Reference number  
DRS 186 -4: 201 8 
© RSB 2018 
  
 RWANDA 
STANDARD  DRS 
186-4 
 
Second  edition  
 
Code of practice for fire safety   
of building — 
Part 4:  
Selection, installation and maintenance of 
automatic fire detection and alarm system  DRS 186-4:2018 
 
 
ii Error! Reference source not found.  
  DRS 186 -4: 2018  
iii                 ©RSB 2018 All rights reserved  
 
 In order to match with technological development and to keep continuous progress in industries, 
Standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
 
 
 
 
© RSB 2018 
All rights reserved. Unless otherwise specified, no part of this publication may be  reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reproduce this document should be addressed to  
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
Tel. +250 252 586103/582945  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  DRS 186 -4: 201 8 
©RSB 2018All rights reserved                  iv 
 
 Contents  Page  
Foreword  ................................ ................................ ................................ ................................ .............................. v 
1 Scope  ................................ ................................ ................................ ................................ ...................... 1 
2 Normative reference  ................................ ................................ ................................ .............................. 1 
3 Terms and definitions  ................................ ................................ ................................ ........................... 1 
4 Requirements  ................................ ................................ ................................ ................................ ...... 10 
4.1 General  ................................ ................................ ................................ ................................ .................  10 
4.2 Detection zones  ................................ ................................ ................................ ................................ .. 10 
4.3 Detection zones that contain non -addressable automatic detection system  ..............................  10 
4.4 Size and number of zones (protected with manual call points)  ................................ .....................  12 
4.5 Size of the analog addressable panel is normally referred by number of signalling line 
circuit (loop) as class b wiring.  ................................ ................................ ................................ .........  12 
5 Automatic fire detectors  ................................ ................................ ................................ ....................  13 
5.1 Heat detectors  ................................ ................................ ................................ ................................ ..... 13 
5.2 Smoke detectors  ................................ ................................ ................................ ................................ . 14 
5.3 Spark/Ember detector  ................................ ................................ ................................ ........................  14 
5.4 UV flame detector  ................................ ................................ ................................ ...............................  14 
5.5 Choice of fire detector  ................................ ................................ ................................ ........................  15 
6 Sitting of fire detectors  ................................ ................................ ................................ ......................  17 
6.1 General  ................................ ................................ ................................ ................................ .................  17 
6.2 Heat detectors  ................................ ................................ ...........................  Error! Bookmark not defined.  
6.3 Sitting and spacing requiremen t of detectors covering general cases Error! Bookmark not defined.  
7 Inspection, testing and maintenance ................................ ................................ ................................  25 
7.1 General  ................................ ................................ ................................ ................................ .................  25 
7.2 Initial installation inspection tests  ................................ ................................ ................................ .... 25 
7.3 Servicing/periodical maintenance ................................ ................................ ................................ ..... 26 
7.4 Maintenance schedule  ................................ ................................ ................................ .......................  26 
7.5 General points about detectors  ................................ ................................ ................................ .........  29 
7.6 Cleaning and maintenance  ................................ ................................ ................................ ................  29 
7.7 Tests following an alarm or fire  ................................ ................................ ................................ .........  29 
7.8 System disconnection during testing  ................................ ................................ ..............................  29 
7.9 Spares  ................................ ................................ ................................ ................................ ..................  29 
Annex  A (informative)  Merits and relative demerits of various types of detectors  ................................ . 30 
 DRS 186 -4: 2018  
v                 ©RSB 2018 All rights reserved  
 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards  Board  (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda  Standards 
adopted by Technical committ ees are ratified by me mbers of RSB Board of Director s for publication and 
gazettment as Rwanda Standards.  
DRS 186-4 was prepared by Technical Committee RSB/TC 28, Fire safety . 
In the preparation of this standard, refe rence was made to the following standard:  
IS 2189:2008; Selection, installation and maintenance of automatic fire detection and alarm system - Code of 
practice   
The assistance delivered from the above source is hereby acknowledged with thanks.  
This second edition cancels and replaces the first edition (RS  186-4: 2013) of which has been technically 
revised . 
DRS 186 consists of the following parts, under the general title Fire safety of building  — Code of practice : 
Part 1: General principles of fire grading and classification  
Part 2: Details of construction  
Part 3: Fire safety in public buildings  
Part 4: Selection, installation and maintenance of automatic fire detection and alarm system  
Part 5: Exit requir ements and personal hazard  DRS 186 -4: 201 8 
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Committee membership  
The following organizations were represented on the Technical Committee on Fire safety  (RSB/TC 28) in the  
preparation of this standard.  
City of Kigali  
College of Science and Technology  
CABLELINE  
Energy Util ity Corporation Limited  
ELECTRICOM  
ISCO  
Institute of Engineers Rwanda  
Ministry of Disaster Management and Refugees  
Ministry of Infrastructure  
Rwanda Housing Authority (RHA)  
Rwanda Motor Ltd  
Rwanda National Police  
REAL  
Société Rwandaise d’Assurance (SONARWA )  
SONATUBES  
Rwanda Standards Board (R SB) - Secretariat  DRS 186 -4: 2018  
vii                 ©RSB 2018 All rights reserved  
 
