewed from the side (e.g. corridors), they should be surface mounted or only  semi -recess  with the 
front face proud of the mounting surface by no less than 15 mm.  
k) In public car parks, any use of an emergency voice com munication system in lieu of MCPs  should  be 
subject to approval by the relevant enforcing authority, and the system should conform t o BS 5839 -9. 
All outstations should be Type B outstations in accordance with BS 5839 -9. The  master station should 
be sited i n a permanently manned location, such as a control room.  
 
21 Types of fire detector and their selection  
21.1 Commentary  
21.1.1  General  
Fire detectors are designed to detect one or more of the four characteristics of  fire, namely:  
• heat;  
• smoke;  
• combustion gas (such as car bon monoxide);  
• infrared or ultraviolet radiation.  
In some fire detection and fire alarm systems, a fire signal is initiated when the characteristic reaches  a 
predetermined threshold. A signal may, instead or in addition, be initiated when the rate of chang e of the 
characteristic is representative of a fire.  
In the case of point detectors, the characteristic is detected at a defined point(s) within the protected  area. In 
contrast "line" detectors are capable of detecting the characteristic along a defined li ne within  the protected 
space. In an "integrating line detector'; the effect of the characteristic on the detector  is integrated along the 
Figure 6 ― Manual call points on escape routes [see 20.2d]  BOS 813 -1:2023  
Edition 1.0 
42 line. In a "non -integrating line detector'; this is not the case, and the detector  behaves effectively as though it 
comprised an infinite number of point detectors arranged along a line.  
In multi -sensor fire detectors, each detector contains more than one sensor and thus monitors more than  one 
of the characteristic fire phenomena (e.g. heat and smoke). By analysis of the  signals received from  the 
sensors, potential response to phenomena other than fire can be reduced while still providing an  adequate 
response to fire.  
When applying the recommendations in 21.2,  refer also to Annex E  for guidance on the selection of  detecti on 
type and any settings of mode or sensitivity. Clause 40.2b)1)  recommends that a designer  record the selection 
of the detector type and configuration using Table E.1.  
21.1.2  Heat detectors  
Heat detectors may take the form of either point type detectors or line type detectors. The detection  system 
may be designed to respond when a fixed temperature is reached. The heat detector may also  include a sensor 
that responds to the rate of rise of temperature. In this case, the detector responds  either the temperature ri ses 
at more than  a certain rate, or when the fixed temperature is reached . 
Heat detectors conforming to BS EN 54 -5 operate in the manner described above. Heat detectors  that operate 
only when the rate of rise of temperature is abnormal, but not when a fixe d temperature is reached, do not 
conform to BS EN 54 -5 and ought not to be used; they can fail to  detect a slowly developing fire.  
21.1.3  Smoke detectors  
Point smoke detectors utilize one (or both ) of two principles:  
• ionization chamber smoke detectors detect smok e by the reduction it causes in the current that flows 
between electrodes in an ionization chamber within the detector;  
• optical smoke detectors detect smoke by means of the light scatter that results from the presence of a 
small light source within the det ector.  
Optical beam smoke detectors are effectively line type smoke detectors. They comprise a light source  (usually 
operating at infrared frequencies} and a receiver. The two are either separated or housed  within a single unit, 
in which case reflectors ar e used to reflect light from the transmitter back to th e associated receiver. Optical 
beam detectors operate by detecting the obscuration of the light sourc e that occurs in the presence of smoke. 
Some optical beam detectors can also detect heat by means of variation in the refractive index of light 
("shimmer effect ’’) that occurs at turbulent interfaces hot and cold air.  
In an aspirating smoke detection system, air samples are drawn, by a pump or fan, through sampling points  
(holes in the pipework ) within t he protected area, to a central detector. The detector can open on ionization 
chamber or optical principles.  
The amount of air entering each sampling point is usually small and  ought not to be considered as  modifying 
air or smoke flows within the protected  space. In general, each sampling point may be  considered as a 
separate point type smoke detector provided that a single sampling point has equivalent sensitivity  to a point 
type smoke detector.  
21.1.4  Combustion gas detectors  
Combustion gas detectors are point -type detectors that respond to one (or more ) of the gases produ ction by 
a fire. For example, carbon monoxide is produced when incomplete combustion occurs as a result  restriction 
of the amount of oxygen available to support the combustion process.  
Carbon mo noxide can spread by diffusion through certain forms of construction. In the event of  fire, therefore, 
carbon monoxide detectors could operate at a considerable distance from the fire, and  floors other than the 
floor of fire origin. Care needs to be taken to ensure that this does not resul t in misleading information for 
firefighters or others responding to a fire signal.  
Electrochemical sensors within combustion gas detectors have a finite life, after which replacement is 
necessary. It is important that the  user is made aware of the likely lifetime of any combustion gas  detector 
used within a fire detection and fire alarm system.  
21.1.5  Flame detectors  
Flame detectors detect the infrared and/or ultraviolet radiation that is emitted by flame. Both types radiation -
sensitive cells that "see" the fire either directly or through built -in lenses or reflectors.   
Infrared flame detectors are usually designed to respond to flame characteristics such as flicker, size of more 
than one specific radiation frequency. Types intend ed for outdoor use can be designed to respond to specific 
infrared frequency bands that are not characteristic of solar radiation.  BOS 813 -1:2023  
Edition 1.0 
43 Ultraviolet flame detectors normally operate within wavelengths that the ozone layer filters out of  solar 
radiation. Hence, u ltraviolet detectors do not normally respond to sunlight and may generally be  used outdoors.  
21.1.6  Multi -sensor fire detectors  
In a fire detection system incorporating multi -sensor detectors, each multi -sensor fire detector contains  more 
than one sensor, each of  which responds to a different physical and/or chemical characteristic  of fire. The 
purpose of combining sensors in this way is to enhance the performance of the system in  detection of  fire, or 
its resistance to at least certain categories of false alarm, or both.  
The method (if any) of combining the signals from each sensor varies between different proprietary  multi -
sensor fire detection systems. In some such systems, there is significant potential for reduction of  many types 
of false alarm.  
With some mult i-sensor fire detectors, it is possible to disable an individual detection sensor. This might  be 
used in a time -related system to reduce false alarms (see 35.2. 7.1). For example, with a heat and  optical 
multi -sensor detector the optical sensor might be di sabled during the day. If this is the case, it is  vital that the 
detectors are spaced for the least sensitive sensor, in this case, heat.  
21.1.7  Video fire detectors  
Fire can also be detected by video techniques, in which video cameras monitor the protected space .  
The images from each camera are analysed electronically to detect the presence of smoke and/or flames  by 
monitoring changes that occur in the camera's field of view.  
Video fire detectors rely on appropriate and continuous illumination of the field of vi ew. Such lighting  can be 
normal lighting, specially installed infrared light sources, or a combination of the two.  
Video fire detectors can also be used as a means of verifying a fire (see Section 3). Where they are the  sole 
means of detection, they need t o be designed, and their suitability and performance verified, by a  qualified 
specialist.   
There are currently no product standards that define the performance of video fire detectors and  reliance is 
placed on manufacturers' recommendations. In many cases,  they tend to be used as  supplemental detection 
or for special applications where other detection techniques are inappropriate  or ineffective.  
21.1.8  Choice of fire detection principle  
No one type of detector is the most suitable for all applications. Final choic e depends primarily on:  
• the speed of response required (to sat isfy, the fire safety objective);  
• the need to minimize false alarms;  
• the nature of the fire hazard.  
However, other factors, such as cost, suitability for the environment and maintenance requirem ents,  might 
need to be considered. In some circumstances, a mixture of different types of detectors  might be  appropriate 
to optimize speed of detection or to minimize false alarms.  
All fire detectors will respond to some extent to phenomena other than fire . Measures to minimize such  false 
alarms and their effects are described in Section 3.  
Heat detectors are generally less sensitive to most fires than all other types of  fire detector, but can  detect 
certain very clean -burning fires, such as those involving  certain flammable liquids (e.g. alcohol)  before a smoke 
or combustion gas detector. They are unlikely to respond to smouldering fires and, as  a simple rule of thumb, 
require the flames from a fire to reach about one -third of the distance to the  ceiling be fore they operate.  
In view of their lack of sensitivity, heat detectors are not suitable for the protection of areas where  warning of 
the presence of smoke is required or where a small fire would cause unacceptable damage.  
On the other hand, heat detectors  generally have a greater resistance to environmental conditions than  other 
types  of detectors . Accordingly, in most situations, they have the greatest immunity to false alarms.  In addition, 
they generally require only the minimum of routine attention duri ng system maintenance.  
Ionization chamber smoke detectors are particularly sensitive to smoke containing small particles, such  as are 
produced in rapidly burning flaming fires, but might be less sensitive to the larger particles found  in optically 
dense sm oke of similar mass, such as can result from smouldering fires, including those  involving polyurethane 
foam or overheated PVC.  
Optical smoke detectors are sensitive to optically dense smoke but  are less sensitive to the small  particles 
found in clean -burni ng fires that produce little visible smoke. Detectors that operate on the  principle of light BOS 813 -1:2023  
Edition 1.0 
44 scatter are more sensitive to light coloured smoke; very dark smoke, by definition,  absorbs light rather than 
scatters it, but will be readily detected by a smoke detector that operates on  the principle of obscuration (e.g. 
an optical beam type detector).  
One of the hazards on escape routes and stairways is visible smoke, which might obscure the visibility  of the 
route and of exit signs. Optical smoke detectors are therefore well suited for use in escape routes  because 
they detect visible smoke and might operate before the escape route becomes impassable.  
Both optical and ionization chamber smoke detectors conforming to BS EN 54 -7 have a sufficiently wide  range 
of response to be suitable for most applications in which a smoke detector is appropriate. In some  premises, 
however, there might be specific risks for which one type is more suitable, either in respect of  sensitivity to the 
type of  fire that is anticipated or resistance to false alarms (see Section 3). In specific  circumstances, it might 
be advisable to install point smoke detectors having a higher or lower sensitivity,  possibly in conjunction with 
a time -related system. Specialist application guidance ought to  be sought  from the manufacturer.  
Optical beam smoke detectors can prove economical and effective for the protection of large, open -plan 
spaces with relatively high ceilings (e.g. warehouses), particularly if access to point smoke detectors  for 
maintenance  could present practical difficulties. It is, however, essential that they are mounted to  solid 
construction that is unlikely to "flex" as a result of changes in temperature or imposed load, as  this can cause 
misalignment of the optical beam and, hence,  fault signals or false alarms. The band  of sensitivities of optical 
beam smoke detectors conforming to BS EN 54 -12 is defined by an absolute  maximum sensitivity 
(corresponding to an obscuration in the near infrared of 0.4 dB) and a minimum  sensitivity that i s defined by 
the ability to pass fire tests TF2 to TFS (typically 5 dB). In specific  circumstances, it might be advisable to 
install optical beam smoke detectors having a higher or lower  sensitivity. Specialist application guidance ought 
to be sought from the manufacturer.  
Conventional smoke detection systems cannot detect the products from clean -burning fires (such as  burning 
alcohol), which do not produce smoke particles. This is not usually a serious disadvantage  because a fire 
normally involves other co mbustibles at an early stage. A fire that involves only a material  that burns without 
the production of smoke can, however, be detected by optical beam smoke detectors  that incorporate thermal 
turbulence detection.  
A multi -sensor fire detector is one that incorporates, in a single mechanical enclosure, sensors which  detect 
more than one physical or chemical phenomenon of a real fire. The overall fire performance is  determined 
using a combination of the detected phenomena. Sensors included in currently avail able multi -sensor fire 
detectors detect smoke, carbon monoxide and heat.  
Single -sensor fire detectors are suitable in most instances. Howe ver, certain multi -sensor fire detectors  can 
provide, depending on the detection algorithm used, some or all of the fo llowing advantages in  certain 
applications:  
• when the expected fire is of a specific type;  
• when the expected fire does not produce smoke particles;  
• when there is a specific threat from a certain type of unwanted alarm (see Clause 35);  
• when the risk varies a t different times of day; or  
• when it is deemed advantageous to standardize on one type of detector for all areas of the building.  
Some multi -sensor detectors can be configured into an operating mode for which they have not been  
certificated or do not confo rm to standards.  Any variation in configuration from that first designed can be 
recorded as explained in Annex E.  
In general, smoke detectors give appreciably faster response to most fires than heat detectors but  are more 
likely to give false alarms (see S ection 3). Where there are production or other processes that  produce smoke, 
fumes, dust, etc., which might operate smoke detectors, an alternative type of  fire detector needs to be used.  
Aspirating smoke detection systems commonly incorporate a detector o f much higher sensitivity than  point or 
optical beam smoke detectors. Such "high sensitivity" aspirating smoke detection systems  are designated 
Class A systems in BS EN 54 -20 and are often used to protect critical electronic equipment  rooms, in which 
even a very small fire can result in unacceptable damage. Guidance on fire protection  of such facilities is given 
in BS 6266.  
Aspirating smoke detection systems are also used to protect spaces in which point,  or beam type smoke  
detectors would present difficult ies on the basis of : 
• aesthetics (aspirating pipework might be run in floor voids, with capillary tubes sampling air from  the space 
below via a small hole drilled in the ceiling);  BOS 813 -1:2023  
Edition 1.0 
45 • height of the space (the cumulative sampling provided by aspirating smoke det ection systems,  coupled 
with the possibility of running pipework vertically on the walls and storage racks, can  provide enhanced 
protection compared with point smoke detectors mounted at ceiling level);  
• temperature of the space (e.g. in cold stores, the de tector can be located outside the space, so that it  is 
not directly exposed to low temperatures);  
• difficult maintenance access (in areas where access for maintenance will be restricted or even  impossible 
after installation, the detector can be located outs ide the restricted space).  
Typically, a Class B (enhanced sensitivity) or Class C (normal sensitivity) aspirating smoke detection  system 
is used in such applications, but it is important to seek advice from suppliers or other competent  persons with 
suffici ent experience and knowledge of aspirating smoke detection systems and  BSEN 54 -20. 
For aspirating systems, specialist application guidance needs to be sought from the manufacturer.  
Where the principal gas to which a combustion gas detector responds is carb on monoxide, the detector  will 
be most sensitive to smouldering fires and fires in which the rate of burning is controlled by the  supply of air. 
Such detectors can be relatively insensitive to free -burning fires supported by a plentiful  supply of oxygen.  
Carbon monoxide detectors can be immune to certain environmental influences that can result in false  alarms 
from certain smoke detection systems, such as dust, steam and cigarette smoke, while responding  to many 
types of fire appreciably faster than heat de tectors.  
Because of their inability to detect smouldering fires,  flame detectors ought not to be considered as  general -
purpose  detectors, and are normally used for specialized applications, such as detection of  fires in plants 
handling or storing highly  flammable liquids or gases.  
Infrared flame detectors are sometimes used to protect very high spaces, such as cathedrals or atria.  The 
detectors do not need to be ceiling -mounted; they can be mounted at relatively low levels on  walls around a 
very high protec ted space, within which only a very large fire could be detected by  ceiling -mounted heat or 
smoke detectors. Ultraviolet flame detectors are not generally suitable for  this application, since ultraviolet 
radiation is greatly attenuated by smoke, whereas in frared radiation  penetrates smoke well.  
While achievement of the fire safety objective (e.g. warning occupants of  fire before escape routes are  
impassable) always takes precedence, avoidance of false alarms needs to be given similar weight in  
consideration  of the detection principle by the designer at the design stage. A high level of false alarms  is not 
merely disruptive to occupants and business activities; it can result in failure to achieve the fire  safety objective 
as a result of disablement of part, o r all, of the system, or of inappropriate response of  occupants to fire signals.  
Choice of fire detection principle therefore needs to take into account:  
• the speed of  fire detection required, based on an assessment of fire risk;  
• the nature and quantity of the combustible materials present, including ease of ignition,  heat release rate, 
likely form of combustion (e.g. smouldering or flaming) and propensity for  smoke production;  
• probable rate of  fire growth and spread;  
• the nature of the environment (e.g. humi dity, temperature, cleanliness, extent of pollutants and  nature of 
work processes);  
• the proposed fire evacuation strategy;  
• the height and geometry of the protected area;  
• the attendance time of the fire and rescue service (particularly in the case of Catego ry P systems);  
• other active and passive fire protection measures present;  
• the susceptibility of contents to heat, smoke and water; and  
• the speed of response to fire, and the probable false alarm rates, of different types of fire detector.  
In general, in a slow smouldering fire, a smoke or combustion gas detector will operate before a heat  detector. 
A fire that evolves heat and flame rapidly and with very little smoke could operate a heat or  flame detector 
before a smoke or combustion gas detector. With a fl ammable liquid fire, a flame detector  could operate first. 
Where speed of response is important in an environment in which false alarms  might result from the type of 
fire detection that is desirable, multi -sensor fire detectors or a system  incorporating co incidence detection can 
enable early detection of fire without an unacceptable rate of  false alarms.  BOS 813 -1:2023  
Edition 1.0 
46 While the fastest achievable response to fire is desirable, it might not always be necessary, given the  objective 
of the system, the other fire protection measures present, the likely nature of a fire and the  potential for fire -
spread; nor is it desirable if the result is an unacceptable rate of false alarms.  
If for example, there were a requirement to protect a transformer chamber in a dirty environment,  consideration 
would need to be given to the reason for the protection. If the reason were concern  regarding the hazard that 
the oil -filled transformer created to adjacent areas, from which it was separated by substantial fire -resisting 
construction, heat det ection might be appropriate. A  fire involving  the flammable oil would be detected quite 
quickly and well before the integrity of the fire -resisting  construction was threatened. Even if earlier warning 
could be given by smoke detection, the increased  potent ial for false alarms and increased maintenance burden 
might not be warranted. If, alternatively,  the reason for the protection were to protect the transformer, on which 
a high revenue earning process  depended, from a fire in cables within the enclosure, sm oke detection might 
be necessary.  
Similarly, it is acceptable, in a Category L2 or L3 system within a building in which people sleep, to  install heat 
detectors in bedrooms. The objective of these detectors is not to provide the earliest possible  warning to  
occupants of a bedroom in which fire starts, but to warn other occupants before the integrity  of the door of the 
bedroom is threatened by fire.  
Earlier warning would be given by smoke detectors, and might be desirable in, for example, rooms  occupied 
by di sabled people, but at an increased risk of false alarms. Earlier warning with a lesser  increase in the risk 
of false alarms might be given by carbon monoxide detectors or by a multi -sensor fire  detection system.  
In order to ensure that the objectives of th e system are satisfied without an unnecessary level of false  alarms, 
early consultation between the interested parties is desirable (see Clause 6). An assessment of  the fire risk 
would be included in this consultation.  
21.2 Recommendations  
The following recomme ndations are applicable.  
a) The type(s) of fire detector used in a system should provide adequate protection of occupants,  property 
or both, as appropriate to the category of system, while minimizing the risk of false  alarms as far as 
practicable (see Section  3). In case of doubt, there should be early consultation  between all interested 
parties (see Clause 6). Maintenance requirements for different types of  detectors  should also be taken 
into consideration, along with any special requirements of the user  (e.g. regarding the impact of the 
fire detection system on aesthetics).  
b) Heat detectors may be used in any area, other than the following:  
1) areas of a Category P system in which a small fire (including any form of smouldering fire)  has the 
potential to cause una cceptable damage;  
NOTE 1 Products of combustion might be corrosive and cause considerable damage without burning the  
contents of the affected area.  
2) escape routes in Category L systems (but heat detectors may be used in other areas,  including 
rooms that ope n onto escape routes);  
3) areas in which the production of smoke could present a threat to occupants' escape before it  is 
likely to be detected by people or heat detection.  
NOTE 2 It is generally accepted that occupants in a room of  fire origin are likely to be aware of a fire before  
it is detected by any form of  fire detector, unless they are asleep. Even if occupants are asleep, the risk to  
occupants of typically sized bedrooms might not be such as to warrant smoke detection within the bedrooms,  
except in th e case of dormitory accommodation or rooms intended for mobility -impaired disabled people who  
require additional time to escape from a fire in their bedroom.  
4) areas in which heat detectors would have a high potential for false alarms (see Section 3).  
c) Smoke detectors may be used in any area, other than the following:  
1) areas in which the principal fire hazard is the presence of flammable liquids or gases that  produce 
little smoke when involved in a fire;  
NOTE 3 If  fire is likely to involve carbonaceous material s, such as wood, paper, textiles, etc., in the early  
stages, smoke detection might be suitable.  
2) areas in which smoke detectors would have a high potential for false alarms (see Section 3),  
unless the risk from fire warrants the provision of automatic fire detection and the use of  other 
forms of fire detection is precluded on the basis of their speed of response to fires of  the type that 
might be anticipated.  BOS 813 -1:2023  
Edition 1.0 
47 NOTE 4 This does not imply that a high rate of false alarms is ever acceptable; methods, such as fil tering , 
might be necessary to avoid an unacceptable rate of evacuation signals and calls to the fire and rescue  
service (see section 3.). 
NOTE 5 Use of an optical smoke detector instead of an ionization chamber smoke detector (or vice versa 
can change the potential for false alarms considerably (see  section 3)  
d) In Category L systems, smoke detectors installed within corridors and stairways that form part  of the 
means of escape should be of the optical type, unless the use of optical detectors would  significa ntly 
increase the rate of false alarms (see Section 3).  
NOTE 6 Multi -sensors containing a smoke detector might be suitable in circumstances referred to in  21.2c) and 
21.2d).  
e) In areas in which early detection of a smouldering fire is required, optical smoke  detectors,  optical 
beam detectors, aspirating smoke detection systems, carbon monoxide fire detectors or  suitable multi -
sensor fire detectors should be used.  
f) In areas in which early detection of a relatively fast and clean -burning flaming fire is required , ionization 
chamber smoke detectors, suitable multi -sensor fire detection systems or flame  detectors should be 
used; suitably sensitive heat detectors may also be considered.  
g)  Carbon monoxide fire detectors may be used to protect any of the following area s: 
1) any area in which the use of a heat detector would be acceptable, other than areas in which  the 
principal fire hazard comprises flammable liquids that, when ignited, result in a rapid  flaming fire;  
2) rooms opening onto escape routes in a Category L3 syste m; 
NOTE 7 Use of carbon monoxide fire detectors in bedrooms provides a higher standard of protection of  
sleeping occupants than heat detectors, but the potential for false alarms will be less than in the case of  
smoke detectors.  
3) all escape routes within Ca tegory L3 or L4 systems, provided carbon monoxide detectors  are used 
in conjunction with smoke detectors. Specialist application guidance should be  sought from the 
manufacturer;  
4) any other area in which the fire hazard (e.g. the nature of the combustible ma terials, the  type of 
fire that could be expected and the amount of ventilation) is of such a nature that  there is test 
evidence to demonstrate that the carbon monoxide detectors proposed would  offer adequate fire 
protection.  
h) Flame detectors should only be used in situations in which it is sufficient for the fire detection  system 
to respond to flaming fires, but not fires that produce smoke without significant flame  (e.g. smouldering 
fires). For flame detectors to be effective, they should have a clear line -of-sight  to the area being 
protected.  
i) Ultraviolet flame detectors should not be used as the sole means of fire detection in areas within  
buildings in which a fire can produce significant quantities of smoke before flaming occurs.  
j) When video fire detectors are used as the sole means of detection, the recommendations of  the 
product manufacturer and/or suppliers in terms of detection performance and application  limitations 
should be followed and, wherever required, specialist knowledge should be sought.  
NOTE 8  It is important that video fire detectors are capable of detecting flame and/or smoke reliably in  the absence 
of the normal lighting in the building and the absence of a mains power supply to any lighting  provided specifically 
to aid the detection off al me and/or smoke.  
k) Where detection can be set to a number of different operating modes ( e.g. a multi -sensor fire  detection 
system with a number of different response characteristics), the basis for selection  of the response 
characteristics selected should b e recorded in the operating and maintenance  manual for the system. 
See 40.2b) and Annex E.  
22  Spacing and siting of automatic fire detectors  
22.1 Commentary  
Heat and smoke detectors depend on convection to transport hot gases and smoke from the fire to  the detect or. 
Spacing and siting of these detectors needs to be based on the need to restrict the time  taken for this 
movement and to ensure that the products of combustion reach the detector in adequate  concentration. In a 
building, the hottest gas and the greatest  concentration of smoke generally form  at the highest parts of the 
enclosed areas, and it is here, therefore, that heat or smoke detectors need  to be sited.  BOS 813 -1:2023  
Edition 1.0 
48 As the smoke and hot gases from a fire rise, they become diluted with clean, cool air, which is dra wn into  the 
plume. Hence, the size of  fire required in order to operate heat or smoke detectors increases rapidly  as the 
height of the ceiling above the fire increases. To some extent, this effect can be countered by the  use of more 
sensitive detectors. Op tical beam detectors and aspirating smoke detection systems are less  sensitive to the 
effects of ceiling height than are point -type detectors, since the increased size of plume  will involve a greater 
proportion of the path length of the optical beam or mor e sampling holes and so  help to alleviate the effects of 
reduced smoke density.  
In addition, the entrainment of air cools the gases. If the ceiling is high and the ambient temperature in  the 
uppermost areas within the protected space is high, the plume of smoke and hot gases might reach  ambient 
temperature before reaching the ceiling. If the temperature of the surrounding air increases  with height (e.g. 
as a result of solar gain ), it is possible for the air at the uppermost levels to be at a  higher temperat ure than 
that of the plume. The plume will then spread out to form a smoke layer before  it reaches the ceiling, as though 
there were an "invisible ceiling" at a specific height within the protected  space. This is known as stratification, 
and, at this stage  of the fire growth, the smoke and hot gases will  not operate ceiling -mounted detectors, 
regardless of their sensitivity.  
It is usually difficult to predict with any degree of certainty the level at which stratification occurs; this  depends 
on the convecti ve heat output of the fire and the temperature profile within the protected space  at the time of 
the fire, neither of which are accurately known quantities. If detectors are mounted at an  expected stratification 
level, and stratification does not occur or occurs at a higher level, detection might  be dangerously delayed, as 
the relatively narrow plume can "bypass" the detectors. In some cases, a high  density of detection at a low 
level might be sufficient to detect any rising plume. Alternatively, multi -level detection can be provided by, for 
example, using sampling holes of an aspirating fire detection system  at multiple levels, or by aiming an optical 
beam detector at an angle to the horizontal, so that it might  detect smoke as it stratifies.  
Ultimately, as  the fire grows and releases more heat, the plume will break through the thermal barrier  and 
ceiling -mounted detectors will operate, albeit at a later stage of the fire than if  no stratification  had occurred. 
[However, a larger fire can normally be "tolera ted" if the ceiling height is greater.) Thus,  where multi -level 
supplementary detection is provided in a high space with the intention of detecting the  stratified layer, ceiling -
mounted detectors need to be used. However, where the design intent of the low  level detection is to detect a 
rising plume (taking into account the fact that since the plume of hot gas  is relatively narrow, the radius of 
coverage of any supplementary detection intended to detect a rising  plume needs to be reduced), omission of 
ceiling-mounted detectors might be considered, provided that  there is no discernible fire risk above the low -
level layer of detectors.  
Flame detectors do not rely on convection, but detect the radiation emitted from flame. Accordingly, they  do 
not need to be mo unted on ceilings, and they are not affected by stratification. Their sensitivity to a  fire does 
decrease, however, as their distance from the fire increases and as the intensity of the radiation  decreases 
approximately in proportion to the square of the d istance from its source. On the one hand,  they may be 
mounted at relatively low level within a high space to maximize sensitivity to a  fire at ground  level; on the other 
hand, since they depend on a clear line -of-sight to the fire, mounting at too  low a he ight can preclude early 
detection of a shielded fire.  
Although, for general protection of any space, the above considerations apply, localized "spot" protection  can 
be provided by additional fire detectors. For example, line -type heat detection systems mig ht be  particularly 
suitable for protecting items of plant or cabling. When used for these purposes, the detector  needs to be 
mounted as close as possible to the place where fire or overheating might occur, and either  mounted above 
the item to be protected or in thermal contact with it.  
The effectiveness of an automatic fire detection system is affected by obstructions between heat or  smoke 
detectors and the products of combustion. It is important that heat and smoke detectors are not  mounted too 
close to ob structions to the flow of hot gases and smoke towards the detector and that  radiation from flame is 
not obscured from flame detectors. At the junction of a wall and a ceiling, there  is a "dead space'; within which 
heat,  or smoke detection would not be adeq uately effective. The effect on  detection efficiency might be less in 
the case of carbon monoxide detection, since transport of carbon  monoxide to the detector is assisted by 
diffusion.  
Similarly, as the hot gases and smoke flow horizontally across a ceili ng, there is a stagnant boundary  layer at 
the surface of the ceiling; this precludes the sensitive element of a heat or smoke detector  from being mounted 
flush with a ceiling. This restriction does not apply to the sampling points of an  aspirating smoke de tection 
system, which can be flush -mounted because the sampled air drawn into the  sampling hole comes from the 
main flow outside the boundary layer. By contrast, a point type smoke  detector relies on the flows across the 
ceiling (outside the boundary layer ) to drive the smoke into  the chamber.  
In siting heat, smoke and combustion gas detectors, consideration needs to be given to the possible  pattern 
of air movement in the premises. Air conditioning and ventilation systems with high air change  rates might BOS 813 -1:2023  
Edition 1.0 
49 adversely affect the response of detectors by drawing fresh air over them, by drawing heat,  smoke and 
combustion gases away from them, or by diluting the smoke and hot combustion gases  produced by a fire. It 
might be necessary to seek specialist advice.  
 Guidance on protection of ceiling voids in this standard  is based on still air within the voids. Where  there is 
significant air flow within a void, such as where the void is  used as an air handling plenum,  special 
consideration might need to be given to the s pacing, siting and sensitivity of detectors within the  void.  
Smoke detectors may be sited to monitor smoke within ventilation extract ducts. In general, such  detectors are 
intended to assist in the prevention of spread of smoke by the ventilation system, b y enabling any recirculation 
to be shut off in the event of a fire. These detectors may be connected to the  fire detection and fire alarm 
system but, if the smoke detectors are of normal sensitivity, they would not  constitute a satisfactory means of 
detect ing a fire in the area from which the air is  drawn, as the smoke  is diluted by the clean air that is extracted. 
Smoke might collect in one or more layers in ventilation  ducts, so as much of the duct needs to be sampled as 
is practical. Duct probe sampling pipes with  adequate holes are therefore arranged to cover the widest 
dimension of the duct.  
Certain very high -sensitivity smoke detection systems (often of the aspirating type) are sensitive  enough to 
detect smoke that has been substantially diluted with c lean air. Experience has shown that  such systems, 
when used to monitor return air to air conditioning units by means of air sampling  points mounted directly in 
the airflow, are capable of detecting very small, incipient fires, involving,  for example, smoul dering of electronic 
components within equipment cabinets in the protected space.  
This arrangement is usually regarded as supplementary to other forms of  fire detection in the protected  space 
(including aspirating systems with air sampling points sited in accordance with practice  normally adopted for 
point smoke detectors), owing to its limited response capability once the air  movement ceases.  
For remotely situated or hard -to-access detection equipment, consideration needs to be given to the  feasibility 
of testing and maintenance at the design stage.  
22.2 Recommendations for provision of automatic fire detectors  
The following recommendations are applicable.  
a)  Fire detectors should be provided in accordance with 8.2 
b) In stairways, fire detectors should be sited at t he top of the stairway and on each main landing.  
c)  Other than in Category L4, LS and P2 systems, if any flue -like structure, shaft for a lift, escalator  or hoist, 
or any enclosed chute, penetrates one or more ceilings, a fire detector should be  sited at the  top of the 
shaft or enclosure and, on each level in the accommodation area, within  approximately 1.5 m of the 
penetration.  
The need for fire detectors in these positions should be considered at the design stage of  Category LS 
and P2 systems.  
 
