ASAP
Amity School of Architecture &
Planning
B. Arch Semester VII
Building Services and Engineering-III
(ARCH409)
Lecture on
Fire Suppression and Fire Fighting
Rajeev Sinha
rsinha2@amity.edu 1
Building Services and Engineering-III ASAP
Student Learning Outcomes
Students will be able to learn:
✓ Fire suppression systems in buildings
✓ About fire detection and fire fighting systems
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 2
Building Services and Engineering-III ASAP
METHODS OF FIRE EXTINGUISHMENT
Triangle of fire states that three factors are essential for combustion,
namely;
• Presence of a fuel, or combustible substances
• Presence of oxygen (usually as air) or other supporter of
combustion; and
• Attainment and maintenance of a certain minimum temperature.
• Fire extinction, consists of the limitation or elimination of one or
more of these factors
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 3
Building Services and Engineering-III ASAP
Methods of extinguishing fire
may be classified under the
following headings:
(a) Starvation
for the limitation of fuel)
(b) Smothering / Blanketing for
the limitation of oxygen)
(c) Cooling for the limitation of
temperature)
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 4
Building Services and Engineering-III ASAP
Figure: Fire Extinguishment (Fourth Factor)
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 5
Building Services and Engineering-III ASAP
1. Starvation
Extinction of fire by starvation is applied in the following ways:
i. By removing combustible materials from the neighbourhood of
the fire.
Examples of these are; the demolition of buildings to create
a fire stop; counter-burning in forest fires;
i. By removing the fire from the neighbourhood of combustible
material as, for instance, pulling apart a burning haystack or a
thatched roof;.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 6
Building Services and Engineering-III ASAP
2. Smothering
• If the oxygen content in the neighbourhood of burning material
can be sufficiently reduced, combustion will cease.
• Preventing the access of fresh air to the seat of the fire, and
reduce the oxygen content in the confined atmosphere until it
the fire extinguishes itself.
• Application of the smothering method is the use of foam.
• It forms a viscous coating over the burning material and limits,
the supply of air. It also tends to prevent the formation of
flammable vapour.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 7
Building Services and Engineering-III ASAP
Smothering contd….
• Application of a cloud of finely divided particles of dry powder
• Usually sodium bicarbonate, from a pressurised extinguisher is
used to extinguish the fire
• The vigorous discharge of an inert gas in the immediate vicinity of
the fire may so reduce the oxygen content of the atmosphere
that combustion cannot be maintained.
• Carbon-di-oxide and nitrogen are familiar examples of this.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 8
Building Services and Engineering-III ASAP
3. Cooling
• Application of a jet or spray of water to a fire is invariably based
on this simple but fundamental principle.
• Cooling principle in fire extinction is the one most commonly
employed, forming the basis of the application of water and
other liquids to burning materials.
• Water is an excellent fire extinguishing agent
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 9
Building Services and Engineering-III ASAP
Tetrahedron of Fire (Fourth factor
contributing to fire)
• Fire scientists have found that there is a
fourth constituent in all flaming fires which
plays a vital part in the fire growth and
sustenance
• It is the unbroken or uninhibited chain
reaction.
• It comes into play only in flaming mode of
combustion which is normally applicable in
the case of flammable liquids and gases.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 10
Building Services and Engineering-III ASAP
Tetrahedron of Fire (Fourth factor contributing to fire)
• The principle applied for fire extinguishment is known as breaking
the chain reaction which is achieved by removal/ suppression of
the free radicals.
• The extinguishing agents used for this purpose are halogenated
hydrocarbons or halons/halon alternatives and several types of dry
chemical powders.
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Building Services and Engineering-III ASAP
Fire Communication: Detection and Alarm System
Fire Alarm System
• Fire Alarm System is designed to alert us to an emergency so that
we can take action to protect ourselves, staff and the general
public.
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Building Services and Engineering-III ASAP
• The “Brain” of the fire detector system
is the Fire Alarm Control Panel.
• It is the central hub for all of the
detector signals to be wired to and
provides a status indication to the
users.
• The unit can also be set up to simulate
an alarm for use in routine Fire and A Fire alarm panel
evacuation drills.
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Building Services and Engineering-III ASAP
Different Types of Alarm Detectors
• At the core of a fire alarm system are the detection devices.
• From sophisticated intelligent smoke detectors to simple manually
operated break glass units
• These can be divided into following:
1. Heat detectors
2. Smoke detectors
3. Carbon Monoxide detectors
4. Multi-sensor detectors
5. Manual Call Points
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 14
Building Services and Engineering-III ASAP
Heat Detectors
1. Heat Detectors detect fires with and without smoke development.
2. This type of detector is useful where rapid fire development and
high temperatures might be expected
3. Heat detectors are also used when smoke detectors cannot be
deployed due to environmental influences.
