ICS 13.220.40  
 
Reference number  
DRS 186 -4: 20 23 
© RSB 2023  
  
 RWANDA 
STANDARD  DRS 
186-4  
 
Third  edition  
2023-mm-dd 
 
Fire safety for buildings — Code of 
practice  —  
Part 4: Selection, installation and 
maintenance of automatic fire detection 
and alarm system  
   
DRS 186 -4: 20 23 
©RSB 2023 - All rights reserved                  ii 
 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 2023  
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  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  
ePortal: www.portal.rsb.gov.rw   DRS 186 -4: 20 23 
iii                ©RSB 2023 - All rights reserved  
 Contents  Page  
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative reference  ................................ ................................ ................................ .....................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Requirements  ................................ ................................ ................................ ..............................  11 
4.1 General  ................................ ................................ ................................ ................................ ........  11 
4.2 Detection zones  ................................ ................................ ................................ ..........................  11 
4.3 Detection zones that contain non-addressable automatic detection system  ......................  12 
4.4 Size and number of zones  ................................ ................................ ................................ .........  13 
5 Automatic fire detectors  ................................ ................................ ................................ ............  13 
5.1 Heat detectors  ................................ ................................ ................................ .............................  13 
5.2 Smoke detectors  ................................ ................................ ................................ .........................  14 
5.3 Choice of fire detector  ................................ ................................ ................................ ...............  15 
6 Sitting of fire detectors  ................................ ................................ ................................ ..............  17 
6.1 General  ................................ ................................ ................................ ................................ ........  17 
6.2 Sitting and spacing of detectors (common to all types of smoke and heat detectors)  ...... 18 
7 Inspection, testing and maintenance  ................................ ................................ .......................  24 
7.1 General  ................................ ................................ ................................ ................................ ........  24 
7.2 Initial installation inspection tests  ................................ ................................ ............................  24 
7.3 Servicing/periodical maintenance  ................................ ................................ ............................  25 
7.4 Maintenance schedule  ................................ ................................ ................................ ...............  25 
7.5 General points about detectors  ................................ ................................ ................................  27 
7.6 Cleaning and maintenance  ................................ ................................ ................................ ........  28 
7.7 Tests following an alarm or fire  ................................ ................................ ................................  28 
7.8 System disconnection during testing  ................................ ................................ ......................  28 
7.9 Spares  ................................ ................................ ................................ ................................ ..........  28 
Annex  A (informative)  Merits and relative demerits of various types of detectors  .........................  29 DRS 186 -4: 20 23 
©RSB 2023 - All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared by Technical Committees and approved by Rwanda 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 committees are ratified by members of RSB Board of Directors 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, reference was made to the following standard:  
IS 2189:2008; Selection, installation and maintenance of automatic fire detection and alarm system - Code of 
practice   
IS 11360, Specification 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.  
The assistance delivered from the above source is hereby acknowledged with thanks.  
This third edition cancels and replaces the second edition (RS  186-4: 2018), Clause 1 and Clause 4 which have 
been technically revised.  
DRS 186 consists of the following parts, under the general title Fire safety  for buildings — 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 requirements and personal hazard  
  DRS 186 -4: 20 23 
v                ©RSB 2023 - All rights reserved  
 Committee membership  
The following organizations were repre sented on the Technical Committee on Fire safety  (RSB/TC 28) in the  
preparation of this standard.  
Bank of Kigali (BK)  
City of Kigali  
CrossTech  
Institution  of Engineers Rwanda (IER)  
Ministry of Infrastructure (MININFRA)  
PRIME Insurance  Ltd 
Rwanda Defence Force (RDF)  
Rwanda Energy Group (REG)  
Rwand a Environment Management Authority (REMA) 
Rwanda Housing Authority (RHA)  
Rwanda National Police (RNP)  
Rwanda Social Security Board (RSSB)  
Sanlam  
Société Rwandaise d’Assurance (SONARWA)  
University of Rwanda - College of Science and Technology  (UR - CST)  
Rwanda Standards Board (RSB) – Secretariat  
 DRS 186 -4: 20 23 
1                ©RSB 2023 - All rights reserved  
 Fire safety for building s — Code of practice  — Part 4: Selection, installation 
and maintenance of automatic fire detection and alarm system  
1 Scope  
1.1 This Draft Rwanda S tandard covers the minimum requirements for planning, design, selection, installation 
and maintenance of fire detection and alarm systems . 
1.2 It covers systems capable of providing signals to alarm in the event of a fire, to initiate  operation s of ancillary 
services, such as fire extinguishing systems 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 . 
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  (applicable part s) 
3 Terms and definitions  
For the purposes of this standard, the following terms and definitions apply.  
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 
addressable device  
fire alarm system component with discrete identification that can have its status individually  identified or that is 
used to indiv idually 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 
control and indicating equipment   
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 3.5 
air sampling -type detector  
detector that consists 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 the 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 
analogue  initiating device (sensor)  
initiating device that transmits a signal indicating varying degrees of conditions as contrasted  with a conventional 
initiating 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, condition 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  
3.12 
authority having jurisdiction  
organization, office, or individual responsible for approving equipment, materials, an installation  or a procedure  DRS 186 -4: 20 23 
3                ©RSB 2023 - All rights reserved  
 3.13 
automatic 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 initiating 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 space 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 examples are a combination of a heat detector with a  smoke detector or a combination 
of rate -of-rise and fixed -temperature heat detector   
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 3.20 
commissioning  
process by which it is determined that the installed system  meets the defined requirements  
3.21 
control 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 assistance t o emergency services.  
3.22 
control unit  
system component that monitors inputs and controls outputs th rough various types of circuits  
3.23  
detection zone  
sub-division of the protected premises such that the occurrence of fire within if will be indicated 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 energy due to either its temperature or the process of  combustion on 
its surface  DRS 186 -4: 20 23 
5                ©RSB 2023 - All rights reserved  
 3.28 
emergency voice/Alarm communications  
dedicated manual or automatic facilities for originating and distributing voice instructions, as well as  alert and 
evacuation signals pertaining to a fire emergency,  to the occupants of a building  
3.29 
evacuation  
withdrawal of occupants from a building  
3.30 
evacuation 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 audible 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 supplied 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 firefighting 
organization or to automatic extinguishers;  
c) is used to monitor automat ically the correct functioning of the system; and   
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 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, automatic 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 alarm  for fire.  The 
system may also in itiative other ancillary action  
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 temperature 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  DRS 186 -4: 20 23 
7                ©RSB 2023 - All rights reserved  
 3.42  
flame detector 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 that detects  either  abnormally high temperature, rate of temperature rise, or both  
3.45 
ionization 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  