NOTE 1 For a ny of these flue -like structures a fire detector within 1.5 m is needed only in the areas protected  by the 
category of system in question . 
d) If the system category is such that automatic fire detection should be provided in any area that  contains a 
horizonta l void of 800 mm or more in height, automatic fire detection should also be  provided in the void. 
Voids less than 800 mm in height need not be protected, unless either:  
1)  the void is such that extensive spread of fire or smoke, particularly between rooms an d 
compartments, can take place before detection; or  
2) on the basis of a fire risk assessment, the fire risk in the void is such as to warrant protection  of the 
void.  
NOTE 2 In Category P systems, it is common practice to protect all floor voids in electronic  data processing  
installations, regardless of their depth, if the voids contain cables. Usually, this is on the basis of the probability  of 
ignition and the amount of combustible material within the void, in conjunction with the consequences of  a fire with in 
the void in respect of business continuity. Guidance on protection of electronic data processing  installations is given 
in BS 6266.  
NOTE 3 In a Category L2 or L3 system, detectors in rooms opening onto escape routes are provided only  to give a 
warning o f fire before it affects the escape routes. Detection in voids above or below the rooms  might not be necessary 
for this purpose (e.g. if  fire-resisting construction separates a void from the adjacent  escape route).  
NOTE 4 If the fire risk within a void of 800 mm or more is considered to be low, consideration might be given to 
omission of  fire detection  from the void, subject to the agreement of the interested parties (see Clause 6),  this ought 
to be recorded as a variation on the relevant system certificate . This might arise, for example, if the probability of BOS 813 -1:2023  
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50 ignition and development of  fire in the void were very low, or if the void were limited in extent  that spread of  fire beyond 
the room of origin, via the void, were unlikely.  
e) If any lantern -light (see.3 .3.1) within a protected area is 800 mm or more in depth, or is used  ventilation, 
a fire detector should be sited in the lantern -light.  
22.3 Recommendations for siting of heat, smoke and multi -sensor detectors  
The following recommendations are applicable.  
a) Under  flat ceilings, the horizontal distance between any point in a protected area and the  detector nearest 
to that point should not exceed:  
1) 7.5 m if the nearest detector is a smoke detector;  
2) 5.3 m if the nearest detector is a heat detector.  
NOTE 1 In corridor s of width not exceeding 2 m, only points close to the centre line of the corridor need be  considered, 
and accordingly the above recommendations will be satisfied if smoke or heat detectors are sited  at intervals of15 m 
and 10.6 m respectively, with the ma ximum dimension from the end wall being 7.5 m and  5.3 m respectively.  
NOTE 2 Where it is the design intention regularly to disable sensors in a multi -sensor fire detection system,  such that 
the sensors rely solely or substantially on a heat detector, the l ocation of sensors is governed  by 22.3a)2).  
b) Where the recommendations of  BS 7273 -4 conflict with the recommendations of 22.3a), the  
recommendations of BS 7273 -4 should take precedence.  
NOTE 3 This might arise only in the case of Category L4 and LS systems in which there are electronically  held-open 
fire doors; in certain circumstances, the maximum spacing between smoke detectors in corridors  recommended in BS 
7273 -4 is less than the maximum specified in this standard . 
c) If the protected area has a pitched cei ling, for detectors at or near the apex, the horizontal  distances 
recommended in 22.3a) may be increased by 1 % for each degree of slope, up to  a maximum increase of 
25%. For detectors not at or near the apex the distances given in  22.3a) apply.  
d) In apex ro ofs, fire detectors should be sited at or near each apex, except that, if the difference in  height 
between the bottom of the roof and top of the apex is less than the following figures, the  roof may be 
treated as flat (see Figure 7):  
1) 600 mm if the area is protected by smoke detectors;  
2) 150 mm if the area is protected by heat detectors.  
NOTE 4 Detectors may be regarded as "near the apex" referred to in 22.3c) and 22.3d) if the vertical  distance from 
the apex to the detector is within the figures given in 22.3 d)1) and 22.3d)2) for the appropriate  type of detector.  
e) Other than within rooms in a Category L3 system  (see 22.3f) or in voids [see 22.3g) or where a  horizontal 
ceiling comprises a series of small cells ( see 22.3 l), fire detectors should be sited on  ceilings, such that 
their sensitive elements are between the following distances below ceilings:  
1) 25 mm to 600 mm for smoke detectors;  
2) 25 mm to150 mm for heat detectors.  
f) Detectors within rooms that open onto escape routes in a Category L3 system should either b e sited in 
accordance with 22.3e) or should be sited on a wall, close to any door that opens onto an  escape route. 
Wall-mounted detectors should be sited such that the top of the detection element  is between 150 mm 
and 300 mm below the ceiling, and the bot tom of the detection element is  above the level of the door 
opening.  
NOTE 5 Particular care is necessary in rooms with a high ceiling height (for example height exceeding 4 m).  
NOTE 6 Where an automatic sprinkler installation initiates a fire alarm signal,  via the fire detection and fire  alarm 
system, on flow of water from a single sprinkler head, a sprinkler head within a room may be regarded  as an automatic 
fire detector for the purpose of this recommendation.  
NOTE 7 Wall mounting may also be adopted in t hose rooms or areas in which the protection afforded by  a Category 
L2 system reflects only the recommendations for a Category L3 system, in that the purpose is  protection of the adjacent 
escape route (i.e. other than in areas in which detector siting needs  to reflect the  objective of protecting the occupant 
of the room of  fire origin, as is the case in bedrooms intended for disabled  people, or giving warning in areas in which 
the likelihood of  fire is high).  
g) In unventilated voids not greater than 1.5 m in d epth, the sensing element of fire detectors  should be sited 
within the top 10% of the void or the top 125 mm, whichever is the greater  (see Figure 8). Voids greater 
than 1.5 m in depth should be treated as a room and the  recommendations of 22.3e) should be  applied. 
In shallow voids, it might be necessary to mount  the fire detector in an unusual orientation, in which case BOS 813 -1:2023  
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51 care should be taken that the deposition  of dust or dirt cannot adversely affect the operation of the detector. 
The manufacturer's  recomme ndations should be followed with regard to orientation and the ingress of dirt 
and dust  and any consequent servicing recommendation.  
h) Heat and smoke detectors should not be mounted within 500 mm of any walls, partitions or  obstructions 
to flow of smoke and hot gases, such as structural beams and ductwork, where  the obstructions are greater 
than 250 mm in depth. (This recommendation does not apply to  detectors within rooms opening into 
escape routes in a Category L3 system).  
NOTE 8 If an enclosed area has no horizontal dimension greater than 1 m, it is impossible to comply with  this 
recommendation; this need not be regarded as a variation if the detector is sited as close as possible to the  centre of 
the space . 
i) Where structural beams, ductwork, light fittings or other isolated ceiling attachments not greater  than 250 
mm in depth create obstacles to the flow of smoke, detectors should not be mounted  closer to the 
obstruction than twice the depth of the obstruction (see Figure 9).  
NOTE 9 In some circumstances, co mpliance with this recommendation might result in non -compliance with  22.3h. In 
such circumstances, non -compliance with 22.3h (or 22.3i) need not be regarded as a variation.  
j) Where an area contains partitions or storage racks that reach within 300 mm of the  ceiling, the  partitions 
or storage racks should be treated as walls that extend to the ceiling (see Figure 10).  
NOTE 10 Where a rack contains high -value or high -risk materials or where the height of the rack exceeds 8 m,  the 
use of in -rack detection might  be considered. For more information, see the FIA Code of Practice for Design,  
Installation, Commissioning and Maintenance of Aspirating Smoke Detector (ASD ) Systems [Z ]. 
k) Ceiling obstructions, such as structural beams, deeper than 10% of the overall ceilin g height  should be 
treated as walls see Figure  11a). 
NOTE 11 Within horizontal voids, beams or obstructions that are deeper than 10% of the overall depth of the  void, 
regardless of whether the void is above the ceiling or below the floor, ought to be treat ed as walls that  subdivide the 
void.  
NOTE 12 For a cellular structure or closely spaced beams in a void, see 22.31.  
l) Where a horizontal ceiling comprises a series of small cells (a honeycomb ceiling), detector  spacing and 
siting should be in accordance with  Table 1 and Figure 14 [see Figure 11b)].  Where there are a number 
of closely spaced structural beams, such as floor joists, the cells  become elongated. Provided that the 
longer dimension of the cells is not more than L, then  across the shorter cell dimens ion, the spacing, M, 
between detectors should be as given in  Table 2 and Figure 15. The spacing for the end detector to the 
end wall is half M. Detectors  should be in the centre of the cells. If the longer dimension of the cells is more 
than L, then the  cell should be stopped to the depth of the beam and at not more than L. If this is impractical,  
detection should be installed in every cell [see Figure 11c)]. 
L = 10.6 m for smoke detectors.  
L = 7.5 m for heat detectors.  
m) Detectors above a perforated false ce iling may be used for protection of the area below the  false ceiling if:  
n) the perforations are substantially uniform, appear across the complete ceiling and  throughout they make 
up more than 40% of the surface; and  
1) the minimum dimension of each perforation in any direction is 10 mm; and   
2) the thickness of the ceiling is not greater than three times the minimum dimension of each  perforation.  
o) In all other cases, detectors should be mounted below the false ceiling, and if protection of the  void above 
the false c eiling is necessary [see 22.2d)], further detectors should be installed on the  true structural ceiling 
within the void.  
p) Detectors should not be mounted within 1 m of any air supply point of a ventilation system.  Where air is 
forced through a perforated cei ling, the ceiling should be imperforate for a radius of  at least 600 mm around 
each detector (see Figure 12).  
q) Detector siting should be such that a clear space of 500 mm is maintained below each detector  (see Figure 
13). BOS 813 -1:2023  
Edition 1.0 
52  
 
 
Key 
 
 1 Roof an gle    3 For roofs with a pitch deeper than 600 mm, smoke detectors  
should be within the top 600 mm and increased coverage  
due to the angle of the roof will then be applicable [see 22.3b)]  
  
2 Detector    4  For roofs with a pitch less than 600 mm, smok e detectors  
       may be anywhere on the roof. [see 22.3c)]  
Figure 7 – Smoke Detectors in Pitched roofs  [see 2 2.3d] 
Figure 8 – Detectors in top 10% of a void [see 22.3 g)] BOS 813 -1:2023  
Edition 1.0 
53  
 
 
 
 
Key 
1  detector            3 Plan view    
2 Storage racks  
NOTE Example of warehouse with storage racks. The gap between the racks and the ceiling is less 
than 300 mm. Ea ch rack is therefore treated as a wall and detection is needed in each aisle.  
Figure 10 – Partitions or storage on racks  
Key 
1 Ceiling            3 Light fitting or other projection    
2 Y should not be less than 2Z     
Figure 9 – Proximity of detectors to ceiling fittings [see 22.3i)]  BOS 813 -1:2023  
Edition 1.0 
54  
  
1 ceiling  
 
2 Beam down stand less than 10% of 
room height ignore  
3 No less than 500 mm  
 
4 Bean down stand greater than 10% 
of room  height Treat as wall  
Key 
Figure 11a – Ceiling s – Obstructions treated as walls [see 22.3k)]  BOS 813 -1:2023  
Edition 1.0 
55  
 
 
 
Key  
  
1 Half M  
2 Detector  
3 Plan view  
NOTE 1 In this example bean downstands are greater than 10% of ceiling height, H. H = 3 m.  
NOTE 2 Smoke detectors are used in this example. Using Table 2, the spacing M should be no more than 2.3 m  
Figure 11 c – Ceilings  – Cells formed from joists [see 22.3k) and 22.3l]  
1 ceiling  
 
2 Depth  
3  Height from floor or likely height of fire to ceiling 
slab 
Key 
Figure 11 b – Ceilings  – Horizontal ceiling obstructions a series of sma ll cells [see 22.3l)]  BOS 813 -1:2023  
Edition 1.0 
56  
 
 
 
Figure 13 – Clear space around a detector  [see 22.3p )] 
Figure 12 – Detector on perforated ceiling [see 22.3 o] 
BOS 813 -1:2023  
Edition 1.0 
57  
 
Table 1- Spacing and siting of detectors on honeycomb and similar ceilings  
Overall ceiling height from floor into cell H (to 
nearest whole metre)  Maximum distance between any point and the 
nearest smoke (heat) detector  
≥3m 4.5 m (3.0 m)  
4m 5.5 m (4.0 m)  
5m 6.0 m (4.5  m) 
≥6m 6.5 m (5.0 m)  
 
 
Figure 1 4 ― Spacing and siting of detectors on honeycomb and sim ilar ceilings  
Figure 15 – Spacing and siting of detectors on ceiling with closely spaced structural beams or joists  BOS 813 -1:2023  
Edition 1.0 
58 Table 2 - Spacing and siting of detectors on ceiling with closely spaced structural beams or joists  
Overall ceiling height from floor into cell H  
(To nearest whole metre)  Maximum distance between any smoke (heat) 
detector s measured across the beam M  
≥3 m 2.3 m (1.5 m) 
4 m 2.8 m (2.0 m)  
5 m 3.0 m (3.2 m) 
≥6 m 3.3 m (2.5 m) 
 
22.4 Recommendations for siting of carbon monoxide fire detectors  
Carbon monoxide fi re detectors should be sited in accordance with all recommendations of 22.3. for  smoke 
detectors . 
22.5 Recommendations for siting of optical beam smoke detectors  
 
The following recommendations are applicable.  
a) Optical beam -type detectors should be sited in such a way that the horizontal distance between  any 
point  in the protected space and an optical beam does not exceed 7.5 m (see Figure 16).  
b) If the protected area has a pitched ceiling, for optical beam detectors at or near the apex,  the figure of 
7.5 m given in  22.5a) may be increased by 1 % for each degree of slope, up to a  maximum increase 
of 25%. For optical beam detectors not at or near the apex the distance given  in 22. 5a) applies.  
c) The recommendations of  22.3d), 22.3e), 22.3g), 22.3j), 22.3k) and 22.3m) sho uld be applied to  the 
exceptions given in 22. 5d). 
d) Optical beam smoke detectors may be installed at a distance of more than 600 mm below ceiling  level 
(or 600 mm below the apex of a pitched roof) in the following circumstances.  
1) When the optical beam detecto rs are intended to provide supplementary detection of a  rising 
smoke plume  within  high space (e.g. an atrium),  
In such cases, the width of the area protected on each side of an optical beam should  be regarded 
as, 2.5 % of the height of the beam above the h ighest likely seat of fire  (see Figure  16) 
NOTE 1 Where there is no discernible fire load above such a layer of detectors it may be justifiable to  forego 
the provision of detection at or near the ceiling.  
2)  When the optical beam detectors are installed at a n angle from the horizontal, pointing  down from 
the ceiling, in order to provide supplementary detection of smoke stratifying and  failing to reach 
the ceiling.  
NOTE 2 The spacing  recommendations for angled optical beam detectors within the three -dimensiona l 
space below a ceiling is beyond the scope of this code of practice. However, while it is possible that a single  
angled optical beam detector will eventually detect a spreading layer of stratified smoke, the installation of  
more beams, strategically posit ioned through the three -dimensional space, will provide a substantially better  
chance of detecting stratifying smoke and reduce detection times. In general te rms, for everyone  optical  
beam detector at the ceiling a further two or three detectors angled thr ough the space might be appropriate.  
3)  When the optical beam is positioned close to the apex of a pitched roof and the physical  features 
in the roof space prevent it being installed in accordance with 2 2.3d).  
In such cases the vertical distance of the opti cal beam from the apex should be minimized  (within 
the practical restraint of the building) and should not exceed the lesser of H/10  (where H  is the 
height of the apex above the floor) and 2.5 m.  
4) Where the physical features in the roof space prevent the op tical beam detector being  installed 
within 600 mm of a horizontal ceiling (in accordance with 22.3e).  
In such cases the distance from the ceiling should be minimized and should not exceed the  lesser 
of H/10 (where H  is the height of the ceiling above the f loor) and 2.5 m. Moreover, the  potential 
negative effects should be compensated by one or more of the following means:  
• reducing the maximum horizontal spacing as given in 22. 5a);  
• use an optical beam detector with enhanced sensitivity compared to the minim um required 
by BS EN 54 -12 (e.g. alarm at 35% attenuation or less): or  BOS 813 -1:2023  
Edition 1.0 
59 • introduce (or consider any existing) restrictions to flow of smoke across (and  potentially 
along) the ceiling which can restrict the spread of smoke and increase  the depth of the smoke 
layer. Containing the spread of smoke in both directions  is preferable.  
The degree of the compensation measures should be sufficiently conservative to compensate for  the 
excessive distance from ceiling and in case of doubt a smoke test should be performed.  
e) Where optical beams run closer than 500 mm to any wall, partition or obstruction to the flow of  hot 
gases, such as structural beams and ductwork, then that section of the optical beam should  be 
discounted from providing detection.  
NOTE 3 Those parts of th e optical beam within 500 mm of the beam's transmitter and receiver or reflector {s) need 
not be considered for the purpose of this recommendation.  
f) If there is a probability of people walking within the area of the optical beam, then the optical  beam 
should  be at least 2.7 m above floor level. Consideration should also be given to the  possibility of the 
optical beam being obstructed by the use of forklift trucks, in which case the  optical beam detector 
should be mounted at a suitable  height.  
NOTE 4 It is als o necessary to comply with 22. 5d). 
g)  Transmitters, receivers and any reflectors should be mounted on solid construction that is not  subject 
to movement, likely to ad versely affect the alignment of the optical beam, as a result of  changes in 
temperature or i mposed load.  
h)  The path length of the optical beam should not exceed that recommended by the manufacturer.  
NOTE 5 Where the optical beam detector  uses a reflector, the path length is the distance from the transmitter  to 
the reflector and back to the receive r. 
i) The area covered by an optical beam detector should not exceed that of a single detection zone  given 
in Clause  13. BOS 813 -1:2023  
Edition 1.0 
60  
22.6 Recommendations for siting of line heat detectors  
The following recommendations are applicable.  
a) Line heat detectors should be sited in such a way that no point in the protected space is further  than 
5.3 m horizontally from the nearest point on a line heat detector.  
b) If the protected area has a pitched ceiling , for line heat detectors at or near the ceiling, the  figure of 53 
m given in 22.6 a) should be increased by 1 % for each degree of slope up to a  maximum increase of 
25%. For line heat detectors not at or near the apex the distance given  in 22.6a) applies.  
c) The recommendations of  22.3d), 22.3e), 22.3g), 22.3j), 22.3k) and 22.3m) apply.  
d) Where a line heat detector runs closer than 500 mm to any wall, partition or obstruction to  the frow of 
hot gases, such as structural beams and ductwork, then that section of the line heat  detector should 
be discounted from providing detection.  
NOTE Those pa rts of a line heat detector within 500 mm of the control equipment need not  be considered  for the 
purpose of this recommendation.  
e) Where a line heat detector is installed to protect a particular item of plant or cabling, as opposed  to 
Figure 16 ― Sitting optical beam detectors  BOS 813 -1:2023  
Edition 1.0 
61 providing general area  protection, the detector should be mounted as close as possible to the  place 
where fire or overheating might occur, and either be mounted above the risk or in thermal  contact with 
it. 
22.7  Recommendations for siting of aspirating smoke detection systems  
The f ollowing recommendations are applicable.  
a) Where an aspirating smoke detection system is intended to provide general area protection,  each 
aspirating sampling point should be regarded as a point smoke detector, provided that a  single 
sampling point has equiv alent sensitivity to a point type smoke detector. Accordingly, the  siting of 
these sampling points should conform to 22,3. However, as the detector actually draws  samples of air 
through sampling points (holes in the pipework), 22.3e) does not apply and the  sampling points may 
be flush with a ceiling.  
b) Where an aspirating smoke detection system is intended to provide very early warning that  is 
supplementary to other forms of automatic fire detection (e.g. by monitoring return air to  air 
conditioning equipment  or monitoring specific items of equipment), the system should be  installed in 
accordance with the guidance of the manufacturer.  
c) Where an aspirating smoke detection system is used to protect  spaces with high ceilings (>25 m)   and 
there is a risk that the s moke could stratify before reaching the ceiling. sampling should be  provided 
at multiple levels using drop -pipe arrangements at the wall and, where practical, within  the main space.  
NOTE For more information see the FIA Code of Practice for Design, Install ation, Commissioning and  
Maintenance of Aspirating Smoke Detector (ASD ) Systems [Z]. 
22.8 Recommendations for siting of flame detectors  
The following recommendations are applicable.  
a) Spacing of flame detectors should be within maximum limits specified by the man ufacturer.  
b)  Where flame detectors are intended to provide general area protection, there should be a clear  line 
of sight between all points within the protected area and one or more flame detectors.  
c) Where flame detectors are intended to provide protection for specific hazard(s), there should  be a 
clear line of sight between the hazard(s) and one or more flame detectors.  
22.9 Recommendations for limits of ceiling height  
Heat,  smoke  and combustion gas detectors should not be mounted on ceilings higher than the lim its 
recommended in column 1 of Table 3. If small sections of ceiling, not exceeding in total 10% of the  ceiling area 
within the protected area, exceed these limits, these higher sections are adequately  protected provided that 
the ceiling height does not ex ceed the limits in column 2 of Table 3.  
The limits recommended in Tab le 3 are intended for ceilings over large, open areas. In vertical or flue  like 
structures, such as lift shafts and stairwells, the limits should be used for guidance.  
NOTE 1 A very high shaft (e.g. exceeding 25 m) would be better protected by detection at several levels and/or  greater 
sensitivity at the ceiling.  
NOTE 2 The recommendations in Table 3 for the Class and minimum number of ASD sampling holes may be  adapted 
for vertical or flue -like structures. For example, the detection provided by 15 Class C sample points on a  ceiling covering 
just 200 m2 can be achieved using fewer sample points at a higher sensitivity, e.g. just 3 sample  points which are 5 
times more sensitive than the Class  C. 
  BOS 813 -1:2023  
Edition 1.0 
62 Table 3 - Limits of ceiling height  
Detector type  Column 1  
Generally applicable 
maximum ceiling 
height  
m Column 2  
Max ceiling height 
for 10% of ceiling 
area 
m 
Heat detectors (BS EN 54 -5) 
Class A1  
Other classes  
Point smoke de tectors (BS EN 54 -7)  
Carbon monoxide detectors (BS EN 54 -26)  
9.0 
7.5 
10.5 
10.5  
10.5 
10.5 
12.5 
12.5 
Optical beam smoke detectors (BS EN 54 -12) 
Normal sensitivity  
Enhanced sensitivity (alarm at 35% attenuation or less)  
Aspirating smoke detection system s (BS EN 54 -20) 
General limit  
Class C with at least 5 holes  
Class C with at least 15 holes  
Class B with at least 15 holes  
Other fire detectors   
25 
40.0 (see Note 1)  
 
10.5 
15.0  
25.0  
40.0 (See Note 2)   
28.0 
43.0 (see Note 1)  
 
12.5 
18.0 
28.0 
43.0 See Note  2 
As specified by the manufacturer  
NOTE 1 The use of supplemental detection is recommended [see 22. 5d) J unless the risk (i.e. probability x 
consequence) of stratification is minimal.  
NOTE 2 The use of multi -level sampling is recommended [see 22.7c) J  unless the risk (i.e. probability x 
consequence) of stratification is minimal.  
 
22.10  Smoke detectors in ventilation ducts  
Where the specification requires smoke detectors within air extraction  ducts, the following  recommendations 
are-applicable.  
 
a) Smoke detect ors-Or duct probes should be installed in straight stretches of ductwork, at a  distance 
downst ream from the nearest bend, corner or junction of at least three times the width  of the duct.  
NOTE 1 See FIA Code of Practice for Design, Installation, Commission ing and Maintenance of Duct Smoke  
Detector (DSD) Systems [8].  
 
