Fire Detection & Alarm System28-08-20 .pdf

REFLECTION
&
DIFFUSION
OF SOUND

FIRE FIGHTING SYSTEM
• Fire is a reaction giving off heat, light, and
smoke;
• The three essential elements for a fire to occur
are: heat, fuel, and oxygen.
• These three elements form what is called the
fire triangle. Removing any one of these
components and a fire cannot occur, or
continue.
5/19/2021 BUILT ENVIRONMENT 1

FIRE TRIANGLE

Sources of Ignition
•Friction
•Hot surfaces
•Electrical shorts and electrical equipment
•Static electricity
•Tools
•Open flames
•Heating systems

Classes of Fire
Classification according to type of material under fire:
Class A fires; involving solid materials - paper, wood, fabrics and so
on. Cooling by water or spray foam is the most effective way of
extinguishing this type of fire.
Class B fires; involving flammable liquids such as petrol, oils, fats;
foam and dry powder extinguishers should be used.
Class C fires; which are fuelled by flammable gases such as natural
gas, butane and so on. Priority must be given to shutting off the
source of fuel and the fire should be tackled with dry powder.
Class D metal fires; involving metals such as aluminum and
magnesium; special powders are required in such situations.
Class E fires; in which live electrical equipment is involved (sometimes
known as ‘electrical fires’). Non-conducting agents such as powder
and carbon dioxide must be used

Classification according to the hazard of occupancy
•Extra light hazard; Non-industrial occupancies like hospitals, hotels,
libraries, office buildings, schools, museums,
nursing homes, and prisons.
•Ordinary hazard; Commercial and industrial occupancies involving
handling combustible materials. Under this class
there are four groups of occupational fire hazards:
Light group; butcheries, breweries, restaurants, coffee shops, and cement works
Medium group; bakeries, laundries, garages, potteries, engineering shops
High group; aircraft factories, leather factories, carpet factories, plastic
factories, warehouses, departmental stores, printing
rooms, saw mills chemical labs, and tanneries
Special group; cotton mills, distillers, film and television studios, and match
factories.
•Extra high hazard; Commercial and industrial occupancies involving
handling highly inflammable materials such as;
celluloid works, foam plastics, rubber factories,
paint and varnish factories, wood and wool
works, oil and other flammable liquids.

Fire Detectors
Heat and flame detectors; have three basic operating
principles:
•Fusion; melting of a metal rather like a normal electrical
fuse which operates a switch thus closing an electrical alarm
circuit.
•Expansion; a bimetallic strip is used which expands when
heated and makes contact with an open electrical circuit,
thus closing it and sounding an alarm.
Flame (heat) and smoke detectors; an infra-red beam is
transmitted across the protected area. The smoke and heat
interfere with the transmission of the beam; this is detected
by the receiving unit and the alarm is initiated.

Smoke Detectors
• Ionization detectors; work on the principle that
ions are absorbed by smoke particles. Some of
the ions are absorbed by the smoke and the ion
flow across the detection chamber is reduced;
this change is detected and the alarm operates.
• Light scatter detectors; contain a photoelectric
cell fitted in a chamber at right angles to a light
source. Smoke entering the chamber scatters the
light and the resulting disturbance triggers an
alarm.
• Obscuration detectors; work on the opposite
basis to the light scattering principle in that
when the light which normally impinges on the
photoelectric cell is obscured by smoke, the
alarm is triggered.

Fire Protection of Buildings
There are four categories of fire protection
systems for buildings
• Portable extinguishers
• Fixed foam, carbon dioxide, and dry
powder extinguishers
• Fixed riser and hose-reel systems
• Sprinkler systems

Portable Fire Extinguishers
• Water or spray foam fire extinguisher; suitable for class A
fires involving solid materials - paper, wood, fabrics and so
on.
• Foam and dry powder extinguishers; suitable for class B
fires involving flammable liquids such as petrol, oils, fats;
should be used.
• Dry powder extinguisher; suitable for class C fires which
are fuelled by flammable gases such as natural gas, butane
and so on.
• Special powder extinguisher; suitable for class D metal
fires involving metals such as aluminum and magnesium.
They work by simply smothering the fire with powdered
copper Non-conducting agents such as powder and carbon
dioxide extinguishers; suitable for class E fires in which live
electrical equipment is involved