 DRS 186 -4: 201 8 
1                 ©RSB 2018 All rights reserved  
 
 Code of practice for fire safety of building  — Part 4: Selection, 
installation and maintenance of automatic fire detection and alarm 
system  
1 Scope  
1.1 This standard covers the minimum requirements fo r planning, design, selection, installation and 
maintenance of fire detection and alarm systems .. 
1.2 It covers systems capable of providing signals to initiate, in the event of a fire, the operation of ancillary 
services, such as fire extinguishing system s and other necessary precautions but it does not cover the 
ancillary services. It covers fire detection and alarm system installed in buildings of different types including 
those installed in industries . 
1.3 It is applicable to simple systems with a few m anual call points as well as to complex installations 
comprising addressable control and indicating panel, non -addressable detectors, manual call points, control 
and indication panels.  
2 Normative reference  
The following referenced document  is indispensable  for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenced 
document (including any amendments) applies.  
ISO 7240 , Fire detection and alarm systems  
IS 11360 , Spec ification for smoke detectors for use in automatic electrical fire alarm system.  
IS 2175 , Specification for heat sensitive fire detectors for use in automatic fire alarm system . 
3 Terms and definitions  
For the purposes of this standard, the follow ing terms a nd definitions apply . 
3.1 
Acknowledge  
conform that a message or signal has been received, such as by the pressing of a button or the selection of a 
software command  
3.2 
Activation device  (Trigger device)   
device capable of being operated automatically or manually to initiate an alarm that is, detector, a  manual (fire 
alarm) call point or a pressure switch  
3.3  
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 Addressabl e device  
fire alarm system component with discrete identification that can have its status individually  identified or that is 
used to indi vidually control other functions  
3.4 
Addressable system  
system in which signals from detectors, manual call points, or any other devices are individually  identified at 
the c ontrol and indicating equipment  
3.5 
Air sampling -type detector  
detector that consis ts of a piping or tubing distribution network that runs from the detector to the  area (s) to be 
protected. An aspiration fan in the detector housing draws air from the protected area  back to the detector 
through air sampling ports, piping, or tubing. At th e detector, the air is analyzed  for fire products  
3.6 
Alarm  zone  
geographical sub-division 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  
3.7  
Alert  tone  
attention getting signal to alert occupants of the pending transmission of a voice message  
3.8 
Analog  initiating device (sensor)  
initiating device that transmits a signal indicating varying degrees of conditions as contrasted  with a 
conventional initiat ing device which can only indicate an on -off condition.  
3.9 
Enunciator  
unit containing one or more indicator lamps, alphanumeric displays, graphical displays or other  equivalent 
means in which each indication provides status information about a circuit, co ndition or  location  
3.10 
Approved  
acceptable to th e authority having jurisdiction  
3.11 
Audibility  
property of a sound which allows it to be heard among  other sounds in the background  DRS 186 -4: 201 8 
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 3.12  
Authority havin g jurisdiction  
organization, office, or individual responsible for approving equipment, materials, an installation  or a 
procedure  
3.13 
Automati c fire direction and alarm system  
fire alarm system comprising components and sub -system required for automatically detecting a  fire, initiating 
an automatic alarm for fire and init iating other action as required  
3.14  
Automatic fire signal  
alarm of fire originated by an automatic devic e, given audibly and/or visibly  
NOTE  The system may also include manual fire alarm call points.  
3.15  
Ceiling  
upper surface of a spa ce regardless of the height. Areas with a suspended ceiling have two  ceilings, one 
visible from the floor and one above the suspended ceiling  
3.16  
Ceiling  height  
height from the continuous floor of a room to the contin uous ceiling of a room or space  
3.17  
Circuit  
assembly of fire alarm components supplied from the same control equipment and protected  against over 
current by the same protective device (s) or c urrent limitation arrangements  
3.18  
Circulation area 
area (including a stairway) used mainly as a means of access between a room and an exit from the  building or 
compartment  
3.19  
Combination/Multifunction  detector  
device that  responds to more than one form of fire phenomena or use more than one principle to  sense one of 
these phenomena. Typical exampl es are a combination of a heat detector with a  smoke detector or a 
combination of rate -of-rise and fixed -temperature heat detector  
3.20  
Commissioning  
process by which it is determined that the installed system  meets the defined requirements   
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 3.21 
Contro l centre  
permanently staffed room within or near the premises at risk for the receipt of emergency calls and equipped 
with means for indicating the situation in each of the protected premises, and the communications needed for 
transmission of calls for assist ance to emergency services.  
3.22 
Control unit 
system component that monitors inputs and controls outputs th rough various types of circuits  
3.23  
Detectio n zone  
sub-division of the protected premises such that the occurrence of fire within if will be indic ated by a  fire alarm 
system separately from an indication of  fire in any other sub -division  
3.24 
Detector  
devise suitable for connection to a circuit that has a sensor that responds to a physical stimulus  such as heat 
or smoke or flame  
3.25 
Display  
visual  representation of outpu t data, other than printed copy  
3.26 
Electrica l conductivity heat detector  
line-type or sport -type sensing element in which resistance vari es as a function of temperature  
3.27  
Ember  
particle of solid material that emits radiant en ergy due to either its temperature or the process of  combustion 
on its surface  
3.28 
Emergenc y voice /Alarm  communications  
dedicated manual or automatic facilities for originating and distributing voice instructions, as well as  alert and 
evacuation signals p ertaining to a fire emergency,  to the occupants of a building  
3.29 
Evacuation  
withdrawal of occupants from a building  DRS 186 -4: 201 8 
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 3.30 
Evacuatio n signal  
distinctive signal intended to be recognized by the occupants as requi ring evacuation of the building  
3.31 
Exit plan 
plan for the emerg ency evacuation of the premises  
3.32 
False  alarm  
alarm of fire that is, false, because the fire reported does not and did not exist. This false alarm may  arise by 
malicious , mistaken or accidental intent  
3.33 
Fault signal  
distinctive au dible and visual signal indicting occurrence of a fault within the system (for example,  break in 
electric circuit, short ci rcuit or fault in power supply)  
3.34 
Fire alarm control and indicating equipment  
equipment through which fire detectors may be suppl ied with power and which:  
a) is used to accept a detection signal and actuate a fire alarm signal;  
b) is able to pass on the fire detection signal, through the fire alarm routing equipment, to the fire  fighting 
organization or to automatic extinguishers;  
c) is used  to monitor automatically the correct functioning  of the system; and  
d) is used to indicate or display the location of fire/alarm activation deice.  
3.35 
Fire alarm  signal  
signal initiated by a fire alarm -initiating device, such as a manual fire alarm box, au tomatic fire  detector, water 
flow switch, or other device in which activation is indicative of the presence of a fire  or fire signature  
3.36 
Fire alarm system   
combination of components intended to give an audible and visible and/or  other perceptible alar m for fire.  The 
system may also in itiative other ancillary action   
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 3.37 
Fire rating  
The classifications indicating in time (hours) the ability of a structure or component to withstand a  
standardized fire test. This classification does not necessary reflect  performance of rated  components in an 
actual fire  
3.38 
Fire safety functions   
building and fire control functions that are intended to increase the level of life safety for occupants  or to 
control the spread  of the harmful effects of fire  
3.39 
Fixed temp erature detector   
device that responds when it’s operating element becomes heated to a predetermined level  
3.40 
Flame  
body or stream or gaseous material involved in the combustion process and emitting radiant  energy at specific 
wavelength bands determined  by the combustion chemistry of the fuel. In most  cases, some portion of the 
emitted radiant ene rgy is visible to the human eye  
3.41   
Flame detector  
radiant energy -sensing fire detector that detects the radi ant energy emitted by the flame  
3.42  
Flam e det ector sensitivity  
distance along the optical axis of the detector at which the detector can detect a fire of specified  size and fuel 
within a given time frame  
3.43 
Floor   
area contained on each storey of the building.  
3.44 
Heat detector  
fire detector tha t detects  either  abnormally high temperature, rate of temperature rise, or both  
3.45 
Ionizat ion smoke detection  
principle of using a small amount of radioactive material to ionize the air between two  differentially charged 
electrodes to sense the presence of smoke particles. Smoke particles entering  the ionization volume decrease 
the conductance of the air by reducing ion mobility. The reduced  conductance signal is processed and used to 
convey an alarm condition when it meets present  criteria  DRS 186 -4: 201 8 
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 NOTE  It is sug gested that the use of such detectors be discouraged/avoided, as they have a radioactive source. 
Multi -function detections may be used instead.  
3.46 
Line detector  
detector which responds to the phenomenon sensed in th e vicinity of a continuous line  
3.47 
Maintenance  
repair service, including periodic inspection and tests, required to keep the fire alarm system and  its 
component parts in an operative conditional at all times, and the replacement of the system or its  components 
when they become undependab le or inoperable for any reason  
3.48  
Manu al call point  
manually operated device used to initiate an alarm signal. It can be manual alarm system or part  of automatic 
alarm system  
3.49   
Mimic panel  
panel in which he floor/area plans of the premises are projecte d to reduced scale to enable easy  identification 
of the sector/zone  
3.50  
Multi-sensor fire detector  
fire detector that monitors more than one physical and/or chemical phenomenon associated with  fire. Typical 
examples are a combination of a heat and smoke detector or combination of heat and  gas detectors  
3.51  
Photoel ectric ligh t obscuration smoke detection  
principle of using a light source and a photosensitive sensor onto which, the principal portion of source 
emissions is focused.  When smoke particles ent er the light path, some of the light is scattered  and some is 
absorbed thereby reducing the light reaching the receiving sensor. The light reduction signal is processed and 
used to convey an alarm condition when it meets preset criteria  
3.52 
Photoe lectric light-scattering smoke detection  
principle of using a light source and a photosensitive sensor arranged so that the rays from the  light source do 
not normally fall onto the photosensitive sensor. When smoke particles enter the  light path, some of the light  is 
scattered by reflection and refraction onto the sensor. The light signal  is processed and used to convey an 
alarm conditio n when it meets preset criteria  
3.53 
Point  detector  
detector which responds to the phenomenon sensed i n the vicinity of a fixed p oint  
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 3.54  
Power supply  
source of electrical operating power, including the circuits and terminals connecting it to the  dependent system 
components  
3.55 
Proje cted beam -type detector  
type of photoelectric light obscuration smoke detector wherein th e beam sp ans the protected area  
3.56 
Prote cted premises  
physical location p rotected by a fire alarm system  
3.57   
Radio Alarm System (RAS)   
system in which signals are transmitted from a radio alarm transmitted (RAT) located at the  protected 
premises through a ra dio channel to two or more radio alarm repeater station receivers  (RARSR) and that are 
annunciated by a radio alarm supervising station receiver (RASSR) located  at the central station  
3.58 
Rate - of - rise detector  
device that responds when the temperature  rises at a rate exceeding a predetermined value  
3.59 
Search distance  
distance which has to be travelled by a searcher within a zone in order to determine visually the  position of fire  
3.60 
Sector  
sub-division of the protected premises larger than a zone. A larger floor may be demarcated into  sectors, that 
is, addressed part of the floor. A sector w ill normally contain many zones  
3.61   
Shap es of ceiling  
shapes of ceilings can be classified as sloping or smooth  
3.62   
Short circuit isolators   
devices which may be connected into a transmission path of a fire detection and fire alarm system,  to limit the 
consequences of low parallel resistance faults between the lines of this transmission path 
3.63 
Stop ping ceiling  
ceiling that that has a slope  DRS 186 -4: 201 8 
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 3.64 
Smo ke detector  
device that detects visible or invisible particles of combustion  
3.65  
Smo oth ceiling  
ceiling surface uninterrupted by continuous projections, such as solid joists, beams, or ducts,  extending more 
than 1 00 mm below the ceiling surface  
3.66    
Spac ing 
horizontally measured dimension related to the allow able coverage of fire detectors  
3.67     
Spark  
moving ember  
3.68  
Spark/Ember  detector  
radiant energy sensing fire detector that is designed to detect sparks, embers or both. These  devices are 
normal ly intended to operate in dark environments and in the infra -red part of the  spectrum  
3.69   
Spark/Ember  detector  
number of watts (or the fraction of a watt) of radiant power from a point source radiator, applied  as a unit step 
signal at the wavelength of  maximum detector sensitivity, necessary to produce an  alarm signal from the 
detector within the specified res ponse time  
3.70  
Standb y supply  
power supply, commonly from a rechargeable battery, which is automatically connected to the fire  alarm 
system when  the normal power supply fails  
3.71  
Trouble signal  
signal initiated by the fire alarm system or device indicative of a fault in a monitored circuit or  component.  
3.72   
Zone     
area or space that has a group of automatic and/or non -automatic fire detect ion devices for which  there is a 
separate common display in the control and indicting equipment.   
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 4 Requirements  
4.1 General  
4.1.1 Automatic fire detection and alarm system should consist  of fire detection and manual call points 
connected by appropriate cables to  sector/zonal panels which in turn are connected to control and indicating 
equipment (C and I). 
4.1.2 The equipment and cables of automatic fire detection and alarm system should be independent of any 
other system or cables, and should not be shared with a ny other system.  
NOTE  Where analog addressable fire alarm system is used, which consists of addressable devices and suitable 
control panel zoning and number of detectors shall be as per 4.2.4.  
4.1.3 If the requir ed number  of detectors in any area is less than 20, division into zones/sectors may not be 
necessary. Similarly, sectorization may not be necessary if the number of zones is not very large and in case 
of bigger premises, the premises may be divided into wings and each wing may have sectors/zones.  
4.1.4 Size of the conventional panels is normally referred by number of zones. Each zone can be 
connected with the conventional detectors not exceeding 20.  
4.2 Detect ion zones  
4.2.1  General  
4.2.1.1  In most of the buildings an alarm of fire may initiate a number of di fferent activities, for example, 
provision of assistance, commencement of fire  fighting operations and emergency evacuation procedures, 
summoning of fire brigade, etc. It is essential that these activities are well co -ordinated.  
4.2.1.2  In the pre -planning  of emergency procedures for a building it is important, for ease of 
communication and synchronization of effort, to fix a convenient number of easily identifiable sectors/zones, 
which the building can be divided into.  
4.2.1.3  In order to direct those resp onding to a fire alarm signal to the area of fire, all buildings with the 
exception of smaller ones need to be divided into detection zones.  
4.2.1.4  The zones need to be small enough for a fire to be located quickly. Even if the system is 
addressable, zoni ng indications needs to be provided as this often p rovides a quicker indication of the location 
of a fire than typical addressable text displays. Zone indicators also provide a simple ‘at  a glance’ overview of 
the extent of fire or smoke spread. Also this would enable fire fighters who are not familiar with the building to 
proceed to the location of fire.  
4.3 Detection zones that contain non -addressable automatic detection system  
4.3.1 Requirements for detection zones that contain non -addressable automatic dete ction system are given 
below:  
a) the floor area of a single zone shall not exceed 2 000 m2; DRS 186 -4: 201 8 
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 b) if the total area of a building is less than 300 m2, a zone can co ver more than one floor;  
c) if the total area of a building is more than 300 m2, each zone shall be rest ricted to a single floor;  
d) voids, if any, above or below the floor area of a room can be included in the same zone as of the room 
provided that the voids and the room constitute a single compartment;  
e) the search distance, that is, the distance that has to be  travelled by anyone responding to a fire alarm 
signal after entry to the zone in order for the location of the fire to be determined visually, shall not exceed 
30 m;  
f) automatic fire detectors within any enclosed stairwell lift well or other enclosed shaft -like structures shall 
be considered as a separate zone;  
g) if manual call points are located on the landings of an enclosed staircase, such points at each level shall 
be incorporated within the zone that selves the adjac ent accommodation on that level;  
h) the de tectors and manual call points within sectors/zones shall be wired to the control and indicting 
equipment;  
i) the entire electrical installation pertaining to the entire fire alarm system as described above shall be 
independent of other systems;  
j) when a signal  of fire is given it is necessary that there shall be no confusion about the  zone from which it 
is received;  
k) to allow quick location of fire, the zone shall be small enough to facilitate fire rescue operation/ response .  
l) adequate fire separation between the  zones  shall be provided ; 
m) in larger premises, the fire alarm system shall be designed and installed to fully function in  compatible 
with the emergency procedures ,  consequently this will allow identification of the zone from which an 
alarm is originated ; 
n) in the case of two stage alarms, clear and unambiguous signals shall indicate which  emergency 
procedure to be adopt ed throughout each zone;  
o) for larges systems covering more than one building it may be necessary to create sectors in addition to 
zones in or der to restrict the number of zones from which alarms originate simultaneously or in 
succession;  
p) the division of sectors/zones shall be decided based on carefull analysis on the type of risk, access to 
zones with to the main circulation routes and the main  control as well as signage. ; 
q) Identical signals shall be used for different zones within same premises unless the background noise in 
one or more zones have different sounders. ; 
r) For buildings with multiple usage, n o zone shall be designed to include areas with more than one type of 
occupancy.   ;  
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 s) Areas with s pecial risk s shall be designed as separate zone within large protected area.   
t) where a zone extends beyond a single compartment, the zone boundaries shall be the boundaries of the 
fire compartments ; and 
NOTE 1  It is permissible to have two complete fire compartments in one zone, or two complete zones in one fire 
compartment . 
NOTE 2 It is not permissible to have a zone, which extends into parts of two zones.  
4.4 Size and number of zones (protected with manual  call points)  
4.4.1  In systems containing only manual call points, location of a fire is usually known to the person 
operating the call point. As it is often difficult to get information in time to the safety personnel, the restriction 
on the size and numb er of zones shall also apply to the systems protect ed w ith manual call points only.  
4.4.2  To prevent misleading indication of the position of the fire, the manual call points shall be indicated in 
the control equipment  separately from the detectors in zone s, which are protected, by both detectors and 
manual call points.  The circuits for the detectors and call points shall be different in case of conventional 
detection systems.  
4.5 Size of the analog addressable panel.  The clause to be rephrased  
4.5.1 Length of  the loop shall not exceed more than 3 000 m where size of wire shall not be less than 1.5 
mm2 or manufacturer recommended length and size may be considered.  
4.5.2 Number of addressable detectors and devices per loop shall be as per manufacturer’s 
recommen dation. It is recommended that number of detectors per loop may not be exceeding 90 % of the full 
capacity. The number of detector and devices per loop varies from 128 per loop, 99 Smoke Detectors, 99 
Devices and 159 Detectors and 159 Devices. Based on the  manufacturer design some devices need external 
power supply and some devices supported by loop power.  
4.5.3 Each loop should not be divided into more than 8 fire zones. Minimum two isolators are required per 
zone. It is recommended that a pair of fault is olator modules be employed for every 20 -30 detectors/manual 
call points.  
4.5.4 In partially addressable system zone addressable module are used in the loop to connect non -
addressable fire detection devices. Wherever non -addressable detectors are connected provisions of 4.1.1 - 
4.2.3 are to be followed.  
4.5.5 The sounders for fire alarm should be electronic hooters/horns/electric bell having a frequency range 
of 500 to 1 000 Hz. The sound of the fire alarm should be continuous although the frequency and ampl itude 
may vary. If a two tone alarm is used, at least one of the major frequencies should be within the frequency 
range of 500 to 1 000 Hz.  
4.5.6 The distribution of fire alarm sounders should be such that the alarm is heard at all sites which can be 
occu pied within the protected area.  
4.5.7 A minimum sound level of 65 dB (A) above any other noise likely to persist for a period longer than 30 
s, whichever is greater should be produced by the sounders at any point which can be occupied in a building. DRS 186 -4: 201 8 
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 Sounde rs should be suitably distributed throughout the building in regard to attenuation of sound caused by 
walls, floors ceilings and partitions. If the fire routine for the premises requires the audible alarm to arouse 
sleeping persons, the minimum sound level  should be 75 dB (A) at the bed head with all doors shout.  
4.5.8 A large number of quieter sounders rather than a few very loud sound ers may be preferable to 
prevent noise levels in some areas from becoming too loud. In sting sounders in corridors to serv e the 
surrounding rooms, account should be taken of the attenuation of the sounder frequency by any dividing 
element. Most single doors will give attenuation greater than 20 dB. Thus it is unlikely that sounder noise 
levels in a room will be satisfactory i f more than one dividing wall or door separates it from the nearest 
sounder. At least one sounder for each fire compartment will be necessary. Sound levels exceeding 120 Db 
(A) in areas which are occupied may produce hearing damage.  
4.5.9 Besides, the cont rol Centre, which may be located anywhere on the ground floor or even the 
basement, wherever necessary repeater or annunciated panel should be provided near the main entrance so 
that the maintenance staff notices the fault condition or isolation, if any, f or rectification.  
4.6 A control Centre should be provided preferably on the ground floor where mimic panels, control and 
indicating equipment and other equipment associated with it should be installed.  
5 Automatic fire detectors  
5.1 Heat detectors  
5.1.1  General  
5.1.1.1 All Heat detectors shall meet the requirements of the relevant part of ISO 7240. Whereas f ixed 
temperature heat detectors are designed to operate when the temperature of the detecto r exceeds a 
predetermined value, Rate -of-rise temperature -cum-fixed detec tor shall be designed to operate within a given 
time:  
a) when the rate of temperature rise at the detector exceeds a predetermined value regardless of the actual 
temperature; and  
b) When temperature at the detector exceeds a predetermined value.  
5.1.1.2  Probe ty pe high temperature bi -metal heat detectors are resettable and highly suitable to use 
above 80  °C where electro nic components cannot be used. T he following  types are examples of application 
for which probe type high temperat ure heat detectors are suitable:  
a) generator enclosure;  
b) turbine  enclosure;  
c) oven and furnace area;  and 
d) kitchen  wood and other place as per the requirement where automatic fire extinguishing/suppression 
systems are used . 
5.1.1.3  Linear heat sensing cables  can be broad ly divided into two cate gories; d igital or analogue , 
depending upon the principle b y which the sensing cable registers a change in temperature.  Digital sensor  
©RSB 2018All rights reserved                  14 
 