b) The suitability of the smoke detector for this type of application should be determined from  guidance 
produced by the manufacturer.  
c) The sampling inlet probe and the holes in the probe should be  arranged, according to the  
manufacturer's instructions, to cover as much of the duct as possible.  
NOTE 2 To comply with this subc lause normally requires the probe to cover the wider dimension of the duct  and 
the length of the probe to be at least two -thirds of that dimension.  
NOTE 3 See FIA Code of Practice for Design, Installation, Commissioning and Maintenance of Duct Smoke  
Detector  (DSD) Systems [8]. 
NOTE 4 It is not considered that detectors, other than smoke detectors, are suitable for detecting produ cts of  
combustion that are circulated by means of forced air ventilation systems.  
23 Control and indicating equipment  
23.1 Commentary  
CIE performs three principal functions:  BOS 813 -1:2023  
Edition 1.0 
63 • automatic monitoring and control of circuits external to the equipment (such as fire detec tion and  fire 
alarm device circuits) and supply of power to these circuits;  
• indication of  fire signals, fault signals and thei r location;  
• manual control to facilitate actions such as testing, disablement of devices, triggering of  fire signals,  
silencing of  audible fire warnings and resetting the system after a fire signal.  
As these facilities are required by different people at different times, all these facilities need not be  provided at 
a single location. For example, according to the premises, indication  of faults might be  required by a site 
engineer, who might not require detailed information on fire signals, whereas accurate  information on the 
location of a fire is essential to the fire and rescue service, who might need no specific  information about 
system faults.  
In small, simple systems, the control, indicating and power supply equipment for the system is normally  housed 
within a single enclosure. In large, complex premises, the main control equipment circuitry  might be installed 
at one location, powe r supplies might be distributed around the building, while main  indicating equipment 
incorporating certain basic controls is installed at another location, such as near a  main entrance to the 
building; repeat indicating equipment, with or, without controls , might be installed  at further locations, such as 
alternative points of entry for the fire and rescue service.  
Since premises vary in size, complexity and fire strategy, it is  essential that the nature and siting of  manual 
controls and all indicating equi pment, in particular, is suitable for the fire and evacuation  procedures that are 
to be adopted and for the persons who will use the system, including security or  reception staff and firefighters 
attending a fire. Siting of control circuitry and power supp lies will more  likely be determined by engineeri ng 
considerations and the preference of the purchaser or user.  
Although the use of text displays (e.g. liquid crystal or vacuum fluorescent displays) might be sufficient  for the 
needs of the user, the provisi on of a separate, light -emitting  indicator for every zone on the  system is regarded 
as valuable to firefighters. This enables a simple "at a glance" overview indication of  all zone(s) in which  fire 
has been detected, without the need for manual interventio n by firefighters, and  enables spread of  fire to be 
easily monitored.  
In at least one multiple -fatality fire, it has been determined that some or all of the deaths could have  been 
avoided if a diagrammatic representation of the premises (commonly described  as a zone plan)  had been 
provided in close proximity to the CIE. Accordingly, it is important to ensure that a suitable  zone  plan is 
provided adjacent to all CIE (including any repeat control and/or indicating equipment),  unless the CIE 
incorporates a su itable display (e.g. an illuminated mimic diagram). The objective is to  ensure that those 
responding to a fire alarm signal (including staff on the premises and firefighters) are  given unambiguous  
information as to the location of  a fire . 
23.2 Recommendations  
23.2.1  The following recommendations are applicable to the siting of C IE. 
a) Indicating equipment, in conjunction with suitable manual control facilities, should be sited at an  
appropriate location for both staff and firefighters responding to a fire signal, such tha t controls  can be 
readily operated and indications are readily visible. This should normally comprise an  area on the 
ground floor dose to the entrance to the building likely to be used by the fire and  rescue service, or a 
suitably sited, continuously manne d control room from which at least initial  control of any fire incident, 
by staff and/ or the fire and rescue service, will be implemented.  
NOTE 1 In complex premises, there could be benefit in consultation between the user or purchaser (or  others 
acting o n their beha lf and the fire and rescue service, regarding the siting of all CIE and the facilities provided. 
Where there are multiple entrances to a complex building, there could also be benefit in consultation  with the fire 
and rescue service regarding th e possible need for repeat control and/or indicating equipment.  
NOTE 2 It is expected that the form of display, including the display at repeat CIE, wilt indicate the location of  the 
first detector to operate without manual intervention.  
b) All control, indic ating and power supply equipment that is likely to need routine attention for  
maintenance should be sited in readily accessible locations that facilitate safe maintenance work.  
c) The ambient light level in the vicinity of all CIE should be such that visual indication can  be clearly 
seen, controls easily operated and any instructions or legends can be easily read.  
d) The ambient noise level in the vicinity of all CIE should not be such as to prevent audible  indications 
(such as the fault warning sounder) from bei ng heard.  
e) The fire alarm CIE, extra low voltage (ELV) power supply equipment for the ClE and other  essential 
control facilities should be sited in areas of low fire hazard level, so that the equipment  is unlikely to BOS 813 -1:2023  
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64 be involved in a fire before adequate wa rning  has been given . 
f) In Category Land Category P systems, the area(s) in which any CIE(s), power supply (or  supplies) for 
the CIE and other essential control facilities should be protected by automatic fire  detection , unless:  
1) the fire hazard level is negl igible and there is an adequate degree of fire separation between  that 
area and any area in which the fire hazard  level is not negligible; or  
NOTE 3 The above conditions often apply to a relatively  low fire risk foyer of a building.  
2) the area is continuousl y manned in the case of Category P systems, or continuously manned  when 
the building is occupied by any person in the case of Category L systems.  
g) In premises in multiple occupation with communal parts, main  CIE should be located within  a 
communal area, suc h as an entrance hall. Where no communal parts exist, the equipment  should be 
sited in an area to which access is possible at all times that the premises are  generally occupied.  
23.2.2  The following recommendations apply to the facilities  provided for visual indi cation of fire signals.  
a) The indicating facilities should be suitable for the fire and eva cuation procedures intended for  the 
building.  In complex premises, there should be adequate consultation between the Interested  parties 
(see 6. 2) to ensure that appro priate indicating facilities are provided.  
b) The primary indication of the area(s) from which a fire signal(s) has originated should comprise  an 
indication of the zone.  
c) The form of zone indication should comprise a separate light -emitting indicator for each zone of  the 
system ( e.g. a LED matrix or illuminated mimic diagram), such that the indicating equipment  is capable 
of simultaneous display of fire signals on every zone.  
NOTE 1 In very large premises it might be acceptable to use a hierarchal arrangement of displays. For  example, 
C/E might indicate the sector of origin, while further indicating equipment in the sector indicates the  detection 
zone(s) of origin.  
d) A visual display unit (VDU) may be used to provide the display recommended in 23.2.2c)  provided 
that: 
1) the VDU can provide a simultaneous display of fire signals in all zones, without manual  
intervention; and  
2) because the reliability of a single VDU is not adequate, a back -up form of zone indication  is 
provided; this may comprise a second method of indi cation conforming to 23.2,2c), a  second VDU 
or a printer configured to automatically print out the fire information.  
NOTE 2 Printers are not considered suitable as a primary indication since, in the event of ink, ribbon  or paper 
being exhausted, the indica tion will be lost. They mi ght, howeve1; be acceptable as a back -up or  supplement to 
another display.  
e) On or adjacent to indicating  equipment, there should be a diagrammatic representation of the  building, 
showing at least the building entrances, the main ci rculation areas and the division into  zones. The 
diagrammatic representation may comprise any of the following:  
1) an illuminated mimic diagram;  
2) a VDU with an appropriate back up; or  
3) a printed, correctly orientated, zone plan (see 3.6.8.).  
NOTE 3 In some comp lex premises, e.g. shoppin g centres, additional information, such as occupier names,  might 
be of value to those who are unfamiliar with the premises. This could be provided by a supplementary  list that, for 
example, enables a unit number on a zone plan to be related to the occupier's  name, such as  the name of a 
retailer in a shopping centre. Where such information is provided, it is important that it is kept up -to-date.  
23.2.3  The following recommendations apply to facilities provided for contro l of the system.  
a) The control facilities should be suitable for the fire and evacuation procedures intended for the  building. 
In complex premises, there should be consultation between the interested parties (see  .6.2.) to ensure 
that appropriate control facilities are provide d 
b) In addition to the sounder silence and re -sound control provided by the CIE there should also  be an 
evacuate control. A clearly labelled facility should be provided on or immediately adjacent  to the control 
equipment to enable fire alarm  sounders to be s tarted. Where evacuate control(s)  comprise manual 
call point(s), t he call points should be clearly labelled to distinguish their  function from that of other 
manual call points in the building. Operation of such a control should  not be dependent on the stat e of BOS 813 -1:2023  
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65 any silencing or disablement device. The evacuate control may  be the same as the re -sound control, 
provided that it starts all of the fire alarm sounders on the  system and is appropriately  labelled.  
c) Where the premises are divided into two or more alar m zones (see 3.3), the strategy for phased  
evacuation should be implemented by the system designer (see 19.2.1 ). Normally a separate  evacuate 
control , conforming to 23.2.3b), should be provided for each part of the protected  premises in which 
an evacuation  signal needs to be given simultaneously. In premises with  phased evacuation, in which 
stairway capacity is inadequate for a single -phase  evacuation, no  single control that initiates an 
"Evacuate" signal in all alarm zones simultaneously should be  provided , but such a control should be 
provided in all other buildings with two or more alarm  zones (see 19.2.1 ). 
d) The operation of certain manual controls (for example, a disablement control) should be limited  to 
authorized personnel. Where this limitation is not provided on the control equipment (for  example, by 
use of a key operated switch), then it may be provided by restricting access to the  equipment by the 
use of a lock or, in a disciplined environment (such as a security control room),  by restriction of acce ss 
to the control equipment to authorized personnel.  
NOTE The operation and access of all manual controls is defined in BS EN 54 -2. Access level 1 has no  security, 
but access level 2 requires authorized access. The control of certain facilities  such as the  manual  evacuate control 
[see 23. 2.3b) and 23.2 .3c)], when included within the CIE, is restricted to personnel  authorized at access level 2.  
24  Networked systems  
24.1 Commentary  
With a networked system, the functions of the C IE are not centralized in one location  or panel  but instead  are 
distributed amongst a number of sub -panels" located remotely from each other. These  panels are then 
interconnected by a network, which usually serves as a data highway. Some sub -panels  might simply act as 
"data gathering" panels a nd provide no indications. Others might be fully functional  control and indicating 
panels, configured so as to "stand alone" and continue to operate normally in the  event of a failure of the 
communications link between sub -panels.  
Networked systems are usu ally installed in the following circumstances:  
a) where the fire detection and fire alarm system is large and beyond the capacity of single CIE; and  
b) where there is a need for centralized  monitoring and/or control of a number of  fire detection and  fire 
alarm s ystems in different buildings in the same vicinity (e.g. on the.  same site).  
The effect of a failure of the communications link and the implications for fire detection and fire alarm  
system operation depends on tile configuration of the networked system the type of network and  whether 
or not the network forms part of the critical signal  path (see 3.14}.  
Ring or loop networks are more resilient to communications failures than radial type networks. Peer to  
peer networks are less vulnerable to loss of  function  than networks with a central processor controlling 
panel to panel communications.  
If all sub -panels can function as "stand alone "detection  and fire alarm systems and do not depend  on the 
network to facilitate primary alarm function  (e.g. sounding the alarm and summoning the fire  and rescue 
service), a communications failure will have no significant effect, and the network can be  considered as 
an ancillary circuit . 
If, however, the cause -and-effect  logic for the operation of the system depends on the netwo rk, the  
communications link needs to be afforded the monitoring, integrity and reliability of a critical signal  path. 
Tile more the networked system is dependent upon the communications link to effect primary  functions of 
the fire detection and fire alarm  system, the greater needs to be the protection afforded to  the 
communication link . 
In the case of a), tile overall integrity, reliability and availability of the networked system needs to be the  
same as that of a single fire detection and fire alarm system  and needs to satisfy the recommendations  of 
all other clauses of this standard. In particular, the network needs to be monitored for faults (see  12.2,1), 
be wired in a suitable cable (see Clause 26) and, beyond the alarm zone of origin, needs to be  capabl e of 
facilitating an appropriate response to the operation of a manual call point within 10s. The  recommendation 
for a three second response within the alarm zone of origin remains unaffected.  
In this case, the communications link between sub -panels needs to be considered as part of the critical  
signal path.  The communications link also needs to be considered as a critical signal path in the case of 
24.1b) if the  communications link is required to facilitate primary alarm  functions.  BOS 813 -1:2023  
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66 24.2 Recommendations  
The foll owing recommendations are applicable.  
a) Sub-panels not required for indication purposes need not incorporate the indication  facilities 
recommended  in 23. 2 and need not be visible, but should still be readily accessible for  maintenance 
purposes. Similarly, au dible warnings may be suppressed or disabled.  
b) The communications link between sub -panels should be monitored in accordance with 12 .2.1 for 
wired networks and BS EN 54 -25:2008, 4. 2.6, for radio networks.  
c) A fault on the communications link between sub -panels  should not affect the operation of  any sub -
panel.  
d) In networked systems in which the communications link forms a critical signal path and  comprises 
one or more cables, the cable installation should conform to 26.2, except that  standard fire -resisting 
cable s [see  26.2 and Figure 17a) and Figure 17b)] may be used in all  circumstances in which:  
1) the network is configured as a loop; and  
2) there is diverse routing of incoming and outgoing circuits, except in the immediate vicinity  of the 
sub-panel; and  
3) there will be no loss of communication to any sub -panel in the event of a single open or  short 
circuit on the loop.  
e) The delay between operation of any manual call point and the giving of an "Evacuate " signal in, at  
least, the alarm zone within which the manual call p oint is located should conform  to 20.2b. The  delay 
in the giving of appropriate alarm signals in alarm zones beyond that  in which the manual  call point is 
located should not exceed 10 s.  
f) In networked systems in which the communications link forms an ancill ary circuit and  comprises one 
or more cables, the cable installation shou ld conform  to 26.6. for the ELV supply  from an external 
power supply unit.  
NOTE subclause  26.2 recommends fire resistance ono, for cables that comprise parts of the critical signal  paths and 
for low voltage (LV) mains supply cables.  
25 Power supplies  
25.1 Commentary  
The normal power supply for the fire detection and fire alarm system is normally derived from the low  
voltage mains supply in the building,  transformed or modified as necessary. Th e mains supply needs  to 
be reliable and capable of supplying the largest load that can be placed on it under normal, fire and  fault 
conditions. If the fault condition relates to the power supply and causes an over current condition  on the 
low voltage suppl y circuit, it is accepted that the low voltage circuit breaker could trip out.  
In order to minimize the potential for failures, the design of the mains supply to the system needs to be  
such that it is unlikely to be affected by faults on other circuits or equipment, or by isolation of supplies  in 
the building for maintenance or economy in consumption of electricity.  
It is, nevertheless, likely that the mains supply will fail at some time during the lifetime of the fire  detection 
and fire alarm system. This can arise from failure of the mains supply to the building or failure  of the final 
circuit serving the fire detection and fire alarm system. Accordingly, the mains supply needs  to be backed 
up by a standby supply that is able to support the system while th e fault in the mains supply  is corrected.  
In most parts of this standard , most failures in public electricity supplies are relatively short in duration,  and 
prolonged failures exceeding  24 h are uncommon. The recommendations in this standard are based  on 
this assumption, and, for Category M  and Category L systems, the duration of standby batteries need  not, 
therefore, normally be capable of supplying power to the system for longer than  24 h. A greater duration 
might, however, be necessary if the probability  of failure of a public or private  electricity supply for periods 
exceeding 24 h is considered to be significant . 
In the event of a more prolonged failure of the supply to a Category M  or Category L system, when  the 
premises are unoccupied, no one is at ri sk. If on reoccupation, the supply to the building is still  isolated, 
most users can reasonably be expected to appreciate the effect on the fire detection and  fire alarm system 
and indeed other safety systems (such as emergency escape lighting) and to take  appropriate action.  
Failure of the final circuit serving the fire detection and fire alarm system is, however, possible. If this  
occurs when the premises are unoccupied (e.g. over a weekend) the system  might be inoperative on  BOS 813 -1:2023  
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67 reoccupation. This will be le ss obvious to the user,  and it is important that the presence of a power supply  
to the system is indicated by a visual indicator  at the indicating equipment to enable total power failure  to 
be identified by the user, who needs to check the fire detection a nd fire alarm system on reoccupation  [see 
47.2a )]. 
Category P systems are required to provide protection when the premises are unoccupied. However,  there 
is a need to set some practical limit on the duration of stand  batteries . If it is considered by the  user that 
the limit recommended in this standard is insufficient  to cater for the longest period for which  premises 
might be unattended, the user needs to consider arrangements for  inspection of the system  during the 
unoccupied period, consider a facility t o transmit power supply fault signals to an ARC, or  consider the 
need for standby batteries with a longer duration.  
If the premises are provided with an automatically started standby  generator,  the capacity of the  standby 
batteries in a Category M  or Categ ory L system  may be reduced, provided the circuits served by  the 
generator include that of the fire detection and  fire alarm system. This relaxation does not apply to  Category 
P systems, as, when the premises unoccupied, there is no one present to detect, and take  action on, a 
failure of the standby generator to start on mains power failure.  
In some complex buildings , such as shopping  centres, additional indicating equipment, such as colour  
graphics terminals, not essential for compliance with this standard , might be provided to assist  the user in 
the monitoring and control of  fire incidents. This additional equipment can sometimes  draw substantial 
current.  If the equipment is not essential/or full compliance of the system with this  standard, it might not 
be necessary for  the power supplies for the equipment to conform in full to the  recommendations of this 
standard, particularly in respect of standby battery capacity. However, if the  equipment is used as the 
normal user interface for the purposes of control  or indication, confusion  of operators and degraded 
monitoring and reduced control of a fire incident might result. In these  circumstances  a standby power 
supply still needs to be provided for the additional monitoring  equipment , but its duration may be re duced 
below that otherwise recommended in this standard.  
25.2 Recommendations for  mains power supplies  
The following recommendations are applicable to the low voltage mains supply to the system.  
NOTE 1 This supply needs to be regarded as an integral part of the  fire detection and fire alarm system,  particularly for 
the purpose of certification  of the system (see Clause 41), regardless of whether the electrical  installation within the building 
is provided by the organization responsible for Installation of the fi re detection and  fire alarm system  
a) For reasons of electrical  safety, the mains supply to all parts of the fire detection and fire alarm  system 
should be supplied, via an isolating protective device (such as a circuit -breaker), from the  load ("dead") 
side o f the main isolating device for the building. Where the user needs to isolate  the building during 
closed hours, a separate supply should be provided for the fire detection and  fire alarm system that 
should not normally be isolated during closed hours.  
b) The mains supply final circuit(s) to all parts of the fire detection and fire alarm system should be  
dedicated solely to the fire detection and fire alarm system and  should serve no other systems or  
equipment. The circuit(s) should be derived from a point in t he building's electrical distribution  system 
close to the main isolating device for the building. The electricity supply should not be  connected via 
a card or coin -operated meter or similar device.  
c) To facilitate local isolation during maintenance, suitable  means should be provided for local  isolation 
of the low voltage supply circuit that serves the power supply and control equipment  [see 29.2e)].  
Note 2 A number of switching devices do not meet the required isolation performance  criteria. BS 7671 for the  
purpose of "isolation  details whether a particular device can actually be used . 
d) Subject to compliance with 25.2a), 25.2b), 25.2c) and BS 7671, the number of isolating  devices  
between the incoming power supply to the building and the fire detection and fire alarm system  power 
supply unit should be kept to the minimum practicable.  
NOTE 3 For example, the supply can comprise a dedicated circuit emanating from the first electrical  distribution 
board in the building electrical  distribution system . 
e) In certain syst ems within very large buildings, in which networked control panels or distributed  power 
supply units are used, the recommendation of 2 5.2d) might be impracticable. If, with  the agreement 
of the interested parties (see Clause  6), a variation is adopted, whe reby the  mains power supply to 
this equipment is derived from one or more local distribution boards in  the building, the number of 
isolating devices between the main incoming supply and the local  distribution board should still be 
kept to the,  minimum  practicable. It should also be ensured  that any need to isolate the supply to the 
local distribution board (e.g. for maintenance) will  be infrequent, and that the risk of inadvertent 
isolation is low. In addition, there should still be  compliance with 25.2b), 25.2f), 25.2g) and 2 5.2h).  BOS 813 -1:2023  
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68 NOTE 4 It is recognized that in such an arrangement the recommendations of Clause 26 in respect  of the  fire 
resistance of the mains power supplies cables, other than the cables  of the final circuit, do  not apply.  
f) Every isolator and protective device that can isolate the supply to the fire detection and fire  alarm 
system, other than the main isolator for the building, should be labelled either:  
1) "FIRE ALARM ": in the case of a protective device that serves only the fire alarm circui t, but  
incorporates  no switch;  
2) "FIRE ALARM. DO NOT SWITCH OFF ", in the case of a switch (whether incorporating a  protective 
device or not) that serves only the fire alarm circuit; or  
3)  "WARNING. THIS SWITCH ALSO CONTROLS THE SUPPLY TO THE FIRE ALARM SYSTEM ", 
in the case of any switch that disconnects the mains supply to both the fire alarm system and  to 
other circuits.  
g) Labels should be clear and in durable fade resistant material.  
h) Every isolator, switch and protective device that is capable of disconnecting the mains supply  to the 
fire detection and fire alarm system should be situated in a position inaccessible to  unauthorized 
persons or be protected against unauthorized operation  
i) The circuit supplying the fire detection and fire alarm system should not be p rotected by  a residual 
current device unless this is necessary to conform to BS 7671. Where a residual  current device is  
necessary for electrical safety, a fault on any other circuit or equipment in the  building should not be 
capable of resulting in isolat ion of the supply to the fire detection and fire  alarm system.  
j) Irrespective of the condition of any standby battery (e.g. disconnected or fully discharged),  the mains 
power supply should be capable of supplying the maximum alarm load of the  system (see 3. 37), 
25.3 Recommendations for fire detection and fire alarm system power supply units  
The following recommendations apply to every power supply unit that forms part of the alarm system.  
a) Transition between the normal supply and the standby supply, and vice versa,  should not cause  any 
interruption to the operation of the system or result in a false alarm.  
b) A fault in the normal supply should not adversely affect the sta ndby supply or vice versa. The  operation 
of a single protective device should not result in failur e of both the normal and the  standby supply.  
c) The presence of the normal or the standby supply should be indicated by a green  indicator, located 
in a position that makes it readily obvious  to any person responsible for  monitoring faults on the fire 
detectio n and fire ala m system ( e.g. at the location of the main  indicating equipment).  
d) Normal and standby supplies should ea ch be independently capable of supplying the maximum  alarm 
load of the system (see 3.37), irrespective of the condition of the other supp ly. 
25.4  Recommendations for standby supplies  
The following recommendations  are applicable.  
a) The standby supply should  comprise a secondary (rechargeable) battery with an  automatic charge  
b) The battery should  be of a type having a life of at least four years unde r the conditions of use  likely to 
be experienced in the fire detection and fire alarm system. Automotive batteries (of the  type used for 
starting car engines) should not be used.  
c)  Labels should be fitted to all batteries indicating their date of installati on. The labels should be  sited 
so that they can be read without disturbing the batteries.  
d)  The charging rate of the battery should be such that, having been discharged to its final voltage,  the 
battery can be charged sufficiently to conform to 2 5.4e) after  a charging period of 24 h.  
NOTE 1 This is the requirement within BS EN 54 -4, but it is included here as a reminder that connecting  larger 
batteries than originally desi gned, for example due to an unforeseen extra load, can result in unacceptably  long 
recharge times.  
e) The capacity of all standby batteries that serve any part of the system which has to operate  correctly 
in order to satisfy the recommendations of this standard  should be such as to  satisfy the following 
recommendations. The capacity required to  satisfy these recommendations  should be calculated in 
accordance with Annex D. 
1) For a Category M  or Category L system, the capacity should be sufficient to maintain the  system 
in operation for at least 24 h, after which sufficient capacity should remain to  provide an ‘’Evacuate" BOS 813 -1:2023  
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69 signal in all alarm zones for at least 30 min, unless the building is  provided with an automatically 
started standby generator [see 2 5.4e)2)).  
NOTE 2 If the premises are likely to be unoccupied for longer than the duration of the st andby battery  capacity at 
any time, and there is a facility for transmission of  fire signals to an ARC, it would be of benefit to  transmit power 
supply fault signals to the ARC  for notification of the user.  
NOTE 3 BS 5839 -6 recommends the provision of 72 h  standby supply for Grade A systems, which are largely  
similar to this standard's systems  
2) For a Category M or Category L system in a building with an automatically started standby  
generator that serves the fire detection and fire alarm system, the capacity  should be  sufficient to 
maintain the system in operation for at least six hours, after which sufficient  capacity should remain 
to provide an "Evacuate" signal in all alarm zones for at least 30 min.  
NOTE 4 If a circuit serving part of the  fire alarm syste m (e g. distributed power supply unit) is not served by  the 
standby generator, the capacity of the standby battery ought to conform to 2 5.4e)1).  
3) For a Category P system in which either of the following apply, the capacity should be  sufficient to 
maintain t he system in operation for at least 24 h, after which sufficient  capacity should remain to 
operate all fire alarm devices for at least 30 min:  
i) where the building is continuously manned, or inspected outside  normal working  hours, such 
that staff in the buil ding would be aware of a power supply fault indication  on the system 
within no more than six hours of its occurrence; or  
ii) where power supply fault signals are transmitted automatically  to an ARC, instructed  to notify 
a keyholder and, if required, the previo usly agreed service provider immediately  on receipt 
of a fault indication from the premises  
4) For all other Category P systems, the capacity should be sufficient to maintain the system  in 
operation for at least 24 h longer than the maximum period for which t he premises are  likely to be 
unoccupied or for 72 h in total, whichever  is less, after which sufficient capacity  should remain to  
operate all fire ala m service  for at least 30 min. If the building is likely to  be unoccupied for more 
than the duration n of t he standby battery capacity at any time, and  there is a facility for 
transmission of fire signals to an ARC, power supply fault signals should  also be automatically 
transmitted to the  ARC, for immediate notification of a keyholder:  
f) If, in addition to the e quipment recommended in Clause 23, additional CIE, over and above that  
necessary for compliance with this standard , is provided, it might not be necessary for  any standby 
battery capacity supplying the additional equipment to conform to 2 5.4e. However,  if the equipment 
is used as the normal method of indication of fire to persons responsible for  monitoring the system, a 
standby supply should still be provided for this additional equipment.  
If the equipment recommended in Clause 23 is suitably sited for use as a "default" in the  event of 
failure of the additional equipment, the capacity of the standby batteries serving the  additional 
equipment should be sufficient to operate the system in the quiescent mode for at  least four hours. If 
the equipment recommende d in clause 23  is not suitably sited to enable  effective control and 
monitoring of a fire incident, the standby power supplies for the additional  equipment should satisfy 
the recommendations of 25.4e ). 
26 Cables, wiring and other interconnections  
26.1 Commentary  
The components of most fire detection and fire alarm systems are connected by cables and wiring, but it  is 
possible to connect them by other means, such as radio or fibre optics. Recommendations for radio  linked 
systems are given in Clause 27. Where fibre o ptic connections are used, they need to provide at  least 
equivalent integrity and reliability to other cables that are recommended for the same purpose.  
It is essential that all interconnections operate correctly at the time of a fire. This is particularly  important in the 
case of cables that link control equipment to manual call points, automatic fire  detectors, fire alarm devices, 
and alarm routing equipment. It is on ly less important in the case of  interconnections between the fire alarm 
system and other  equipment that are so arranged that failure  of interconnecting cables during a fire would not 
lead to a dangerous condition (e.g. because the  failure  causes the other equipment to change state to that 
appropriate to the fire condition).  
It is not normal ly possible to predict, with any accuracy, those areas of a building in which fire can  or cannot 
occur. At the design stage, the exact routes that cables will follow might also be unknown.  Therefore, to ensure 
that cables used for critical signal paths (see 3.14) remain operational for an  adequate duration, cables with BOS 813 -1:2023  
Edition 1.0 
70 an inherent ability to resist attack by fire need to be used throughout  such critical signal paths. Unless cables 
are supported in such a manner that they remain supported for a duration simila r to that for which the cable 
itself can survive a fire, early failure of the circuit might  occur because of strain on terminations as a result of 
collapsing cables.  
The integrity of the mains supply to the system is also regarded as essential, even though  the system  has a 
standby supply. Accordi ngly, mains supply circuits need to be adequately  protected against the  effects of  fire. 
Once a fire alarm signal occurs, fire alarm devices ought not to be dependent  on a continued signal from  any 
fire detector or manual call point In large buildings and buildings with multi -stage alarm systems,  the ability of 
the system to provide indications from further  ;fire detectors  and manual call points during  the course of a fire 
might be of value to the fire and r9c e serv ice or might be essential to ensure that  the need for "Evacuate" 
signals in additional alarm  zones  can be identified.  
This standard makes recommendations for two levels of fire resistance of  fire-resisting cable systems,  termed  
"standard" and "enhanced: Th ese terms defined  by the fire tests in 26. 2d) and e); BS 7629 -1 now includes 
these requirements, which clarifies  cables that fall within the Scope of that standard using  the same 
terminology. In general, cables of standard fire resistance are suitable for most applications.  However, for 
certain critical applications in which prolonged circuit integrity is necessary in the event  of fire, cables of 
enhanced fire resistance are recommended. Examples are unsprinklered  high-rise buildings with phased 
evacuation arrangements and premises of such a nature or size that areas remote  from the fire could continue 
to be occupied for a prolonged duration during a fire that might then  damage cables serving parts of the fire 
alarm system in occupied areas.  
The probability of disablement of any part of the fire detection and fire alarm system as a result of  mechanical 
damaged  to cables can be reduced by the use of sufficientl y robust cables, careful selection of  cable routes 
and by the provis ion of protection against mechani cal damage in areas where cables are  susceptible  to 
mechanical damage. Monitoring of circuits does not ensure that cable faults do not occur but  is essential to 
minimize the time between occurrence and identification (and hence repair) of the  fault. Monito ring of circuits 
and protection of cables against damage are, therefore, complementary  precautions, rather than alternatives.  
It is the responsibility of the designer to ensure that the electrical characteristics of the cables, including  current 
carrying c apacity and voltage drop, are suitable for the system. The choice of cable and routes  selected need 
to take into account the need to avoid electromagnetic interference from other cables  and sources of 
electromagnetic radiation, particularly in the case of systems in which cables are used  for transmission of data 
(such as addressable device circuits). In the latter case, the cable selected also  needs to be compatible with 
the characteristics of the data transmission e.g. speed and waveform, and  remain so for  an adequate length 
of time during the relevant exposure to fire for the category of cable.  
The circuits of  fire alarm systems need to be segregated from the cables of other circuits to minimize  any 
potential for other circuits to cause malfunction of the fire alarm system arising from:  
• breakdown of cable insulation of other circuits and/or fire alarm circuits;  
• a fire caused by a fault on another circuit;  
• electromagnetic interference to any fire alarm circuit as a result of the proximity of  another circuit;  
• or damage resulting from the need for other circuits to be installed in, or removed from, ducts or  
trunking containing a fire alarm circuit.  
In order to facilitate identification off ire alarm circuits, cables ought preferably to be red in colour,  unless 
another form of colour coding is appropriate. By this means, the possible need for appropriate  segregation can 
be identified, and there is less likelihood of inadvertent manual interference with the  circuits of  fire alarm 
systems (e.g. during work on other  electrical circuits).  
26.2 Recommendations  
The following recommendations are applicable.  
 
a) The electrical characteristics of all cables, such as voltage drop for the ELV supply from an  external 
power supply, current carrying capacity, impedance and, where appro priate, ability to  transmit data, 
should be suitable for the system.  
b) Cables used for all parts of the critical signal paths (see .3 .14.), for the ELV supply from an  external 
power supply unit and for the final circuit providing low voltage mains supply to the system, should 
conform to 26.2d) or 26.2e) and comprise one of the following:  
1) mineral insulated copper sheathed cables, with an overal l polymeric covering. Conforming  to BS 
EN 60702 -1, with terminations conforming to BS EN 60702 -2; BOS 813 -1:2023  
Edition 1.0 
71 2) cables that conform to the requirements of BS 7629 -1, and that satisfy the definition of  standard 
or enhanced fire resistance in 26.2d) or 26. 2e); 
3) cables that conform to the requirements of BS 7846 and that satisfy the definition of  standard or 
enhanced fire resistance in :26 .2d) or 26.2e );  
4) cables rated at 300/500 V (6r greater) that provide the same degree of safety to that  afforded by 
conformity to the  requirements  of BS 7629 -1 for standard or enhanced  fire resistance.  
c) Cable systems used for all parts of the critical signal  paths, and for the low voltage mains supply  to 
the system, should adequately resist the effects of fire. For most fire detection and fire alarm  systems, 
standard fire -resisting cables [see 26.2d)] should be considered to provide sufficient  resistance to t he 
effects of fire, with appropriate methods of support and jointing [see 26.2g)].  
For fire detection and fire alarm systems for the following applications, cable systems comprising  
"enhanced" fire -resisting cables [ see 26.2e )], with appropriate methods of support and jointing  should  
generally be used [see 26.2g)]:  
1) in unsprinklered buildings (or parts of buildings) in which the fire strategy involves  evacuation of 
occupants in four or more phases;  
NOTE 1 In a building  with a networked system (see clause  24}, individual, self -contained fire detection and  
fire alarm systems sometimes serve parts of the buildi"9 that are evacuated in less than four phases, even  
though the entire building is evacuated in four or more phases. in such cases, cables of enhanced fire 
resistance  need not be used for these systems, but there might be a need to use cables of enhanced fire 
resistance for the  network [see Figure 17a.) and Figure 17b)).  
2) in unsprinklered buildings greater than 30 m in height;  
NOTE 2 Height of a building is taken as the height  from the lowest level of the ground around the perimeter  
of the building  to the floor level of the top storey.  
3) in unsprinklered premises and sites in which a fire in one area could affect cables of critical  signal 
paths associated wi th areas remote from the fire, in which it is envisaged people  will remain in 
occupation during the course of the fire [see Figure 17c)]. Examples might  be large hospitals with 
central control equipment and progressive horizontal evacuation  arrangements, a nd certain large 
industrial sites;  
NOTE 3 If the single range of buildings shown in Figure  17c) were served by a networked system, and each  
of the independently evacuated sections shown were served by individual self-contained  fire detection and 
fire alarm  systems, cables of enhanced fire resistance would not be necessary except, in the case of the 
network  cables, if required to satisfy the recommendations of Claus e 24.  
4) in any other buildings in which the fire engineer designer or installing company specif ier or  
enforcing authority, on the basis of  a fire risk assessment that takes fire engineering considerations 
into account, considers that  the use of enhanced fire -resisting cables is necessary;  
NOTE 4 Effects of fire include discharge of water from exting uishing systems or equipment and  impact by  
falling objects.  
NOTE 5 A cable system comprises the cables, the means by which cables are secured and the means by 
which  cables are jointed.  
NOTE 6 For the purpose of 26. 2c), a building is regarded as sprinklered  only if an automatic sprinkler  
installation conforming to BS EN 12845 is provided throughout the building, except that the requirements of  
BS EN 12845 for life safety installations need not be applied.  
NOTE 7 In some fire engineering solutions used for complex  buildings, a reduction in the normal level  of 
other fire protection measures throughout  the building might be acceptable to an enfordn9 authority  provided 
an automatic fire detection system is installed.  In such cases, an enforcing authority might or  might  not, as 
part of the fire engineering solution, require cables of enhanced fire resistance, and early consultation  with 
the authorities responsible for enforcing fire safety legislation is strongly recommended (see Clause 6).  
d) Standard fire -resisting cables should have a duration of survival of 30 min when tested in  accordance 
with BS E N 50200.  
NOTE 8 This correspond to class PH 30 as detailed in BS EN 50200:2015, Annex D.  
In addition, the cables should meet the 30 min survival time when tested in acc ordance with  BS EN  
50200:2015, Annex E.  
e) Enhanced fire -resisting cables should have a duration of survival of 120 min when tested in  
accordance with BS EN 50200.  
NOTE 9 This corresponds to class PH 120 as detailed in BS EN 50200:2015, Annex D.  BOS 813 -1:2023  
Edition 1.0 
72 In addition,  the cables should meet the 120 min survival time when tested in accordance  with BS 8434 -2. 
f) Methods of cable support should be non -combustible and such that circuit integrity is not  reduced 
below that afforded by the cable used and  should withstand a simil ar temperature and  duration to that 
of the cable, while maintaining adequate support.  
NOTE 10 In effect, this recommendation precludes the use of plastic cable clips, cable ties or trunking, where  
these products are the means of cable support.  
NOTE 11 Expe rience has shown that collapse of cables, supported only by plastic cable trunking, can create a  
serious hazard for ftrefi9hters, who could become entangled in the cables.  
g) Cables should be installed without external joints wherever practicable. All termina tions and  other 
accessories should be such as to minimize the probability of early failure in the event of  fire. Other 
than in the case of joints at or within system components such as control equipment,  manual call 
points, fire detectors and sounders, ter minals used to joint cables should be  constructed of materials 
that will withstand a similar temperature and duration to that of the  cable. All joints, other than those 
within system components, should be enclosed within junction  boxes, labelled with the w ords "FIRE 
ALARM" to avoid confusion with other services.  
NOTE 12 Examples of suitable terminals include metal components mounted in ceramic terminal  blocks.  
NOTE 13 At the time of draftin9 this standard, no definitive guidance can be given on the means fo r ensuring  that 
the entire cable system, as opposed to the cable itself, can provide adequate resistance to the effects of  fire. The 
manufacturer's recommendations need to be followed.  
h) Except in particularly arduous conditions, mineral insulated copper she athed cables conforming  to BS 
EN 60702 (Parts 1 and 2) and steel wire armoured cables conforming to BS 7846 may be  used 
throughout all parts of the system without additional mechanical protection. Other cables  should be 
given mechanical protection in any a reas in which physical damage or rodent attack  is likely. Particular 
consideration should be given to all areas that are less than 2 m above floor  level; other than in 
relatively benign environments (e.g. offices, shops and similar premises)  in which cable is clipped 
directly to robust construction, mechanical protection shou ld be provided in these areas. Protection 
may be provided by laying cable on a tray; protecting it by  burying in the structure of the building, or 
by installation in conduit, ducting or trunking. Where  particularly arduous conditions might be 
experienced (such  as impact by forklift trucks or goods  trolleys), additional, robust protection should 
be given to all cables by burying the cable in the  structure of the building or installation in  metal conduit 
or trunking.  
i) Where conduit is used to satisfy the recommendations of 26.2h), the conduit should conform to  the 
relevant part of BS EN 61386. Any non -metallic trunking used in the system should conform  to 
BS 4678 -4. 
j) All conductors should have  a cross -sectional area of at least 1 mm2. 
k) To avoid the risk of mechanical damage to fire alarm cables, they should not be installed within  the 
same conduit as the cables of other services. Where fire alarm cables share common  trunking, a 
compartment of th e trunking, separated from other compartments by a strong, rigid  and continuous 
partition, should be reserved solely for fire alarm cables.  
l) To avoid electromagnetic interference  with fire alarm signals, any recommendations by the  
manufacturer of the fire a larm equipment in respect of separation of fire alarm cables from the  cables 
of other services should be followed.  
m) Where multicore cable is used for interconnection of fire alarm circuits, none of the conductors  should 
be used for circuits  other than those  of the fire alarm system.  
NOTE 14 This recommendation  does not preclude the multiplexing of signals of other systems with those of the  
fire detection and fire alarm system. Guidance on such integrated systems is given in DD CLC/TS 50398.  
n) Fire alarm cables  carrying power in excess of ELV should be segregated from ELV fire alarm  circuits 
by use of cables conforming to 26.2b) and with 26.21). In particular, the mains supply  cable to any 
control, indicating or power supply equipment should not enter the equipm ent through the same cable 
entry as cables carrying ELV. Within the equipment, low voltage (LV) and  ELV cables should be kept 
separate to the extent practicable.  
 
o) All fire alarm cables should be of a single, common colour that is not used for cables of gen eral 
electrical services in the building. to enable these cables to be distinguished from those of  other 
circuits . 
 