Note 1 to entry:  It is suggested 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  
manual call point  
manually operated device used to initiate an alarm signal. It can be manual alarm system or part  of automatic 
alarm system   
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 3.49 
mimic panel  
panel in which he floor/area plans of the premises are projected 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  
photoelectric light 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 enter the light path, some of the light is scattered and some is absorbed thereby 
reducing the light reachi ng the receiving sensor. The light reduction signal is processed and used to convey an 
alarm condition when it meets preset criteria  
3.52 
photoelectric 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 
condition when it meets preset criteria  
3.53 
point detector   
detector which responds to the phenomenon sensed i n the vicinity of a fixed point  
3.54  
power supply  
source of electrical operating power, including the circuits and terminals connecting it to the  dependent system 
components  
3.55 
projected beam -type detector  
type of photoelectric light obscuration smoke detector wherein th e beam spans the protected area  DRS 186 -4: 20 23 
9                ©RSB 2023 - All rights reserved  
 3.56 
protected 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 radio channel to two or more radio alarm repeater station receivers (RARSR) and that are annunciated 
by a radio alarm supervising stati on 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   
shapes 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 
stopping ceiling   
ceiling that that has a slope   
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 3.64 
smoke detector  
device that detects visible or invisible particles of combustion  
3.65  
smooth ceiling  
ceiling surface uninterrupted by continuous projections, such as solid joists, beams, or ducts, extending more 
than 100 mm below the ceiling surface  
3.66    
spacing  
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 normally 
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 response  time 
3.70  
standby 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.  DRS 186 -4: 20 23 
11                ©RSB 2023 - All rights reserved  
 3.72   
zone 
area or space that has a group of automatic and/or non -automatic fire detection devices for which  there is a 
separate common display  in the control and indicting equipment.  
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 any other system.  
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 Detection zones  
4.2.1  General  
4.2.1.1  In most of the buildings an alarm of fire may initiate a number of different activities, for example, 
provision of assistance, commencement of firefighting 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 responding 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, 
zoning 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.   
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 4.3 Detection zones that contain non -addressable automatic detection system  
4.3.1 Requirements for detection zones that contain non -addressable automatic detection system are given 
below:  
a) the floor area of a single zone shall not exceed 2 000 m2; 
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 restricted 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 b e 
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 detectors 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 order 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 careful  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, no zone shall be designed to include areas with more than one type of 
occupancy;  DRS 186 -4: 20 23 
13                ©RSB 2023 - All rights reserved  
 s) areas with special risks shall be designed as separate zone within large protected area; and   
t) where a zone extends beyond a single compartment, the zone boundaries shall be the boundaries of the fire 
compartments  
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  
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 number of zones shall als o apply to the systems protect ed with manual call points only.  
4.4.2  To prevent misleading indication of the position of the fire, th e manual call points shall be indicated in the 
control equipment  separately from the detectors in zones, which are protected, by both detectors and manual call 
points.  The circuits for the d etectors and call points shall be different in case of conventional detection systems.  
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 detector 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 type 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 .  
©RSB 2023 - All rights reserved                  14 
 5.1.1.3  Linear heat sensing cables  can be broad ly divided into two categories; d igital or analogue , depending 
upon the principle b y which the sensing cable registers a change in temperature.  Digital sensor consists of two 
core cable in which the conductors are separated by a heat sensitive insulator. When a specified temperature 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. Hea t 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 dete ctors include the following:  
a) ambient light ; and  
b) electromagnetic interference (EMI, RFI); and  electrostatic discharge in the fuel stream.  
5.2.2 All Spark/Ember detectors shall 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 µm to 260 µm which is insensitive to visible light.  
5.2.2.2  All UV Frame detectors shall meet the requirements of the relevant part of ISO 7240.  DRS 186 -4: 20 23 
15                ©RSB 2023 - All rights reserved  
 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 participate in the flaming combustion emit ultraviolet ration to some degree during flaming 
combustion, whereas only carbon -containing fuels emi t 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 flaming fires can occur, such as aircraft hangers, petrochemical producti on 
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 smoke, 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) performance  of the contents  for each part of the building with respect to their susceptibility  to heat, smoke 
and water damage  
b) processes taking place or planned  to take place in building; and   
c) 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.  
5.3.1.5 It is possible to reduce 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 disturbances on the 
premises.   
©RSB 2023 - All rights reserved                  16 
 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 
compromise. Final choice will depend primarily on  the factors listed below.  However, other factors such as cost, 
suitability for the environment and maintenance requirements shall also need to be considered . 
a) speed of response required;  
b) need to m inimize false alarms; and  
c) nature of the fire hazard.  
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 provide 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 give 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 %, 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 emanate 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 detectable 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; 
b) ensure operation of detectors on escape route before optical 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 premises  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 example,  kitchen 
and pantry, etc…) is used in closets or other unsupervised spaces compact areas with low  value contents.  DRS 186 -4: 20 23 
17                ©RSB 2023 - All rights reserved  
 5.3.3  Property safety installation  
5.3.3.1 Installation of fire detectors enables early detection and easy extinction by reducing delay between 
ignition and start of firefighting measures . It is important to minimize incidence of false alarms p articularly when 
detectors are hooked  up to actuate means of automatic extinction. Automatic extinction should generally be 
initiated only on confirmation 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 ceiling 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 in 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.  
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 t o 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 diluting 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.) ;  
©RSB 2023 - All rights reserved                  18 
 d) air movement (within the protected area below the detectors) ; 
e) supply air inlets (in the vicinity of detectors), HVAC systems (with high air change rates) ; and 
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 smoke 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 detector.  
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 detectors.  
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 structural 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.  
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. Addi tional 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 protected 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 landing within the staircase.  DRS 186 -4: 20 23 
19                ©RSB 2023 - All rights reserved  
 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 decoration 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 more 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 fal se 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 independent 
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, howeve r, 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 parameter(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 
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 adopted from charts of Fire Detecting Institute of America, adopting the parameters 
mentioned in 7.3 (nearest/rounded off values).   
©RSB 2023 - All rights reserved                  20 
 NOTE 2 It is presumed that ‘No chance’ means ‘No change’.  
 