 consists of two core cable in which the conductors are separated by a heat sensitive insulator. When a 
specified temperat ure is reached, the cable insulation breaks down and an alarm is indicated.  
5.1.1.4  In the case of analogue sensor, cores are separated by a negative temperature co -efficient 
polymer whose resistance will reduce in proporti on to the temperature increase.  These cables are used for 
detecting fire and overheating in certain specific occupancies such as:  
a) cables tunnels, trays and vaults;  
b) material conveyors;  
c) bulk storage multi -racked areas;  
d) rim seals of floating roof tanks storing hazardous chemicals; and  
e) a few  other special occupancies.  
5.1.2  Heat detectors  application  
Heat detectors are suitable for use in situation where sufficient heat is likely to be generated and damage 
caused by heat generated by the fire constitutes main hazard. This is to be minimized through  early detection. 
In many buildings, especially non -air-conditioned buildings, these conditions prevail where heat detectors can 
be advantageously used. Heat detectors are however, not suitable for protection of places where larger losses 
can be caused by small fires and where safety of life is involved.  
5.2 Smoke  detectors  
5.2.1  Spark/Ember  detector  
5.2.1 A spark/ember -sensing detector usually uses a solid state photodiode or phototransistor to sense the 
radiant energy emitted by embers typically between 0.5 µ m and 2.0 µ m in normally dark environments. These 
detectors can be made extremely sensitive (microwatts), and their response times can be made very short 
(microseconds). Spark/ember detectors are installed primarily to detect sparks and embers that could, if 
allowed to continue to burn, precipitate a much larger fire or explosion. Spark/ember detectors include the 
following:  
a) ambient light.  
b) electromagnetic interference (EMI, RFI); and  
c) electrostatic discharge in the fuel stream.  
5.2.2 All Spark/Ember detectors sha ll meet the requirements of the relevant part of ISO 7240.  
5.2.2  UV flame detector  
52.2.1  UV Flame detector makes use of ultraviolet sensitive photocathode for detecting flame. It has a 
narrow spectral sensitivity of 185 to 260 µm which is insensitive to visible  light.  DRS 186 -4: 201 8 
15                 ©RSB 2018 All rights reserved  
 