NOTE 15 The colour red is preferred  BOS 813 -1:2023  
Edition 1.0 
73  
 
Figure 17 a - Example of a networked fire alarm system  BOS 813 -1:2023  
Edition 1.0 
74  
 
 
Figure 17 b Example of a networked fire alarm system  (continued)  BOS 813 -1:2023  
Edition 1.0 
75  
 
 
27  Radio -linked systems  
27.1 Commentary  
Some of the recommendations of this standard, applicab le to wired systems, are unsuitable for, or  cannot be 
applied to, radio -linked systems. These Include, in particular, those relating to power supplies  and fault 
monitoring. Additional recommendations apply to radio -linked systems in order to address the  integrity and 
performance of the radio communications link between components and the C IE. 
 
In practice, no systems can have total reliability, but one of the objectives of good system design is to  reduce 
the probability of the system being inoperative in th e area of a fire when the fire starts. It is useful that the 
advantages and disadvantages between the two technologies, hardwired, and radio  linked, are different 
because this allows for a system to be installed that suits the site. Great care needs  to be taken when assessing 
a site and choosing the technology to use, as neither the radio nor hardwired  system is singularly suitable for 
every site.  
 
Components of a system interconnected by radio links can include fire alarm devices, such as fire alarm  
sounde rs, as well as detectors and manual cal l points. However, exercising the  fire detection and fire  alarm  
system with testing and evacuation drills in excess of those recommended by the manufacturer  can reduce 
the life of the radio -linked fire alarm sounder b atteries. Automatic silencing of radio -linked  sounders is 
sometimes employed to overcome the potential for undue discharge of sounder batteries.  
However, sounders with this facility need to reactivate with any new fire or phased evacuation  command. Such 
a facility ought not to impair the system ability to provide an adequate audible  warning to the occupants of the 
building in the event of fire.  
 
Other components of a radio -linked system can include  radio relay units, which are installed remote  from the 
ClE so as to extend the range of the system. Where such relay units are separate control and  indicating panels, 
this Is a form of netwo1 ed system (see Clause 24).  Radio communications can also be used to link a small 
number of detectors and other components  to what is essentially a wired system Radio communication  are 
sometimes adopted for temporary  installations during construction or refurbishment work, as well as 
permanent installations. The  recommendations  of this standard apply equally to integral radio -linked systems 
of this nature . 
Figure 17 c - Example of a networked fire alarm system  (continued)  BOS 813 -1:2023  
Edition 1.0 
76 27.2 Recommendations  
The following recommendations are applicable.  
a) Components of a radio -linked system should conform to BS EN 54 -25. 
b) Although BS EN 54 -25 permits the use of  a sing]e battery in each device, radio -linked systems  should 
also conform to the following:  
1) all radio -linked components should be supplied from at least two independent  power  supplies. 
These can be either:  
i) the normal mains supply plus a reserve battery (primary or continuously charged  secondary); 
or 
ii) a primary ba ttery plus a second primary battery; or  
iii) a primary battery plus a secondary battery.  
NOTE 1 Where secondary batteries are specified, capacitors with an appropriate specification may be  used  as 
alternative . 
2) components, other than CIE, may utilize batteries t o provide the normal power supply;  
3) at the point at which any power supply to any radio -linked component can maintain the  component 
in normal operation for not more than 30 days, and, in addition, in the case of  fire alarm devices, 
30 min in the alarm condi tion, a fault warning should be given at the CIE.  
NOTE 2 A separate maintenance warning may be given at an earlier stage to indicate an impending need to  
replace a battery.  
c) Cables of antennae that are external to components of a radio -linked system should be monitored for 
open and short circuits. A fault condition should be given at the CIE within 300s  of the occurrence of 
such a condition.  
d) Cables of antennae that are external to components that form part of the critical signal path  should 
satisfy the recom mendations of 26.2. However, cables that do not conform to 26.2b)  may be used 
provided they are routed through areas of low fire risk or  are protected against  exposure to fire by 
burial in at least 12 mm of plaster or by separation from any fire risk by  materials that would afford a 
fire resistance of at least 30 min if tested in accordance with the  relevant part of BS 476.  
e) Facilities for automatic silencing of radio -linked fire alarm sounders may  be provided, in which  case 
these should conform to 16.2.1h).  
f) Unless the visual indication at the detector of initiation of a fire alarm signal is manually reset  at the 
control panel, it should remain illuminated for not Jess than 20 min after initiation. The  illumination may 
then automatically extinguish.  
g) Installat ion of a radio -linked system should only take place  after a comprehensive radio survey  has 
been undertaken to ascertain the following:  
1) there are no other sources of radio transmission that could interfere with, or block, radio  
communication between the CIE  and other components of the system;  
2) there is adequate signal strength f or communication both to and from components as  appropriate 
in all areas of the building(s) in which radio -linked components are to be  located. This should take 
into account the minimu m acceptable signal level defined by the  manufacturer in respect of the 
level of background radio "noise" at the time of the survey;  
3) where the system is networked it should be established that the communication conditions  
described in item 2) are achieved throughout the network;  
4) records of signal strength readings for each radio device taken at the time of the survey, and  of 
the background noise level, should be kept for future reference.  
NOTE 3 The record  of signal strength and background radio noise may b e combined into a single record of  
signal -to-noise ratio.  
h) Only radio survey test equipment that has been approved by the manufacturer, and regularly  calibrated  
in accordance with the recommendations of the manufacturer, should be used to carry  out the surv ey. 
NOTE 4 The survey capability may be incorporated within the installed system.  
i) At the time of commissioning and after the installation of all equipment, including remote  antenna(e), 
the following records relating to the radio data should be recorded whe re applicable:  BOS 813 -1:2023  
Edition 1.0 
77 1) the system coding (i.e. system address) which should, where possible, be unique to avoid the  
possibility of interference;  
2) the system's channel/frequency;  
3) details of the signal levels received at, or from, each of the receiver units. These da ta should 
include signal levels relating to all the radio devices and the background noise  level, and 
confirmation that these signal levels are in compliance with the manufacturer's  recommendations. 
In the case of a networked system (i.e. multiple panel sy stem), this  should also include the signal 
levels for the radio -links between panels. In addition to other  servicing recommendations in other 
parts of this standard, this should be undertaken at  each routine service visit.  
j) The signal levels recorded should  be within the specifications set by the manufacturer of the  radio 
system. If not within the specification, appropriate remedial action should be undertaken.  
k) A copy of the signal levels should be kept on site with the system logbook  
28 Electromagnetic compati bility  
28.1 Commentary  
Particular care needs to be taken for the design and installation of the fire detection  and fire alarm  system to 
avoid electromagnetic interference, particularly received from,  but also transmitted to,  other equipment.  
Electromagnetic int erference to a fire detection and fire alarm system can  result from mobile  telephones,  radio 
transmitters, other equipment used within the building  lighting  and power  transients. It is known that 
ma/performance of some fire detection and fire alarm systems  has occurred due to electromagnetic 
interference as a result of close -proximity  of fire alarm cables to power cables  with high current, inductive 
loads. The extent to which this might occur depends on a number of  factors including:  
• the susceptibility of  the particular fire alarm equipment to electromagnetic interference.  
• the level of screening afforded by the cable; and  
• the separation  distance between the fire alarm cables.  and the  cables of other services.  
All cables recommended in 26.2b ) provide a degree of screening, but care needs to be taken to ensure  good 
installation practice in,  for example, terminations, and that where practicable, fire alarm cables  do not run 
unnecessarily long distances (say, more than 35 m in aggregate) in close proximity to high  current power 
cables, particularly  if these serve high inductive loads.  
Electromagnetic interference  can be reduced where there is a metal partition between the fire alarm  cables 
and the power cables (as in the case of compartmented trunking). Achi evement of separation  between  fire 
alarm  cables and the cables of other services throughout an entire installation might not  dictate that fire alarm 
cables share ; for example, economy of installation might dictate that fire alarm cables share common  tray o r 
ducts with cables of other services. Care ought, however, to be taken to minimize the extent to  which 
separation is not maintained, particularly in addressable and networked systems, unless guidance  "from the 
system manufacturer indicates that separation  is unnecessary; the extent will be minimized if,  for example, fire 
alarm cables always cross the cables of other services at right angles.  
More definitive guidance cannot be offered in this standard, but it is necessary to ensure compliance  with any 
more specific recommendations of the fire alarm equipment manufacturer.  
28.2 Recommendations  
The following recommendations are applicable.  
a) Fire detection and fire alarm systems should be so designed and installed that they do not cause,  and 
are not unduly susceptibl e to, electromagnetic interference.  
b) To ensure electromagnetic compliance of the installed system, there should be conformity  with, at 
least, the following recommendations, although these might not, alone, be sufficient to  ensure 
compliance:  
1) every system co mponent should satisfy the relevant requirements of the product standard  for that 
component in respect of electromagnetic capability (see Clause 11);  
2) cables should be segregated in accordance with 26.21) and 26.2n);  
3)  installation workmanship should conform  to the relevant recommendations of Section 4,  
particularly in relation to quality of terminations and continuity of screens. For mineral  insulated 
copper sheathed cables, terminations of screens should be effective around the  entire 360° of the BOS 813 -1:2023  
Edition 1.0 
78 screen. Fo r other cables, care should be taken to ensure that the scree  of the cable is continued 
to the appropriate terminal in the control panel or device. This  is normally achieved using cables 
where an uninsulated circuit protective conductor is in  constant cont act with the screen throughout 
its length;  
4)  any cable specifications stipulated by the manufacturer should be adhered to. However,  cables 
not compliant with the recommendations of this standard should only be used with  the prior 
agreement of all interested  parties and should be recorded as a variation;  
5) correct earthing of equipment is vital for adequate EMC performance as well as electrical  safety. 
The recommendations of Clause 29. 37.2f) and Figure 18 should also be followed;  
6) exposure of the cores outside of the screen should be kept to a minimum, consistent with  practical 
installation requirements;  
7) where the manufacturers of the control equipment advise that the system is sensitive to  multiple 
screen earths for each circuit, then their instructions in resp ect of these should be  followed (see 
37.2f) and Figure 18);  
8) where required, the screen should have continuity throughout the whole circuit (see 37.2f)  and 
Figure 18;  
9) where it is necessary to crossfire  detection and fire alarm system cables with those that  can 
potentially cause interference, the cables should be crossed at right angles.  
29 Electrical earthing  
29.1 Commentary  
Fire alarm power supplies need to conform to BS EN 54 -4. If terminals for extra low voltage (ELV)  circuits can 
be exposed, when for example a detector is removed from its base, the fire alarm  power  supply needs to meet 
the requirements of a separated extra low voltage (SELV) installation. Any  SELV protective measure by 
definition confo rms to the relevant requirements of Section 414 of  BS 7671:20 08+A3.To achieve this, it is 
essential that all connections to low voltage {LV) supplies or  equipment are made by components that are 
rated for connection to LV. This would include all power  supplies and all interface d to LV components used in 
the fire ala rm system. Where the fire alarm is  interfaced to ELV equipment that might not be intended for use 
with removable components, such as fire  detectors, the ELV equipment ought to be treated as if it was LV, so 
as to maintain electrical safety.  
29.2 Recommendations  
The following recommendations are applicable.  
 
a) The system design should be such as to satisfy the relevant requirements of BS 7671. In  particular, 
CPCs should be adequately rated.  
b)  The CIE manufacturer's instructions or product marking should be followed,  particularly in  respect of 
earthing arrangements.  
c) LV and ELV circuits should be segregated throughout in accordance with 26.2n) and Clause 28.  In 
particular, if any ELV fire alarm cables share the same wiring containment with other cables,  the cable 
insulation of the fire alarm cables should be rated for the highest voltage.  
d) For ELV circuits with removable components (e.g. detectors or parts of detectors) that expose to  touch 
conductive circuit parts at ELV potential, the following applies.  
1) All relevant po wer supplies for the fire detection and fire alarm system should conform to BS EN 
54-4. 
2) In dry conditions, fire detectors do not have to be locked into their bases.  
3) In areas where conditions are wet, the arrangement should be one or more of the following:  
i) circuit voltages are less than 1 5 V ripple free d .c. or 6 V a .c. rms; 
ii) a tool or special technique is necessary to remove parts exposing  ELV parts; or  
iii) the parts are positioned out of reach of persons other  than authorized  maintenance 
personnel.  
NOTE 1 Wet a reas include the following:  BOS 813 -1:2023  
Edition 1.0 
79 • locations containing a bathtub or shower basin;  
• swimming pools;  
• hot air saunas;  
• agricultural and horticultural premises: and 
• abattoirs, cold stores and certain food preparation areas.  
e) Means should be provided  for local isolation  of the mains supply to all parts of the system; the  isolation 
facilities should be suitably sited, in the vicinity of the equipment served, for use by  maintenance 
technicians without the need for access to remote parts of the building. It should  be possib le to lock 
facilities  in both the normal  and isolate positions to prevent unauthorized  use. See Clause 25, 
NOTE 2 The contractor  responsible for supplying the 230 V mains power supply needs to ensure that the 
particular  device used does actually afford Iso lation. A number of switching  devices do not meet the required 
isolation  performance criteria. BS 7671 :2008+A3:201 5, Table 53.4, details whether a particular device can be 
used for the  purpose of isolation . 
 BOS 813 -1:2023  
Edition 1.0 
80 Section 3: Limitation of false alarms and unwan ted fire  alarm signals  
30 Responsibility for limitation of false alarms and unwanted fire alarm signals  
30.1 Commentary  
False alarms cause disruption to the normal operation of  business and create a drain on fire and rescue  service 
resources. False alarms can even  seriously prejudice the safety of occupants, who might not  react correctly 
when the system responds to a real fire if they have recently experienced a number of  false alarms.  
Responsibility for limitation of false alarms and unwanted fire alarm signals re sts with every party  involved in 
the specification, design, installation, commissioning, management at operational level and  maintenance of 
the fire detection and fire alarm system.  
The major part of the responsibility for limitation of false alarms and un wanted fire alarm signals rests  with the 
designer, but it is important that enforcing authorities and insurers have a good knowledge  of the guidance 
contained in this section, so that requirements for forms of automatic fire detection, which,  realistically , are 
unsuitable for the conditions in the building, are not  imposed.  
The role of the installing company is simply to install the system in accordance with the requirements of  the 
designer. However, where, during installation, if an installing company iden tifies conditions in the  building (eg. 
environmental conditions) that might result in an unacceptable rate  of false alarms and  unwanted fire alarm 
signals, the designer, purchaser or user needs to  be informed, so that the need for  modification of the desig n 
can be considered. Any installing company purporting to have specialist  capability in installation of  fire alarm 
systems needs to have a good understand ing of the guidance  contained in this section.  
At commissioning (see Clause 39), a special check needs  to be carried out to ensure that there is no  obvious 
potential for the system to generate an unacceptable rate of false alarms and unwanted fire  alarm signals.  
Where there is cause for concern  regarding possible potential for false alarms and unwanted fir e alarm  signals 
that is not definite enough  to warrant action at commissioning, this needs to be recorded so that  particular 
attention ca n be given to the matter in examining the false alarm record at the time of the  first ( and, if necessary, 
subsequent) s ervice visits.  
Any party responsible for accepting a fire detection and fire alarm system needs to ensure that they are  
satisfied that the ultimate user is aware of the need, and means, for limiting false alarms and unwanted  fire 
alarm, signals. Verificati on of compliance with this standard includes verification that suitable steps  have  been 
taken by all parties to ensure that false alarms and unwanted fire alarm signals can be  limited as far as 
reasonably practicable.  
Once a compliant system has been hande d over to the user, it is incumbent on the user to ensure that the  
system and the building itself are suitably managed to avoid unnecessary false alarms and unwanted  fire alarm 
signals. Where an unacceptably high rate of false alarms does occur, it is the responsibility of  the user to 
ensure that appropriate steps are taken to reduce the rate at which they occur. It is also the  responsibility of 
the servicing organization to consider the recorded false alarm experience on each  occasion  that the system 
is se rviced, so that unacceptable rates of false alarms can be identified and that  appropriate advice can be 
given to the user.  
Systems in which the parties responsible have not taken adequate care to limit false alarms and  unwanted fire 
alarm signals, and syst ems that produce unacceptab le high rates of  false alarms and  unwanted fire alarm 
signals, need to be regarded as non -compliant with this standard  
30.2 Recommendations  
The following recommendations are applicable.  
a) When Imposing requirements for automatic fire d etection, enforcing authorities and property insurers 
should take the guidance contained in this section into account, so that, subject to the overriding need 
for adequate protection of life and/or property , the form of detection specified does not have th e 
potential to create an unacceptable rate of false alarms and unwanted fire alarm signals.  
b) The system designer should ensure that system design takes account of the guidance contained in 
this section. As evidence of compliance with this recommendation, t he measures incorporated within 
the design to limit false alarms and unwanted fire alarm signals should be recorded on the design 
certificate (see Annex G).  
c) Where an installing company identifies any circumstances that might lead to a high rate of false a larms 
and unwanted fire alarm signals, the designer, purchaser or user should be informed accordingly [see 
also 7.2b)].  BOS 813 -1:2023  
Edition 1.0 
81 d) At commissioning, a check should be carried out to ensure that there is no obvious potential for an 
unacceptable rate of false alarms a nd unwanted fire alarm signals. As evidence of compliance with 
this recommendation, the completion of the check should be recorded on the commissioning 
certificate, along with any potential fa lse alarm and unwanted fire alarm signals problems that should 
be subject to further consideration at the time of service visits.  
e) The designer and the supplier of the system should jointly provide the user (or a suitable representative 
of the user) with sufficient information to enable a user who is unfamiliar with th e technology of fire 
detection and fire alarm systems to minimize the rate of false alarms and unwanted fire alarm signals. 
Any person responsible for acceptance of the system (See Clause 42) should confirm that this 
information bas been provided to the us er.  
f) Any person responsible for verification of the compliance of a system with this standard (see Clause 
43) should verify, as far as reasonably practicable, that adequate account has been taken of this 
section in the design, installation and commissionin g of the system.  
g) The user should arrange for suitable investigation and, if appropriate, action to be taken on every 
occasion that a false alarm occurs. This may, for example, comprise managerial changes within the 
building, modifications to the fire dete ction and fire alarm system or an investigation by the organization 
that maintains the system.  
h) The user should record appropriate details regarding every false alarm and/or unwanted fire alarm 
signal that occurs. Information recorded should include the fo llowing:  
1) date and time;  
2) identity and location of device (if known);  
3) category of false alarm (if known) (see 3.1.2.);  
4) reason for false alarm (if known);  
5) activity in the area (if the reason for the false alarm is unknown);  
6) action taken on the cause of the false alarm;  
7) whether the fire and rescue service were called;  
8) whether the fire and rescue service attended; and  
9) the person responsible for recording the information.  
i) At the time of every service visit, the system false alarm record should be checke d carefully to 
determine the following:  
1) the rate of false alarms during the previous 12 months, expressed as number of false alarms per 
100 detectors per annum (the rate should be recorded in the logbook by the service technician};  
2) whether; since the tim e of the previous service visit, two or more false alarms, other than false 
alarms with good intent (see 3.19), have arisen from any single manual call point or fire detector 
(or detector location);  
3) whether any persistent cause of false alarms can be iden tified; and  
4) whether the number of unwanted fire alarm signals during the previous 12 months is recorded in 
the logbook.  
NOTE 1 The user needs to make historic events records available.  
j)  At least , a preliminary investigation should be carried out as part  of the service work if any of the 
following apply:  
1) the rate of false alarms over the previous 12 months has exceeded one false alarm per 25 
detectors per annum;  
2) 11 or more false alarms have occurred since the time of the previous service visit (i.e. typ ically, 
within the previous 6 months);  
3) two or more false alarms (other than false alarms with good intent) have arisen from any single 
manual call point or fire detector (or detector location) since the time of the last service visit;  
4) any persistent caus e of false alarm is identified; or  
5) more than two unwanted fire alarm signals have occurred in the previous 12 months.  BOS 813 -1:2023  
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82 The purpose of the preliminary investigation is to determine whether any action could be taken to reduce the 
potential for false alarms and/or unwanted fire alarm signals; the user should be informed of the outcome of 
the investigation and be given appropriate advice, including advice regarding the need for a more in -depth 
investigation (see 32.2 
31 Categories of false alarms  
31.1 Commentary  
It is a common misconception that most false alarm arise from faults in equipment. In fact, most false alarms 
arise from a combination of environmental influences, fire -like phenomena, inappropriate action by people in 
the building and accidental damage. The te rm "unwanted alarms (see 3.19) is now used to describe this latter 
group of false alarms, to distinguish these false alarms from those arising from malfunction of equipment, 
which are now described as "equipment false alarms: Two further categories of false alarm  are "malicious false 
alarms arising from malicious action, and false alarms with good intent involving genuine belief by a person 
that there is a  fire (see 3.19).  
 
In order for any investigation of false alarms to be successful, and for appropriate  action to be taken on false 
alarms, it is important that  false alarm records record the category of false alarm whenever this can be 
accurately determined.  
31.2 Recommendations  
When false alarms are recorded by the user (see 30.2h) the category of false alarm (if known) should also be 
recorded. Where any doubt exists, the cause should be recorded as "unknown" ( e.g. it should not be assumed 
that. in the absence of other information, a false alarm needs to have arisen from an equipment fault . 
 
32 Acceptable rate of  false alarms  
32.1 Commentary  
From the point of view of the user and the fire and rescue service, any false alarm is undesirable. Nevertheless, 
it needs to be accepted that particularly in installations that Incorporate a large number of automatic fire 
detecto rs, complete elimination of false alarms is impossible. From time to time, events will occur that give rise 
to a false alarm. The objective of all parties Involved, from specification and design to everyday use of the 
system, ls to minimize the number of f alse alarms and unwanted fire alarm signals that occur.  
 
It follows, therefore, that there is a need to define an "acceptable" rate of false alarms. As recommended in 
30.2/), the service organization needs to make, at least, a preliminary investigation if , at the time of a service 
visit, It is determined that the rate of false alarms in the previous 12 months has exceeded one false alarm per 
25 detectors per annum. The user needs to in vestigate an in -depth special investigation at an even higher 
rate. This  can be undertaken by the servicing organization, the manufacturer of the system or a suitably 
qualified third party (such as fire engineer consultant).  
 
On a more routine basis, false alarm rates need to be monitored periodically by the "premises managem ent" 
(see Clause 47). Little information Is available as to the "average" rate of false alarms from fire detection and 
fire alarm system and a benchmark, against which false alarm performance can be judged, cannot be defined 
with any real precision. The ke y to quantifying false alarms is the examination of historic system records.  
 
