fire detection system

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Fire Detection and Alarm
System Basics
Prepared
By
Engr.AL-AmranMEESHU Sharker

Fire Detection and Alarm Systems
 A key aspect of fire protection is to identify a developing fire emergency in a
timely manner, and to alert the building's occupants and fire emergency
organizations.
 This is the role of fire detection and alarm systems. Depending on the
anticipated fire scenario, building and use type, number and type of
occupants and criticality of contents and mission, these systems can provide
several main functions:
 First, they provide a means to identify a developing fire through either manual
or automatic methods.
 Second, they alert building occupants to a fire condition and the need to
evacuate.
 Another common function is the transmission of an alarm notification signal
to the fire department or other emergency response organization.
 They may also shut down electrical, air handling equipment or special
process operations, and they may be used to initiate automatic suppression
systems.

Fire Detection Principles
Manual Fire Detection - Pull Stations
Manual fire detection is the oldest method of detection. In the simplest form, a person yelling
can provide fire warning. In buildings, however, a person's voice may not always transmit
throughout the structure. For this reason, manual alarm stations are installed. The general
design philosophy is to place stations within reach along paths of escape. It is for this reason
that they can usually be found near exit doors in corridors and large rooms.
The advantage of manual alarm stations is that, upon discovering the fire, they provide
occupants with a readily identifiable means to activate the building fire alarm system. The
alarm system can then serve in lieu of the shouting person's voice. They are simple devices, and
can be highly reliable when the building is occupied. The key disadvantage of manual stations is
that they will not work when the building is unoccupied. They may also be used for malicious
alarm activations. Nonetheless, they are an important component in any fire alarm system.
2007 NFPA 72, 3.3.63.3 Manual Fire Alarm Box. A manually operated device used to initiate an alarm signal.

Automatic Detectors – Spot type
2007 NFPA 72, 3.3.43.21 Spot Type Detector. A device in which the detecting ,Element is concentrated at a
particular location. Typical examples are ,Bimetallic detectors, fusible alloy detectors, certain pneumatic rate-of-rise
Detectors, certain smoke detectors, and thermoelectric detectors.

Automatic Detectors – Photoelectric
2007 NFPA 72, 3.3.181.4 Light Scattering Smoke Detection. The 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 inter 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.
Hochiki SLR-24V detector

Automatic Detectors – Photoelectric
A – Light Source
In the normal case, the light from the light source on the left shoots straight across
and misses the sensor.
When smoke enters the chamber, however, the smoke particles scatter the light
and some amount of light hits the sensor.

Automatic Detectors – Ionization
Ionization smoke detectors use an ionization chamber and a source of ionizing radiation to detect
smoke. This type of smoke detector is more common because it is inexpensive and better at
detecting the smaller amounts of smoke produced by flaming fires.
Inside the ionization detector is a small amount (perhaps 1/5000th of a gram) of Americium-241. The
radioactive element americium has a half-life of 432 years, and is a good source of alpha particles.
An ionization chamber is very simple. It consists of two
plates with a voltage across them, along with a radioactive
source of ionizing radiation.
2007 NFPA 72, 3.3.181.2 Ionization Smoke Detection. The 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 preset criteria.
Hochiki SIJ-24 detector

Automatic Detectors – Ionization
Ionization Smoke detectors
The alpha particles generated by the americium have the following
property: They ionize the oxygen and nitrogen atoms of the air in the
chamber. To "ionize" means to "knock an electron off of." When you
knock an electron off of an atom, you end up with a free electron
(with a negative charge) and an atom missing one electron (with a
positive charge). The negative electron is attracted to the plate with
a positive voltage, and the positive atom is attracted to the plate
with a negative voltage (opposites attract, just like with magnets).
The electronics in the smoke detector sense the small amount of
electrical current that these electrons and ions moving toward the
plates represent.
When smoke enters the ionization chamber, it disrupts this current -- the smoke particles attach to the
ions and neutralize them. The smoke detector senses the drop in current between the plates and sets
off the horn.