 5.2.2.2  All UV Frame detectors shall meet the requirements of the relevant part of ISO 7240.  
5.2.3   IR flame detector   
Single or multiple wavelength infra -red flame detector sense wavelength in the infra - red  spectrum; almost all 
the materials that par ticipate in the flaming combustion emit ultraviolet ration to some degree during flaming 
combustion, whereas only carbon -containing fuels emit significant radiation at the 4.35 micron (carbon 
dioxide) band used by  many de tector types to detect a flame. Flame detectors are suitable  for: 
a) high-calling, open -spaced buildings, such as warehouses and aircraft hangers;  
b) outdoor or semi -outdoor areas where winds or draughts can prevent smoke from reaching a heat or 
smoke detector.  
c) areas where rapidly developing flam ing fires can occur, such as aircraft hangers, petrochemical 
production areas, storage and transfer  areas, storage and transfer areas, natural gas installations, paint 
shops, or solvent areas;  
d) areas needing high fire risk machinery or installations, often  coupled with an automatic gas extinguishing 
system; and  
e) environments those are unsuitable for other types of detectors.  
5.3 Choice of fire detector  
5.3.1  General  
5.3.1.1  Fire detectors are designed to detect one or more of three characteristics of a fire that is s moke, 
heat or radiation (flame). No one type of detector is the most suitable for all applications and final choice is 
dependent on the individual circumstances.  
5.3.1.2 It is often useful to employ a combination of different types of detectors. Most fire detectors are 
affected not only by the level of the detected phenomena but also by the behavio ur of the phenomena with 
time. In some cases it is the rate of change of phenomena; in others it is the effect, for example, delays in 
smoke entry or thermal lags . 
5.3.1.3  A combination of various detectors is necessary  due to the following factors:  
a) The performance  of the contents  for each part of the building with respect to their susceptibility  to heat, 
smoke and water damage  
b) the processes taking place or planned  to take place in building   
c) the design of the building.  
5.3.1.4 Every fire alarm system is a compromise. It is possible to increase the sensitivity of detectors but 
that would probably increase the frequency of false alarms.   
©RSB 2018All rights reserved                  16 
 
 5.3.1.5 It is possible to redu ce the losses by reducing the spacing between the detectors or using several 
types of detectors in the same area but these would increase the cost of the system.  
5.3.1.6 It is possible to increase the frequency of testing but this might lead to increase di sturbances on 
the premises.  
5.3.1.7 Since each type of detector has its own advantages and disadvantages, and no one type o f 
detector is most suitable for all applications, the choice of a detector to be used for a particular application is 
always a compro mise. Final choice will depend primarily on:  
a) the speed of response required;  
b) the need to m inimize false alarms; and  
c) the nature of the fire hazard.  
However, other factors such as cost, suitability for the environment and maintenance requirements shall al so 
need to be considered.  
5.3.1.8 In any automatic detection system a detector has to discriminate between a fire and the  normal 
environment existing within the building. The system chosen shall have detectors that are  suited to the 
conditions and that pro vide the earlier reliable warning.  
5.3.1.9 Each type of detector responds at a different rate to different kinds of fire. With a slowly  
somnolent fire such as the initial stages of a fire involving cardboard, a smoke detector would  probably 
operate first. A fire that evolves heat rapidly and with very little smoke could operate a heat  detector before a 
smoke detector could operate first.  
5.3.1.10 In general, smoke detectors would give appreciably faster responses than heat detectors  but may 
be liable to giv e false alarms.   
5.3.2  Life safety installation  
5.3.2.1 Whenever optical density of smoke exceeds 0.1dB/m (10 m visibility), temperature rises beyond 
66°C and concentration of carbon mon oxide in atmosphere exceeds 0.0 4 percent, and  human survival is 
endangered. An alarm should be initiated before these limits are reached so that the occupants are able to 
escape to safety. Time overriding priority is to be given for detection of smoke because of the following 
factors:  
a) main threat to li fe in a fire emergency emanat e from smoke and toxic fumes;  
b) smoke and lethal gases travel rapidly to areas away from fire due to strong convection currents , which  
threaten s the life of the occupants even at faraway places; and  
c) detectable quantity of smoke from a hostile fire precedes d etectable heat level and the development of 
lethal atmosphere.  
5.3.2.2 In a life safety installation, it is therefore, essential to:  
a) pay attention to detection of smoke and to protect escape route s; DRS 186 -4: 201 8 
17                 ©RSB 2018 All rights reserved  
 