For any given system, the "average" rate of false alarms depends on many factors, Including:  
• the number of automatic fire detectors;  
• the environment in which automatic fire de tectors are installed;  
• the activities in the building;  
• the degree of control over the activities of third parties (such as contractors);  
• the extent to which strong electromagnetic fields are present;  
• the level of occupation of the building (e.g. day sh ift or 24 h working); and  
• the propensity for malicious action.  
The number of false alarms that can be anticipated is virtually proportional to the number of automatic fire 
detectors installed. The constant of proportionality will normally be highest wher e the fire detectors are smoke BOS 813 -1:2023  
Edition 1.0 
83 detectors. Systems incorporating only manual call points or manual call points in conjunction with heat 
detectors do not normally produce many false alarms; the regular occurrence of false alarms in such systems 
warrants part icular attention by the user and/or servicing organization.  
Experience suggests that, in a relatively benign environment, in which there is no tendency for dust, fumes or 
insects to occur, and in which there is a good standard of management, false alarm r ates equal to, or less 
than, one false alarm per 100 detectors per annum are possible, even if the proportion of smoke detectors is 
very high. On industrial sites with shift working, this figure ought to be regarded as a possible target, but not a 
norm; a figure of one false alarm per 75 detectors per annum is probably a more realistic expectation.  
In general, false alarm rates of one false alarm per 50 detectors per annum can be readily achievable with 
modern technology systems, unless there are severe en vironmental challenges for automatic fire detection; 
where such challenges occur; consideration needs to be given to whether automatic fire detection is 
appropriate and/or whether it is necessary for a signal from a single automatic fire detector (particul arly a 
smoke detector) to initiate an evacuation or result in summoning of the fire and rescue service.  
It follows that, while a rate of one false alarm per 50 detectors per annum might represent quite reasonable  
and, hence, "acceptable' performance on an  industrial site with processes that create an unfavourable 
environment for automatic fire detectors, this rate might not be regarded as acceptable in a controlled 
environment, such as a computer room.  
In general, in systems with more than 40 automatic fi re detectors, a rate of more than one false alarm per 20 
detectors per annum is never to be regarded as acceptable, particularly if the false alarms result in evacuation 
of the premises or summoning of the fire and rescue service. In premises with 40 autom atic fire detectors or 
less, more than two false alarms per annum is to be regarded as unacceptable.  
Notwithstanding the above, the user has a duty to mitigate all instances of false alarms.  
In the future, it is possible that a fire and rescue authority will take appropriate action against the user if a fire 
detection and fire alarm system consistently produces false alarms and unwanted fire alarm signals at such 
unacceptable rates.  
32.2 Recommendations  
The following recommendations are applicable.  
a) In syste ms that incorporate more than 40 automatic fire detectors, the user should instigate an in -
depth investigation by suitable specialists if, in any rolling period of 12 months, either:  
1) the average rate of false alarms. exceeds one false alarm per 20 detecto rs per annum:  or  
2) three or more false alarms are initiated by any single manual call point or automatic fire detector 
(or detector location).  
b) In systems that incorporate 40 or less automatic fire detectors, an in -depth investigation, as described 
in 32.2a ), should be instigated by the user if, in any rolling 12 months period, three or more false 
alarms occur.  
33 Causes of false alarms  
33.1 Commentary  
In many premises, most false alarms take the form of unwanted alarms (see 3.19). Recognized causes of 
unwanted a larms (albeit, in some cases only from certain types of automatic fire detector) are as follows:  
• fumes from cooking processes [including toasting of bread);  
• steam (from bathrooms, shower rooms and industrial processes);  
• tobacco smoke;  
• dust (whether bui lt up over a period of time or released from an industrial process);  
• insects;  
• aerosol spray (e.g. deodorants and cleaning fluids);  
• high air velocities;  
• smoke from sources other than a fire in the building (e.g. from an external bonfire);  
• cutting, weld ing and similar "hot work";  BOS 813 -1:2023  
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84 • processes that produce smoke or flame (e .g. flammable of food);  
• cosmetic smoke (e.g. in discotheques and theatres];  
• incense;  
• candles;  
• electromagnetic interference;  
• high humidity,·  
• water ingress;  
• substantial fluctuation in temperature;  
• accidental damage (particularly to manual call points);  
• testing or maintenance of the system, without appropriate disablement of the system or warning to 
building occupants and/or an ARC; and  
• pressure surges on water mains serving automa tic sprinkler systems that are interfaced with the fire 
detection and fire alarm system.  
Most of these causes can be minimized by appropriate choice of detection system and suitable management 
arrangements.  
False alarms can also arise from faults in equi pment (equipment false alarm). These can be minimized by 
choice of good quality equipment that satisfies relevant standards (see Clause 11), has third -party certification 
and has been regularly serviced and maintained in accordance with Section 6 of this s tandard.  
Malicious false alarms (see 3.19) tend to occur with most frequency in certain premises to which the public 
resort in large numbers, such as shopping centres, places of entertainment, public car parks and sports 
centres, and in educational establ ishments, such as universities and schools. Mainly, malicious operation of 
manual call points is involved. Manual call points in certain public houses can also be subject to malicious 
operation. Where there is significant potential for malicious false alar ms, or an existing system is subject to 
these, consideration needs to be given to the locations of manual call points and to the possible use of two -
action devices.  
Little can be done to prevent false alarms with good intent (see 3.19). These are unlikely  to present a significant 
problem, and it is important that people are never discouraged from operating a manual call point if they 
suspect that there might be a fire.  
However, in some premises where frequent good intent false alarms occur, investigation and consideration  
can be given to addressing the incident frequency. It is possible that processes causing smoke -like odours 
and a mistaken belief of fire could be better controlled and staff could be better informed. In situations involving 
manual call poi nts, where these are being mistaken for exit door releases, better signal  and alarm covers can 
be employed to address the problem It is also possible that applying variations is an appropriate resolution.  
33.2 Recommendations  
Any person responsible for specifi cation, design, commissioning or maintenance of fire detection and fire alarm 
systems should be conversant with the major causes of false alarms. Particular care should be taken to limit 
the potential for unwanted alarms and, in certain vulnerable premises , malicious false alarms.  
34 Design process for limitation of false alarms and unwanted fire alarm signals  
34.1 Commentary  
The majority of false alarms arise from automatic fire detectors, particularly smoke detectors, rather than 
manual call points. Although, in most circumstances, automatic fire detection greatly enhances the level of fire 
safety, and any risk assessment needs to take into account the benefit of automatic fire detection compared 
with the potential for false alarms and unwanted fire alarm signa ls. Examples include simple buildings in which 
all areas are occupied on a 24 h basis (e.g. certain small factories).  
Normally, it ls inappropriate to avoid automatic fire detection simply to avoid false alarms and unwanted fire 
alarm signals. Limitation o f false alarms and unwanted fire alarm signals normally involves, firstly, identification 
of the likely conditions that could give rise to false alarms from the form of detection proposed. By suitable 
choice of system type, detection principle and detector  siting, in most cases the likely frequency of false alarms 
will be acceptable.  BOS 813 -1:2023  
Edition 1.0 
85 However, the designer needs to, at the design stage, make a judgement as to the likely frequency. This need 
not be quantitative in all cases, but can be expressed qualitativel y (e.g. low, medium, high). Alternatively, in 
very large systems with many smoke detectors, it might be of value for the designer to give the user some very 
approximate rate at which false alarms could occur; the information contained in Clause 32 may form  a basis 
for estimation. If this frequency is unacceptable, whether on the basis of the guidance in Clause 32 or on the 
basis of consultations with the user or purchaser, additional measures might need to be incorporated into the 
design to further limit fa lse alarms and unwanted fire alarm signals or their effects.  
Additional measures to control false alarms and unwanted fire alarm signals might involve a change in 
detection principle from that originally proposed, a change in system type to a more complex,  sophisticated 
system, or a form of '’’filtering" false alarms so that those that do occur do not lead to evacuation of the building 
or summoning of the fire and rescue service. It is essential, however, that any additional measures do not 
compromise the p rotection afforded by the system to a degree that its objectives (whether in respect of 
protection of life, protection of property, protection against business interruption or protection of the 
environment) are no longer satisfied; in the case of some meas ures, agreement of the interested parties (see 
Clause 6) might be necessary.  
Each major area of the building needs to be considered separately and the design process might need to be 
iterative, in that, if the initial design is not adequately robust in its  limitation of false alarms and unwanted fire 
alarm signals, further measures might need to be considered until the potential for false alarms and unwanted 
fire alarm signals is suitably minimized. A schematic of the recommended design process is shown in Annex 
E. 
34.2 Recommendations  
The following recommendations are applicable:  
a) at the design stage of every system, there should be formal consideration of the potential for false 
alarms and unwanted fire alarm signals, with a view to confirming that design is s uch that the frequency 
of false alarms and unwanted fire alarm signals is likely to be acceptable (see Clause 32);  
b) any relevant design information regarding false alarms and unwanted fire alarm signals  should be 
recorded and documented in accordance with Clause 40.  
35 Measures to limit false alarms and prevent unwanted fire alarm signals  
35.1 Commentary  
In principle, measures to limit false alarms and unwanted fire alarms signals can be divided into eight groups:  
• siting and selection of manual call points;  
• selection and siting of automatic fire detectors;  
• selection of system type;  
• protection against electromagnetic interference;  
• performance monitoring of newly commissioned systems;  
• filtering measures;  
• system management; and  
• regular servicing and maintena nce .  
35.2 Recommendations  
35.2.1  General  
The following recommendations constitute general guidelines that should be taken into account by any parties 
responsible for specification, design, commissioning or verification of a fire detection and fire alarm system, 
and by maintenance organizations at the time of consideration of false alarm problems. The recommendations 
should not, however, be regarded as definitive "rules".  
35.2.2  Recommendations for siting and selection of manual call points  
The following recommendations are applicable.  
a) This standard recommends manual call points shall be fitted with protective covers [see 20.2b )]. While 
that recommendation is not retrospective, in existing systems in which there is frequent unwanted 
operation of manual call points, prot ective covers shall be fitted.  BOS 813 -1:2023  
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86 b) Manual call points should not be sited where they are likely to be exposed to accidental damage (e.g. 
by normal operations In the building, trolleys or forklift trucks). Where compliance with 20.2 makes 
such siting essential , suitable guards should be provided to prevent impact on the manual call points.  
Examples include manual call points located adjacent to fire exits from sports halls and gymnasia in 
which ball sports are played. Protective covers shall be provided for th is purpose.  
c) In areas in which manual call points are exposed to moisture, suitably water -resistant devices shall be 
used.  
NOTE 1 Examples include external locations, wet areas of Industrial buildings, food -processing  areas that are 
subject to periodic wa shing down and certain  kitchens.  
d) To minimize the potential for malicious operation, manual call points should not normally be located 
within the malls  of covered shopping complexes. Subject to the agreement of all relevant enforcing 
authorities, it might also be appropriate either  to omit manual ca ll points from areas accessible to the 
public or to site them so that they are accessible only to authorized persons, provided there is adequate 
surveillance of the entire premises by persons (or by CCTV) and tha t manual call points are provided 
at suitably staffed locations; examples of such premises include some public houses, cinemas, 
theatres and nightclubs.  
NOTE 2 In public car parks, consideration can be given  to the use of a suitable  emergency voice commun ication 
system in lieu of manual call points [ see 20.21 k].  
35.2.3  Recommendations for selection and siting of automatic fire detectors  
The following recommendations are applicable.  
a) In areas with high levels of dust and dirt which could contaminate detectors a nd/or lead to an unwanted 
alarm, preference should be given to the use of aspirating smoke detectors as long as these 
incorporate mechanical filtrations of the air samples  before they are analysed for the presence of 
smoke. It should be confirmed that the filters used for any such detectors are covered under the 
detectors' certification in accordance with BS EN 54 -20. Furthermore, account should be taken of the 
consequences of blocked filters to the detection capability of the system and a rigorous regular 
maintenance regime established if needed.  
b) In areas in which automatic fire detectors are likely to result in a high level of unwanted alarms, it 
should be confirmed whether the provision of automatic fire detection is necessary to ensure that the 
objectiv es of the fire detection and fire alarm system are satisfied (see Clause 4).  
c) Since, in most premises, heat detectors are likely to give rise to lower rates of unwanted alarms than 
other forms of automatic fire detector, before other types are used it shou ld be confirmed that the use 
of heat detectors would not satisfy both the objectives of the fire detection and fire alarm system and 
the recommendations of this standard  (see Clause 5 and Clause 21).  
d) The minimum static response temperature (see 3.39) of h eat detectors should not be less than 29 °C 
above the ambient temperature that the detector can be expected to experience for long periods of 
time, and not less than 4 °C above the maximum temperature that the detector can be expected to 
experience for sho rt periods of time, under normal conditions.  
NOTE 1 BS EN 54 -5 specifies six classes of heat detector for use in high ambient temperatures (between 40 °C 
and 140 °C).  
e) Rate of rise heat detectors should not be installed in locations in which rapid fluctua tions in temperature 
might occur; examples include kitchens. boiler rooms, loading bays with large doors to open air and 
lantern -lights.  
f) In the absence of overriding considerations (particularly in respect of effective detection of fire), the 
guidance con tained in Annex E should be taken into account when considering the use of point and 
optical beam smoke detectors, or when selecting the principle of operation of these detectors.  
g) Optical beam smoke detectors should not be installed in areas in which obst ruction of the beam might 
occur in normal  circumstances.  
h) Where optical beam detectors are installed in any area, they should be suitably mounted [see 22.5g)].  
i) Certain fire detection and fire alarm systems which incorporate multi -sensor detectors have the 
potential to reduce greatly the potential for unwanted alarms. The extent to which the potential can be 
reduced depends on the characteristics of each proprietary multi -sensor detector and on the potential 
causes of unwanted alarms. The provision of more t han one sensor within one fire detector does not, 
alone, necessarily have a significant impact on potential for unwanted alarms.  BOS 813 -1:2023  
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87 j) Many aspirating smoke detection systems can operate at a level of sensitivity much higher than normal 
point type smoke detecto rs. Special consideration should be given to the potential for false alarms 
when a high sensitivity (Class A) or enhanced sensitivity (Class B) aspirating smoke detection system 
is proposed, to ensure that an unacceptable rate of unwanted alarms is not lik ely to result.  
NOTE 2 Such systems  are often used to provide signals intended to be managed as a ''pre-alarm warning '' (to 
indicate that an alarm addition  is approaching) or as a very early warning (to alert staff of abnormal conditions 
that are worthy of  investigation). Such signals might not be suitable (or intended) to be managed as an alarm 
signal that triggers  alarm devices and evacuation of the building. However, such pre -alarm warnings or very early 
warning signals can be used to avoid false alarms,  unnecessary evacuations and unwanted fire ala rm signals to 
the fire and rescue service. In some applications in which Class A and/or Class B aspirating smoke detection 
systems are used, a Class C (normal sensitivity) signal is provided which Is managed as  an alarm condition.  
k) Carbon monoxide fire detectors should not be used in locations in which carbon monoxide might occur  
under normal circumstances, in quantities sufficient to create the potential for unwanted alarms.  
NOTE 3 Such areas include badly ventilated kitchens , some laboratories and areas for which vehicle  or other 
exhaust fumes occur.  
l) Carbon monoxide fire detectors should not be used in locations in which contamination of the electro -
chemical cell could result in unwanted alarms. The guidance o f the manufacturer on avoidance of 
unwanted alarms should be taken into account  
m) Flame detectors should not be located in areas in which sources of infrared or ultraviolet radiation 
create the potential for unwanted alarms. Since various techniques can be adopted in the design of 
the detector to minimize the potential for unwanted alarms as a result of radiation from non -fire 
sources, the guidance of the manufacturer  of the detector  in respect of sensitivity of detectors to such 
sources, should be taken int o account.  
35.2.4  Recommendations for selection of system t ype  
The following recommendations are applicable.  
a) Unless there are overriding considerations, systems that incorporate a high number of smoke  
detectors should be of the analogue type.  
NOTE 1 Analogue smoke detection systems are likely to offer better immunity to false alarms than conventional 
two-state fire detection  systems, particularly if signal processing incorporates techniques specifically intended to 
discriminate between certain unwanted alarms and real fires. Some two -state fire detection systems also employ 
such signal processing. Many analogue systems also provide a pre -alarm warning {see 1:15), which enables 
investigation of conditions that, if no action is taken, would lead to an unwanted al arm  
NOTE 2 A high number of smoke detectors might be regarded as more than 100 detectors.  
b) In systems that incorporate a very high number of automatic fire detectors (other  than heat detectors), 
the use of systems that Include multi -sensor fire detectors and Incorporation of suitable measures to 
minimize the potential for unwanted alarms should be considered at the design stage.  
NOTE 3 At the time of publication of this standard, a very high number of detectors might be regarded as more 
than 1000 detector s.  
35.2.5  Recommendations for protection against electromagnetic interference  
The following recommendations are applicable :  
a) In order to minimize the potential for electromagnetic interference to cause unwanted alarms. the 
recommendations of Clause 28 should be  followed.  
b) The designer should take into account the likely sources of electromagnetic radiation in the building 
(e.g. mobile telephones, two -way radios, mobile telephone base stations and other high power 
transmitters).  
c) In special cases where unusually high electromagnetic field strengths occur ( e.g. radio transmitter 
sites, airport terminals and radar stations), guidance should be sought from the system manufacturer 
in respect of suitability of the proposed system and any special measures (such  as incor poration of 
filters on external circuits) to reduce the potential for unwanted alarms. In the case of an existing 
building, information provided to the system manufacturer should include field strength measures.  
35.2.6  Recommendations for performance monitoring of newly commissioned systems  
The following recommendations are applicable.  
a) In the case of systems incorporating more than 50 automatic fire detectors, after commissioning. a 
soak period (see 3.58) should follow. The duration of the soak period should be  at least one week but  BOS 813 -1:2023  
Edition 1.0 
88 should be defined by the designer and incorporated within any tender specification. Systems that 
incorporate connection to an ARC should have this connection disabled during the soak period.  
b) Until successful completion of the u nsoak  test, the system should not be regarded'  as the operational 
means of giving warning of fire in the building. During the soak period, each manual call point should 
bear an indication that it is not to be used .  
c) The "soak  test" should only be regarded as su ccessfully completed if:  
1. during the soak period, no false alarm occurred; or  
2. investigation of all false alarms that occurred, by the supplier of the system, identified the cause 
of every false alarm and enabled any relevant measures to be taken to minimi ze potential for 
similar false alarms to occur in the future.  
NOTE A purchasing specification might require that, on completion of any relevant measures, a further soak test 
be carried out.  
35.2.7  Filtering measures  
35.2.7.1  Commentary  
The recommendations of 35.2.2, 3 5.2.3, 35.2.4, 35.2.5 and 35.2.6 apply to all systems. It might be considered 
at the design stage (see Clause 34), or following unsatisfactory operational experience, that the rate, or the 
periodicity , of false alarms, is likely to be (or has proved to be)  unacceptable. Under these circumstances, it 
might  be necessary to take further measures to ensure that false alarms do not result in continual evacuation 
of people or summoning of the fire and rescue service.  
There are two principal means by which potent ial false alarms can be filtered. The first, which is only applicable 
to those systems provided for property protection, is to disable automatic fire detectors ( particularly  smoke 
detectors) automatically at certain times of day (or night), when environmen tal conditions (such as those arising 
from an industrial process) are likely to give rise to unwanted alarms.  
In effect, the system might then become a Category M system during normal working hours, when people are 
present and can detect a fire, but a Cat egory P system outside normal working hours (when the automatic fire 
detectors would be of most value in any case).  
A system that operates in this manner is described as a "time -related system" (see 3.62), and, in effect, it filters 
out unwanted alarms, r ather than obviating their cause. Other forms of time -related system may a/so be 
considered.  
For example, rather than totally disabling automatic fire detectors, their sensitivity might be reduced 
automatically at certain times, so that a (reduced) standa rd of protection can still be afforded. In a multi -sensor 
fire detection and fire alarm system, one of the sensors (e.g. a smoke sensor) might be disabled (or reduced 
in sensitivity) at certain times, so that some protection is still afforded by another se nsor (e g. a heat sensor). 
(The detectors would then need to be sited in accordance with the recommendations for heat detectors. ) 
The second form of  filtering involves the use of a staff alarm arrangement (see Clause 19). This permits  an 
investigation peri od following activation of an automatic fire detector, prior to operation of  fire alarm sounders 
and/or summoning of the fire and rescue service. Staff alarms that incorporate such an investigation period 
are now quite common in well -managed buildings that  are protected by a high Umber of smoke detectors. The 
staff alarm arrangement can apply at all times or only at certain times of the day, such as normal working 
hours; in this case, the system is also a time -related system.  
Where an investigation period is employed, the fire and rescue service ought not to be called until the outcome 
of the investigation is known (except in residential care premises where It is necessary to summon the fire and 
rescue service as soon as the fire detection and fire alarm sy stem operates).  
Equally, in a Category P system, consideration needs to be given to the overall period between operation of 
the fire detection and fire alarm system and the ultimate attendance of the fire and rescue service, as a 
combination of an investi gation period and a long fire and rescue service attendance time might preclude the 
objective of the system from being satisfied.  
Filtering might sometimes be applied solely to the summoning of the fire and rescue service. ln this case, the 
building, or p art of it, would be evacuated when the fire detection and fire alarm system operate , but the 
automatic summoning of the fire and rescue service would be delayed pending an investigation to confirm 
whether the alarm signal ls false or the result of a real f ire.  
The use of a staff alarm normally incorporates certain safeguards to ensure that there is still early response to 
a real fire. This includes a full fire alarm signal if a manual call point ls operated,  or a heat actuated device BOS 813 -1:2023  
Edition 1.0 
89 (such as a heat detect or or sprinkler head) operates. A staff alarm arrangement also incorporates coincidence 
detection, so that the delay is cancelled if two detectors operate . See also Clause 19  
35.2.7.2  Recommendations  
The following recommendations are applicable.  
a) Filtering measur es should be adopted under the following circumstances:  
1. in the case of -category P systems in which it is proposed to Incorporate an investigation period 
prior to the summoning of the fire and rescue service (whether manually or automatically), after 
consu ltation with the insurers; and  
2. where it is considered that either the rate of false alarms and unwanted fire alarm signals 
expressed as number of false alarms per 100 detectors per annum), or the actual number of false 
alarms, cannot be limited to a level  acceptable to the user and the fire and rescue service by other 
means; and  
3. where it is considered that the Incorporation of filtering measures does not negate the objectives 
of the system in terms of protection of  life, property, business continuity or t he environment  
b) Filtering should not be applied to signals initiated by manual call points, heat detectors or sprinkler 
systems.  
c) ln time -related systems, the change of state of the system to unmanned mode should not rely on 
human action; it should occur a utomatically at predetermined times. The change of state to manned 
mode should be by human action at the fire alarm system to ensure persons are present.  
NOTE 1 The control of these features might be possible either manually, through a day/night mode cont rol, or 
automatically through a clock provided within the CIE. A combined system can be employed where the CIE 
automatically switches to the more sensitive mode with no filtering applied at a certain time, e.g. 6pm, and the 
less sensitive day mode is then manually selected on the initial occupation of the building the next day. However, 
these systems are liable to inappropriate activation due to circumstances such as when people remain in 
occupation later than expected leading to unwanted alarms. A better c onfiguration might be to link the activation 
of filtering to the intruder alarm system, which is set or unset according  to the building occupation status.  
d) Staff alarms should conform to .19.2.2  
NOTE 2 19.2.2 recommends that, in residential care premises,  the fire and rescue service is summoned 
immediately when the fire detection and fire alarm system operates.  
e) If the fire and rescue service is not summoned immediately at the start of any investigation period 
associated with a staff alarm, it is essential  that they are summoned immediately on expiry of this 
period, unless it has been determined that the alarm signal is a false alarm.  
NOTE 3 Reliability in compliance with this recommendation would be aided by a monitored facility for automatic 
transmission  of an alarm signal to an ARC on expiry of the investigation period.  
f) Any arrangements for filtering of automatic summoning of the fire and rescue service by an ARC 
should conform to this standard. Such filtering should not be applied to signals from fire alarm systems 
in residential care premises.  
g) Where a signal from an automatic sprinkler system that is supplied from water mains is used as an 
input to the fire detection and fire alarm system ( e.g. by means of a pressure or flow switch), there 
should be liaison with the organization responsible for installing or maintaining  
h) the sprinkler system to minimize the potential for unwanted alarms as a result of water pressure 
surges. A hydraulic or electronic time delay facility should be considered.  
35.2.7.3  Recommend ations for system management  
The following recommendations are applicable.  
a) The user should ensure that staff in the building and visiting contractors are aware of the presence of 
any automatic fire detectors, and of the measures necessary to minimize the  likelihood of false alarms 
and unwanted fire alarm signals.  
b) Tender documents for contact work to be carried out in a protected area should contain a clause 
making the contractors responsible for informing their staff of the presence of any automatic fire  
detectors, and of the precautions to be adopted when working.  
c) Where temporary work involving the generation of dust, smoke, paint spray, etc., is to be carried out 
in an area protected by smoke detectors, precautions should be taken to prevent unwanted a larms.  BOS 813 -1:2023  
Edition 1.0 
90 NOTE 1 One method of managing such work would be the operation of a permit to work system. Other suitable 
measures may include the following:  
i) temporary replacement of smoke detectors by other types of detectors  that are less susceptible to the eff ects 
of the pollutants in question;  
ii) provision of a temporary screen between the work and the detectors. The flammability of the screen ought 
to be considered to ensure that it does not increase the fire risk;  
iii) provision of brightly coloured temporary cove rs over detectors to prevent the ingress of contamination:  
iv) disablement of automatic fire detectors. On completion of the work, the premises management (see Clause 
47) should ensure that proper reinstatement of the protection occurs;  
v) disablement of commun ication with any ARC. On completion of the work, the premises management (see 
Clause 47) should ensure that proper reinstatement of the monitoring occurs.  
NOTE 2 Unless the work involving generation of dust etc. is to be carried out throughout a large par t of the 
building, the measures described in c)4) are preferable, as these still permit remote monitoring of fire alarm signals 
from areas where work is not being carried out  
d) Suitable notification of building occupants, and any ARC to which fire alarm sig nals are transmitted, 
should occur prior to routine testing or maintenance work on the fire alarm system that might result in 
the occurrence of a fire alarm signal.  
e) The user should ensure that building defects (e.g. leaking roofs), plant defects (e.g. steam leaks) and 
environmental problems (such as inadequate ventilation) that could cause unwanted alarms receive 
suitable attention.  
f) All false alarms should be properly recorded by the user in the system logbook (see 30.2h, .31.2 ) and 
Clause 48.  
g) Suitable a ction should be taken by the user when false alarms occur (see 30.2g and 32.2 ).  
35.2.7.4  Recommendations for service and maintenance  
Service and maintenance on the system should be carried out by a competent organization in accordance with 
Section 6 of this stand ard.  BOS 813 -1:2023  
Edition 1.0 
91 Section 4: Installation  
36 Responsibility of installer  
36.1 Commentary  
This section gives recommendations for the work associated with installation of the fire alarm equipment in a 
building . This work might be undertaken by the same organization that desi gned the system or by a different 
organization. For example, the designer and installer might be a single specialist fire alarm contractor. 
Alternatively, the purchaser might be responsible for the design of a fire detection and fire alarm system (which 
might be undertaken by consultants acting on behalf of the purchaser), and the design might then be 
communicated, by means of a specification and/or drawings, to a specialist fire alarm company or to an 
installing company which would, in either case, then be  responsible for installation.  
Various contractual arrangements are possible, but it needs to be ensured that one organization is responsible 
for compliance with this section of the standard and that this responsibility is agreed prior to the start of the  
installation contract (see Clause 6).  It is the responsibility of the installing company to chec k or verify whether 
the design of the system complies in  full with the recommendations of this standard  
In general, the responsibility of the installer is to insta lI the system fully in accordance with the requirements 
of the designer and to follow good practice in the installation work. However, in practice compliance with a 
number of recommendations of Section 2 impact on both design and installation, and mi9 ht, therefore, be 
delegated by the designer to the installer, provided the responsibility for compliance is clear in any specification 
or contract, that the installer is competent to address the issues and that the responsibility is accepted by the 
install er. For example, the designer might delegate decisions regardir19 cable routes to the installer, by simple 
reference in the design to compliance with Clause 26, with which it would then be the responsibility of the 
installer to comply.  
At the design stage , the designer might have inadequate information to enable compliance with all 
recommendations of Section 2. For example, it is rarely possible, at the design stage, to warrant that the 
recommendations  of 16.2 in respect of sound pressure levels will be sa tisfied by a particular number and 
distribution of  fire ala m sounders unless the number is greatly over -specified). Similarly, drawings on which 
the design is based might not show sufficient information about structural features of the building to enable t he 
design to comply with Clause 22. Accordingly, it is often necessary for compliance with certain clauses of 
Section 2, or verification of compliance, to rest with an installer.  
Nevertheless, the designer needs to provide sufficient information and guida nce to the installer to enable the 
installer to satisfy the relevant recommendations of Section 2 in the absence of expertise design of  fire 
detection and fire ala m systems. In this respect, the installer is then, in effect, simply  complying with specified  
requirements of the designer.  
Even though identification of design shortcomings is not generally the responsibility of an installer, good 
practice would dictate that, if the installer is aware of such shortcomings, particularly those arising from feature s 
of the building that might not have been known to the designer, they be drawn to the attention of the designer, 
user or purchaser.  
36.2 Recommendations  
The following recommendations are applicable to the responsibility of an installer.  
a) The responsibilities associated with the installation of the system should be clearly defined, agreed 
and documented prior to the commencement of the installation work.  
b) The installer should comply with 6.2c).  
c) The installer should comply with 7.2b) .  
d) The installation of MCPs should be in accordance with 20.2d) to 20.2k).  
e) When installing point, heat, smoke and carbon monoxide detectors, the installer should, at least, 
ensure compliance with 22.3e), 22.3h) and 22.3n).  
f) When installing beam -type smoke detectors, the installer sh ould, at least, ensure compliance with the 
recommendations of 22.5d), 22.5e) , 22.5f) and 22.5g) and any manufacturer's recommendations for 
the mounting distance below the ceiling.  
g) When installing line heat detectors, the installer should, at least ensure compliance with 22.3e), 22.3g), 
22.6c) and 22.6e).  BOS 813 -1:2023  
Edition 1.0 
92 h) When installing smoke detectors in ventilation ducts, the installer should, at least, ensure compliance 
with 22.10a) and 22.10c).  
i) Where an installer identifies any circumstances that might lead to a high  rate of false alarms, the 
designer, purchaser or user should be informed accordingly [see also 7.2b)].  
j) The installer of the mains power supplies to the fire alarm system should ensure that the supplies 
comply with 25.2.  
k) The installer should ensure that all control, indicating and power supply equipment that is likely to need 
routine attention for maintenance is sited in readily accessible locations that facilitate safe 
maintenance work  
l) All metallic parts of the installation, including conduit, trunking.  ducting. cabling and enclosures, should 
be suitably separated from any metalwork forming part of a lightning protection system.  
NOTE 1 Further guidance is given in BS EN 62305.  
m) The installer should comply with the requirements of 40.2c) unless it has be en agreed that this is to 
be the responsibility of others.  
n) On completion of their works, the installer should issue a certificate in accordance with the model given 
in G.2, signed by installing company.  
NOTE 2 Under BS 7671, the installer of the mains su pply is required to issue an electrical installation certificate 
in accordance with the requirements of that standard. If the installer of the fire detection and fire alarm system 
does not install the mains supply, the installer of the mains supply ought a lso to issue a certificate in accordance 
with the model given in G.2. solely in respect of the mains supply.  
NOTE 3 A designer might accept responsibility for variations from any of the above recommendations and 
communicate this in the form of specific wr itten requirements (e.g. within a specification). In this case, the installer 
ought to record the relevant variations within the installation  certificate issued by the installer (see clause 41 ) 
37 Installation Practices and workmanship  
37.1 Commentary  
The nature a nd the quality of the installation work needs to be such as main the integrity of the fire detection 
and fire alarm, system and minimize the duration and extent of disablement of the system during maintenance 
or modification. Installation's  practice and wo rkmanship need to conform to BS 7671 .  
Penetration of construction (e  g for passage of cables, conduits, trucking or tray) needs to be made good to 
avoid the free passage of fire of smoke, regardless of whether the construction has a recognized  degree of 
resistance .  
37.2 Recommendations  
The following recommendations are applicable.  
a) The entire system should conform to the requirements of BS 7671. In general, the  recommendations 
of this standard supplement, but do not conflict with, these requirements.  Where any such conflict is 
considered to exist, the recommendations of this standard, should  take precedence.  
b) Cables which are directly fixed to surfaces should be neatly run and securely fixed at suitable  intervals, 
in accordance with the recommendations of the cab le manufacturer . Cables should not  rely on 
suspended ceilings for their support.  
c) The installer should ensure that all wiring complies with, at least, 26. 2f) to 26.2 o). 
d) Joints in cables, other than those contained within the enclosures of equipment, should be avoided 
wherever practicable [see 26.2g)].   
e) So far as is reasonably practicable, cable routes should be selected to follow the  recommendations in 
26g. 
f) Arrangements for earthing should be in accordance with the recommendations of the  manufacturer. 
Care s hould be taken to ensure th at electrical  continuity of electromagnetic  screens, including metallic 
sheaths of cables [see Figure 18 a) and b)],  
g) Where new conduit, trunking or tray is installed, its capacity should be in accordance  with BS 7671.  
h) Where a ca ble passes through an external wall, it should be contained in a smooth -bore sleeve of 
metal or other non -hygroscopic material sealed into the wall. This sleeve should  slope downwards BOS 813 -1:2023  
Edition 1.0 
93 towards the outside and should be plugged with a suitable non -hardening  waterproof compound to 
prevent the entry of rain, dust or vermin.  
i) Where a cable passes through an internal wall, a small clearance hole should be provided.  If additional 
mechanical protection is necessary, a smooth -bore sleeve should be sealed  into the wal l. 
j) Care should be taken to ensure that the ends of any sleeves are free from sharp edges which  might 
damage cables during installation.  
k) When a cable passes through a floor, the considerations of  37.2h), 37.2i) and 37.2j) apply. But  the 
sleeve should extend  as far above floor level as is required for protection of the cable it is to  carry, but 
never less than 300 mm.   
l) Where cables, conduits, trunking or tray pass through floors, walls, partitions or ceilings, the  
surrounding hole should be as small as reason ably practicable and made good with fire -stopping  
materials that ensure that the fire resistance of the construction is not materially reduced.  Spaces 
through which fire or smoke could spread should not be left around the cable, conduit,  trunking or tray.  
m) If cables or conduits are installed in channels, ducts, trunking or shafts that pass -through  floors,  walls, 
partitions or ceilings, barriers with the appropriate level of fire resistance should be  provided within the 
channels, etc. to prevent the spread of  fire unless, in the case of ducts and  shafts, the construction of 
the duct or shaft affords equivalent fire resistance to the structure  penetrated. In the latter case, fire 
stopping need only be provided where cables pass into, or out  of, the duct or shaf t. 
 
  
Figure 18 a - Examples of screen connection for continuity -loop wiring  BOS 813 -1:2023  
Edition 1.0 
94  
 