6.2.1  Compensation to the spacing of detectors.  
6.2.1.1  Height consideration  
Spacing of 7.5 m in length for smoke detectors i s 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 for ceiling heights between 5 m and 7 m, 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.  
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 least 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   
Air changes/h 
Inside block  Multiplying factor for modified  
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 
 DRS 186 -4: 20 23 
21                ©RSB 2023 - All rights reserved  
 6.2.2  Additional requirements for optical beam detectors  
Optical beam -type detectors shall be sited in such a way that 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 the 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 side 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;  
e) the path length of the optical beam shall be within the limits  specified by the manufacturers;  
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 shall 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 beam 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 application within the 
protected area installation shall comply with the manufacturer’s specifications;  
c) maximum air sample transport time from the farthest sampling point shall not exceed 120 s; and  air 
sampling detectors shall give a trouble signal if the airflow within the enclosure is outside the 
manufacturer’s specified range.   
©RSB 2023 - All rights reserved                  22 
 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.  
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 and 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 distance from 
the fire will, therefore, lead to an incre ase 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 least 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 fire;  
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;  DRS 186 -4: 20 23 
23                ©RSB 2023 - All rights reserved  
 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.  
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 ta king 
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 be tween 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 inversely 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 engineering 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;   
©RSB 2023 - All rights reserved                  24 
 f) manual call point shall be located preferably near entry to staircases at various levels; and  
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 C ontrol and Indicating 
equipment  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 holes 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 the 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  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 reinserting them in proper position.  DRS 186 -4: 20 23 
25                ©RSB 2023 - All rights reserved  
 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.  
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 have 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/periodical 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 to 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 basi c 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 are 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 instructions are obtained 
from the manufacturer/supplier or installer regarding the routine attention and test procedures.   
©RSB 2023 - All rights reserved                  26 
 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 environmental conditions may be checked more thoroughly and at more frequent 
intervals .  
Care sho uld be taken that all equipment  are properly reinstated after testing and t he occupants of the premises 
should be notified of any test of the system that 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 a ttention 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 operation 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 c ircuits;  
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 responsible 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 necessary action taken ; 
b) batteries and their connections should be examined and tested to ensure that they ar e in good serviceable 
condition;  DRS 186 -4: 20 23 
27                ©RSB 2023 - All rights reserved  
 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 fau lt 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 the sitting of trigger devices (manual call points, smoke detectors and heat detectors). 
The visual inspection should also confirm that a clear sp ace of at least 750 mm radius is preserved in all 
directions below every detector, that the detectors are preferably 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 and tes t sequence should be carried out : 
a) the instruction and  test routines detailed in 7.4.4  
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 detectors 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 clause 7 .2.2 - 7.2.5 in respect of 
heat detectors and clause 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 s 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 register in respect of defects found. 
After the defects are rectified the entries should then again be made.  
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. Sensit ivity 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 are maintained during the entire service spa n of the installation as specified in clause 7.2.7.   
©RSB 2023 - All rights reserved                  28 
 7.6 Cleaning and maintenance  
7.6.1 Dete ctors require periodic cleaning to remove dust or dirt 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 adjustment 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 cl eaning heavy greasy deposits, following partial disassembly or the 
cleaning 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 tested 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 extent 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 
detector 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 worked out based on installation.  DRS 186 -4: 20 23 
29                ©RSB 2023 - All rights reserved  
 Annex  A 
(informative)  
 