 b) ensure operation of detectors on escape route before opti cal density exceeds 0.05 dB/m tha t is, visibility 
falls below 20  m; and  
c) take into account any scheme of pressurization/smoke control while installing  detectors  
5.3.2.3 Heat detectors are not suitable for detecting fire in slow burning/air -conditioned prem ises where 
temperatures required to operate them may only be reached after the smoke density in the  escape 
route/circulation areas has reached to the critical level.  
5.3.2.4 Heat detectors are suitable in compartments where heat producing equipment (for ex ample,  
kitchen and pantry, etc…) is used in closets or other unsupervised spaces compact areas with low  value 
contents.  
5.3.3  Property safety installation  
5.3.3.1 Installation of fire detectors enables early detection and easy extinction by reducing delay 
betwee n ignition and start of fire  fighting measures . It is important to minimize incidence of false alarms 
particularly when detectors are hooked  up to actuate means of automatic extinction. Automatic extinction 
should generally be initiated only on confirmatio n of two detecting signals to avoid possibility of false actuation  
5.3.3.2 Computer/ cent re/other electronic equipment which have a very high value should be protected 
by smoke detectors.  
5.3.3.3 Archives, high value libraries, and museums with high value combustibles should be protected  by 
combination of heat, flame and smoke detectors.  
5.3.3.4  The heat detectors should be used on the racks and cupboards and smoke detectors in open 
space on the ceiling. Flame detectors should be  used where height of the c eiling is more than 9 m.  
5.3.3.5 Flammable liquid in small quantities stored in confined spaces where chances of rapid heat build -
up exist (such as garages, repair shops, store areas, battery rooms, etc) heat or flame detectors should be 
provided.  
6 Sitting of fire detectors  
6.1 General  
6.1.1  At the time of installation and prior to commissioning, every fire detector should be allotted an 
identification number, preceded by alphabetic initials showing the type  of detectors.  A record of this should be 
maintained i n the control cent re. For example:  
a) Z1/SDI/20 meaning Smoke Detector, Ionization, Zone 1, and 20th Detector;  
b) Z2/SDOT/3 meaning Sm oke Detector Optical, Zone 2, 3rd Detector;  
c) Z4/HFT/4 meaning Fixed Temperat ure Heat Detector,  Zone 4, 4th Detector;  and 
d) Z3/HR R/2meaning Rate o f Rise Heat Detector,  Zone 3,  2nd Detector etc.   
©RSB 2018All rights reserved                  18 
 
 6.1.2  Heat and smoke detectors depend on convection to transport hot gases and smoke from the fire to 
the detectors. Spacing and sitting of detectors should  be based on the need to restrict the  time taken for this 
movement and to ensure that the products o f combustion reach the detectors in adequate concentration. In a 
building, the hottest gas and the greatest concentration of smoke will generally form at the highest part of the 
enclosed areas,  and it is here, therefore, that heat and smoke detectors need to be sited  
Spacing and s itting of detectors shall consider  the following constraints for optimum protection:  
a) heights of the ceiling (more the height means more cooling of hot gases, thus dilut ing the performance of 
the detectors),  
b) effects of stratification (where smoke does not rise to the ceiling at all),  
c) type of roof (with beams extending deep below, etc.),  
d) air movement (within the protected area below the detectors),  
e) supply air inlets (i n the vicinity of detectors), HVAC systems (with high air change rates),  
f) obstructions (in the path of rise of hot gases and smoke like ducts, machinery parts, false ceilings, light 
fixtures, etc.)  
6.2 Sitting and spacing of detectors (common to all types of s moke and heat detectors ) 
6.2.1 Under flat ceilings, the horizontal distance between any point in a protected area and the detector 
nearest to that point shall not exceed  length of 7.5 m in case of smoke detector, and  length of 5.3 m in case 
of heat detec tor. 
6.2.2 In case of a sloping roof or pitched ceiling (where the distance between the top of apex and 
bottom of the roof exceeds 600 mm), spacing of detectors at or in the vicinity of apex should be  spaced 
between 7.5 m and 8.5 m of distance for smoke de tectors.  
6.2.3 Detectors shall not be mounted within distance of 500 mm from  walls, partitions or obstructions 
to flow of smoke or hot gases, such as structural beams and ductwork, where the obstructions are greater 
than 250 mm in depth.  
6.2.4 Where struc tural bea ms or ductwork for light fittings or any other ceiling attachments, not greater 
than 250 mm depth, cr eate obstacles to the flow of smoke, detectors shall not be mounted closer to the 
obstruction more than twice the depth of the obstruction.  
6.2.5 Where partitions or storage racks that reach within 300 mm of the ceiling, they shall be 
constru cted as walls that extend to the ceiling for the purpose of sitting the detectors.  
6.2.6 Similarly, ceiling obstructions, such as structural beams, deeper than 10 percent of the overall 
ceiling heights shall be constru cted as walls for the purpose of sitting the detectors, that is, each bay formed 
by such beams shall be treated as separate enclosure for provision/spacing of detectors.  
6.2.7 Detectors shall not be  mounted within distance of 1 m from any air inlet (supply air inlets of HVAC 
system) or a forced ventilation system.  DRS 186 -4: 201 8 
19                 ©RSB 2018 All rights reserved  
 
 6.2.8 Detector sitting shall be such that a clear space of 500 mm is maintained below each detector.  
6.2.9 Where detectors are constrained  to be fixed to the wall, they shall be sited in such a way that the 
top of the detection element is between 150 mm and 300 mm below the ceiling and the bottom of the 
detection element is above the level of door opening. Additional detector shall be placed  on the ceiling at a 
position 1.5 m from any opening which might act like a flue.  
6.2.10 A detector shall be placed on the protected side of the premises on the ceiling 1.5 m from any 
door, window or any opening in the wall partitions separating the protec ted premises from the other premises.  
6.2.11 All stairwells, lift shafts, other utility shafts, shall have a detector at the top. Lift machine rooms 
shall be provided with a detector.  
6. 2.12 All unenclosed staircase shall have one detector at each main la nding within the staircase.  
6..2.13  The detector shall also be provided in cable tunnels, ducts, false floors, AC and AHU  (Air 
Handling Unit)  room, long AC return ducts and distribution boards.  
6. 2.14 No detector shall be subjected to any interior decorat ion treatment that is painting, alteration of 
exterior cover, etc., to conform to the environment.  
6. 2.15 Every enclosure (that is, room or cabin) shall have a detector at ceiling level and also under false 
ceiling, if provided.  
6. 2.16 Where there is mor e than one such enclosure per floor, a response indicator shall be installed at 
the entrance to such enclosures to indicate where the detector has actuated. This arrangement shall also be 
followed in case of all concealed detectors in false floors, plenums , shafts, tunnels, etc.  
6. 2.17 Voids as in false ceiling/flooring more than 800 mm  height  shall be protected with detectors 
spacing like in normal installation.  
6.2.18  Voids as in false ceiling/flooring less than 800 mm height need not necessarily have i ndependent 
coverage unless the void is such that the spread of fire products between the rooms or compartments take 
place through it. Bathroom, lavatories, WC, etc, however, need not be protected.  
6.2.19 For irregular shaped areas, the spacing between the detectors may be greater than the 
determined  spacing provided the maximum spacing from the detector to the farthest point of a side wall or 
corner within its zone of protection is not greater than 0. 7 times the determined spacing.  
Table 1 gives spacing pa rameter(s) at different ceiling heights for open areas under smooth and flat ceiling 
with no -forced ventilation/air -flows.   
Table 1 — Spacing(s) at different ceiling heights  
Type of detector  Spacing for ceiling height(s) m  Remarks  
Up to:  3.5 4.0 5.0 6.0 7.0 8.0 9.0 10.0  
©RSB 2018All rights reserved                  20 
 
 Smoke detectors   
   
9  
  
  
  
7.5  
6.5  
6.0  
5.0 The spacing in 
corridors  should  
not be greater  
than 3S/2  
Heat  detectors   
 Grade (time 
instant  20 s)   
7  
No 
chance   
6  
5  
5  
4  
3  
-  
Grade (time 
instant 40 s)   
6  
5.5  
5  
4  
3.5  
3  
-  
- Spacing  from the  
boundary wall 
should  be kept S/2  
Grade (time 
instant 60 s)                                                                                                                  
5  
4.5  
4  
3  
3.5  
-  
-  
Nil  
NOTE:  
1 The spacing has been ado pted from charts of Fire Detecting Institute of America, adopting the parameters mentioned in 7.3 
(nearest/rounded off values).  
2 It is presumed that ‘No chance’ means ‘No change’.  
  