Heat Detectors
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Building Services and Engineering-III ASAP
• Heat detectors can work on a fixed temperature basis, where it will
trigger an alarm if the temperature exceeds a pre-set value.
• They can work on the rate of change in temperature.
• Detectors contain a eutectic alloy which is heat sensitive.
• When a certain temperature is reached the alloy turns from a solid
to a liquid which in turn triggers the alarm
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 16
Building Services and Engineering-III ASAP
Smoke Detectors
There are three basic types of smoke detectors including:
1. Ionization type
2. Light Scattering type
3. Light Obscuring type
1. Ionization Type Smoke detector
• It contains two chambers.
• The first is used as a reference to compensate for changes in
ambient temperature, humidity or pressure.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 17
Building Services and Engineering-III ASAP
• The second chamber contains a radioactive source, which ionizes
the air passing through the chamber where a current flows
between two electrodes.
• When smoke enters the chamber the current flow decreases.
• This drop in current flow is used to initiate an alarm.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 18
Building Services and Engineering-III ASAP
2. Light Scattering Type
• A photocell and light source are separated from each other by a
darkened chamber such that the light source does not fall on the
photocell.
• The passage of smoke into the chamber causes the light from the
source to be scattered and fall on the photocell.
• Photocell output used to initiate an alarm.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 19
Building Services and Engineering-III ASAP
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 20
Building Services and Engineering-III ASAP
3. Light Obscuring Type
• In this type of detector, smoke interferes with a light beam between
a light source and photocell.
• The photocell measures the amount of light it receives.
• Variation in photocell output, is used to initiate an alarm.
• This type of detection can be used to protect large areas with the
light source and photocell positioned some distance apart.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 21
Building Services and Engineering-III ASAP
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 22
Building Services and Engineering-III ASAP
Manual Call point
• A Manual Call Point or Break Glass Call Point is a device which
enables personnel to raise the alarm by breaking the frangible
element on the fascia; this then triggers the alarm.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 23
Building Services and Engineering-III ASAP
Different Types of Fire Alarm Systems
• There are four main alarm systems
1. Conventional
2. Addressable
3. Intelligent
4. Wireless
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Building Services and Engineering-III ASAP
1. Conventional
• Physical cabling is used to interconnect several call points and
detectors, the signals from which are wired back to the main
control unit.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 25
Building Services and Engineering-III ASAP
• Call points and detectors are arranged in “Zones” to simplify
locating the cause of the alarm
• Each zone is indicated at the Fire Alarm Control Panel either
with an indicator lamp, a text display or in some cases both.
• This is important for both the fire brigade and general building
management.
• More divisions are made in a building into a number of zones,
becomes more accurate locating the alarm trigger
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 26
Building Services and Engineering-III ASAP
2. Addressable
• The detection principle of an Addressable System is the same as
a Conventional System except that each detector is given a set
Address (usually by means of a dip-switch)
• The Control Panel then determines exactly which detector or
call point has initiated the alarm.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 27
Building Services and Engineering-III ASAP
• The detection circuit is wired as a loop and up to 99 devices
may be connected to each loop.
• It is common for the loop to be fitted with Loop Isolation Modules
so that the loop is sectioned in order to ensure that a short circuit
or single fault will only cause the loss of a small part of the
system; allowing the rest of the system to function normally.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 28
Building Services and Engineering-III ASAP
3. Intelligent
• In an Intelligent Fire Alarm system, each detector effectively
incorporates its own computer
• It evaluates the environment around it and communicates to
the Control Panel whether there is a fire, fault or the detector
head needs cleaning.
• Essentially Intelligent Systems are far more complex and
incorporate far more facilities than Conventional or
Addressable Systems.
• Their primary purpose is to help prevent the occurrence of false
alarms.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 29
Building Services and Engineering-III ASAP
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 30
Building Services and Engineering-III ASAP
4. Wireless
• These are an effective alternative to traditional wired fire alarm
systems for all applications.
• They utilize secure, license-free radio communications to
interconnect the sensors and devices with the controllers.
• It is a simple concept, which provides many unique benefits
and is a full intelligent fire detection system without the need for
cabling.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 31
Building Services and Engineering-III ASAP
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 32
Building Services and Engineering-III ASAP
1. Assignment
• Write a report on Smoke detectors, Heat detectors, Multi sensor
detectors and flame detectors. Also write about the optimum
spacing between detectors as required in a building.
Rajeev Sinha, Associate Professor, ASAP, rsinha2@amity.edu 33
Building Services and Engineering-III ASAP
References
https://realpars.com/fire-alarm-system/
https://www.securiton.com/en/products/fire-detection.html
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