Automatic Detectors – Heat/Thermal
2007 NFPA 72, 3.3.43.9 Heat Detector. A fire detector that detects either abnormally high temperature,
or rate of temperature rise, or both.
Heat detectors are the oldest type of automatic fire detection device. They began development of automatic
sprinklers in the 1860s and have continued to the present with proliferation of various types of devices.
Heat detectors that only initiate an alarm and have no extinguishing function are still in use. Although they
have the lowest false alarm rate of all automatic fire detector devices, they also are the slowest in fire
detecting. A heat detector is best situated for fire detection in a small confined space where rapidly building
high-output fires are expected, in areas where ambient conditions would not allow the use of other fire
detection devices, or when speed of detection is not a prime consideration.
Heat detectors are generally located on or near the ceiling and respond to the convected thermal energy of
a fire. They respond either when the detecting element reaches a predetermined fixed temperature or to a
specified rate of temperature change. In general, heat detectors are designed to operate when heat causes
a prescribed change in a physical or electrical property of a material or gas.
Heat detectors can be sub-divided by their operating principles:

Automatic Detectors – Fixed Temp.
2007 NFPA 72, 3.3.43.7 Fixed-Temperature Detector. A device that responds when its operating
element becomes heated to a predetermined level.
Fixed-temperature heat detectors are designed to alarm when the temperature of the
operating elements reaches a specific point. The air temperature at the time of alarm is usually
considerably higher than the rated temperature because it takes time for the air to raise the
temperature of the operating element to its set point. This condition is called thermal lag. Fixed-
temperature heat detectors are available to cover a wide range of operating temperatures -
from about 135'F (57'C) and higher.
Hochiki DFE Series Heat
Detector
Higher temperatures detectors are also necessary so that
detection can be provided in areas normally subject to
high ambient temperatures, or in areas zoned so that only
detectors in the immediate fire area operate.

Automatic Detectors – Rate-of-Rise
2007 NFPA 72, 3.3.43.18 Rate-of-Rise Detector. A device that responds when the temperature rises at a
rate exceeding a predetermined value
however, will function when the rate of temperature
increase exceeds a predetermined value, typically
around 12 to 15'F (7 to 8'C) per minute. Rate-of-rise
detectors are designed to compensate for the normal
changes in ambient temperature that are expected
under non-fire conditions.
Hochiki DSC-EA
Heat Detector
One effect that flaming fire has on the surrounding area is to rapidly increase air
temperature in the space above the fire. Fixed-temperature heat detectors will not
initiate an alarm until the air temperature near the ceiling exceeds the design operating
point. The rate-of-rise detector,

Automatic Detectors – Combination
2007 NFPA 72, 3.3.43.4 Combination Detector. A device that either responds to more than one of the fire
phenomena or employs more than one operating 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. This device has listings for each sensing method employed.
Combination detectors contain more than one element which responds to fire. These detectors may be designed
to respond from either element, or from the combined partial or complete response of both elements. An
example of the former is a heat detector that operates on both the rate-of-raise and fixed-temperature principles.
Its advantage is that the rate-of-rise element will respond quickly to rapidly developing fire, while the fixed-
temperature element will respond to a slowly developing fire when the detecting element reaches its set point
temperature. The most common combination detector uses a vented air chamber and a flexible diaphragm for the
rate-of-rise function, while the fixed-temperature element is usually leaf-spring restrained by a eutectic metal.
When the fixed-temperature element reaches its designated operating temperature, the eutectic metal fuses and
releases the spring, which closes the contact.
Hochiki DCD Series
Fixed Temp/Rate of
Rise Heat Detector
Hochiki
Photoelectric/Heat
Smoke Detector