6.2.1  Com pensation to the spacing of detectors.  
6.2.1.1  Height consideration  
Spacing o f 7.5 m in length for smoke detectors is valid up to a height of 7 m only and that of 5.3 m  in length for 
heat detectors is valid only up to a height of 5 m ; beyond these heights; spacing between the detectors shall 
be adjusted as follows:  
a) smoke detectors f or ceiling heights between 5 m and 7m, the spacing should be 3.5 m  length ; 
b) beyond 10 m ceiling height, the only beam detecto rs or aspirating type detection systems;  
c) heat detectors for ceiling heights between 5 m and  7 m; the spacing should be 3.5 m  length  ; and  
d) heat detectors should not be install beyond 7 m  ceiling   heights.  DRS 186 -4: 201 8 
21                 ©RSB 2018 All rights reserved  
 
 6.2.1.2  High air movement consideration  
Spacing between detectors shall be suitably reduced in areas where high air movement or where high air 
changes prevail. Modified values of spacing are given in the Table 2.  
a) detectors shall not be located in the vicinity of supply air diffusers. Minimum distance between the 
detector and the air inlets/di ffusers shall be at least 1.5 m;  
b) detectors shall be so mounted as to favour the air f low towards return  air openings;  
c) the above provisions shall not disturb the normal  population (count) of detector,  which is provided 
assuming th at air -handling systems are off; and  
d) after designing the detector spacing, it shall be cross -checked to ensure that there I at lea st one smoke 
detector for every 100 m2 or one heat detector for every 50 m2 or one heat detector for every 50 m2 of the 
compartment area.  
Table 2 — Modified spacing for high air movement areas  (see 6.3.3)  
Air changes/h 
Inside block  Multiplying factor for m odified  
Spacing  Area coverage  
< 7.5 1.00 1.00 
8.5 0.95 0.91 
10.0 0.91 0.83 
12.0 0.83 0.70 
15.0 0.74 0.55 
20.0 0.64 0.40 
60.0 0.38 0.15 
 
6.2.2  Additional requirements for optical beam detectors  
Optical beam -type detectors shall be sited in such a way th at no point in the protected space is farther than 
7.5 m from the nearest point of optical beam  as follows:  
a) in case of a sloping roof or pitched ceiling (‘where he distance between the top of apex and bottom of the 
roof excee ds 600 mm), distance of 7.5 m  may be increased to 8.5 m ; 
b) where optical beam type smoke detectors are used at more than 600 mm from ceiling level in order to 
provide supplementary detection of rising smoke within a high space (like Atrium etc.), the width of the 
area protected on each si de of optical beam shall be regarded as 12.5 % of the height of t he above beam 
from ground level;  
c) where there is a probability of people walking through the beam or where the beam is likely to be 
obstructed by forklifts, etc., detectors shall be mounted at  a suitable height;  
d) transmitters, receivers and/or reflectors shall be mounted on a solid construction which shall withstand 
vibrations, t emperatures or any imposed load;   
©RSB 2018All rights reserved                  22 
 
 e) the path length of the optical beam shall be within the limits  specified by the manuf acturers;  
f) beam detection area shall not exceed the detectio n zone in which it is installed;  
g) the effects of stratification shall be fully evalua ted when locating the detectors;  
h) if mirrors are used with the projected bea ms (reflective beam detectors),  the sh all be installed as per  
manufacturer’s recommendations;  
i) projected beam detectors and their mirrors (reflective beam detectors) shall be mounted on stable 
surfaces to prevent false or erratic operation due to vibration s and movements in the vicinity;  
j) the be am shall be designed so that small angular movements of the light source or receiver do not 
prevent operation due to smoke a nd do not cause nuisance alarms; and  
k) the light path of projected beam detectors (reflective beam detectors) shall be kept clear of  opaque 
obstacles at all times.  
6.2.3  Additional requirements for aspirating type detection systems.  
6.2.3.1 When an aspirating type smoke detection system is intended to provide general area protection, each 
aspirating sampling point shall be regarded as a point type smoke detector, provided that a single sampling 
point has equivalent sensitivity to a point type smoke detector.  Accordingly, all requirements specified below 
are applicable.  
a) the detector actually draws samples of air through sampling points (holes in  pipe work); it shall be 
possible to mount the sampling points flush with a ceiling, provided otherwise the system’s effectiveness 
is confirmed by the manufacturer;  
b)  if the system is intended to co -exist with other types of detection system for specific ap plication within 
the protected area installation shall comply with the manufacturer’s specifica tions;  
c) maximum air sample transport time from the farthest sampli ng point shall not exceed 120 s;  and air 
sampling detectors shall give a trouble signal if the a irflow within the enclosure is outside the 
manufacturer’s specified range.  
6.3.3.2 However, as the detector actually draws samples of air through sampling points (holes in pipe work), 
it shall be possible to mount the sampling points flush with a ceiling, provided otherwise the system’s 
effectiveness is confirmed by the manufacturer.  
a) if the system is intended to co -exist with other types of detection system for specific application within the 
protected area installation shall comply with th e manufacturer’s specifications;  
b) maximum air sample transport time from the farthest sampli ng point shall not exceed 120 s; and  
c) air sampling detectors shall give a trouble signal if the airflow within the enclosure is outside the 
manufacturer’s specified range.  
 DRS 186 -4: 201 8 
23                 ©RSB 2018 All rights reserved  
 
 6.2.4  Sitting of  flame detectors  
6.2.4.1  The location and spacing of th e detectors shall be based on soun d engineering evaluations taking 
into account the following:  
a) size of the fire requiring detection,  
b) fuel involved,  
c) sensitivity of detectors,  
d) distance between the fire a nd detector,  
e) radiant energy absorption of the atmosphere,  
f) presence of other sources of emission,  
g) purpose of detection system, and  
h) response time required.  
6.2.4.2  Certain flame detectors respond to the instantaneous level of radiation received while others 
depend upon the level received over a period.  
6.2.4.3  In either case the response will depend on the distance between the flame detector and the fire, 
since the radiation level received is inversely proportional to the square of this distance. Increased di stance 
from the fire will, therefore, lead to an increase in the size of the fire at detection.  
6.2.4.4  A clear line of sight to the area being protected is of great importance but at the same time care 
shall be exercised to avoid a direct line of sight to  likely sources of non -fire radiation to prevent false alarms.  
6.2.4.5  Sufficient number of detectors shall be used and they shall be positioned such that no point requiring 
detection in the hazard area is obstructed or outside the field of view of at leas t one detector.  
6.2.4.6  In applications where, the fire to be detected could occur in an area not on the optical axis of the 
detector, the distance shall be reduced or alternatively more detectors added to compensate for the angular 
displacement of the fir e; 
6.2.4.7  The spacing of the detectors shall vary from fuel to fuel. It is, therefore, necessary to fix the 
distances as per the recommendations of the manufacturers;  
6.2.4.8  The location of the detectors shall also be such that structural members or any other opaque 
objects or materials do not impede their line of sight; and  
6.2.4.9  When installed outdoors, detectors shall be shielded to prevent diminishing sensitivity due to rain, 
snow, ice, etc., and allow a clear vision of the hazard area.   
©RSB 2018All rights reserved                  24 
 
 6.2.5   Sitting of spark/ember detectors  
6.2.5.1  The location and spacing of the detectors shall be based on sound engineering evaluations taking 
into account the following;  
a) size of the spark or ember that is to be detected;  
b) fuel involved;  
c) sensitivity of detectors;  
d) Distance between the fire and the detector;  
e) Radiant ener gy absorption of the atmosphere;  
f) Presen ce of other sources of emission; and  
g) Purpose of detection sys tem. 
6.2.5.2  The system design shall be positioned so that all the points within the cross -section of  the 
conveyance duct, conveyor or chute, where the detectors are located, are within the field of view  of at least 
one detector.  
6.2.5.3  In any case the response will depend on the distance between the detector and the fire,  since the 
radiation level received is i nversely proportional to the square of this distance. Increased  distance from the fire 
will, therefore, lead to an increase in the size of the fire at detection.  
6.2.6  Sitting of manual call points  
Sitting manual call point shall be done  based on sound engineeri ng evaluations taking into account the 
following : 
a) manual call points shall be so located that, to give an alarm, no person in the premises has to travel 
distance of more than 30 m to reach them. When manual call points are also installed external to the 
building, th e travel distance shall be 45 m;  
b) where necessary, the travel distance may require to be reduced to less than 30 m . For example, where 
there is difficulty in free access within the risk or  in potentially dangerous risks;  
c) call points shall be fixed  at a height of 1.4 m above the surrounding floor level, at easily accessible well -
illuminated and conspicuous positions, which are free of  obstructions;  
d) where the call points are not visible from the front as in the case of a long corridor, they shall be surface 
mounted or semi -recessed in order to present a side profile area of not less than 750 mm2; 
e) manual call points shall be housed in dust proof and moisture proof enclosure pro perly sealed with 
appropriate material ; 
f) manual call point shall be located p referably near entry to staircases at various levels; and  DRS 186 -4: 201 8 
25                 ©RSB 2018 All rights reserved  
 