• Halotron 1 extinguishers; like carbon dioxide units, are for use on
class B and C fires. Halotron 1 is an ozone-friendly replacement for
Halon 1211. It discharges as a liquid, has high visibility during
discharge, does not cause thermal or static shock, leaves no residue,
and is non-conducting. These properties make it ideal for computer
rooms, clean rooms, telecommunications equipment, and
electronics.
• FE-36 (Hydrofluorocarbon-236fa) extinguishers; The FE-36 agent is
less toxic than both Halon 1211 and Halotron 9. In addition, it has
zero ozone-depleting potential.
• Water mist extinguishers; are ideal for Class A fires where a potential
Class C hazard exists. Unlike an ordinary water extinguisher, the
misting nozzle provides safety from electric shock and reduces
scattering of burning materials. This is one of the best choices for
protection of hospital environments, books, documents, and clean
room facilities. In non-magnetic versions, water mist extinguishers
are the preferred choice for MRI or NMR facilities or for deployment
on mine sweepers.

Fixed Fire Extinguishers
• Fixed Foam Extinguishers: Buildings containing flammable
liquids normally have a piping system installed in the
protected areas in the building with an inlet in the street
through which foam is pumped. The opening is protected
by a strong glass panel and is marked ‘FOAM INLET’. The
fire brigade will smash the glass to feed the inlet.
• Fixed Carbon Dioxide Extinguishers: This system consists
of a piping network with nozzles attached and located in
the protected areas. The system is connected to a fixed
supply of CO2. This system does not cause any side effect
as it leaves no residue after its application.

Fixed Fire Extinguishers (cont..)
• Dry Powder Systems: Dry powdered
extinguishing chemical agents under pressure of
dry air or nitrogen are discharged over the
burning materials. Normally, this system is
suitable for application on liquid and electrical
equipment fires.

Standpipe/Riser and Hose-reel System
A rising main consists essentially of a pipe
(of 50 mm minimum diameter) installed vertically
in a building with a fire service and has inlet at the
lower end and outlets at each floor inside the
building. (See next page)

BREAK TANK
PUMP SYSTEM
HOSE REEL

There are two types of risers:
• WET RISERS; Wet risers are kept permanently charged
with water which is then immediately available for use on
any floor with an outlet. Buildings above 60 meters in
height should be provided with wet risers. Wet risers in
building should not be used for any other purpose.
The water supply system to the riser should be capable of
providing a pressure of 410 kPa at the highest outlet.
Lower outlets should be protected against excessive
pressure whereby pressures should limited to 520 kPa
maximum at any outlet.
Wet riser system is always the preferred system unless
freezing conditions may occur. In this case the dry riser
system is to be used.

• Dry risers; Dry risers are similar to wet risers but
are kept empty of water. When required, they will
be charged by fire service pumps at ground level.
Dry risers should only be installed where prompt
attention can be relied upon or where buildings
are not fire sensitive such as all-concrete
buildings. Appropriate occupants training will be
required when such systems are installed.
The most common material used for standpipes is
steel.
Internal hose reels may be fitted inside buildings
and should be sufficiently light and easily
manipulated to be used by employees for a first
aid fire protection.

Automatic Sprinkler Systems

Types of
• In general, sprinkler systems may be classified into two
main types: wet-pipe and dry-pipe systems
• Wet-pipe System; In the wet-pipe system the pipe
work is fully charged with water at all times and thus, it is
the fastest system in delivering water. This system is
recommended except when freezing conditions may exist or
accidental mechanical damage to sprinkler head may result
in property loss or damage. Therefore, this system should
not be used in spaces designated for electrical equipment
such as computers, switch boards and alike.

Wet-pipe System
Schematic of wet-pipe sprinkler system

Types of
• Dry-pipe system: In this system no water is introduced
into the piping network until a fire occurs. The dry-pipe
systems are used where conditions are such that freezing
may occur due to weather or other conditions such as cold
stores where the temperature is artificially maintained close
to, or below freezing. In dry type systems the pipes are kept
charged, at all times, with air or nitrogen under pressure.
Activation of a sprinkler head by heat released from a nearby
fire results in a pressure loss which in turn activates a dry
pipe valve which opens allowing water to enter the piping
network and sprayed through opened sprinkler heads. The
disadvantage of this system is that accidental damage to a
sprinkler head or gas leakage may falsely indicate the
existence of fire and activate the system causing property
damage. To avoid these unfavorable characteristics of dry-
pipe system a preaction valve is used resulting in what is
termed the "preaction system".