Automatic Detectors – Flame
2007 NFPA 72, 3.3.43.8 Flame Detector. A radiant energy-sensing detector that detects the radiant energy
emitted by a flame.
2007 NFPA 72, 3.3.43.16 Radiant Energy-Sensing Fire Detector. A device that detects radiant energy, such as
ultraviolet, visible, or infrared, that is emitted as a product of combustion reaction and obeys the laws of optics.
A flame detector responds either to radiant energy visible to the human eye (approx. 4000 to 7700 A) or
outside the range of human vision. Similar to the human eye, flame detectors have a 'cone of vision', or
viewing angle, that defines the effective detection capability of the detector.
With this constraint, the sensitivity increases as the angle of incidence decreases. Such a detector is sensitive
to glowing embers, coals, or flames which radiate energy of sufficient intensity and spectral quality to
actuate the alarm. Each type of fuel, when burning, produces a flame with specific radiation characteristics.
A flame detection system must be chosen for the type of fire that is probable. For example an ultraviolet
(UV) detector will respond to a hydrogen fire, but an infrared (IR) detector operating in the 4.4 micron
sensitivity range will not. It is imperative therefore; that a qualified fire protection engineer is involved in
the design of these systems, along with assistance from the manufacturer's design staff.

Automatic Detectors – Flame
Due to their fast detection capabilities, flame detectors are generally used only in
high-hazard areas, such as fuel-loading platforms, industrial process areas, hyperbaric
chambers, high-ceiling areas, and atmospheres in which explosions or very rapid fires
may occur. Because flame detectors must be able to 'see' the fire, they must not be
blocked by objects placed in front of them. The infrared-type detector, however, has
some capability for detecting radiation reflected from walls.
Hochiki HF-24 Flame
Detector

Automatic Detectors – Linear Type
2007 NFPA 72, 3.3.43.10 Line-Type Detector. A device in which detection is continuous along a path. Typical
examples are rate-of-rise pneumatic tubing detectors, projected beam smoke detectors, and heat sensitive cable.
2007 NFPA 72, 3.3.43.15 Projected Beam-Type Detector. A type of photoelectric light obscuration smoke
detector wherein the beam spans the protected area.
2007 NFPA 72, 3.3.181.3 Photoelectric Light Obscuration Detection. The principle of using a light source and a
photosensitive sensor onto which the principal portion of the source emission is focused. When smoke particles
enter the light path, some of the light is scattered and some of the light is absorbed, thereby reducing the light
reaching the receiving sensor. The light reduction signal is processed and used to convey an alarm condition when
it meets preset criteria.

Automatic Detectors – Air Sampling
2007 NFPA 72, 3.3.43.1 Air Sampling-Type Detector. A 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 draws air form the protected area back to the detector through air
sampling ports, piping, or tubing. At the detector, the air is analyzed for fire products.

Building Notification
Notification Appliances
2007 NFPA 72, 3.3.113 Notification Appliance. A fire alarm system component such
as a bell, horn, speaker, light or text display that provides audible, tactile, or visible
outputs, or any combination thereof.
2007 NFPA 72, 3.3.113.1 Audible Notification Appliance. A notification appliance that
alerts by the sense of hearing.
2007 NFPA 72, 3.3.113.3 Visible Notification Appliance. A notification appliance that
alerts by the sense of sight.

Fire Alarm Circuit Classes
2007 NFPA 72, 6.4.2.1 Class. Initiating device circuits, notification appliance circuits,
and signaling line circuits shall be permitted to be designated as either Class A or
Class B, depending on their performance during no simultaneous single circuit fault
conditions as specified by the following:
(1) Initiating device circuits and signaling line circuits that transmit an alarm or supervisory
signal, or notification appliance circuits that allow all connected devices to operate during a
single open or a no simultaneous single ground fault on any circuit conductor, shall be
designated as Class A
(2) Initiating device circuits and signaling line circuits that do not transmit an alarm or
supervisory signal, or notification appliance circuits that do not allow all connected
devices to operate beyond the location of a single open on any circuit conductor, shall
be designated as Class B
2007 NFPA 72, 6.4.2.2. An open or ground fault condition shall result in the annunciation of
a trouble signal at the protected premise within 200 seconds as required in 4.4.7

Class B Initiating Device Circuit
4.7K
EOLR
4.7K
EOLR
Class B Notification Appliance Circuit
Class B Circuits
End of line supervision resistors are required to supervise
the integrity of the loop.