 g) the gl ass surface shall be 30 cm2 minimum in area and gla ss thickness shall not exceed 2 mm.  
h) Once the glass is broken the alarm shall sound on the floor as well as on the Control and Indicating 
equipments and light shall glow to indicate its operation. The alarm shall be maintained by the control and 
indicting equipment even if someone presses the button subsequently.  
6.2.7  Detectors (smoke) in ventilation ducts  
6.2.7.1  The sampling inlet probe and the ho les in the probe shall be installed , according to the 
manufacturer’s  specifications.  
6.2.7.2  Smoke detectors or probes shall be installed in straight stretches of ductwork, at a distance from 
the nearest bend, corner or junction of at least three times th e width of the duct; and  
6.2.7.3  The suitability of the smoke detector for duct type application shall be evaluated within the 
parameters defined by the manufacturers.  
6.2.7.4  The probe shall cover  at least two third of the wider dimension of the duct and the length of the 
probe  
7 Inspection, testing and maintenance  
7.1 General  
Even a well -designed and properly installed automatic fire alarm system will not be able to render reliable and 
trouble -free service unless high standard of maintenance and supervision are  ensured during the entire 
service period of the system.  
Regular inspections and scheduled preventive maintenance are critical and should include all the components 
of the system.  
7.2 Initial installation inspection tests 
7.2.1 After installation, a visual inspecti on of all the detectors should be made to ensure that they are 
properly sited , mounted and connected .. 
7.2.2 Restorable h eat detectors and restorable elements of combination detectors should be tested  and 
reset  with precaution  by a heat source, such  as a hair dryer, or a shielded heat lamp until it responds  to avoid 
avoid damage of the non -restorable fixed temperature element of a combination rate of rise/fixed temperature 
detector .  
7.2.3 Non-resettable fixed temperature heat detectors which are not  heat-tested should be tested 
mechanically or electrically for fire alarm function.  
7.2.4 Heat detectors with replaceable fusible alloy element should be tested first by removing the element 
to check  whether the contact operate s properly and then reinserti ng them in proper position.  
7.2.5 In periodic testing, heat detectors should be visually examined for damage or other conditions (such 
as heavy coats of paints, etc) likely to interface with the correct operation.   
©RSB 2018All rights reserved                  26 
 
 7.2.6 Each smoke detector should be tested  to initiate an alarm at its installed location with smoke or other 
approved aerosol which demonstrates that the smoke can enter the chamber and initiate an alarm.  
7.2.7 In order to ensure that each smoke detector is within its sensitivity range, it should  be tested using 
either:  
a) a calibrated test method,  
b) a manufacturer’s/supplier’s approved calibrated sensitivity test instrument,  
c) approved control equipm ent arranged to the purpose, or  
d) other approved calibrated sensitivity test method.  
Detectors found to h ave sensitivity outside the approved range should be replaced.  
NOTE  Detector sensitivity cannot be tested on measured using any spray/smoke producing device that administers 
an unmeasured concentration of aerosol/smoke into the detector.  
7.3 Servicing/ periodic al maintenance  
7.3.1 To ensure that regular and reliable servicing/ maintenance of the systems and its components is 
carried out; any of the following methods should be adopted:  
a) through an agreement/contract with the competent contractor who should attend t o the 
maintenance/repair, when necessary, promptly, and  
b) where no such service contract can be entered into for any reason, at least one qualified employee of the 
user with suitable experience of electrical equipment should undergo special training to deal with all 
aspects of basic servicing and maintenance, including routine sensitivity test/checks of the detectors, as 
and when required.  
7.3.2 For institutional occupancies, such as hospitals, hotels, old people’s homes, etc, the  provision should 
be on call at all times and that request over the telephone for emergency service  should be executed 
promptly, within 24 h.  
Servicing arrangement should be made immediately on  completion of the installation whether the premises 
are occupied or not. If the premises a re note  occupied, special precautions should be taken, if necessary, to 
protect the system against damage  by dampness or other causes.  
7.4 Maintenance schedule  
7.4.1  General  
7.4.1.1  It is the responsibility of the user of the equipment to ensure that proper instruc tions are obtained 
from the manufacturer/supplier or installer regarding the routine attention and test procedures.  DRS 186 -4: 201 8 
27                 ©RSB 2018 All rights reserved  
 
 7.4.1.2  The routine to be adopted in individual premises may vary with the use of the premises; 
equipment installed in corrosive or dirty en vironmental conditions will need to be checked more thoroughly 
and at more frequent intervals .  
Care should be taken that all equipments are properly reinstated after testing and t he occupants of the 
premises should be notified of any test of the system th at may result in the sounders being operated.  
7.4.2  Daily attention by user 
A check should be made every day to ascertain that:  
a) the panel indicates normal operation; if not, that any fault indicated is recorded in the log book and is 
receiving urgent attention; and 
b) any fault warning recorded the previous day has received attention  
7.4.3  Monthly  attention by the user 
The following tests should be made every week to ensure that the system is capable of operating under alarm 
conditions:  
a) once a month , at least one trigger  device or end of line switch on one zone circuit should be operate d to 
test the ability of the control and indicating equipment to receive a signal , to sound the alarm and operate 
other warning devices.  
b) If there is more than one zone on a system having a  monitored wiring, each unmonitored zone should be 
tested every month , but without soun ding the alarm more than once.  
c) For systems having monitored wring and up to 13 zones, each zone should be tested in turn but if there 
are more than 13 zones, more than one zone may need to be tested in any month  so that the interval 
between tests on one zone does not exceed 13 weeks.  
 It is preferable that each time a particular zone is tested; a different trigger device shall be  used to initiate the 
test. 
if the operati on of the alarm sounders and/or the transmission of the alarm signal has been prevented by 
disconnection, then a further test should be carried out to prove the final reinstatement to the sounders, and if 
permissible, the alarm transmission circuits;  
d) a visual examination of the battery and connection should be made to ensure that they are in good 
condition. Action should be taken to remedy any defect, including low electrolyte level.  Any defect notice 
should be recorded in the log book and reported to the r esponsible person, and action should be taken to 
correct it.  
7.4.4  Quarterly inspection and test by the user 
The following check -list and tes t sequence should be carried out : 
a) entries in the log book since the previous inspection should be checked and any necessa ry action taken ;  
©RSB 2018All rights reserved                  28 
 
 b) batteries and their connections should be examined and tested to ensure that they ar e in good 
serviceable condition;  
c) where applicable secondary batteries should be examined to ensure that the specific gravity of electrolyte 
in each cell is  correct. Necessary remedial action should be taken and an appropriate entry made in the 
log book. Care should be taken to ensure that hydrometers, vessels, etc., used in the servicing of alkaline 
secondary cells are not contaminated by a cid and vice versa ;  
d) primary batteries, including reserves, should be tested to verify than they are sa tisfactory for a further 
period;  
e) the alarm function of control and indicting equipment should be checked by the operation of a trigger 
device in each zone as described. The operation of alarm sounders and an y link to a remote manned 
centre  should be tested. An ancillary function of the control panel should also be tested where 
practicable. All fault indictors and their circuits should be checked preferably by simulation of fault 
conditions. The Control and i ndicating equipment should be visually inspected for signs of moisture 
ingress and other deterioration; and  
f) a visual inspection should be made that structural or occupancy changes have not affected the 
requirements for th e sitting of trigger devices (manual call points, smoke detectors and heat detectors). 
The visual inspection should also confirm that a clear space of at least 750 mm radius is preserved in all 
directions below every detector, that the detectors are prefer ably sited and that all manual call points 
remain unobstructed and conspicuous.  Any defected should be recorded in the log book and reported to 
the responsible person, and action should be taken to correct it.  
7.4.5  Annual inspection tests 
The following checks a nd tes t sequence should be carried out : 
a) the instruction and  test routines detailed in 7.4.4 a) - f); 
b) operation of at least 20 % of the detectors in an installation should be checked each year and the 
selection should be done in such a way that all the dete ctors in an installation shall have been checked 
once in every 5 years - replacement by a new one;  
c) each detector should be checked for correct operation using specified test  equipment and method, except 
non-resettable detectors. The checks to be carried out  are specified in 7.2.2 - 7.2.5 in respect of heat 
detectors and 7.2.6 and 7.2.7 in respect of smoke detectors;  
d) visual inspection should be mad e to confirm that al l cable fittings and equipment are secure, u ndamaged 
and quantity protected;  
e) at least once in  every three year at the annual inspection, the electrical installation should be tested. Any 
defect should be recorded in log book and suitable re medial action should be taken;  and 
f) on completion of the annual inspection, the entry should be made in regist er in respect of defects found. 
After the defects are rectified the entries should then again be made.  DRS 186 -4: 201 8 
29                 ©RSB 2018 All rights reserved  
 