 
38 Commentary  
On completion of wiring, or sections of wiring, the installer needs to carry out tests to ensure the integrity of 
cable insulation and adequacy of earthing. Usually, the tests on cables are carried out with equipment 
disconnected an d prior to completion of the entire system Further tests need to, therefore, be carried out on 
completion of the system; these tests can form part of the commissioning process.  
In some (usually addressable) systems, maximum circuit impedance might be speci fied by the system 
manufacturer, in which case any measurements of impedance recommended by the manufacturer also need 
to be carried out, either on completion of installation or at commissioning (see Clause 39). As the entire fire 
alarm installation is an electrical installation, as defined in BS 7671, there is a need for inspection, testing and 
certification of the wiring in accordance with the requirements of BS 7671 before  commissioning.  
38.1 Recommendations  
The following recommendations are applicable.  
a) All installed cables with a manufacturer's voltage rating suitable for mains use should be subject to 
insulation testing at 500 V d.c. Prior to this test, cables should be disconnected from all equipment that 
could be damaged by the test.  
b) Insulation resistance,  measured in the above test, between conductors, between each conductor  and 
earth, and between each conductor and any screen, should be at least 2 M Ω. 
NOTE  CIE can have fault sensing for wiring insulation resistance to earth. If this is, for example, set  at 1 Mn, the 
combined effect of all wiring earth insulation resistance ought to be well above this to avoid  nuisance fault 
indications. For large systems, this 2 M Ω minimum needs to be much  higher than this to achieve  something in 
excess of 1 M Ω overall. F or a small non -addressable system up to about four zones, 2 M Ω might  be acceptable.  
c) Earth continuity and, for mains supply circuits, earth fault loo p impedance, should be tested to  ensure 
compliance with BS 7671.  
d) Unless there is specific agreement that the  following tests form part of the commissioning process, the 
tests should be carried out on completion of the installation work:  
1. where maximum circuit resistance for any circuit is specified by the manufacturer or supplier; 
measurement of the resistance of  every such circuit;  
2. any other tests specified by the manufacturer of the system; and  
3. correct polarity of circuits is checked where this is required for correct monitoring (to ensure 
operation of any manual call point while all detectors on a circuit are r emoved).  
Figure 18 b - Examples of screen connection for continuity - Network conditions  BOS 813 -1:2023  
Edition 1.0 
95 e) The results of all tests should be recorded and made available to the organization responsible for 
commissioning the system.  BOS 813 -1:2023  
Edition 1.0 
96 Section 5: Commissioning and handover  
39 Commissioning  
39.1 Commentary  
The process of commissioning involves thorough testing of t he installed system to ensure that it operates 
correctly in accordance with the recommendations of this standard and with the purchasing specification. At 
completion of commissioning, it also needs to be confirmed that all relevant documentation has been h anded 
over to the user (see Clause 40). The installing organization is responsible for commissioning the system.  
It is not, in general, the responsibility of the commissioning engineer to verify conformity of the design,  or of 
the installation work, to thi s standard  (i.e. with Section 2 and Section 4 of this standard). In general, the 
responsibility of the commissioning engineer is to verify that the system operates correctly in the manner 
designed and that the installation workmanship is generally of an ad equate standard. However, in practice, it 
might be difficult to ensure that the system complies in full with all recommendations of Section 2 until the time 
of commi ssioning . For example, commissioning might represent the first (and only) opportunity to de termine 
whether the number and distribution of fire alarm sounders is sufficient to enable compliance with 16.2 in 
respect of sound pressure levels. Similarly, commissioning presents an opportunity to ensu re that structural 
features of the building, of whi ch the designer might have been unaware, do not compromise the effectiveness 
of the system as it was  originally designed.  
Accordingly, it is necessary fo r anyone responsible for commissioning a fire detection and fire alarm system 
to possess at least basic  knowledge of fire alarm design practices and of the recommendations of Section 2 
and Section 4 of this standard. It is also necessary for the commissioning engineer to be provided with the 
specification for the system. In view of the importance now attach ed to the avoidance  of false alarms, it is als o 
essential that the commissioning engineer is able to verify compliance with, at  least, the principles discussed 
in Section 3 of this standard.  
39.2 Recommendations  
The following recommendations are applicable to n ew systems, and to modifications and additions to systems.  
a) The system should be commissioned by a competent person (see 3 .12), who has access  to the 
requirements of the designer (i.e. the system specification) and any other relevant  documentation or 
drawin gs. 
b) Any person responsible for commissioning a fire detection and fire alarm system in accordance  with 
the recommendations of this standard shall be, competent person with  understanding of Section 2. 
Section 3 and Section 4 of this standard.  
c) At commissioni ng, the entire system should be inspected and tested to ensure that it operates  
satisfactorily and that, in particular:  
1) all manual call points and automatic fire detectors function correctly in accordance with 45.4  
2) if the specification requires labelling o r other means of visual identification of manual call points, 
automatic fire detectors, fire alarm devices or ancillary devices, this has been carried out;  
3) every manual call point and automatic fire detector, on operation, results in the correct zone 
indication, and, in the case of addressable systems, correct text display, at all indicating 
equipment;  
4) where an optical beam detector uses a combined transmitter/receiver unit in conjunction with a 
reflector, care should be taken to minimize the effect of refl ections (e.g.  from surfaces close to the 
transmitter/receiver unit) from dominating the received signal.  Unless the equipment has specific 
features to compensate for such effects, at commissioning, the installed unit should be tested by 
partial obscuration  of the beam near to the reflector.  
5) sound pressure levels throughout all areas of the building conform to16.2 and, where appropriate 
for voice alarms, an acceptable level of intelligibility is achieved in accordance with BS 5839 -8 
throughout all areas of t he building;  
6) any facility for remote transmission of fire alarm signals (and, where appropriate, fault signals) to 
an ARC operates correctly;  
NOTE 1 It is essential that any ARC to which fire alarm signals are relayed is notified before, and immediately 
after completion of, any tests that could result in a fire alarm signal.  BOS 813 -1:2023  
Edition 1.0 
97 7) any cause and effect requirements of the designer (e.g. in respect of staged alarms or initiation of 
operation of other fire protection systems a d equipment, safety measures, etc.)  are fully satisfied;  
8) all alarm, control, indicating, printing, and ancillary  functions of the system operate correctly and 
are adequately labelled or identified;  
9) no changes to the building since the time of original design have compromised the compliance of 
the system with this standard ( e.g. by erection of new partitioning that affects the adequacy of 
siting of fire detectors or the effectiveness of warning devices);  
NOTE 2 Particular care is advised where a system is commissioned in a "shell" property in adv ance of final 
occupation or fitting out.  
10) siting of manual call points conforms to, at least, the recommendations of 20.2h) and 20.2i);  
11) siting of point heat, smoke and carbon monoxide detectors conforms to 22.3d) to 22.3 j) and 22.3m) 
to 23p);  
12) siting of beam -type smoke detectors conforms to 22.3d), 22.3f), 22.3i), 22.3j), 22.3k), 22. 5e), 
22.5f) and 22. 5g); 
13) siting of line heat detectors conforms to 22.3d), 22.3f), 22.3i), 22.3j), 22.6d) and 22.6e);  
14) siting of aspirating smoke detection systems conforms to the g uidance of the manufacturer;  
15) siting of flame detectors conforms to 22.8b) and 22.8c) ; 
16) siting of any smoke detectors in ventilation ducts conforms to 22.10a);  
17) siting of control, indicating and power supply equipment conforms to 23.2.1b), 23.2. 1b), 23.2. 1c), 
23.2. 1d), 23.2.1 e) and 23.2.1g);  
18) there is a suitable diagrammatic representation of the premises that satisfies the 
recommendations of 23.2.2e);  
19) the provision of any visual alarms conforms to Clause 17: of this standard  
20) mains power supplies are inspected as far as is reasonably practical to ensure confo rmity to 25.2; 
21) standby power supplies conform to 2.4 and that the system's actual load currents in all 
circumstances are close to the predictions used by the designer to determine the specified battery 
capac ity; 
22) as far as it is reasonably practicable to ascertain, the specified cable type has been used in all 
parts of the system and the workmanship conforms to 37.2; 
23) as far as is reasonably practicable to ascertain, the system conforms to Sect ion 3 of this sta ndard;  
24) there are no other obvious shortcomings in compliance with Section 2 of this standard ( e.g. 
unprotected areas within a Category L1 or P1 system, or incorrect spacing  or siting of fire 
detectors):  
NOTE 3 This recommendation  is not intended to imply that it is the responsibility of the commissioning 
engineer to verify or certify compliance of the system design with this standard. 'However, if variations are 
identified by the commissioning engineer, particularly variations related to circumstances  that might not have 
been known to the designer, they need to be documented for referral to the designer, user or purchaser for 
agreement or action (see 7.2). 
25) in radio -linked systems, radio signal strengths are adequate throughout all areas of the protected 
premises to ensure reliable operatio n of the system;  
26) records of  insulation resistance, earth continuity  and, where appropriate, earth loop impedance 
tests exist;  
27) all fault indicators and their circuits should be checked, where practicable, by simulation of fa ults 
conditions;  
28) all relevant  documentation (see Clause 40) has been provided to the user or purchaser.  
d) Unless  already undertaken and documented by the installer, the tests recommended in 38 .2d) should 
be carried out and the results recorded. Where specifi cally agreed that the tests  recommended in 8.2d) 
should be carried out at commissioning, these tests should be carried  out and the resul ts recorded . 
e) Labels, visible when batteries are in their normal position, should be fixed to batteries, indicating  the 
date of installation.  BOS 813 -1:2023  
Edition 1.0 
98 f) On completion of the commissioning. a certificate, signed by a competent person in accordance  with 
the model given In G. 3, should be issued.  
40 Documentation  
40.1 Commentary  
On completion of the system, it needs to be ensured that adequate rec ords and other documentation  are 
provided to the user or purchaser. (The user and purchaser might, or might not, be the same  organization.)  
The responsibility for provision of the documentation might rest with more than one organization  and needs to 
be def ined before an order for the system is placed. At commissioning , it needs to be  ensured that, either the 
documentation has been provided to the relevant parties, or that any absent  documentation is identified for 
appropriate action (see Clause 39). 
Particu lar importance needs to be attached to the preparation and accuracy of as -fitted drawings and  operation 
and maintenance manuals. The manuals need to be adequately specific to the system. Without  these drawings 
and manuals, maintenance or  future modificatio n of the system might be difficult . 
40.2 Recommendations  
The following documentation should be provided to the purchaser or user of the system.  
NOTE 1 The organization to which each form of documentation is provided needs to be defined in any contract for  decis ion 
supply, installation and commissioning of the system  
a) Certificates for design, installation and commissioning of the system (see Clause 41).  
b) An adequate operation and maintenance manual for the system; this should provide information, specific  
to the sy stem in question, regarding the following:  
1) detector type, selection and configuration as documented by the designer using the  template given in 
Table E. 1 
2) the equipment provided and its  configuration, including, for radio -linked equipment to  which Clause 27  
applies, the data referred to in 27.2g)4);  
3) use of all controls;  
4) recommendations for investigation of a fire alarm or fault signal after the incident is over  and the 
building declared safe for reoccupation;  
NOTE 2 This is not intended to be the emergency o r evacuation plan,  which  is the responsibility of  the occupant.  
5) recommendations for investigation in the event of a false alarm (see Section 3);  
6) routine weekly and monthly testing of the system by the user or their appointed agent  (see Clause 44);  
7) service and maintenance of the system  in accordance with Section 6 of this standard;  
8) avoidance of false alarms (see Section 3):  
9) the need to keep a clear space around all fire detectors and manual call points;  
10) the need to avoid contamination of detectors during con tractors' activities;  
11) the importance of ensuring that changes to the building, such as relocation of partitions, do  not affect 
the standard of protection;  
12) other use responsibilities described in Section 7.  
c) As-fitted drawings indicating at least the followi ng: 
1) the positions of all control, indicating and power supply equipment;  
2) the positions of all manual call points, fire detectors and fire alarm devices;  
3) the positions of all equipment that might require routine attention or replacement ( e.g.  
4) short circuit  isolators and remote indicators);  
5) the type, sizes and actual routes of cables.  
NOTE 3 The cable routes shown need to comprise a reasonable representation of the route followed, such as  to enable a 
competent person to locate the cable in the event of a fau lt or need for modification or extension  of the system; a simple 
schematic showing the sequence in which devices are wired is unlikely to satisfy this  recommendation, other than in small, 
simple systems.  BOS 813 -1:2023  
Edition 1.0 
99 NOTE 4 In the case of extensions or alterations, exi sting as -fitted drawings need to be updated.  
d) A logbook in which all events, including fire alarm signals, faults signals, system tests and  maintenance 
visits, can be recorded (see Clause 48).  
NOTE 5 A model format for a lo gbook is given in Annex E  
e) A record of any agreed variations from the original design specification.  
f) Such other records as are required by any purchase specification (e.g. insulation resistance test  records or 
commissioning records).  
41 Certification  
41.1 Commentary  
On completion of design , installation and commissioning, a separate certificate needs to be issued for  each of 
these three processes, confirming compliance with the recommendations of this standard for the  stage in 
question (i.e. design, installation or commissioning) or identif ying variations. All three processes  might be 
undertaken by one organization or  might be carried out by independent organizations;  whichever arrangement 
applies, three separate certificates ultimately need to be issued. It needs to  be possible for an organ ization to 
issue a certificate for the process for which they are responsible,  regardless of whether a certificate has been 
issued for either of the other processes.  
It is essential that the person who signs these certificates is competent to verify whethe r the recommendations 
of this standard in respect of the process  to which the certificate refers have, or have  not, been satisfied. The 
purchaser or user might, subsequently, rely on the certificate as, for example,  evidence of compliance with 
legislation.  Liability could arise on the part of any organization that issues  a certificate without due care in 
ensuring its validity . 
On completion of the system, it is handed over to the purchaser or user; at this stage, the organization  bearing 
contractual respons ibility to the  purchaser for the system needs to issue a certificate of  acceptance to the 
purchaser Jo.[ completion by the purchaser. The purpose of this certificate is to  constitute objective evidence  
that the  purchaser  is satisfied, to the extent that th e purchaser is  competent to ensure that the  system satisfies 
the requirements of the purchaser and the user. The  certificate also needs to confirm that adequate 
documentation has been handed over to the user, that  the user has been instructed in the use of  the system 
and understands their obligations to ensure the  system is maintained in a functional state and is regularly 
inspected and tested. The purchaser might  wish to carry out an independent inspection of the system, or to 
witness certain tests (which might  include any o all commissioning tests) as a prerequisite for completion of 
the acceptance certificate  (see Clause 42).  
For certain (usually  large and/or complex systems ), the purchaser or user might wish to arrange for an  
independent inspection, and possibly test, of the system to verify compliance with the recommendations  of this 
standard in respect of design, installation and commissioning. If so, the organization that  commissions the 
independent verification needs to require that a verification cer tificate be issued.  
41.2 Recommendations  
The following recommendations are applicable.  
a) On, or as soon as practicable after, completion of each of the following processes, a certificate  should be 
issued by the organization responsible for the process, certifying  compliance with  the recommendations 
of this standard in respect of the process or, if variations exist, clearly  identifying these variations:  
1) design;  
2) installation;  
3) commissioning.  
b) Following completion of the installation, the organization bearing contractu al responsibility to  the purchaser 
for the system should issue a certificate of acceptance to the purchaser (see  for completion by the 
purchaser.  
c) If a purchaser or user commissions an independent audit of the system to verify, as far as  practicable, that 
design, installation and commissioning conform to the recommendations of this  standard (see Clause 43), 
the purchaser should request that the organization responsible for the  audit issues a verification certificate.  
NOTE 1 Model certificates of design, inst allation, commissioning , acceptance and verification are  contained in Annex G.  
NOTE 2 The certificate issued for any of these five processes can vary in format from that shown in Annex G but, as a 
minimum, the information and statements of compliance withi n the model certificates ought to  be provided . BOS 813 -1:2023  
Edition 1.0 
100 42 Acceptance  
42.1 Commentary  
On completion of the system, arran9ements need to be made for formal handover of the system to  the 
purchaser or user, and formal acceptance oft he system by the purchaser (or representat ive of  the purchaser).  
Before accepting the handover of the system, the purchaser or a representative  need s to ensure that they  are 
satisfied with the installed system, that the user has an  adequate understanding of the operation  of the system 
and the meas ures necessary to prevent false alarms, and that relevant documentation  has been provided. In 
the case of small, simple systems, or systems installed in the premises of small  organisation with little relevant 
in house expertise, acceptance might involve li ttle more than a brief  inspection of the system by the user, 
demonstration of its operation by the commissioning en9ineer, and  handover of the relevant documents to the 
user. In large, complex systems, it is likely that the purchaser  would wish to witness relevant tests, as part of 
a formal and structured acceptance procedure.  
As evidence of acceptance, an acceptance certificate needs to be signed by the purchaser (see Clause 41).  
42.2 Recommendations  
The following recommendations are applicable.  
a) A purchase spec ification should define the acceptance procedures required by the purchaser,  including 
any tests that are to be witnessed [see 6.2d)] and details of the witnessing procedure,  e.g. notice to be 
given.  
b) Before accepting a system, the purchaser (or appropriate  representative of the purchaser)  should ensure, 
at least, the following:  
1) that all installation work appears to be satisfactory;  
2) that the system is capable of giving a fire alarm signal;  
3) that any facility for remote transmission of faults and alarms to an ARC operates correctly;  
NOTE 1 An appropriate representative of the purchaser might be the user.  
NOTE 2 It is essential that any ARC to which fire alarm signals are relayed be notified before, and  immediately after 
completion of, any tests that could resul t in a fire alarm signal.  
4) that the following documents have been provided to the purchaser or user:  
i) as-fitted drawings;  
ii) operating and maintenance instructions;  
iii) certificates of design, installation and commissioning ( see Clause 41 );  
iv) a logbook in which all  events, including fire alarm signals, fault signals, system tests and  
v) maintenance visits can be recorded;  
5) that a suitable diagrammatic representation of the premises is provided close to all CIE  [see 23.2.2e)]:  
6) that sufficient representatives of the user have been properly instructed in the operation of  the system, 
including. at least, all means of triggering fire signals, silencing and resetting the  system and avoidance 
of false alarms;  
NOTE 3 In the case of large, complex systems, this is likely to neces sitate a formal training  course for a  number 
of people . The requirements for such training need to be defined in the purchase  specification.  
7) that the premises management (see 3.46) have been advised of their responsibilities and  how these 
might be discharg ed (see Clause 4 -7); and  
8) that all relevant tests, defined in the purchase specification  have been witnessed.  
NOTE 4 Some, or all, of these tests can be witnessed when commissioning ca rried out, although this would be 
less appropriate in large, complex syst ems.  
c) As evidence of acceptance, the purchaser (or appropriate representative of the purchaser) should  sign an  
acceptance certificate (see Clause 41).  BOS 813 -1:2023  
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101 43 Verification  
43.1 Commentary  
Small fire detection and fire alarm systems are often designed, supplied, installe d and commissioned  by a 
single organization, or a substantial  part of these tasks is undertaken by one organization. For  example, the 
organization might  be the system manufacturer or an electrical contractor.  
While this might also be so even  the largest, m ost complex systems, often, at least one of the above  processes 
(e.g. design) is undertaken  by a different organization from the others. Sometimes several  organizations might 
be involved. For example, design might be undertaken by consultants, supply and  commission by the 
manufacturer, and installation by an electrical contractor. The relevant certificates  are then each completed by 
different organizations, no one of which has overall responsibility for the  provision of a fire detection and fire 
alarm syste m that is suitable for its purpose and in accordance  with the structural features of the building.  
While the contractual arrangements whereby a system is designed, supplied, installed and  commissioned are 
outside the scope of this standard, it needs to be noted that division of responsibility  for these processes 
introduces scope for system shortcomings for which, in practice, none of the  parties involved is directly 
responsible. For example, in a new building, the designer of the fire  detection and fire ala rm system might not 
be given all the relevant information regarding structural  features of the building [e.g. deep beams, obstructions 
to the flow of smoke and similar features to  which 22.3h), 22.3i), 22.3 j), 22.3k) and 22.3 l) apply ]. Alternatively, 
the d esign of the building, or its  internal layout, might change after design of the fire detection and fire alarm 
system, but before its  installation . 
It is accepted in this standard that it is not the responsibility of the installer or the commissioning  engin eer [or 
those carrying out routine maintenance (see 45.1)] to identify shortcomings in design,  although, if these are 
identified, they need to be drown to the attention of the relevant person [see  7.2b )]. A purchaser might consider 
that, as a result of di vision of responsibilities for design, supply,  installation and commissioning, or for any 
other reason, there is significant potential for the installed  system to deviate from the recommendations of this 
standard in these circumstances, verification  needs to be obtained from a single organization.  This 
organization needs to issue a single verification  certificate. This verification needs to confirm that, as far as 
can reasonably be determined, the system  complies with all recommendations of this standard (i ncluding the 
recommendations of Section 3 ), or that variations have been agreed and documented (see Clause 40 and 
G.5). 
The verifying organization can be one of those involved in the design, supply, installation or  commissioning 
processes ( e.g. the system  supplier or the designer) or an independent third party.  It needs to be appreciated 
that, nevertheless, after completion of installation, it is unlikely that any one  organization, particularly a third 
party, would be able to verify in full the compliance of the system  with every recommendation of this standard. 
For example, much of the wiring might be impossible to  inspect The scope and extent of the verification process 
needs, therefore, to be subject to agreement  between the purchaser or user and the org anization responsible 
for verification. An indication of  the scope and extent needs to be given in the veri fication certificate or 
documents associated  therewith (e.g. a report).  
43.2 Recommendations  
The following recommendations are applicable.  
a) Where a purchas er or user considers that, as a result of division of responsibility for the design,  supply, 
installation and commissioning processes, there is significant potential for the installed  system to deviate 
from the recommendations of this standard , verificatio n of compliance  with this standard should be 
arranged.  
b) Any person responsible for verification should be co mpetent in the design of fire detection  and fire alarm 
systems, in accordance with this this standard  and familiar with the relevant  installation pra ctices.  
c) The scope and extent of the verification process  should be agreed between the purchaser or  user and the 
organization responsible for verification but  should address the recommendations  of Section 3.  
d) On completion of verification, a verification cer tificate should be issued, verifying that the  system conforms 
to the recommendations of this standard, or identifying variations from these  recommendations (see 
Clause 41). The certificate should also contain information on the scope  and extent of the veri fication 
carried out or identify where this information is available.  
NOTE A verification  certificate can be of value to an enforcing authority or property insurer.  BOS 813 -1:2023  
Edition 1.0 
102 Section 6: Maintenance  
44 Routine testing  
44.1 Commentary  
Although modern fire detection and fire a larm systems can incorporate a high de gree of monitoring, so  that 
faults are indicated automatically, it is still necessary for the premises management to ensure that  fault 
indications at the panel are identified for appropriate action. It is also vital fo r a regular test to be  carried out to 
ensure that there has not been any major failure of the entire system, or a significant  part of the system.  
Routine testing of the system also provides an opportunity for occupants of the build ing to become,  and remain , 
familiar with the fire alarm signal(s) that the system produces. In systems with staged  alarms that incorporate 
an "Alert" and an "Evacuate" signal, both sig nals need to be operated on the  occasion of each test to ensure 
that occupants are aware of the e xistence of both signals and their  different meaning.  
44.2 Recommendations for weekly testing by the user  
NOTE 1 When testing the fire detection and fire alarm system  there  might be a need to disable ancillary outputs.  
The following recommendations are applicab le. 
a) Every week, a manual call point should be o perated during normal working hours. It should be  confirmed 
that the control equipment is capable of processing a fire alarm signal and providing  an output to fire alarm 
sounders, and to ensure that the fire a larm signal is correctly received at  any ARC to which fire alarm  
signals are transmitted. It is not necessary to confi rm that all fire  alarm sounder circuits operate correctly 
at the time of this test.  
NOTE 2 It is essential that any ARC is contacted immed iately before, and immediately after, the weekly test to  ensure 
that unwanted alarms are avoided and that fire alarm signals are correctly received at the ARC.  
NOTE 3 The user nee d to take account of the manufacturer's recommendations, particularly when ba ttery powered 
devices are being tested, e.g. within radio -linked fire detection and fire alarm systems.  
b) The weekly test should be carried out at approximately the same time each week; occupants  should then 
be instructed that they should report any Instance  of poor audibility of the fire alarm  signaI. In systems with 
staged alarms incorporating an "Alert" and an "Evacuate" signal, the two  signals should be operated, 
where practicable, sequentially in the order they would occur at the  time of a fire (i.e. "Al ert'' and then 
"Evacuate").  
c) In premises in which some employees only work during hours other than that at which the fire  detection 
and fire alarm system is normally tested, an additional test(s) should be carried out at  least once a month 
to ensure familia rity of these employees with the fire alarm signal(s).  
d) A different manual call point should be used at the time of every weekly test, so that all manual  call points 
in the building are tested in rotation over a prolonged period. There is no maximum  limit f or this period ( 
e.g. in a system with 150 manual call points, the user will test each manual  call point every 150 weeks). 
The result of the weekly test and the identity of the manual call  point used should be recorded in the system 
logbook [see 40.2d)].  
e) The duration for which any fire alarm signal is given (other than solely at CIE) at the time of the  weekly 
test by the user should be at least 5 s, but should not normally exceed 60 s, so that, in the  event of a fire 
at the time of the weekly test, occupant s are warned by the prolonged operation of  the fire alarm devices.  
f) Voice alarm systems should be tested weekly in accordance with BS 5839 -8. 
44.3 Recommendations for monthly attention by the user  
The following recommendations are applicable.  
a) If an automatically  started emergency generator is used as part of the standby power supply [see  25.4e)2)], 
it should be started up once each month by simulation of failure of the normal power  supply and operated 
on-load for at least one hour. The test should be carried out in accordance  with the instructions of the 
generator manufacturer, including instructions on the load that  should be operated.  
At the end of the test, the fuel tanks should be left filled, and the oil and coolant levels should be  checked 
and topped up as n ecessary.  
b) b) If vented batteries are used as a standby power supply, a visual inspection of the batteries and  their 
connections  should be made to ensure that they are in good condition . Action  should be  taken to rectify 
any defect, including low electrolyt e level.  BOS 813 -1:2023  
Edition 1.0 
103 NOTE Care is necessary to ensure that any person undertaking  these tasks is competent to do so safely and  has 
the relevant technical knowledge and training.  
45 Inspection and servicing  
NOTE According to best practice, safe isolation is carried  out p rior to working on or near live parts. In this context, safe 
isolation includes confirmation that isolation has  been successful.  
45.1 Commentary  
It is essential that the system is subject to periodic inspection and servicing so that faults are identified,  
preve ntive measures can be taken to e nsure the continued reliability of the system, false alarm problems  are 
identified and suitably addressed, and the user is made aware of any changes to the building that  affect the 
protection afforded by the system.  
Periodic  inspection and servicing needs to be carried out by a competent person with specialist  knowledge of  
fire detection and fire alarm systems, including knowledge of the causes of false alarms,  sufficient information 
regarding the system, and adequate access to spares.  
This is normally an outside fire alarm servicing organization; care needs to be taken to ensure that,  if, for 
example, in  house  employees are used for this task, they have equivalent competence to the  technicians of a 
typical fire alarm servicin g organization. Competence of a fire alarm servicing  organization can be assured by 
the use of organizations that are third -party certificated, by a  accredited certification body, to carry out 
inspection and servicing of  fire alarm systems.  
Routine servici ng of a fire detection and fire alarm system does not constitute a fresh review of system  design; 
it is a verification of the functionality and serviceability of the existing system. Accordingly, it is  not necessarily 
the case that non -compliances with Sec tion 2 of this standard will be identified at the  time of routine servicing; 
in any case, the maintenance technician might not be aware as to whether an  apparent non -compliance is, in 
fact, simply an agreed variation, particularly if the design certificate  is not available. However, at their own 
prerogative, the maintenance organization can point out aspects of  non-compliance with Section 2. 
Nevertheless, any such advice provided to the user by the maintenance  organization cannot be regarded {by 
users, enfo rcing authorities or any other party) as an implication  that the maintenance technician has identified, 
or has endeavoured to identify, all such areas of noncompliance,  or that there has been any review of the 
original design.  
45.2 Recommendation for quarterly inspection of vented batteries  
All vented batteries and their connections should be examined by a person competent in battery  installation 
and maintenance technology. Electrolyte levels should be checked and topped up  as necessary.  
NOTE In many large premi ses and sites, in -house maintenance personnel might be competent to carry  out this task.  
45.3 Periodic Inspection and test of the system  
Some fire detection and fire alarm systems and components claim to include features that permit  functions to 
be automaticall y monitored, and faults or warnings to be annunciate d, or otherwise  made available to 
authorized persons. In cases where this is proven, the recommendation  for routine testing under this subclause 
and in  45.4 may be modified to omit testi ng which is proven  to be unnecessary by the equipment manufacturer, 
provided it can be proven that the automatic  monitoring achieves the same objective as the appropriate test 
recommended in this subclause  and/or 45.4. ln the case of detectors (all types), tests should ensu re that 
products of combustion  are capable of passing unhindered from the protected area to the sen sing 
chamber/elements of the  detector and not simply test the ability of the detector to sample / verify the status of 
the atmosphere  already in the sensing c hamber.  
The periodic inspection  and service in this clause shall be carried out  by a competent person (see  3.12.). The 
period between successive inspection and servicing visits shall not exceed six months. If  this is not 
implemented, it should be consid ered that the system is no longer compliant with this  Standard  
The following recommendations are applicable . 
a) The system logbook shall be examined. It shall be ensured that any faults recorded have  received 
appropriate attention.  
b) A visual inspection should  be made to check whether structural or occupancy changes have  affected the 
compliance of the system with the recommendations of this standard for the siting  of manual call po ints, 
automatic fire detectors and fire alarm devices. Particular care should be  taken to verify whe ther: 
1) all manual call points remain unobstructed and conspicuous;  
2) any new exits that lead to a place of  ultimate safety have been created without the  provision of an BOS 813 -1:2023  
Edition 1.0 
104 adjacent manual call point;  
3) any new or relocated partitions have been erec ted within 500 mm horizontally of any  automatic fire 
detector [see 22.3g)];  
4) any storage encroaches within 300 mm of ceilings, such as to obviate compliance  with 22.3i);  
5) a clear space of 500 mm is maintained below each automatic fire detector [see 22.3o) ], and that the 
ability of the detector to receive the stimulus that it has been designed to detect has  not been impeded 
by other means;  
6) any changes to the use or occupancy of an area makes the existing types of automatic fire  detector 
unsuitable for detectio n of fire or prone to unwanted alarms;  
7) any building alterations or extensions require additional fire detection and fire alarm  equipment to be 
installed.  
c) The records of false alarms should be checked in accordance with 30. 2i). The rate of false alarms  during 
the previous 12 months should be recorded (see 30. 2i). Action taken in respect of false  alarms recorded 
should comply with 30. 2j). 
d) The battery voltage should be measured with the mains on to check the steady state charge  voltage and 
check it is within t he manufacturer's recommendations before any other tests that  might discharge the 
battery and with no load on the power supply other than the quiescent or  standing load.  
e) The standby battery should be disconnected, the alarms activated and the power supply output  voltage 
checked that it is close to the nominal voltage.  
NOTE 1 If applying the full alarm load is not practicable, then the full load may be simulated.  
NOTE 2 It would be reasonable to expect the power supply voltage to achieve at least 95% of  nomi nal voltage.  
f) Batteries and their connections should be examined and momentarily load tested with the mains  
disconnected (other than those within devices such as manual call points, detectors and fire  alarm 
sounders of a radio -linked system), to ensure that  they are in good s erviceable condition  and not likely to 
fail before the next service visit Vented batteries should be examined to ensure  that the specific gravity of 
each cell is correct.  
g) The fire alarm functions of the CIE should be checked by the opera tion of at least one detector  or manual 
call point on each circuit. An entry should be made in the logbook indicating which  initiating devices have 
been used for these tests.  
h) It should be confirmed that a fire alarm signal is given on operation of at least  one manual call  point or fire 
detector.  
i) All controls and visual indicators at CIE should be checked for correct operation.  
j) The operation of any facility for automatic transmission of alarm signals to an ARC should  be checked. 
Where more than one form of a larm signal can be transmitted (e.g. fire and fault  signals), the correct 
transmission of each signal should be confirmed.  
k) All ancillary functions of the CIE should be tested.  
l) All fault indicators and their circuits should be checked, where practicable, by  simulation of  fault conditions.  
m) All printers should be tested to ensure that they operate correctly and that characters are legible.  It should 
be ensured that all printer consumables are sufficient in quantity or condition to  ensure that the printer can 
be expected to operate until the time of the next service visit . 
n) Radio systems of all types should be serviced in accordance with the recommendations of the  
manufacturer.  
o) All further checks and tests recommended by the manufacturer of the CIE and other com ponents  of the 
system should be carried out . 
p) On completion of the work. any outstanding defects should be reported to the premises  management, the 
system logbook [see 40.2d)] should be completed and an inspection and  servicing certificate should be 
issued (see G.6).  
45.4 Recommendations for inspection and test of the system over a 12-month  period  
In addition to the work recommended in 45.3 the following work should be carried out every year.  
NOTE 1 The work described can be carried out over the course of two or more service visits during each  12-month period.  BOS 813 -1:2023  
Edition 1.0 
105 a) The switch mechanism of every manual call point should be tested, either by removal of a  frangible 
element, insertion of a test key or operation of the device as it would be operated in the  event of fire.  
b) All automatic fire detectors and remote detectors should be examined, as far as practicable, to  ensure that 
they have not been damaged, painted, or otherwise adversely affected. Thereafter,  every detector should 
be functionally tested.  
NOTE 2 The tests used need prove on ly that the detectors are connected to the sys tem, are operational and  are 
capable of responding to the phenomena they are designed to detect.  
Where fitted, detector remote indicators should also be checked for correct operation.  Information 
regarding the configuration of multi -sensor detectors and selection of type of detectors suitable for the 
application is given in Table E .1. 
c) Every heat detector should be functionally tested by means of a suitable heat source, unless  operation of 
the detect or in this manner would then necessitate replacement of part or all of  the sensing element (e.g. 
as in fusible link point detectors or non -integrating line detectors).  
Special test arrangements are required for fusible link heat detectors. The heat source should not  have 
the potential to ignite a fire; live flame should not be used, and special equipment might be  necessary in 
explosive atmospheres.  
d) Point smoke detectors should be functionally tested by a method that confirms that smoke  can enter the 
detecto r chamber and produce a fire alarm  signal (e.g. by use of apparatus that  generates simulated 
smoke or suitable aeroso ls, around the detector). It should be ensured  that the material used does not 
cause damage to, or affect the subsequent performance of, th e detector: the manufacturer's guidance o n 
suitable  materials shou ld be followed.  
e) Optical beam smoke detectors shou ld be functionally tested by introducing signal attenuation  between the 
transmitter and receiver, either by use of an optical filter (or any similar method of  simulating obscuration 
by smo ke), smoke or simulated smoke.  
f) Aspirating fire detection and fire alarm systems should be functionally tested by a method that  confirms 
that smoke can enter the detector chamber and produce a fire alarm signal . It should be  ensured that the 
material used does not cause damage to or affect the subsequent performance of the detectors; t he 
manufacturer's guidance on suitable materials should be followed . 
Furthermore, appropriate testing should be performed to veri fy that smoke is able to enter each  sampling 
point (or collection of sampling points that are recommended by the manufacturer to  cover the same area 
as a point smoke detector).  
Note 3  This can be achieved by introducing smoke into each sampling point in tu rn and verifying a response  at the 
detector.  
However, where access is restricted or other site conditions prevent this, other verification  techniques 
should be employed such as:  
1) verifying transport time from furthest hole or a dedicated test point and comp aring with  previously 
recorded results to identify deviations;  
2) confirming that the flow monitoring is capable of detecting loss of a single sampling point  (or collection 
of sampling points that are deemed to be acceptable for the risks involved);  
3) inspectio n of flow readings and comparing with previously recorded results to identify  deviations which 
would indicate a loss of detection performance; or  
4) measurement of the pressure at each sampling point and comparing with previously  recorded results 
to identify deviations which would indicate a loss of detection  performance.  
The technique used is dependent on the particular features of the ASD technology, the risk and  details of 
the specific application. Such techniques may also be supported by visual inspection  of sampling points 
where this is possible but it should be verified that adequate detection  performance is maintained.  
Details of the techniques used should be recorded and agreed with all parties.  
NOTE 4 For further guidance see the FIA Code of Practice f or Design, Installation, Commissioning and  Maintenance 
of Aspirating Smoke Detector (ASD) Systems [2]. 
g) Carbon monoxide fire detectors should be functionally tested by a method that confirms that  carbon 
monoxide can enter the detector chamber and produce a fire alarm signal (e.g. by use  of apparatus that 
generates carbon monoxide or a gas that has a similar effect on the electro  chemical cell as carbon 
monoxide).  BOS 813 -1:2023  
Edition 1.0 
106 WARNING . Carbon monoxide is a highly toxic gas, and suitable precautions should be  taken in its use. 
NOTE 5 It is necessary to ensure that any test gas used does not cause damage to,  or affect the subsequent  
performance of the detector and that the manufacturer's guidance on suitable test gases is followed.  
h) Flame detectors should be functionally test ed by a method that confirms that the detector  responds to a 
suitable frequency of radiation and produces a fire alarm signal. The  manufacturer's guidance on the 
testing of detectors should be followed.  
i) In fire detection systems that enable analogue values  to be determined  at the CIE, it should be  confirmed 
that each analogue value is within the range specified by the manufacturer.  
j) Multi -sensor detectors should be operated by a method that confirms that products of  combustion in the 
vicinity of the detector  can rea ch the sensors and that a fire signal can be  produced as appropriate.  
1) The guidance of the manufacturer on tire manner in which the detector can be functionally  tested 
effectively should be  followed.  
2) Multi -sensor fire detectors should be physically  tested by a method that confirms that  products of 
combustion in the vicinity of the detector can reach the sensors and that the  appropriate response is 
confirmed at the CIE.  
NOTE 6 Suitable test methods for each type of sensor are as described in this sub clause, e.g. for heat  sensors, 
see 45.4c).  
3) Where the detector or system design permits, each sensor on which a fire detection decision  depends 
(e.g smoke, heat, CO) should be physically tested individually.   
Alternatively, individual sensors may be physica lly tested together if the detection system  design 
allows simultaneous stimuli and individual sensor responses to be verified either  individually or 
collectively.  
NOTE 7 Where individual sensors cannot be tested individually, this recommendation does not a pply.  
NOTE 8 Where a system includes a time -related configuration of detection, care needs to be taken to ensure  that 
a sensor is not excluded from being tested as a result of the time -dependent mode.  
4) On completion of tests the system should be returned to  its normal configuration.  
k) All fire alarm  devices should be checked for correct operation. It should be confirmed that visual  fire alarm 
devices are not obstructed from view and that their lenses are clean.  
NOTE 9 This test is intended to ensure that every  fire alarm device operates in response to a fire alarm signal.  It is not 
intended that sound pressure level measurements are made.  
l) All unmonitored, permanently illuminated filament lamp indicators at CIE should be replaced.  
m) Radio signal strengths in radio -linked systems to which Clause 27 applies should be checked for  
adequacy, and the results recorded.  
n) A visual inspection should be made to confirm that all readily accessible cable fixings are secure  and 
undamaged.  
o) The cause and effect programme should be confirmed as being correct by activating at least one  cause 
and observing the operation of the effects. Where there are different types of devices (e.g.  manual call 
points and automatic fire detectors), one cause and its effects should be tested for  each t ype of device.  
NOTE 10 Testing of  a single cause is deemed acceptable and satisfies the recommendations of 45.3o). On a  site with 
multiple cause and effect operations, if the user deems further causal testing is required, it is  necessary for the user 
to sp ecify this to the maintenance provider. Where no agreement is specified, testing of  one cause will satisfy the 
recommendations.  
p) The standby power supply capacity should be checked to establish it remains suitable for  continued 
service.  
NOTE 11 Further guid ance on testing of the batteries is given in FIA guidance : Testing of lead acid batteries  used in 
Fire Detection & Alarm System Power Supplies [11]. 
q) A check should be made to determine whether a suitable zone plan (or other suitable  diagrammatic 
representa tion) of the premises is provided on or adjacent to all CIE and repeat  indicating equipment  
NOTE 12 Where repeat indicating equipment relate s only  part of the premises, the adjacent zone plan need  only relate 
to that part of the premises.  
r) All further annua l checks and tests recommended by the manufacturer of the CIE and other  components 
of the system should be carried out.  BOS 813 -1:2023  
Edition 1.0 
107 s) Video fire detectors should be subject to the manufacturer's guidelines in relation to annual test  and 
inspection. Any lighting provided  specifically to aid the detection of flame or smoke should be  regarded as 
an integral part of the video fire detection system. As such, its correct operation  should be confirmed, both 
it: the presence of any mains supply to the lighting and the absence of  such a supply.  
On completion o 'the work, any outstanding defects should be reported to the premises  management and 
a record of the inspection and test should be made on the servicing certificate.  
NOTE 13 Since stimulus of the sensing element through intr oduction of the phenomena or surrogate  phenomena 
which the above detectors are designed to detect forms part of the test, use of a test button or  a test magnet (for 
example) or compliance with 45.4i) does not satisfy the recommendations given.  
46 Non-routine attention  
46.1 Commentary  
The arrangements in Clause 45 are intended to maintain the system in operation under normal  circumstances. 
However, from time to time, the fire detection and fire alarm system is likely to require  non-routine attention, 
including speci al maintenance. Non -routine maintenance includes:  
• a special inspection of an existing fire detection and fire alarm system when a new servicing  
organization takes over servicing the system;  
• repair of faults or damage;  
• modification to take account of extens ions, alterations, changes in occupancy or false alarms;  
• action to address an unacceptable rate of false alarms; and   
• inspection and test of the system following  a fire.  
46.2 Recommendations for special inspection on appointment of a new servicing  
organization  
The following recommendations are applicable.  
a) When a servicing organization takes over servicing arrangements for an existing system, a  special 
inspection should be carried out, and existing records (see Clause 40), where available,  should be studied, 
to obtain sufficient information to be documented for effective future  servicing of the system.  
b) Major areas of non -compliance with this standard should be documented and identified to the  premises  
management . The classification of a non -compliance as major is subjective, but the  following non -
compliances should be regarded as major:  
NOTE 1 It is not implied that non -compliances need to be rectified; this is a matter for the user to  determine,  based on 
the advice of the servicing  organization, the enforcing auth orities, the insurer and any third -party  advisers engaged by 
the user, as appropriate.  
1) an inadequate number of call points to conform to  20.2; 
2) inadequate provision of fire detection to conform to this standard for the category of system  that the 
system was  designed to meet;  
3) sound pressure levels that fail to conform to the recommendations of 1 6.2.;  
4) standby power supplies that fail to conform to 25.4 The absence of any standby  power supply should 
be highlighted to the premises management . 
5) cabling with fire resistance that fails to conform to 26.2c );  
NOTE 2 Serious shortcomings in ca ble support that could result in collapse of a significant length of cable in  the 
event of  fi re might also be regarded as a major non -compliance.  
6) monitoring of circuits that fai l to conform to 12 .2.1; 
7) standards of electrical safety such that the recommendations of Clause 29 are not satisfied;  
8) exposure to, or experience of, false alarms, such as to preclude compliance with Section 3:  
9) changes in the use, layout and construction of the protected premises that might impact on  the 
effectiveness of the system;  
10)  the absence of a zone plan or other suitable diagrammatic representation of the premises  [see 
23.2.2e) ]. BOS 813 -1:2023  
Edition 1.0 
108 c) If no logbook suitable for enabling compliance with 48.2 exists, a suitab le logbook should be  provided by 
the servicing organization.  
46.3 Recommendations for arrangements for repair of faults or damage  
The following recommendations are applicable.  
Where maintenance is carried out by a third party, such as a fire alarm maintenance  organization, there should 
be an agreement for emergency call out to deal with any fault or  damage that occurs to the system.  
The agreement should be such that, on a 24 h basis, a technician of the maintenance organization  can normally 
attend the premises w ithin 8 h of a call from the user.  
NOTE It is accepted that this might not be possible in very remote areas in  which case this ought to be regarded as a 
variation from the recommendations of this standard in respect of maintenance arrangements. Such a vari ation would 
need to be recorded in the system logbook.  
The name and telephone number of any third party responsible for maintenance of the system  should be 
prominently displayed at the main CIE, and the records and documentation as  identified in Clause 40 should 
be kept updated.  
The user should record all faults or damage in the system logbook. and should arrange for repair  to be carried 
out as soon as possible.  
46.4 Modifications to the system  
46.4.1  Commentary  
Modifications to the system can arise for a number of rea sons. Examples include:  
• extension of the system to protect areas of the building previously unprotected or newly  constructed;  
• change of detector type as a result of changes in occupancy or the occurrence  of false alarms;  
• re-siting of, or increase in the nu mber of, detectors and/or fire alarm devices to take account of  
changes in the layout of the building; and  
• reconfiguration of the system (in hardware, software pr both) to change the cause and effect logic  in 
order to facilitate filtering of false alarms.  
Since modification of a system effectively involves an element of re -design, responsibility for modification  of a 
system needs to rest with a person who has a sufficient degree of design competence.  
Even simple modifications can give rise to the need for s ignificant re -testing of the system. This is  particularly 
true of software -controlled systems. For example, a software change to facilitate a different  cause and effect 
for a single automatic fire detector can result in the introduction of software errors that affect the operation of 
entirely  non-related parts of the system.  
It is possible, in some systems, for modification of the system configuration to be carried out remotely,  via a 
modem. Great care needs to be taken, regardless of whether modifications are undertaken on site  or remotely, 
to ensure that:  
• the system continues to conform in full to this standard , or that existing non -compliances are  not made 
more non -compliant; if new variations are introduced, it needs to be ensured that a new  certificate , 
reflecting the variations, is issued;  
• suitable tests are carried out at the protected premises to confirm that, after modification,  the system 
operates as intended and that errors have not resulted in changes to other parts  of the system;  
• as-fitted drawin gs and other records are updated as appropriate; and  
• details of the modification are documented and provided to the premises management [see 47.2)].  
Although the modifications can often be carried out remotely by the maintenance organization, it is  appropr iate 
for a competent person from the maintenance organization to visit the premises before  the modification is 
carried out, to confirm the validity of the modification and consider its effect on  compliance with this part of BS 
5839. It might also be necess ary to visit the premises to undertake  certain tests immediately after the 
modification has been carried out.  
46.4.2  Recommendations applicable to all modification work  
The following recommendations apply to all modification work, regardless of whether it is carr ied out  on site or 
remotely.  BOS 813 -1:2023  
Edition 1.0 
109 a) Responsibility for modification of a fire detection and fire alarm system should rest, ultimately,  with a person 
who is competent in fire detection and fire alarm system design and is conversant  with this standard  
NOTE 1 This p erson might, for example, be the original designe r; or might be a competent representative of  the user 
or maintenance organization.  
b) Before modifying a fire detection and fire alarm system, care should be taken to ensure that  the proposed 
modifications do n ot detrimentally affect the compliance of the system with  fire safety legislation; where 
doubt exists, there should be consultation with the relevant  enforcement authority.  
c) The user (see Clause 47)  should be aware of, and agree, in writing, any modificatio ns proposed  for the 
system. Where appropriate, modifications should also be subject to the agreement of the  enforcing 
authorities and/or insurers.  
d) All components, circuits, system operations and site -specific software fu nction s known to be  affected by 
the modifications should be tested for correct operation following the modifications.  
e) In addition to the tests recommended in 46.4.2d), the  followi ng tests should be carried out to  ensure that 
there is no adverse effect on the overall system:  
1) if one or more de vices have been added to or  removed  from a circuit, at least one other  device on the 
same circuit should be tested;  
2) if the control equipment has been modified, a least one device on every circuit  should be tested;  
3) if any additional load has been placed on the system, tests should be carried out to prove  that the 
rating of the powe r supply unit and the capacity of the standby batteries remain  adequate, see 45.3e ) 
and f); and  
4) if software has been modified, further random testing of other parts of the system s hould  be carried 
out to ensure that seemingly unrelated parts of the system have not been  adversely affected.  
NOTE 2 The nature and extent of these tests cannot be specified in this standard ; this depends on the  nature and 
extent of the software changes an d ought to be defined by the organization responsible for the  software changes.  
f) On completion of the modifications, all as -fitted drawings and other relevant system records  shou ld be 
updated as  appropriate and made available with the system documentation  (see Clause 40).  
g) On commissioning of the work and completion of the tests, a modification certificate should be  issued, 
confirming that the work has been carried out in accordance with the recommendations  of this standard , 
or identifying any variations. A model modification certificate is set out  in Annex G. Where responsibility 
for the conformity, or otherwise, of the modified system with  Section  2 of this standard rests with any 
person other than the organization carrying out the  modification, that person should sign the appropriate 
section of the modification certificate and  ensure it is made available with the system documentation (see 
Clause 40).  
46.4.3  Recommendations applicable to modifications carried out remotely  
In addition to the recommendations of 46.4.2 , the following recommendations are applicable.  
a) Any person carrying out modifications remotely should have access to current as -fitted drawings  of the 
system and to the current system configuration, indicating full details of cause and effect  logic, availa ble 
with the system documentation (see Clause 40).  
b) Any person carrying out modifications remotely should be conversant with this standard . 
46.4.4  Recommendations for action to address an unacceptable rate of false alarms  
The following recommendations are applicab le. 
a) Any investigation into an unacceptable rate of  false alarms, and any subsequent modifications  to the 
system, should take into account the guidance contained in Section 3 of th is standard . Where  causes of 
false alarms cannot be determined, each of the r ecognized causes discussed  in Clause 33 should be 
formally considered.  
b) Following any modifications, the system should either continue to conform to this standard ,or should not  
be more non -compliant than prior to the modifications  unless agreed with  all int erested parties.  
c) Any relevant documentation should be made available with the system documentation  (see Clause 40).  
46.4.5  Recommendations for Inspection and test of the system  following any fire  
The following recommendations should be carried out as soon as poss ible after any fire.  
a) Every manual call point, automatic fire detector. and fire alarm device that might have been  affected by BOS 813 -1:2023  
Edition 1.0 
110 the fire or fire -fighting action should be inspected and tested in accordance with 45.4. 
b) A visual examination and suitable tests s hould be carried out on any other part of the system that  lies 
within the fire area and  other areas affected by corrosive smoke from the fire and that might  have been 
damaged by the fire (e.g. power supplies, control equipment and cable), extinguishing  media (e.g. water 
or fire -fighting action. Where there is evidence of damage, suitable action  should be taken.  
c) Circuits ext ernal to the CIE that could have been affected by the fire should be tested for  correct operation.  
d) On completion  of the work, any defect s found should be recorded in the system logbook, and the  premises 
management should be notified accordingly.  
46.4.6  Recommendation for inspection and test of the system following long periods of  disconnection   
The recommendations for inspection and test of the s ystem over a 12 month period (see 45.4) should  be 
undertaken.  
NOTE If there is a major change in occupation or use of a building it might  be appropriate for the cause and  effects of 
the system t:o be checked.  BOS 813 -1:2023  
Edition 1.0 
111 Section 7: User's responsibilities  
47 Premises man agement  
47.1 Commentary  
The user or landlord needs to appoint a single, named member of the premises management to  supervise all 
matters pertaining to the fire detection and fire alarm system. The role of this person is to  ensure that the 
system is tested and m aintained in accordance with the recommendations of this standard , that appropriate 
records are kept and that relevant occupants in the protected premises are  aware of their roles and 
responsibilities in connection with the fire detection and fire alarm sy stem. This  person also needs to ensure 
that necessary steps are taken to avoid situations that are detrimental to  the standard of  protection afforded 
by the system and to ensure that the level of  false alarms is  minimized.  
47.2 Recommendations  
A single, named m ember of the premises management should be appointed to supervise all matters  pertaining 
to the fire detection and fire alarm system. This person should normally be the keeper of  the documentation 
as described in Clause 40 and should be given sufficient au thority to carry out the  following duties.  
a) Ensuring that the CIE is checked at least once every 24 h to confirm that there are no faults  on the system.  
b) Ensuring that arrangements are in place for testing and maintenance of the system in accordance  with 
Section 6 of this standard.  
c) Ensuring that the system logbook (see Clause 48) is kept up -to-date and is available for  inspection by any 
authorized person ( e.g. representatives of enforcing authorities and  property insurers).  
d) Ensuring that all relevant occupan ts of the protected premises are instructed in the proper  use of the 
system. Particular care should be taken to ensure that relevant occupants are able to  interpret fire, pre -
alarm (see 47.3) and fault indications, and that they are adequately familiar  with the appropriate controls, 
including those associated with initiation of fire alarm signals,  silencing of fire ala m signals and resetting 
the system. It should also be ensured that all  occupants are aware of the measures necessary to avoid 
the generation of false alarms. Relevant  occupants should also be instructed in the facilities for 
disablement and the circumstances in  which they should, and should not, be used. In premises in multiple 
occupation, it should be  ensured that sufficient representatives of  each occupier are instructed.  
NOTE 1 Different levels of instruction might be necessary for different occupants.  
e) Ensuring that appropriate action is taken to limit the rate of false alarms [ see 30.2g), 30.2h)  and 35 .2.7.3]. 
f) Ensuring  that a clear space of  at least 500 mm is preserved in all directions around and below  every fire 
detector  and that all manual call points remain unobstructed and conspicuous.  
g) Establishing a liaison between those responsible for changes in, or maintenance of, the building  fabric 
(including redecoration, etc.) to ensure that the work does not unnecessarily compromise  the protection 
afforded by the system, create system faults or cause false alarms (see Section 3),  If structural or 
occupancy changes occur or are planned, it should  be ensured that any necessary  changes to the fire 
alarm system are considered at an early stage.  
h) Ensuring that, when changes are made to the system, record drawings and operating  instructions, supplied 
in accordance with 40.2b) and 40.2c) respectively, ar e updated.  
i) Ensuring that, where necessary, a suitable zone plan is displayed and is kept up -to-date [see 23.2.2e)].  
j) Ensuring that the following spare parts are held within the premises:  
1) six frangible elements and appropriate tools for manual call points, u nless there are less  than twelve 
manual call points in the protected premises, in which case only two spare  frangible elements with ap 
propriate tools need be held; and  
2) such other spare parts agreed between the user and the organization responsible for  servicing the 
system.  
NOTE 2 It would be of value for the premises management to be aware of the policy of the relevant fire and rescue  
service with regard to response to calls from the premises and/or any ARC, in the event of operation of the fire  
detection and fire alarm system.  
  BOS 813 -1:2023  
Edition 1.0 
112 47.3 Action in the event of pre -alarms  
A pre -alarm can be a response to a slow growing fire or to indicate detector contamination. Whatever  the 
reason, the following actions should be taken:  
a) determine and thoroughly inspect the area fro m whence. the pre -alarm has originated;  
b) if a fire is discovered, carry out the predetermined fire routine; and  
c) if no fire is discovered, record the events or activities near the suspect detector in the logbook  and, if there 
is need for work to be undertake n on the fire detection and fire alarm system,  inform the maintenance 
company.  
48 Logbook  
48.1 Commentary  
A logbook needs to be kept for the purpose of recording all events that occur in respect of the system,  including 
fire signals, fault -signals and work on the system. This information can be of value to the  organization that 
services the system and if special action is taken to address false alarm problems.  The logbook might provide 
evidence of compliance with  fire safety standards and legislation  
48.2 Recommendation s 
NOTE 1 A model format for a logbook is contained in annex E 
The following information should be recorded in the logbook  
a) the name(s) of the member(s) of the premises management to whom responsibility for the fire  detection 
and fire alarm system is delegat ed; 
b) brief details of maintenance arrangements;  
c) dates and times of all fire alarm signals (regardless of whether the signal is a false alarm or is  initiated as 
the result of a test, fire drill or genuine fire); if the fire alarm signal has resulted  from the  operation of a 
manual call point or fire detector, the device and its location should  be recorded;  
d) causes, circumstances surrounding and category of all false alarms (see Section 3);  dates, times and 
types of all tests;  
e) dates, times and types of all fault s and defects; and  
f) dates and types of all maintenance ( e.g. service visit or non -routine attention).  
NOTE 2 The logbook may be kept in electronic form but needs to be accessible fer all interested parties.  
 BOS 813 -1:2023  
Edition 1.0 
113 Anne x A 
(normative ) 
 