Single open circuit condition causes a trouble on the panel
and renders all devices beyond the fault inoperative.
Class B Initiating Device Circuit
4.7K
EOLR
4.7K
EOLR
Class B Notification Appliance Circuit
Class B Circuits

Class A Initiating Device Circuit
Class A Notification Appliance Circuit
Class A Circuits
End of line supervision resistors are not necessary as the loop
returns to the panel and is driven from both ends.

Class A Initiating Device Circuit
Class A Notification Appliance Circuit
Class A Circuits
Single open circuit condition causes a trouble on the panel.
All devices on the loop remain operative.

Addressable Device - A fire alarm system component with discreet identification that can have its
status individually identified or that is used to individually control other functions.
Analog Addressable Sensor - An initiating device that transmits a signal indicating varying degrees of
condition as contrasted with a conventional or addressable initiating device, which can only indicate an
off/on condition.
Signaling Line Circuit (SLC) - A circuit or path between any combination of circuit interfaces, control
units, or transmitters over which multiple system input signals or out put signals or both are carried.
SLC Interface - A system component that connects a signaling line circuit to any
combination of initiating devices, initiating device circuits, notification appliances,
notification appliance circuits, system control outputs and other signaling line circuits.
Protocol - A language for communicating between control panels and their proprietary devices.
Additional Fire Alarm Terminology

 Conventional control panels range in size from 1 zone to
over 100 zones.
 Zones typically consist of some or all of the initiating
devices in an area or floor of a building.
 Some control panels zone capacity is expandable while
others are not, limiting its usefulness if a facility adds
additional buildings or rooms.
Comparing System Types
To better understand today’s newer technology, a firm understanding of the types of systems available
is necessary. The three most popular types of systems installed today are:
•Conventional
•Addressable
•Analog Addressable
Conventional Systems

Zone 1
4.7K
EOLR
Zone 2
FIREFIRE
SILENT KNIGHT
FIREFIRE
SILENT KNIGHT
FIREFIRE
SILENT KNIGHT
FIREFIRE
SILENT KNIGHT
FIREFIRE
SILENT KNIGHT
FACP
NAC 1
Multiple devices are combined into a single zone. Zones can
contain 30 or more devices.
4.7K
EOLR

Care must be taken when laying out zones to comply with
code requirements.
Zone 1
4.7K
EOLR
Zone 2
FIREFIRE
SILENT KNIGHT
NAC 1
4.7K
EOLR

Zone Considerations
• 2007 NFPA 72 6.8.5.5.2 Limits the number of waterflow
switches in a single zone to 5.
• 2007 NFPA 72 6.8.5.6.2 Limits the number of
supervisory devices in a single zone to 20.
• 2007 NFPA 72 Annex A.4.4.6.6 Suggests that the
maximum number of square feet in a single zone be
limited to no more than 22,500.

Wiring must be installed in a supervised manner either Class A,
or Class B with an EOLR.
Zone #1
4.7K
EOLR
4.7K
EOLR
Zone #2
NAC #1

Alarm conditions are annunciated by zone only. Inspection
is required to determine the device.
Zone #1
4.7K
EOLR
4.7K
EOLR
Zone #2
NAC #1
FIRE!