Dry-Pipe System
Schematic of dry-pipe sprinkler system

Types of
• Preaction System: This system is a dry-pipe
system with a preaction valve activated by a
separate fire detection system that is more
sensitive to fire than sprinkler heads. The fire
detection system may consist of smoke- or
flame-sensitive detection sensors that signal the
actuators to open the preaction valve allowing
water to flow through the sprinkler heads that
are already opened by heat from fire. Thus, this
system is much safer than the dry-pipe system
as the water is allowed to enter the piping
system only if fire occurs.

Preaction System
Schematic of preaction sprinkler system

Types of
• Deluge System: This system is also a dry-
pipe system with sprinkler heads (or
nozzles) open all the time. The system is
equipped with "deluge" valve operated by
heat, smoke, or flame sensitive sensors.
Upon valve opening water discharges out of
all sprinkler heads simultaneously.

Deluge System
Schematic of deluge sprinkler system

SPRINKLER

SPRINKLER
Upright sprinkler Pendent sprinkler

Discharge Diagram For Standard Sprinklers

SPRINKLER

Temperatures and Identification Colors of Sprinklers
Operating Temperature
oC
Identification Color
57 Orange
68 Red
79 Yellow
93 Green
141 Blue
182 Mauve
227/288 Black

PARTS IDENTIFICATION

SPRINKLER DISTRIBUTION ARRANGEMENTS

Design of Hose Reel System
General guidelines for the design of hose-reel systems
have been developed by different codes of practice. These
are:
• Nozzle:
(a) Minimum pressure at the nozzle, P = 200 kPa
(b) Flow rate at each nozzle: q = 0.4 l/s (Hall, p. 39)
q = 0.5l /s (Code, p. 55)
(c) Hose-reel type and size:
Type: Rubber hose/flexible (BS3169)
Size: Lengths for two different diameters are given in
the following table
(d) Coverage: 418 m2/hose

General guidelines for the design of hose-
reel systems (Jordanian Code)
• Nozzle Size:
Operating pressure (bar) Hose diameter (mm)
3.5 65
3.0 40
3.0 19 0r 25*
1.25 19 or 25**
* Nozzle diam 4.5mm
** nozzle diam. 6.4 mm

Pressure at the
hose base***
Hose diameter
(mm)
Min. Hose
length (m)
4.5 bar 65 23
5.5 bar 65 46
4.0 bar 40 23
4.0 bar 19 or 25* 30 or 25
1.5 bar 19 or 25** 30 or 25
* Nozzle diam 4.5 mm, ** nozzle diam 6.4 mm, *** it is allowed to lower the
pressure according to hydraulic calculation but not less than operating pressure.

Hose diameter
(mm)
Flow rate
(lt/min)
Nozzle diam
(mm)
65 473 (7.88 lt/s) 19
40 189 (1.48 lt/s) 12
25 30* (0.5 lt/s) 4.8
19 30** (0.5 lt/s) 6.4
* Operating pressure 3 bar, ** operating pressure 1.25 bar

Hazard
classification
Max Area
covered by a
hose m2
Hose diameter
(mm)
Light 800 19, 25
Ordinary 600 19,25
High 400 40
* Operating pressure 3 bar, ** operating pressure 1.25 bar

SYSTEM FLOW RATE
• For systems using 65mm diameter hose:
– 31.5 – 78.8 lt/s for high and special hazards
– 15.8 – 78.3 lt/s for light and ordinary hazards
• For systems using 40 mm diameter hose .
– 6.3 lt/s for light and ordinary hazards.
• For systems using 19 or 25 mm diameter hose
– 1 lt/s

D = 19 mm D = 25 mm
18
23
30
37
40
18
23
24
30
37
Table 1 hose diameter vs. length

• Supply Pipe/Riser:
– Minimum number of hoses operated simultaneously:
– 3 at 0.4 l /s giving 1.2 l/s (Hall, p. 39)
– 2 at 0.5 l /s giving 1.0 l/s (Code, p. 55)
• Pressure at the connection to the hose reel (Code, p.
55):
– P=1.25 bar for a nozzle of 9.4 mm diameter (Code)
– P= 3.0 bar for a nozzle of 4.8 mm diameter (Code)