Choice of appropriate category of fire detection and fire alarm system 
and frequency of servicing fire alarm systems  
This annex describes the category of system that is typically installed in various types of premises, see Table 
A.1.The information in this annex is mandatory, and on the interpretation of fire safety standards and 
legislation.  Decisions regarding the appropriate category of system for any specific building rest with the 
authorities  responsible for enforcing legislatio n in the building: there can be more than one such enforcing 
authority, like  fire prevention department and fire chief.  
Table  A.1 — Choice of appropriate category of fire detection an d fire alarm system and frequency of 
servicing fire alarm systems  
 Public houses with 
residential 
accommodation  Large public houses 
(No residential 
accommodation)  Hotels, hostels, 
student 
accommodation, 
houses in multiple 
occupation and similar 
premises wi th 
sleeping 
accommodation  Common places of 
work,  such as offices, 
shops,  factories, 
warehouses  and 
restaurants  Type  of premises  
L2 M L1 or L2  M or P2/M  A 
or P1/M  Typical  
category  of 
system  
- - In bedroom areas, the design requirements are 
usually based o n the recommendations for a 
Category L3 system. Detectors are, however, 
typically installed in most other rooms and areas, 
as a fire in almost any area of the building could 
pose a threat to sleeping occupants; the system 
category is, therefore, at least L 2. In practice, few, 
if any, areas are left unprotected and the system 
category is effectively L1, except that a variation 
from the recommendations applicable to a 
Category L2 system might apply to the siting of 
heat, smoke or carbon monoxide detectors in 
bedrooms; this often follows the 
recommendations of 22.3e) for detectors in a 
Category L3 system.  Category M system normally satisfies the  
requirements  of legislation. It is, however, often  
combined with a Category P system to satisfy 
the requirements  of insurers,  as company  
policy  for protection  of assets,  or to protect  
against  business  
interruption.  Comments  
Quarterly  Quarterly  Quarterly  Bi-annual  Frequency 
of 
servicing  BOS 813 -1:2023  
Edition 1.0 
114 Table  A. 1 — Choice of a ppropriate category of fire detection and fire alarm system and frequency of 
servicing fire alarm systems  (Continue)  
Buildings in which other 
fire precautions, such as 
means of escape, depart 
from 
recognized guidance  Phased evacuation 
buildings  Prisons  Residential care premises  Covered shopping 
centres  Transportation terminals  Places of assembly, (e.g. 
cinemas, theatres, 
nightclubs, exhibition 
halls, museums and 
galleries, leisure centres 
and casinos):  
 Small premises (e.g. 
accommodating less than 
300 pers ons) 
Other premises  Hospitals   Schools, other than 
small single -story 
schools with less than 
160 pupils  Type  of premises  
M/L5  L3 M/L5  L1 to L3  L1 to L3  M/L5  L1 to L4  L1 (with possible 
minor variations)  M or M/P2 or M/P2/ L4 
or M/P2/L5  Typical  category  of 
system  
Automatic fire detectors are sited in such a way as to compensate for the 
lower standard in other fire precautions  - - L1 systems are often provided in large or complex buildings.  The exact design needs to be "tailor made" and often forms part of a  fire 
engineering solution.  - L1 is regarded as appropriate for large premises  - System category is normally based on a fire risk assessment. In many 
schools, a Category P system is installed to combat the hazard of arson. 
In schools that are partly occupi ed at certain times (e.g. during evening 
classes or community use), a Category L4 or L5 system is sometimes 
considered appropriate  Comments  
Quarterly  Quarterly  Quarterly  Quarterly  Quarterly  Quarterly  Quarterly  Monthly  Quarterly  Frequency of 
servicing  
Table A.1 — Choice of appropriate category of fire detection and fire alarm system and frequency of BOS 813 -1:2023  
Edition 1.0 
115 servicing fire alarm systems (Continue)  
 Filling stations  Flammable depots LPG, Depots  Any building  in which automatic 
fire detection is provided as a 
requirement of a property 
insurer or  to attract an insurance  
premium discount  Situations in which fire could 
readily spread from an 
unoccupied area and prejudice 
means of escape from occupied 
areas  Build ings in which automatic fire 
detection is required to operate 
other fire protection systems  
(e.g. magnetic door holders)  Buildings with "inner rooms", 
from which escape is possible 
only by passing through another 
("access") room, where ther e is 
inadequate  vision between the 
inner room and the acesss room  Type  of premises  
P1 or P2  P1 or P2  M/P1 or M/P2  M/L4 or M/L5  M/L5  M/L5  Typical  category  
of system  
Flammable  Flammable   Custom and practice does not involve siting automatic fire 
detectors in all unoccupi ed areas, such as plant rooms and 
storage areas.  Care is necessary to ensure that automatic fire detectors are sited 
such that cool smoke cannot pass below the level of the detectors 
that cause release  of the magnetic door holders, and through the 
(still o pen) doors.  Smoke detectors are sited in the access room.  Comments  
Quarterly  Monthly  Quarterly  Quarterly  Quarterly  Quarterly  Frequency of 
servicing  BOS 813 -1:2023  
Edition 1.0 
116 Annex B  
(informative)  
 
Typical noise levels in buil dings  
Table B.1 gives typical expected background noise levels for a range of building types. It needs to be  borne in 
mind, however, that background noise levels can vary significantly from building to building  of the same 
occupancy; likewise, occupancy ca n vary in any given building. Sound level readings for  the table were  taken, 
as far as possible, at the busiest periods and short -term bursts of very high -level or very low -level noise were 
ignored, for each type of building a typical range of background n oise sound pressure levels is given.  
On the whole, measurements for the table were made in large buildings. In some buildings, the range  of 
background noise levels is very wide,  and the type of occupancy has been subdivided into, for  example, quiet 
and noi sy categories.  The table is intended only as a guide but where it is used to assess fire alarm system 
requirements,  the higher of the two dB(A) figures in the appropriate range ought always to be used.  Wherever  
possible, "real" measurements ought to be mad e in the building where the fire alarm system is to  be installed.  
Table  B.1 — typical expected background noise levels for a range of building types  
Area  Lp 
dB(A)  
Airport  terminals : check in,  arrivals  and departures  concourses  59 to 72 
gate rooms  and pier walkways   
customs  - baggage  reclaim  54 to 64  
63 to 71  
- channels  59 to 70 
- departure  lounge  49 to 64 
Arenas,  auditoria: A concert  halls,  cinemas,  theatres,  etc. 60 to 75 
Banks, building  societies:  public  areas  50 to 64 
Bus stations:  Quiet 58 to 68 
 Noisy 63 to 73 
Cafeterias:  Quiet 55 to 65 
 Noisy 68 to 78 
Classrooms:  Quiet 56 to  68 
Noisy 64 to 72 
Conference/  meeting rooms:   40 to 45 
Corridors:     uncarpeted:  - quiet  45 to 55 
- noisy  66 to 76 
   carpeted : 28 to 32 
Court  rooms : 40 to 50 
Dealing  rooms:   computerized  60 to 70 
 traditional  80 to 90 
Exhibition halls:  63 to 73  
 
  BOS 813 -1:2023  
Edition 1.0 
117 Table  B.2 — typical expected background noise levels for a range of building types  
(continue d) 
Area  Lp 
dB(A)  
Factories:  control rooms  70 to 75 
light assemblies  80 to 85 
heavy engineering  95 to 105 
Hospitals:  See note 
Hotel  bedrooms:  TV off  28 to 35 
TV on  60 to 70 
Kitchens  (commercial):  65 to 75  
Leisure  centres:  squash courts  65 to 80  
ice-rinks (public sessions)  69 to 80 
swimming/diving pools  72 to  79 
fun pools  81 to 87 
Bowling  78 to 85 
Libraries:  book/reading areas - quiet  35 to 45 
 - noisy (e.g. h eavily air -conditioned)  50 to 60 
Receptions  50 to 60 
Museums,  galleries:  Quiet 48 to 60 
Noisy 60 to 73 
Offices:  Cellular  40 to 50 
open -plan 50 to 70 
noisy  70 to 85 
Plant  rooms:  boiler  - quiet  
              - noisy  66 to 72 
76 to 86 
Railway stat ions (surface):  waiting rooms  
                       concourses  
platforms  – Electric trains   
     Diesel trains   54to 65  
60 to 66  
60 to 72  
75 to 85  
Restaurants:   72 to 75  
Shop stores:                                              quiet 
noisy  50 to 60  
65 to  75 
Shopping malls:  70 to 75  
 
  BOS 813 -1:2023  
Edition 1.0 
118 Table B.1 — typical expected background noise levels for a range of building types  
(continue d) 
Area  Lp 
dB(A)  
Sport Shops                       quiet 
                       noisy 
    Loud ball games  60to 72  
72 to 82  
78 to 93 
Warehouses                           quiet 
                          noisy  47 to 63  
63 to 80  
A) In these occupancies, management procedures are normally that performances cease prior to a 
general "Evacuate" signal being given; the background noise is then significantly lower than that 
occurring during the performance. It is the latter noise level, as given here, that is to be used for 
designing the system.  
NOTE Special considerations apply in the case of hospitals because, for example, in many areas th e fire signal is 
intended primarily for staff rather than patients. The staff shall have been trained in fire Marshall including basic 
fire fighting. Fire Marshall shall be in charge of monitoring, managing the system together with installing company  
 
 BOS 813 -1:2023  
Edition 1.0 
119 Annex C  
(normative)  
 
Control and transmission equipment for tactile alarm devices provided 
for people who are Deaf and hard of hearing  
C.1 Control and transmission equipment for tactile alarm devices provided  for people who are Deaf and  hard 
of hearing should be designed in accordance with the principles of BS EN 54 -2, other than in  respect of 
the colours used for visual indicators . 
 
C.2 The control and transmission equipment should conform to  the relevant  requirements of  
BS EN 54 -2:1997+A1.  
• 5.1 
• 5.2 
• 5.3 
• 5.4 
• 5.6 
• 6 
• 7.6 
 
NOTE  1 This subclause does not apply if resetting of the control and transmission equipment is achieved  by receipt  
of a data signal from, or by the operation of relay dedicated to this function ( i.e. not the relay that  indicated the fire 
signal) at the fire alarm CIE.  
 
• 8.2.1  
• 8.2.2  
• 8.2.3  
• 8.2.4b)  
• 8.2.4d)  
• 8.2.4e)  
• 8.2.6a)  
• 8.5 
• 8.6.1  
• 8.6.2  
• 8.6.3  
• 8.7 
• 8.8  
• 10.2a)  
Note 2 This subclause is applied  except that, instead of  a separate light emitting indicato r, visual indication of the test 
condition may be given by a combination of a fault indication  and an appropriate text display.  
• 12 .3  
• 12.4.3  
• 12.4.4  
• 12.5.1  
• 12.5.4  BOS 813 -1:2023  
Edition 1.0 
120 • 12.6 
• 12.7 
• 12.8 
• 12.9 
• 12.10  
• 12.11  
• 13 (excluding 13.2.and 13.7 ) 
•  except that in 14a) the equipmen t should be marked as compliant with Annex C of BS 5839 -
1:2017, and not with BS EN 54 -2:1997+A1.  
• 15 
NOTE 3 Where Clause 15 refers to a fire detection circuit, this is to be regarded as the circuit that interconnects the 
control and transmission equipment w ith the fire detection and fire alarm system CIE.  
C.3 Since BS EN 54 -2:1 997+Al was not  drafted  to take account of tactile alarm devices provided for people 
who are Deaf and hard of hearing, care should be taken to ensure that each of the  requirements list ed in  
are met.  
 
C.4 Special  attention should be given to the following design considerations.  
a) Mains failure or low battery condition at the control and transmission equipment should 
result in a suitable fault warning  at the fire alarm CIE within 30 min of its occurrence.  
b) All other fault conditions that are required to be identified at the control and transmission 
equipment in order to satisfy the recommendations of  18.2 should result in a fault warning 
at the fire alarm CIE within 100 s of their occurrence.  
c) A visible indication should be given at the equipment by means of an independent light -
emitting indicator while the equipment is supplied with power.  
d) Multiple fire signals received at the equipment should not stop, or inhibit, the transmission 
of fire war ning signals.  
e) Any controls that cause transmission of fir e alarm signals to cease should be capable for 
use 
Any controls that cause transmission of fire alarm signals to cease should be capable of use only  at 
access level 2, as defined in BS EN 54 -2. 
 
Repeat transmission of fire alarm signals should continue until either manual action is taken  or a reset 
signal is received from the fire alarm CIE; repeat transmissions should not cease  automatically after 
any predetermined period or number of transmissions.  
 