 7.5 General points about detectors  
It is essential (particularly for installations involving life hazard) to ensure specified range of sensitivity of the 
detectors being installed and that the correct degree of sensitivity is maintained. Users should satisfy 
themselves on this point. Sensitivity range should be checked on equipment as already specified. It is 
essential to apply frequent sensitivity checks and routine tests as prescribed in the standard  so that the 
correct sensitivity levels/degree is maintained during the entire service span of  the installation (see 7.2.7).  
7.6 Cleaning and maintenance  
7.6.1 Dete ctors require periodic cleaning to remove dust or dir t that has accumulated. The frequency of 
cleaning depends upon the type of detector and local ambient conditions. In any case, the interval should not 
exceed a period of 3 months.  
7.6.2 For each detector, the cleaning checking, operating and sensitivity a djustment should be attempted 
only after consulting manufacturer’s instructions. These instructions should detail methods such as creating 
vacuum to remove clause dust and insects, and cleaning heavy greasy deposits, following partial disassembly 
or the cl eaning or the washing of detectors to remove contamination, the sensitivity test requirements in 
accordance with the relevant clauses should be performed.  
7.7 Tests following an alarm or fire 
All detectors suspected of exposure to a fire condition should be te sted in accordance with the provisions 
contained in this standard  pertaining to annual inspection tests. In addition, a visual check of the battery 
charger should be carried out to ensure perfect serviceability. However, a check should be made to the exten t 
of damage, if any, to the cables and other components and also the opera tion of the systems as a whole.  
7.8 System disconnection during testing  
Care should be taken to minimize the disruption of the normal use of the building by alarm sounding during 
detecto r testing. If detectors are removed for testing or servicing, replacement detectors should be provided.  
7.9 Spares  
It may not be necessary to keep spares in premises other than covers for manual call point and fuses and 
other essential spares which should be w orked out based on installation.   
©RSB 2018All rights reserved                  30 
 
 Annex  A 
(informative)  
 
Merits and relative demerits of various types of detectors  
Type of d etector  Suitability and m erits  Unsuitabil ity and d emerits  
Smoke detectors  
(General)  Slow burning fires, smoldering fires most of the 
areas  where principal fire hazard is not from 
the presence of flammable liquids. Fires 
involving wood, paper, textile, etc, in earlier 
stages  Not sensitive for clean burning fires which 
does not produce smoke particles; areas in 
which the principal fire hazard is the 
presence of flammable liquids or gases, that 
produce little smoke during a fire  
Ionization smoke detector  General purpose smoked detector ━ better for 
smoke containing small particles, such as 
rapidly burning fast flaming fires  Less sensitive to th e larger particles found in 
optically dense smoke of similar mass, such 
as can result from smoldering fires including 
those involving polyurethane  foam, or 
overheated PVC. Areas subject to smoke, 
steam, dust or dirt during normal use. 
Usages of these detec tors are on way to 
phase out due to radiation problems.  
Optical smoke detector  General purpose smoke detector ━ better for 
smoldering fires  Area subject to smoke, steam, dust or dirt 
during normal use.  
Light scattering type (smoke 
detector)  Sensitive to light colo ured smoke  Less sensitive to very dark smoke which 
absorbs light rather than scattering it  
Photo -thermal multi -criteria 
detector  General purpose detector ━ good for 
smoldering and fast flaming fires, optically 
dense smoke  Areas subject to smoke, steam, dust or dirt 
during normal use, less sensitive to small 
particles found in clean burning fires that 
produce little visible smoke.  
Optical beam smoke detector   Large and high rooms, open plan spaces with 
relatively high ceilings (for example 
warehouses), fires not involving production of 
smoke (with built in thermal turbulence 
detection). Suited for applica tions where 
anticipated fire would produce black smoke. 
Sensitive to cumulative obscuration presented 
by a smoke field.  Areas subject to smoke, steam, dust or dirt 
during normal use. Less sensitive to colour 
of smoke. Cannot detect clean colourless 
smoke.  
Aspirating (air -sampling) type 
smoke detector  They are suitable for use where usage of other 
types of smoke detectors present difficulties, 
such as aesthetics, height and temperature of 
the enclosure. Sampling points can be located 
almost anywhere unlike detectors which 
cannot be installed on walls, storage racks, 
machinery space, floor voids, etc. Each 
sampling point is a detector itself. Suitable for 
cold storage. Higher sensitivity levels, ease of 
installation and most suitable for protection of 
high va lue and critical equipment.  Air-sampling detectors are not suitable if the 
air movement due to HVAC requirements is 
outside the range specified by the 
manufacturers  
Hear detectors (general)  Clean burning fires, such as those involving 
certain flammable li quids. Areas subject t to 
smoke, steam, dust or dirt during normal use, 
fires that evolve heat and flame rapidly, 
suitable for rooms where heat producing 
equipment like kitchen, pantry, boilers, DG 
sets, etc, are installed/used.  Unlikely to respond to smo ldering and slow 
burning fires, unsuitable for high value areas 
where a small fire can cause major damage. 
Areas in which presence of smoke can pose 
a potential threat to the occupants.  DRS 186 -4: 201 8 
31                 ©RSB 2018 All rights reserved  
 
  
Rate -of-rise heat detector  Areas subject to smoke, steam, dust or dir t 
during normal use.  Areas subject to rapid changes of 
temperature or temperatures over 43°C  
Fixed temperature heat 
detector  Areas subject to smoke, steam, dust or dirt 
and rapid changes of temperature during 
normal use.  - 
Multi -sensor fire detector  Comb ines the characters of two types of 
detectors, each of which responds to different 
physical and/or chemical characteristics of fire. 
The purpose of combining sensors in this way 
is to enhance the performance of the system in 
detection of fire or its resist ance to at least 
certain categories of false alarms or both. 
There is significant potential for reduction of 
many types of false alarm. It is also possible to 
disable an individual sensor depending on the 
circumstances at the place of installation.  - 
Flam e detectors (general)  High ceiling, open spaced buildings like 
warehouses/aircraft hangers, outdoor/semi -
outdoor areas, areas where rapidly developing 
flames occur like petrochemical/refinery/gas 
installations/paint shops, etc.  Not sensitive to smoldering/ slow burning 
fires and hence cannot be called general 
purpose detectors. Not suitable for the type 
of fires where flaming can occur only after 
substantial release of smoke.  
Intra red flame detector  Same as above, these detectors penetrate 
through smoke we ll. High speed, moderate 
sensitivity. Suitable for indoor/outdoor 
applications;  Affected by temperature range in the vicinity, 
subject to false alarms caused by blackbody 
radiation like heaters,, incandescent lamps, 
halogen lamps., flickering sunlight, etc  and  
hence usage in such areas to be avoided. 
Sensitive to IR radiation from sources like 
any hot surface, ovens, furnaces, lamps, 
etc. also and due care shall be taken while 
installation.  
Ultraviolet flame detector  Highest speed, highest sensitivity. Su itable for 
indoor applications  Not sensitive for high ceiling, etc, as the 
radiation from fire is attenuated by smoke. 
Random UV radiation from sources, such as 
lightning, are welding, etc, can cause f alse 
alarms and hence usage in such areas to be 
avoided  Blinded by thick smoke and oil 
vapours on optics.  
IR/IR  flame detector  High speed, moderate sensitivity, low false 
alarm rate, most suitable for chemical and 
hydrocarbon flame in particular as signal 
received is processed at two sensors. Suitable 
for ind oor/outdoor applications.  Somewhat affected by temperature range in 
the vicinity, suffer from atmospheric 
attenuations, especially on long range 
detection applications.  
UV/IR detector  Highest speed, highest sensitivity and low 
false alarm rate.  Blinded by  thick smoke and oil vapours on 
optics. Suitable for indoor/outdoor 
applications.  
IR/IR/IR  (IR3)  
 Highest speed, highest sensitivity, lowest false 
alarm rate. Most suitable for chemical and 
hydrocarbon flames in particular as received  
signal is processed at three sensors.  No significant disadvantages. Suitable for 
indoor/outdoor applications  
 
Spark detector   Spark Detectors are suitable for detection of 
sparks some types of duct or conveyor, 
monitoring the fuel, etc., as it passes by. 
Usually, it is neces sary to enclose the portion 
of the conveyor where the detectors are 
located, as these devices generally require a 
dark environment.  Extraneous sources of radiant emissions 
that have been identified as interfering with 
the stability of spark detectors inc lude: (a) 
ambient light (b) electromagnetic 
interference (EMI. RFI), and (c) electrostatic 
discharge in the fuel stream.   
©RSB 2018All rights reserved                  32 
 
  
 
Ember detector  Same as above except that ember detectors 
can also detect fires in lit environment like coal 
conveyors, etc.  Detector w indow clarity shall always be 
ensured.  
Linear heat sensing cables  Cables tunnels, trays and vaults, material 
conveyors, bulk storage multi -racked areas, 
rim seals of floating roof tanks storing 
hazardous chemicals, and a few other special 
occupancies  Not suitable at all application other than 
what is specified  
 
 DRS 186 -4: 201 8 
33                 ©RSB 2018 All rights reserved  
 
  RS 186 -4: 2013  
ICS 13.220.40  
 
 
©RBS 2013  All right s reserved