Trouble conditions are annunciated by zone only. Inspection
is required to determine the cause.
4.7K
EOLR
Zone #1
4.7K
EOLR
Zone #2
NAC #1

Information transmitted to the central station is by zone
at best. Many panels send Alarm, Supv, Trbl only.
RJ RJ
Zone #1
4.7K
EOLR
4.7K
EOLR
Zone #2
NAC #1

Addressable Systems
• An addressable systems point capacity is
determined by the amount of SLC “Signaling
Line Circuits” it contains.
• Each SLC circuit provides power,
communication, & supervision for all of the
devices connected to it.
• Each SLC can accommodate over 100
addressable devices, depending upon the
manufacturer.
FACP

Addressable Systems
FACP
Each SLC loop can contain a variety of addressable devices. Non-addressable
devices are connected via addressable module.
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Heat Detector
4.7K
EOLR
NAC #1
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
Addressable
Relay Module
(Fan Shutdown)

Addressable Systems
Each point on the SLC loop is given a unique address
when installed.
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
NAC #1
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector

Addressable Systems
Supervision is accomplished from the panel by polling the
devices on the SLC loop.
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1

Addressable Systems
Supervision is accomplished from the panel by polling
the devices on the SLC loop.
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1

Addressable Systems
Supervision is accomplished from the panel by polling the
devices on the SLC loop.
001 002
003
004
005
006
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
FACP
NAC #1

Addressable Systems
Supervision is accomplished from the panel by
polling the devices on the SLC loop.
< Replay
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1

Addressable Systems
Alarm conditions are annunciated by point allowing responding
personnel to quickly find the fire.
ALARM POINT 006
LOBBY SMOKE DETECTOR
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1
FIRE!

Addressable Systems
Trouble
conditions can
be located more
quickly by
analyzing the
affected points.
TRBL POINT 006
DISCONNECTED
LOBBY SMOKE DETECTOR
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1

Addressable Systems
More detailed information can be sent to the central
station aiding in a quick resolution to the problem.
RJRJ
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1

Addressable Systems
Since supervision is accomplished through polling, t-tapped
wiring is permitted. (Class B wiring)
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1

Addressable Systems
Many systems support flexible input/output programming to
link initiating devices to outputs.
001 002
003
004
005
006
FACP
FIREFIRE
SILENT KNIGHT
Addressable
Pull Station
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
4.7K
EOLR
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
Addressable
Smoke Detector
NAC #1
FIRE!

Comparison
• Conventional
– Lower initial equipment
costs.
– Wide range of compatible
devices.
– Can be easier to program.
– Limited expansion
capability.
• Addressable
– Easier to install.
– More system status
information at the panel
and central station.
– Input/Output programming
much more flexible.
– Usually much more room
available to expand.

Analog Addressable Systems
• Detectors in an analog addressable systems
become “sensors” relaying information to the
control panel corresponding to how much
smoke or heat that detector is sensing.
• The control panel makes the decisions based
on this information when to alarm etc.

Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
10K
EOLR
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
HEAT DETECTOR
MECHANICAL ROOM
POINT 001 A=062
NORMAL F=190
Supervision is still
checked by polling. In
addition an analog value is
transmitted to the panel
for processing.
NAC #1

SMOKE DETECTOR
LOBBY NORTH
POINT 002 A=060
NORMAL F=188
Supervision is still checked by polling. In
addition an analog value is transmitted to
the panel for processing.
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
10K
EOLR
NAC #1

RELAY MODULE
FAN SHUTDOWN
POINT 003 A=N/A
NORMAL F=N/A
addition an analog value is transmitted to the
panel for processing.
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

INPUT MODULE
WATERFLOW
POINT 004 A=N/A
NORMAL F=N/A
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

INPUT MODULE
MANUAL PULL
POINT 005 A=N/A
NORMAL F=N/A
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

SMOKE DETECTOR
FRONT DESK
POINT 006 A=061
NORMAL F=189
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

HEAT DETECTOR
MECHANICAL ROOM
POINT 001 A=062
NORMAL F=190
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

SMOKE DETECTOR
LOBBY NORTH
POINT 002 A=060
NORMAL F=188
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

SMOKE DETECTOR
FRONT DESK
POINT 006 A=061
NORMAL F=189
< Replay
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