C.5 Power supplies should conform to the requirements of BS EN 54 -4. repeat transmission  of fire alarm , 
signal  BOS 813 -1:2023  
Edition 1.0 
121 Annex D  
(normative )  
 
Method for calculating standby battery capacity  
D.1   Valve regulated lead acid batteries  
D.1.1  The minimum capacity of valve  regulated lead acid batteries  should  be calculated in accordance with 
following fom ula: 
 
𝐶𝑚𝑖𝑛==1.25(𝑇1𝐼1+𝐷𝐼2
2) 
 
D.1.2   Where Cmin /20 is equal  to or greater than I2, it can be assumed that D = 1 . When Cmin /20 is less 
than /2 the value o f D should either be based on the battery manufacturer's data or should be 1.75.  
D.1.3 In practice, Cmin is unlikely to correspond exactly to an available battery capacity and therefore the 
next highest available capacity size should be used.  
  
D. 2  Batteries other than valve -regulated lead acid batteries  
The minimum capacity of batteri es, other than valve regulated lead acid batteries, should be determined 
by consultation with the battery manufacturer and should take into account the standby load, the alarm 
load, any required derating to take account of the higher current drawn in the a larm condition  and a 
derating factor to take account of battery ageing  during the anticipate d life of  the battery.  
where  
Cmin  minimum capacity of  the battery when new at  the 20 h  discharge  rate and at 20°C in 
ampere  hours;  
T1  total battery standby period in hours;  
I1,  total battery standby  load in amperes;  
I2,  total battery alarm load in amperes; and  
D  a derating facto r BOS 813 -1:2023  
Edition 1.0 
122 Annex E  
(informative)  
 
The Selection and Application of Fire Detectors  
During the design o f a fire system, consideration is given to the fire risk(s) and the false alarm risk(s).  Fire 
detectors are selected depending on the nature of the protected area and the risks associated  with it Often, 
this involves utilizing different fire detector techn ologies in order to meet the diverse  needs of both fire detection 
and false alarm rejection in each scenario.  
Single sensor detectors (e.g. optical smoke detectors, heat detectors)  are suited to the detection of certain fire 
risks Selection choices need to  be made carefully to  optimize  the detection of  fire but minimize the occurrence 
of false alarms. The deployment of multi -sensor detectors means· that the system could potentially detect fires 
earlier and yet avoid troublesome false alarms to a greater ext ent too.  
The choices and decisions concerning which detector types to use are initially made during fire system design,  
but are also sometimes re visited and even modified during commissioning and/or maintenance. They are not 
always well recorded, nor is t he rationale behind them. At  later time e.g. during a maintenance visit, this can 
give rise to confusion. A clear understanding of the original  reasons behind the choice of detectors and how 
they are configured is needed in order to verify continued suitab ility. 
Aside from multi -sensor detectors, a visual inspection of a fire detector can often provide sufficient information 
to a maintenance technician to allow in -situ functional testing to be undertaken (e.g. in the case of a smoke 
detector or a heat detec tor). However, in the case of multi -sensor fire detectors, the type of detection employed  
with in it and its settings, modes or specific configuration which govern its detection performance to the risk, 
are not apparent from a  visual inspection. This infor mation might not even be available from the CIE. In all 
cases, however, there remains the need to know the detection principles and to understand the reason for the 
choice of that detection, relative b to the risks perceived in the protected area.  
Annex E  is intended to assist with the task of selecting and clearly recording the type, sensitivity and settings 
selected for all detectors, including multi -sensor detectors, relating to the perceived risks. A detector selection 
table is shown in Table E.1. lt is  a template to allow the documentation of the main risks, and all decisions and 
reasoning behind the detection choices made either during system design or at the time of any subsequent 
change to the fire detection. It is intended to assist designers, commi ssioning engineers and 
service/maintenance technicians to keep good records of their detection choice decisions and rationale.  
A flowchart is also provided in Figure E.1 which demonstrates the process of detector choice and is provided 
as a guide for compl eting Table E.1. The notes in Table E.1 give further guidance on its completion, including 
reference to relevant recommendations within BS 5839·1.  
 
  BOS 813 -1:2023  
Edition 1.0 
123  
 
Record the responses to the questions given in Figure E.1 in Table E.1, For guidance on completion of  
this-table, see the table footnotes  
  
Figure E 1 Flow chart for the selection of detector and application verificationBOS 813 -1:2023  
Edition 1.0 
124 Table  E.1 — Detector Selection  
Protected area/type of area  A Choose from : 
Hotel bedroom en -suite   
Hotel bedroom non en -suite  
Hotel suite  
Bedroom  dormitory style  
Office cellular  
Office open plan  
Kitchen (main)  
Kitchenette  
Restaurant/ Canteen  
Corridor  
Escape route  
Reception area  
Lobby  
Workshop (clean)  
Workshop (moderate)  
Workshop (dirty)  
Warehouse / storage  Others: please specify   
Predominate u se of area  B Choose from:  
Sleeping  
Cooking  
Unoccupied  
Storage non -flammable  
Storage flammable  
General office work  
Meetings  
Circulation route  
Escape route  
Manufacturing  
Manufacturing (hot works)  
Assembly  Others: please specify  
Fire phenomenon  C Choos e from:  
Smouldering white smoke  
Smouldering dark smoke  
Smouldering changing to flaming  
Flaming (clean burn)  
Flaming (dirty)  Others: please specify  
 
  BOS 813 -1:2023  
Edition 1.0 
125 Table E.1 — Detector selection  (continued)  
 
False alarm risk (S)  D Choose from:  
None  
Steam  
toaster  
Oven usage  
Cooking  
Dust  
Smoking  
Aerosol spray  
Hot works  Others: please specify  
Detector type  E Choose from  
Optical  
Heat (static)  
Heat (RoR)  
Ionization  
Multi -sensor  
Optical/ Heat  
Heat/CO  
Optical/CO  
Optical/ Heat/CO  
Optical beam  
Linear heat  
ASD Clas s C  
ASD Class B  
ASD Class A  
Flame  
Video  
CO Other please specify   
Detector setting F Please specify detail of detector 
setting(s)   
Certificated mode(s) 
chosen? G Choose from:  
Yes 
No  
Acceptable to interested 
parties?  H Choose from  
Yes 
No – then speci fy  
  BOS 813 -1:2023  
Edition 1.0 
126 Table E.1 — Detector selection  (continued)  
 
Fire strategy met?'  Choose from  
Yes 
No – then specify   
Fire strategy met?'  Choose from  
Yes 
No – then specify   
Detector type/ setting 
choice rationale'  J Please specify in detail   
Comments/  
Action  K Deta ils as appropriate   
 
Table E.1 — Detector selection (continued)  
 
A Protected area needs to be related to the system category as defined in Clause 5. In the case of 
time-related settings (e.g., day/night mode), a new selection process needs to be undertaken  and 
recorded for each setting.  
B Anticipated use(s) of the protected area - does not need to be an exhaustive list but needs to cover 
the main use(s).  
c  Risks anticipated in the protected area. This can either be described as the fire type or in terms 
of the expected causes of fire. Only the main fire risks need to be identified in Table E.1 - this need not 
be an exhaustive list.  
D Only the predominant false alarm risks need to be identified in Table E.1 - this does not need to 
be an exhaustive list. Thes e needs to be described in terms of the expected causes of false alarms. 
See Clause 35 for assistance with selection of detector types for the minimization of false alarms.  
E See Clause 21 for further information on detection types and their selection.  
F Different detector settings can include various response speeds, delays, variations of sensor 
performance, sensitivity of alarm level, etc. Other risks (e.g. evacuation strategy/ timescales) need to 
be considered when choosing these settings.  
G Some detecto rs might have modes of operation which are not certificated to the relevant BS EN 
54 standards. These modes are to be avoided if at all possible but where such modes are used, that 
decision needs to be agreed in writing by all interested parties following a fire risk assessment, noted 
here and explained in the rationale in Table E 1. Information concerning non -compliance of a specific 
mode has to be provided by the manufacturer by clearly marking the detector or within the associated 
data (as per BS EN 54 s tandards, On -site adjustment of response behaviour).  
H Refer to Clause 6 for the definition of relevant interested parties.  
I The implications of future changes to the detection type or setting need to be understood and 
continue to support the fire strateg y. 
L The reasoning behind decisions concerning the choice of detector technology, type, setting, 
sensitivity, etc. need to be given here.  
K Any additional, relevant information concerning the detector selection needs to be given here, 
including required or  agreed actions.  
 
To assist in completion of the fire phenomena column in Table E.1. the following summary of individual 
sensor detection performance (as found within point type fire detectors) is provided in Table E.2. It also 
shows some indication of ho w a typical multi -sensor detector can be used to improve detection.  
 Table E.1 — Example of fire risks  BOS 813 -1:2023  
Edition 1.0 
127  
Fire 
phenomenon  Smouldering white smoke  
  Smouldering 
dark smoke  Smouldering 
changing to 
flaming  Flaming 
(clean burn)  Flaming 
(dirty)  
Example 
fire(s)  Smouldering 
electrical fire  Smouldering 
wood  Smouldering 
furnishings  Wastepaper  bin 
fire Burning 
solvents  Burning 
oils 
Ionization 
detection  ** *** ** **** * ** 
Optical 
(scatter) 
detection  ***** ***** **** **** * *** 
CO detection  * **** ***** ** * ** 
Heat 
detection  * * * ** *** *** 
Flame 
detection  * * * *** ***** ***** 
Typical multi - 
sensor 
detection e.g. 
optical -heat A  ***** ***** **** **** *** **** 
Typical multi - 
sensor 
detection  
e.g. optical -
heat- COA  ***** ***** ***** **** **** **** 
Key to fire h azard detection: very good = *****       good = ****      moderate = ***            poor = **     very poor =*  
   A Multi -sensor detector  responses  could  be a combination  of the single -sensor  responses,  but the 
behaviour  of a multi -sensor  is dependent  on the manner  in which  the sensors  are combined  within  
the detector.  The combination  of sensors  within  a multi -sensor  detector could  provide  an 
enhancement  to performance  overall  and cannot  be considered  to be the linear sum of the  individual 
sensor responses . The response of multi -sensors  is not common across all detector manufacturers  
due to differences in construction  and internal  algorithms. The response of a chosen  multi -sensor, 
including its mode and settings, should be properly understood to ensure that  the risks are 
adequately covered. This table  shows  some  typical  examples of  multi -sensor  responses  and does  
not represent  an exhaustive  list of all possible  sensor  combinations  and algorithms.  
 
  BOS 813 -1:2023  
Edition 1.0 
128  False Alarm  
phenomenon  Example False 
Alarm fire(s)  Ioniza tion 
detection  Optical (scatter) 
detection  CO detection  Heat detection  Flame detection  Typical multi - 
sensor detection  
e.g. optical -heatA Typical multi - 
sensor detection  
e.g. optical -heat 
COA 
Steam  Shower or 
bathroom  **** ** ***** ***** ***** *** *** 
Smoke Smoking 
kitchen/ 
cooking 
fumes  * *** **** ***** ***** *** **** 
Dust Warehouse  *** ** ***** ***** ***** *** *** 
Other 
particular  Aerosol 
canister 
product, 
artificial 
smoke  *  *  ***** ***** ***** *** **** 
Sparks/ 
naked flames  Welding  ** ** *** *** * **** **** 
Substance 
ingress  Insects  *** *** ***** ***** ***** **** **** 
High ambient 
air flow  Air 
conditioning 
open doors/, 
window  ** ***** ***** ***** ***** ***** ***** 
Rapid 
thermal 
Change  Opening of 
ovens  ** ***** ***** * ***** **** **** 
Key choice  to avoid false alarms: very good = ***** good = **** moderate = *** poor = ** very poor =*  
A Multi -sensor detector responses could be a combination of the single -sensor responses, but the 
behaviour of a multi -sensor is dependent on the manner in which th e sensors are combined within 
the detector. The combination of sensors within a multi -sensor detector could provide an 
enhancement to performance overall and cannot be considered to be the linear sum of the individual 
sensor responses. The response of mult i-sensors are not common across all detector 
manufacturers, due to differences in construction and internal algorithms. The response of a chosen 
multi -sensor, including its mode and settings, should be properly understood to ensure that the risks 
are adequ ately covered. This table shows some typical examples of multi -sensor responses and 
does not represent an exhaustive list of all possible sensor combinations and algorithms.  
 
 BOS 813 -1:2023  
Edition 1.0 
129 Annex F  
(normative ) 
  
Model format for system logbook  
Logbook  
It is mandatory that this logbook be maintained by a relevant member of the premises management, to ensure 
that every entry is properly recorded. It is also mandatory that installing company provide logbook and monitor 
this entry  during their visits. This is necessary to satisfy the requirements of this standard , conformity to which 
might be a  requirement of legislation.  
In order to satisfy the requirements of this standard , the following need be recorded.  
− The names of the  members of the premises management.  
− Brief details of the maintenance arrangements.  
− Dates and times of all tests, including fire drills.  
− Dates and times of all fires to which the system responds.  
− Dates and times of all false alarms.  
− Causes, circumstances s urrounding, and category, of all false alarms (if known).  
− The identity of any manual call point or automatic fire detector  that triggers any of the above fire  
− alarm signals (if known).  
− Dates, times and types of all faults and defects.  
− Dates and types of al l maintenance ( e.g. service visit or non -routine attention).  
Reference data  
Address of protected premises : ......……………… ………… …..………… ...……………………… ..….……………  
............................................................. .......................................... ......................................................................  
Person within premises management responsible for the fire detection and fire alarm system:  
………………………………………………………………………………………………………………………………  
The system was designed by: ………………………………… ……..…………………………………………………  
The system was installed  by: ………………………………… …………………………….. ………….. ….…………..  
The system was c omissioned by: ………………………………… …………………. ………… .....…………………..  
The system was accepted by: ……………………………………… ………. ……………………... …………………..  
Verification was undertak en by: …………………… ……………… ….………… ……………………………………..  
The system is maintained under contract by  :............................ ................. until: ... ........... .................................  
Telephone number: .................................... ............. ......., who should be contacted if maintenance is required.  
Normal maximum attendance time for a maintenance technician is  :....................... ....................... .................. .. 
Expendable component replacement periods (list): …………… …………………… ……………………………… .. 
……………………………………………………………………………………………………………… .……… …….. . 
………………………………………………………………………………………………………………………………  
 
 BOS 813 -1:2023  
Edition 1.0 
130 This fire detection and fire alarm system comprises the following devices:  
− Manual call points : ......................................... ..................................................... .............. .....................  
− Smoke detectors :  .................................................................................... ................. .............................  
− Heat detectors ; ......................................... .............................................................. .......... ......................  
− Beam detectors ............................................................................... .................. ............. ........................  
− Aspirating detectors : ............................................................................................................................. . 
− Other detectors (specify) ......................................................... ...............................................................  
− Shut down devices : .......... .......................................................................... .......... .......... ................ ........  
− Interface units :  .......................... ......................................................................................... ........... ........ 
  BOS 813 -1:2023  
Edition 1.0 
131 Table F-1- Events other than false alarms or maintenance work  Initials   
A For example test, fire alarm signal, fault.  
B Where applicable.  Date completed B 
 Action required B 
 Device B  Zone B  Event   A  Time   Date   
 
False alarms  
Action 
Completed  B  
A Where cause is unknown, record activities in this area  
B Where applicable  Further 
actions 
required B  Category 
of false 
alarm   Findings of 
maintenance 
technician B  Maintenance 
visit 
required? 
(Yes / No)   Brief 
circumstances   Cause  
(if known) A  Device that 
triggered 
alarm signal   Zone   Time   Date   
 
Maintenance Work  
Signature   
B Where applicable  Further Wo rk required B  Work carried out   Reason for work   Device   Zone   Time   Date   BOS 813 -1:2023  
Edition 1.0 
132 Annex G  
(informative ) 
 
Model certificates  
G.1 Design certificate  
 
 
 
 
Certificate of design for the fire detection and fire alarm system at:  
 
Address  :............................................................................................... ............................. ......... ................  
............................................................................................................................. ................ .................... ... 
I/we being the competent person(s) r esponsible (as indicated by my/our signatures below) for the design 
of the fire detection and fire alarm system, particulars of which are set out below, CERTIFY that the said 
design for which I/we have been responsible complies to the best of my/our knowle dge and belief with 
the recommendations of Section 2 of this standard for the system category described below, except for 
the variations, if any, stated in this certificate.  
Name  (in block letters)  :…………………………………………….. Position: …………………… …..……….… 
Signature:  ............................................................................... Date:  ............................. ................. ............ 
For and on behalf of:  ……………………………………….……………………………………… ………..…….  
Address·....................................... ................................................................................ .............. .......... ....... 
.......... …………………………….......................................................................................... ......... ............ .... 
.......................................................................... Postcode· ............................................ ................ ............  
The extent of liability  of the signatory is limited to the system described below.  
 
System category (see Clause 5):……………………………………………………………………… …….. …..  
Variations from the recommendations of Section 2 of this standard  
............................................................................................................................. .................. ................. ..... 
............................................................................................................... ......................................... ........ ..... 
Extent of system covered by this certificate:  
……………………………………………………… ……………………………………………………… ……... … 
…………………………………………………………………………………………………………… ……... …… 
Brief description  of areas protected (not applicable for Category M, L1 or P 1 systems):  
....................................................................................... ................................................................ .......... .... 
............................................................................................................................. ............................. .......... . 
............... ............................................................................................................................. .........................  
......................................................................................................... ............................................................  
 BOS 813 -1:2023  
Edition 1.0 
133 Design certificate (continue d)  
 
 
G.2 Installation certificate  
Measures incorporated to limit false alarms. Account has been taken of the guidance contained in 
Section 3 of this standard  and, more specifically (tick as appropriate):    
The system is manual Type and siting of manual call p oints takes account of the guidance 
contained in Section 3 of this standard.  
An appropriate multi -sensor system has been specified.      
Fire signals from automatic fire detectors result initially in a staff alarm, which delays general  alarm  
/transmission  of signals to an alarm rece iving centre ( delete as applicable) for ………... min  
An appropriate analogue system has been specified.  
The system incorporates automatic fire detectors, and account has been taken of reasonably  
foreseeable causes of unwanted a larms, particularly in the selection and siting of detectors.   
A time -related system has been specified. Details: …….. ....................................... .................... ....  
…………………………………………………………………………………………..……………………  
In accordance with the reco mmendations of 35.2.6 of this standard , it Is recommended that, 
following commissioning. a soak period of .................... should follow. (Enter a period of not less 
than one week.)   
As the system incorporates no more than 50 automatic fire detectors,  no soak test ls necessary to 
satisfy  the recommendations of  this standard . 
Installation and commissioning   
It is strongly recommended that installation and commissioning be undertaken in accordance with  the 
recommendations of Section 4 and Section 5 of this standard  respectively.   
Soak test  
Other measures as follows: ....................... ............... .............................................. .................……  
………………………………………………………………………………………………………………..  
Appropriate guidance has been provided f or the user to enable limitation of false alarms  .  
Verification   
Verification that the system c  complies  with this standard  should be carried out, on completion,  In 
accordance with Clause 43  
Maintenance   
It is strongly recommended that, after completio n, the system is maintained in accordance with Section 
6 of this standard  
User responsibilities  
The user should appoint a relevant member of the premises management to supervise all matters  
pertaining to the fire detection and fire alarm system In accordan ce with the recommendations of Section 
7 of this standard  
Yes  
No 
To be decided by the purchaser or user  BOS 813 -1:2023  
Edition 1.0 
134  
Certificate of Installation for the fire detection and fire alarm system at:  
 
Address: ……… .......................................................... ....................................................................................  
................................. ............................................................................................................................. .........  
 
We being the competent installing company responsible (as indicated by my /our signatures below) for the  
installation of the fire detection and fire alarm system, particulars of which are set out below, CERTIFY 
that the said installation for which we have be en responsible complies to the best of our knowledge  and 
belief  with the specification described below and with the recommendations of Section 4 of this standard 
except for the variations, if any, stated in this certificate.  
Name  (in block  letters)  :……………… ………………………..  Position: …..……………… .…...………………  
Signature  :............................................................................ .....Date:  ................. .................................. ....... 
For and on behalf of:  ……………………………………….……………………………………………… ……….  
Address·............................................... .................. ........................................................................ ...............  
.......... …………………………… .......................................... ................. .......... ................................... ............. 
Postcode· ............................................ ..................  
The extent of liability of the signatory is limited to the system described below.  
Extent of installation work covered by this certifi cate:  
.......... …………………………… .......................................... ................. ............................................... ........... 
.......... …………………………… .......................................... ................. ............................... ................ ........... 
.......... …………………………… .......................................... ................. ............................................... ........... 
.......... …………………………… .......................................... ................. ......... ...................................... ........... 
Specification against which system was installed:  
.......... …………………………… .......................................... ................. ............................................... ........... 
.......... ………………… ………… .......................................... ................. ............................................... ........... 
.......... …………………………… .......................................... ................. ............................................... ........... 
.......... …………………………… .......................................... ................. ............................................... ........... 
Variations from the specification and/or Section 4 of  this standard  (see Clause 7):  
.......... …………………………… .......................................... ................. ............................................... ........... 
.......... …………………………… .......................................... ................. ............................................... ........... 
..........…………………………… .......................................... ................. ............................................... ........... 
.......... …………………………… .......................................... ................. ........................................... ............... 
Wiring has been tested in accordance with the recommendations of Clause 38 of  this standard  
Test results have been recorded and provided to: ............................................................................ .......... . 
Unless supp lied by others, the as -fitted drawings have been supplied to the person responsible for  
commissioning the system.  
…………………………………………………………………………………………………………………………  BOS 813 -1:2023  
Edition 1.0 
135 G3 Commissioning certificate  
 
 
 
  
Certificate of Commissioning for the fire detection and fire alarm system at:  
 
Address :..... ...................................................................................................... .......... .................................  
.............................................................................................................. ................................... .......... .......... 
We being the competent installing company responsible ( as Indicated by our signatures below) for the  
commissioning of the fire detection and fire alarm system, particulars of which are set out below,  CERTIFY  
that the said work for which we have been responsible complies to the best of our knowledge and belief 
with the recommendations of Clause 39 of this standard  except for the variations, if any, stated in this 
certificate.  
Name(in  block  letters): ……… ………………… .…………………..  Position: …………… ……… ………………  
Signature:  ............................................................................. ...... Date:  ......................... ..................... ........  
For and on behalf of:  ……………………………………….……………………………… ……. ………… ……. .. 
Address·..................................................................................................................... ............ ........... ...........  
.......... …………………………… ..................................................................... .................... ....................... .... 
.......................................................................... Postcode· ................ ........... ............................ ..................  
The extent of liability of the signatory is limit ed to the system described below.  
Extent of system covered by this certificate  
………………………………………………………………………………………… ……… ………………………  
……………………………………………………………………………………………… ……… …………………  
................................................................................... .................................................... .......... ....................  
............................................................................................................... ......................... ........ ................... .. 
Variati ons from the recommendations of Section 39 of this standard  
………………………………………………………………………………………………… ……… ………………  
…………………………………………………………………………………………………………… ……… …… 
...................................................................................................... ........................................ .......... .............  
Installation work is, as far as can reasonably be ascertained, of an acceptable standard .  
All equipment operates correctly    
The entire system has been inspected and tested in accordance w ith the recommendations of 
39.2c) of this standard   
The system performs as required by the specification prepared by a copy of which I/we have 
been given.    
The documentation described in Clause 40 of this standard has been provided to the user  
Taking into account the guidance contained in Section 3 of this standard , we have not identified 
any obvious potential for an unacceptable rate of false alarms    BOS 813 -1:2023  
Edition 1.0 
136 Commissioning certificate (continued)  
 
 
The following work should be completed before/after (delete as applicable} the system becomes  
operat ional:  
……………………………………………………………………………………………………………...…………
…………………………………………………………………………………………………………………...……
………………………………………………………………………………………………………………...………
………………………………………………………………………………………………………………………  
The following potential causes of false alarms should be co nsidered at the time of the next service visit:  
……………………………………………………………………………………………………………...…………
…………………………………………………………………………………………………………………...……
………………………………………………………………………………………………………………...………
………………………………………………………………………………………………………………………  
Before the system become  operational, it should be soak tested In accordance with the recommendations 
of 35.2.6 of  this standard  for a period of: .................. (Enter a period of either one week, such  period as  
required by the specification, or such period as recommend ed by the signatory to this certificate,  
whichever ls the greatest, or delete if not applicable.)   BOS 813 -1:2023  
Edition 1.0 
137 Acceptance certificate  
 
 
The following work is required before the system can be accepted:  
…………………………………………………………………………………………………………… ..……….…  
......................................... ............................................................................................................................  
Sufficient representatives of the user have been properly instructed in the use of the system, 
including, at least, all means of t riggering fire signals, silencing and resetting the system and  
avoidance of false alarms.  
All relevant tests, defined in the purchasing specification, have been witnessed. (Delete if not 
applicable.)  
A logbook.  
Electrical Installation Certificate in acc ordance with BS 7671 for the supply to all mains related 
wiring  
Operating and maintenance instructions.  
Certificates of design, installation and commissioning    
As-fitted drawings  
The following documents have been provided to the purchaser or user : 
All installation work appears to be satisfactory  
A suitable zone plan (or other suitable diagrammatic representation) of the premises is  provided 
on or adjacent to all control and Indicating equipment (Delete if not applicable.)  
The system is capable of gi ving a fire alarm signal.  
The facility for remote transmission of alarms to an alarm receiving centre operates correctly.  
Certificate of acceptance for fire detection and fire alarm system:  
 
Address …...................................................... ..............................................................................................  
................................................................................................... ..................................................................  
We being the competent installing company responsible (as indicated by my/our signatures below ) for 
the acceptance of the fire detection and fire alarm system, particulars of which are set out below, ACCEPT 
the system on behalf of  
Name  (in block letters):…………………………………………….. Position: ……………...……………………  
Signature: ................................................................................. Date: .......................... .................. ............  
For and on behalf of: ……………………………………….………………………….………………….………..  
Address·..................................................................................................................... .................................  
..........…………………………… ...................................................................................................................  
.......................................................................... Postcode· ........................................ ............... .................  
The extent of liability of the signatory is limited to the systems described below.  
Extent of system covered by this certificate:  
………………………………………………………………………………………………………..…………….…  
………………………………………………………………………………………………………………..……….  BOS 813 -1:2023  
Edition 1.0 
138 G.5 Verification certificate (optional)  
 
Certificate of commissioning for the fire detection and fire alarm system at:  
 
 
 
 
 
Address  
………………………………………………………………………………………………………………... ......… 
…………………………………………………………………………………………………… ………………..…  
............................................................................................................................. ................................... .... 
We being the competent person(s) responsible (as indicated by our signatures belo w) for the verification  
of the fire detection and fire alarm system. particulars of which are set out below, CERTIFY that the  
verification work for which we have been responsible complies to the best of our knowledge and belief  
with the recommendations of Clause 43 of this standard  
Name (in block letters):………………………………………….. Position: …………………… .…………… .... 
Signature: ............................................................................... Date: ............................ .............................  
For and on behalf of: ……………………………….…………………………………………………………… ... 
Address·............................................... ...................................... .................................................................  
..........……………………………................ ...................................................................................................  
.......................................................................... Postcode· ........................................ ............................... . 
The extent of  liability of the signatory is limited to the system described below.  
Extent of system covered by this certificate:  
……………………………………………………………………………………………………………………..…  
............................................................................. .......................................................................................  
……………………………………………………………………………………………………………………..…  
Scope and extent of the verification work:  
……………………………………………………………………………………………………………………..…  
............................. ............................................................................................................................. ..........  
……………………………………………………………………………………………………………………..…  
........................................................................ ............................................................................................  
In my/our opinion, that as far as can reasonably be ascertained from the scope of work described  
above, the system complies with, and has been commissioned in ac cordance with, the 
recommendations of this standard , other than in respect of variations already identified in the 
certificates of design, installation,  or commissioning,  
 
The entire system has been inspected and tested in accordance with the recommendati ons of 
39.2c) of  this standard .  
The following non -compliances with the recommendations of this standard , have been identified (other  
than those recorded as variations in the certificates of design, installation or commissioning):  
……………………………………………………………… ……………………………………………………..…  
............................................................................................................................. .......................................  
……………………………………………………………………………………………………………………..…  
 BOS 813 -1:2023  
Edition 1.0 
139 Bibliography  
Standards publications  
For dated references, only the edition cited applies. For undated references, the  latest edition of the  
referenced document (including any amendments) applies.  
 
BS 5979, Remote centres receiving signals from fire and sec urity systems - Code of practice  
BS 5839 -6, Fire detection and fire alarm systems for buildings - Part 6: Code of practice for the  design, 
installation, commissioning and maintenance of  fire detection and fire alarm systems in  domestic premises  
BS 62 66 , Fire protection for electronic equipment installations - Code of practice  
BS 7974 , Application of  fire safety engineering principles to the design of buildings - Code of practice  
BS EN 54 -13, Fire detection and fire alarm systems - Part 13: Compatibility an d connectability  assessment of 
system components  
BS EN  12 845 , Fixed firefighting systems - Automatic sprinkler systems - Desi9n, installation  and maintenance  
BS EN 50136 -1, Alarm systems - Alarm transmission systems and equipment - Part 1: General  require ments 
for alarm transmission systems  
BS EN 61672 -1, Electroacoustics -Sound level meters - Part 1 : Specifications  
BS EN 62305  (all parts), Protection against lightning  
BS EN ISO 9000 , Quality management systems – Fundamentals and  vocabulary  
DD CLC/TS 50398 , Alarm systems - Combined and integrated systems - General requirements  
PD 6669 , Guidance for the provision of  Alarm Transmission Systems (ATS) for alarm systems in the UK  
PD 7974 -4, Application of  fire safety engineering principles to the design of building s Part 4: Detection  of fire 
and activation of  fire protection systems  
 
Other publications  
1. LOSS PREVENTION CERTIFICATION BOARD /BRE GLOBAL LTD. AND FIRE INDUSTRY 
ASSOC/ATION. CoP 0001 Issue  1: Code of practice for visual alarm devices used for fire warning.  
ERE Global Ltd, 2012  
2. NORTHERN IRELAND. Building Regulations (Northern Ireland). The Stationery Office,  London, 2012  
3. Construction Products Regulations 2013 (CPR)  
4. GREAT BRITAIN. The Building Regulations 2010, Approved Document M, Access to and use of 
buildi ngs. RIBA, London, 2010  
5. FIRE INDUSTRY ASSOCIATION (FIA). Code of Practice for Design, Installation, Commissioning and 
Maintenance of Aspirating Smoke Detector {ASD} Systems. Oldfield Road, Hampton: FIA. (Available 
at: www.fia.uk.com/resourceLibrary/cop -commissioning -and-maintenance -of-asds .html- 6) 
6. FIRE INDUSTRY ASSOCIATION (FIA). Code of Practice for Design, Installation, Commissioning and 
Maintenance of Duct Smoke Detector (DSD) Systems. Oldfield Road, Hampton: FIA. 2012. (Available 
at: www.fia.uk.com/re sourceLibrary/cop -duct-detector -systems. html-7) 
7. GREAT BRITAIN. Health and Safety (Safety Signs and Signals) Regulations. The Stationery Office, 
London, 1996  
8. Electricity at Work Regulations. 1989  
9. FIA Guidance: Testing of  lead acid batteries used in Fire Det ection & Alarm System Power Supplies.  
10. GREAT BRITAIN. The Regulatory Reform (Fire Safety) Order. The Stationery Office,  London, 2005  
11. SCOTLAND. Fire (Scotland) Act. The Stationery Office, Edinburgh, 2005  
12. SCOTLAND. Fire Safety (Scotland) Regulations. The Stat ionery Office, Edinburgh, 2006  BOS 813 -1:2023  
Edition 1.0 
140 13. GREAT BRITAIN. Fire and Rescue Services (Northern Ireland) Order. The Stationery Office,  Belfast, 
2006  
14. NORTHERN IRELAND. Fire Safety Regulations (Northern Ireland). The Stationery Office, Bel fast, 
2010