Merits and relative demerits of various types of detectors  
Type of detector  Suitability and merits  Unsuitability and demerits  
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 the 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. U sages of these detectors 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 coloured 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 
applications where anticipated fire would produce 
black smoke. S ensitive 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 value 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 liquids. Areas subject t to 
smoke, steam, dust or dirt during normal use, Unlikely to respond to smoldering and 
slow burning fires, unsuitable for high 
value areas where a small fire can cause  
©RSB 2023 - All rights reserved                  30 
 fires that evolve heat and flame rapidly, suitable 
for rooms where heat producing equipment like 
kitchen, pantry, boilers, DG sets, etc, are 
installed/used.  major damage. Areas in which presence 
of smoke can pose a potential threat to 
the occupants.  
Rate -of-rise heat detector  Areas subject to smoke, steam, dust or dirt 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  Combines 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 resistance to at least certain 
categories of false alarms or both. There is 
significant potential for red uction of many types of 
false alarm. It is also possible to disable an 
individual sensor depending on the 
circumstances at the place of installation.  - 
Flame 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 well. 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. Suitable 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 false 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 indoor/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, Extraneous sources of radiant 
emissions that have been identified as DRS 186 -4: 20 23 
31                ©RSB 2023 - All rights reserved  
 monitoring the fuel, etc., as it passes by. Usually, 
it is necessary to enclose the portion of the 
conveyor where the detectors are located, as 
these devices generally require a dark 
environment.  interfering with the stability of spark 
detectors include: (a) ambient light (b) 
electromagnetic interference (EMI. RFI), 
and (c) electrostatic discharge in the fuel 
stream.  
Ember detector  Same as above except that ember detectors can 
also detect fires in lit environment like coal 
conveyors, etc.  Detector window 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 -5: 20 23 
 
Price based on 3 1 pages  
©RSB 2023 - All right s reserved