This analog value corresponds to the amount
of heat or smoke in that detectors area of
coverage. Higher = more.
HEAT DETECTOR
MECHANICAL ROOM
POINT 001 A=062
NORMAL F=190
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

If the analog value exceeds the alarm
threshold, an alarm occurs. This alarm
threshold is calculated by the panel.
HEAT DETECTOR
MECHANICAL ROOM
POINT 001 A=062
NORMAL F=190
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

INPUT MODULE
WATERFLOW
POINT 004 A=N/A
NORMAL F=N/A
Input/output modules do not relay analog
values to the panel as they are monitoring
or controlling on/off devices.
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Sensor
Addressable
Smoke Sensor
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
10K
EOLR
NAC #1

Analog Addressable
Features
• An analog addressable control panel is capable of
several enhanced features not available on conventional,
and some addressable systems.
– Drift Compensation / Maintenance Alert
– Adjustable Detector Sensitivity
– Day/Night Detector Sensitivity Adjustment
– U.L. Calibrated Sensitivity Test Instrument

Drift Compensation
• Drift compensation is the process by which an
analog addressable control panel automatically
adjusts an analog detectors alarm threshold to
compensate for contaminants such as dust.
• This ensures the detector maintains a consistent
sensitivity level, helping to avoid false alarms due to
dirty detectors.

Maintenance Alert
• Drift compensation occurs until it is nearing a point
where it can no longer compensate and remain within
U.L. requirements. This point is called “Maintenance
Alert”
• Some systems handle a maintenance alert condition
as a trouble while others flag the condition only, and
continue to operate normally.

Calibration Trouble
• A detector in a maintenance alert condition
will eventually go into calibration trouble if
not serviced.
• A detector in calibration trouble is not
functioning correctly and requires service
immediately.

Adjustable (Day/Night)
Sensitivity
• In order to allow for varying environmental
conditions or to provide quicker detection,
analog systems typically allow you to change
the sensitivity of a detector within a range of
U.L. tolerances.
• This is typically made user friendly by giving the
installer choices such as high-medium-low.

Adjustable (Day/Night)
Sensitivity
• By changing a detectors sensitivity you are
instructing the panel to adjust its alarm threshold
(analog) value up or down accordingly.
• Some systems allow this sensitivity adjustment to
happen automatically on a day/night schedule.

U.L. Calibrated Sensitivity Test
• 1996 NFPA 72 7-3.2.1
Detector sensitivity shall be tested within 1 year after installation and
every alternate year thereafter. After the second required calibration
test, where sensitivity tests indicate that the detector has remained
within its listed and marked sensitivity range, the length of time shall be
permitted to be extended to a maximum of 5 years. …
• Testing Methods
– A calibrated test method; or
– Manufacturers calibrated sensitivity test instrument; or
– Listed control equipment arranged for the purpose; or
– Smoke detector/control unit arrangement whereby the
detector causes a signal at the control unit where its
sensitivity is outside the acceptable range; or
– Other approved calibrated method acceptable to AHJ

• Analog addressable control panels are UL listed for
the purpose of performing the calibrated sensitivity
testing internally.
• A printout from the panel is usually available to
provide evidence to the AHJ that the test was
performed.
U.L. Calibrated Sensitivity Test

How Analog Works
1% 2% 3% 4%.5% per foot obscuration
210
60
90
120
150
180
30
240
255
Detectors range of analog values
Range (.5% - 4% per foot obscuration)
that U.L. requires, to be listed as a
smoke detector.