Diameter, D
(mm)
Building height
(m)
50
64
15
> 15
Table 2: Riser diameter vs. building height
Riser size:

• Tank: water supply/storage tank size
= 1.6 m3 (Hall)
= 1.125 m3 (Code, p. 55)
• Hose-Reel assembly type:
– Fixed: the least expensive
– Swinging: more flexible for drawing off the hose
– Recessed-swinging: good for corridors
• Pumping specifications (if needed):
– 2.3 l / s discharge capacity
– duplicate pumps for maintenance

Example:
A five storey building with floor area of 800m2
(28x15 m) is to be equipped with hose-reel fire
fighting system. Size the system for down-feed
and up-feed water supply for a light fire hazard
classification. The height of each floor is 3.2m.

Solution:
• According to the coverage of 412 m2 per hose
reel, two hose-reels on each floor is sufficient to
cover the whole floor area.
• Assume 2 hoses operating simultaneously, the
riser flow rate is then 1.0 l/s (0.5 l/s, each.)
• The hose length is chosen from Table 1 as 30m
with diameter of 19mm.

A storage tank of 1.6 m3 is capable of providing two
hose reels at 1.0 l/s total flow rate for 1600 seconds
(or 27 minutes) duration.
We also choose a nozzle with 4.8 mm diameter
(Pressure connection to reel=3.0 bar.)
We further choose the riser to be 50 mm in diameter since
the building height is just slightly greater than 15 m (i.e.,
16 m) as the pump will take care of the difference.

The only item left is the pump size. So, we size
the pump as follows:
Pressure required at point A is 3 bar (3.0e+5 Pa or 30.6 m
head).
Static pressure head at point A is 15 m (up-feed) or 3.0
m down-feed.
Friction head loss Hf calculated using Thomas Box
formula
q = {(d5 *Hf)/(25*L*105)}1/2
Hf = q2*25*L*105/d5
f
H f
H
5
5
10
25 


L
H
d
q
f

Hf = q2*25*L*105/d5 = 0.18 m
(up-feed)
= 0.04 m (down-feed)
Taking L= 1.5 L physical= 1.5*15 = 22.5 m
(up-feed)
= 1.5*3 = 4.5 m (down-feed)

=30.6+0.04-3.0 = 27.64 m
(downfeed)
• Thus the system specifications are:
Total head is then:
Htotal =HA + H f + Hstatic
=30.6+0.18+15=45.78 m
(up-feed)

BREAK TANK
PUMP SYSTEM
HOSE REEL

Design of Sprinkler Installations
Sprinklers heads may be
arranged in two different
arrangements;
Standard and Staggered
arrangements as shown.
Sprinkler Heads
Arrangements

• The requirements and
design parameters for a
sprinkler system are given in
the table next:

Parameter Light and Extra Light Ordinary High
1 Maximum area covered per system (m2) 4800 3600 2300
2 Maximum area covered per head (m2) 15, 21* 12, 9 for HPS 8, 9*
3 Maximum distance between heads (m) 4.6 4.5, 4.0*, 3.75 for HPS 3.7
4 Maximum distance between branches (m) 4.6 4.5, 4.0*, 3.75 for HPS 3.7
5 Maximum number of heads per branch line 8 8 6
6 Maximum number of heads per system
a. Wet pipe system
b. Dry pipe system
i.With accelerator
ii.Without accelerator
500
250
125
1000
500
250
1000
500
250
7 Head orifice diameter (mm)
Minimum pressure at outlet (bar)
10
1
15
1
20
a
8 Piping network diameters Table 12, p. 59 Tables 13&14, p. 64 Table 15, p.66
9 Flow rate in the riser (l/min)
Corresponding time duration (min)
1890-2830
30-60
2650-3780
60-90
b
60-120
10 Discharge density required by the total area covered
by sprinklers
See Fig. 7, p.59 See Fig. 7, p.59 See Fig. 7,
p.59
11 Discharge capacity of sprinkler head (l/min)
12 Values of k coefficient. 45-50 78-85 110-120
* Hall, p. 46
(a) or from catalog
(b) determined by official authority
(c) can be reduced to 0.5 bar according to the building type (see item 2, p. 58)
(d) use lower limit when early warning system is installed or when the building is close to fire fighting squad center
(e) C = 1.5 wooden installations
= 1.0 ordinary installations
= 0.8 installations made of noncombustible materials
= 0.6 installations made of fire resistant materials
Table 3

In designing sprinklers system two approaches are
available:
1. The occupancy hazard fire control approach
2. The special design approach
1- The occupancy hazard fire control approach includes:
• The Pipe Schedule, and
• The Hydraulic Calculation approach
which can follow any of the following methods:
Area/density method
Room design method
Special design method; building service chute corridors

2- The special design approach includes
• Residential sprinklers
• Quick- response early suppression sprinklers
• Large drop sprinklers
• Exposure protection
• Water curtains

Will consider only the
PIPE SCHEDULE METHOD

Pipe Schedule Method
where p is the pressure at the head's
outlet (bar) and k is a constant given
in Table 3, item 12.
Basic information:
The discharge capacity of sprinkler
head (l/min) is given by:
Q = k √p

Basic information:
Max number of sprinklers per branch is 8.

This method is used for the pipe materials; copper and
steel. It consists of the following steps:
1- Determine the hazard type applicable to the
given space/building . See note next slide.
2- Select the type of sprinklers arrangement, i.e.,
Standard or Staggered.
3- Distribute the sprinklers according to the rules
given in Table 3
4- Size the piping system according to item 7 of
Table 3

• Sprinkler systems having
sprinklers with orifices other
than 1/2 in. (13 mm) nominal,
extra hazard, Groups 1 and 2
systems, and exposure
protection systems shall be
hydraulically calculated.

The number of automatic
sprinklers on a given pipe size
on one floor shall not exceed
the number given in Tables 4a&
b. for a given occupancy.

• Table 4a. Light Hazard Pipe Schedules
• Steel Copper
• 1 in. 2 sprinklers 1 in. 2 sprinklers
• 11/4 in. 3 sprinklers 11/4 in. 3 sprinklers
• 4 in. See NFC 4 in. See Section 5-2
• For SI units, 1 in. = 25.4 mm.

Table 4b Ordinary Hazard Pipe Schedule (source; NFC)
Steel Copper
1 in. 2 sprinklers 1 in. 2 sprinklers
11/4 in. 3 sprinklers 11/4 in. 3 sprinklers
8 in. See Section 5-2 8 in. See Section 5-2
For SI units, 1 in. = 25.4 mm.

• Table: Number of Sprinklers; Greater than 12-ft
(3.7-m) Separations (source NFC)
• Steel Copper
• For SI units, 1 in. = 25.4 mm.
• Note: For other pipe and tube sizes, see Table 8-
5.3.2(a).

• A 5-story building with floor plan view shown
below. Design a sprinkler system using Pipe
Schedule method. The hazard classification is light
hazard.
EXAMPLE:

• Floor area is calculated to be A =471 m2
• Number of sprinklers on the floor= 471/15 = 31 sprinklers.
• According to Table 3 the following sizes are selected for a steel
piping:
• Line A-B: there are 16 sprinklers. The diameter DA-B = 65 mm
• Line B-C: there are 12 sprinklers. DB-C = 65 mm
• Line C-D: there are 8 sprinklers. DC-D = 50 mm
• Line D-E: there are 4 sprinklers. DD-E = 40 mm
• Branches: each branch has 4 sprinklers, 2 on each side. Thus,
• DB-F =DC-G =…=DE-I =25 mm
• The riser size supplying the floor; 100 mm
Solution:

Parameter Light and Extra Light Ordinary High
1 Maximum area covered per system (m2) 4800 3600 2300
2 Maximum area covered per head (m2) 15, 21* 12, 9 for HPS 8, 9*
3 Maximum distance between heads (m) 4.6 4.5, 4.0*, 3.75 for HPS 3.7
4 Maximum distance between branches (m) 4.6 4.5, 4.0*, 3.75 for HPS 3.7
5 Maximum number of heads per branch line 8 8 6
6 Maximum number of heads per system
a. Wet pipe system
b. Dry pipe system
i.With accelerator
ii.Without accelerator
500
250
125
1000
500
250
1000
500
250
7 Head orifice diameter (mm)
Minimum pressure at outlet (bar)
10
1
15
1
20
a
8 Piping network diameters Table 12, p. 59 Tables 13&14, p. 64 Table 15, p.66
9 Flow rate in the riser (l/min)
Corresponding time duration (min)
1890-2830
30-60
2650-3780
60-90
b
60-120
10 Discharge density required by the total area covered
by sprinklers
See Fig. 7, p.59 See Fig. 7, p.59 See Fig. 7,
p.59
11 Discharge capacity of sprinkler head (l/min)
12 Values of k coefficient. 45-50 78-85 110-120
* Hall, p. 46
(a) or from catalog
(b) determined by official authority
(c) can be reduced to 0.5 bar according to the building type (see item 2, p. 58)
(d) use lower limit when early warning system is installed or when the building is close to fire fighting squad center
(e) C = 1.5 wooden installations
= 1.0 ordinary installations
= 0.8 installations made of noncombustible materials
= 0.6 installations made of fire resistant materials
Table 3

Water Supply
to
Water Based Systems
Riser-Hose-Real
and
Sprinkler Systems
Water Supply
to
Water Based Systems
Riser-Hose-Real
and
Sprinkler Systems

Water Supply to Water Based Systems
(riser-hose-real and sprinkler systems)
• Community Water Supply System
• There are three principle components to the water based fire
protection system; storage, distribution and the hydrants
themselves. While functional hydrants and a good water
delivery system are important, everything starts with proper
storage.
• Water for fire protection should be provided by gravity storage
wherever possible. This is because using elevation as the means
for developing proper water pressure in water mains and
hydrants is reliable, not dependent on pumps that could fail or
be shut down as a result of an electrical outage. Storage can be
provided through one or more large reservoirs or by multiple
smaller reservoirs throughout the community that are linked
together.

(riser-hose-real and sprinkler systems
Elevation of Storage Reservoir
Every meter of head will produce 10.1 kPa of
pressure. therefore to generate 410 kPa in
the water distribution system, storage
reservoirs must be located at an elevation of
approximately 50 meters above the service
area. Adequate system pressures are generally
accepted to be between 410 to 575 kPa.
Accordingly, reservoirs should be placed at
elevations between 45 and 57.5 meters above
service areas.

Since most communities are not perfectly flat, there
will be some variation in service pressure. While it
may be possible to establish a reservoir level to most
of a hilly community, it is often possible to design a
system where the predominance of the community
falls within the 450-575 kPa range with pressures in
some portions experiencing less desirable but
acceptable ranges as low as 340 kPa and as high as
810 kPa.
In locations where pressure gradients may fall outside
these less desirable pressure ranges, additional
reservoirs should be set at appropriate elevations to
serve these areas or main-line pressure regulators
should be installed to protect low-lying areas from
excessive pressurization.

• Reservoir size; most municipal water systems for
fire protection provide combination service for
fire hydrants and domestic (private and
commercial) use. Thus the determination for
volume of water stored is based on a number of
factors.
• Reservoirs should have adequate capacity to
provide continuous domestic flow in the event of
a disruption of the reservoir refilling system. They
must also have adequate storage to provide
anticipated fire flows for a reasonable duration.

• A reasonable rule of thumb is that storage should be
sufficient to provide at least two days of peak domestic
consumption plus required fire flows as determined by the
Fire fighting authorities in the city.
• For example, in a typical residential neighborhood with no
unusual hazards, storage based on a fire flow of 3785
L/min for two hours may be appropriate.
• In commercial or industrial zones, flows on the order of
19,000 L/min for 3 hours may be required. Reserve
capacity may have to be balanced by water quality issues.
There must be sufficient water changeover in reservoirs to
keep water fresh and healthful.

Typical reservoir tank on hillside

Multiple tank reservoir

Private water supply system
The supply of water to the water based fire protection
system in private buildings should be done from a special
reservoir devoted for this purpose. If the building is
provided by a continuous water supply at a rate of not less
than 1.6 m3 /min, a break tank of only 11.5 m3 would be
sufficient.
In the absence of adequate or dependable water main a
reservoir of not less than 45.5 m3 in volume should be
available on site of the building. The reservoir should be
provided with a pipe outlet of 150 mm diameter at the
street level and branched into four 64 mm instantaneous
couplings for connection to fire trucks.

Fire Detection & Alarm System28-08-20 .pdf

Fire Detection & Alarm System28-08-20 .pdf

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