How Analog Works
On the other side of the graph, the range
of analog values for the detector is
plotted. In this case the range is 0-255.
210
60
90
120
150
180
30
240
255

How Analog Works
193
During power-
up the detector
performs a self
test simulating
4% per foot
obscuration.
This value is
plotted, in this
case 193.
210
60
90
120
150
180
30
240
255

How Analog Works
193
The system
them initializes
and records the
0% per foot
obscuration
(normal no
smoke) value
for that
detector. In this
case 60.
210
60
90
120
150
180
30
240
255

How Analog Works
193
A line is drawn
connecting
these two
points. This line
is referred to as
the detectors
calibration
curve.
Calibration Curve
210
60
90
120
150
180
30
240
255

How Analog Works
Once the
calibration curve
is established
the panel can
calculate an
alarm threshold
value for any
valid sensitivity
setting.
145
193
210
60
90
120
150
180
30
240
255
112

How Analog Works
The panel also
calculates the
initial ranges for
the drift
compensation &
maintenance
alert functions.
Normal
Maintenance
Calibration Trouble
Alarm
193
210
60
90
120
150
180
30
240
255
145

As the detector
gets dirty the
clear air value
will increase.
Drift
compensation
adjusts the
alarm threshold
value
accordingly.
Normal
Maintenance
Calibration Trouble
Alarm
Normal
Maintenance
Calibration Trouble
Alarm
193
1% 2% 3% 4%.5%
per foot obscuration
210
60
90
120
150
180
30
240
255
145
How Analog Works

As the
detector gets
dirty the clear
air value will
increase.
Drift
compensation
adjusts the
alarm
threshold
value
accordingly.
Normal
Maintenance
Calibration Trouble
Alarm
Normal
Maintenance
Calibration Trouble
Alarm
193
1% 2% 3% 4%.5%
210
60
90
120
150
180
30
240
255
145
How Analog Works

As the detector
gets dirty the
clear air value
will increase.
Drift
compensation
adjusts the
alarm threshold
value
accordingly.
Normal
Maintenance
Calibration Trouble
Alarm
Normal
Maintenance
Calibration Trouble
Alarm
193
1% 2% 3% 4%.5%
210
60
90
120
150
180
30
240
255
How Analog Works

How Analog Works As the detector
gets dirty the
clear air value
will increase.
Drift
compensation
adjusts the
alarm threshold
value
accordingly.
Normal
Maintenance
Calibration Trouble
Alarm
Normal
Maintenance
Calibration Trouble
Alarm
193
1% 2% 3% 4%.5%
210
60
90
120
150
180
30
240
255
155

How Analog Works As the detector
gets dirty the
clear air value
will increase.
Drift
compensation
adjusts the
alarm threshold
value
accordingly.
Normal
Maintenance
Calibration Trouble
Alarm
Normal
Maintenance
Calibration Trouble
Alarm
193
1% 2% 3% 4%.5%
210
60
90
120
150
180
30
240
255
160

How Analog Works
< Replay
Even though the
detector has
gotten dirty, it
has still
maintained a
2.5% sensitivity
level.
Normal
Maintenance
Calibration Trouble
Alarm
Normal
Maintenance
Calibration Trouble
Alarm
193
1% 2% 3% 4%.5%
210
60
90
120
150
180
30
240
255
165

Communication Protocols
• Each manufacturer of (analog) addressable fire alarm systems
utilize a unique communications protocol on the SLC loop to
communicate between the control panel and the addressable
devices.
• Most protocols are developed by detector manufacturers.
• Many manufacturers subtly modify standard protocols, developed by
detector manufacturers, to provide a proprietary environment for
their equipment & distributors.

Communication Protocols
• Many of the panels installation requirements and operational
parameters are based on the communication protocol used.
– SLC Loop Length
– SLC Loop Wire Type
– SLC Loop Communications Speed
– SLC Loop Alarm Response Time
• Communication protocols can be broken down into two
categories.
– Non-Digital
– Digital

Comparing Protocols
To take a closer look at
communication protocols we can
look at non-digital and digital SLC
Loops through an oscilloscope.
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006

Non-Digital Protocol
Each detector when polled
responds to the panel with
square wave pulses.

The panel reads these
square wave pulses and
determines the values by
measuring the length (time)
of each.

Various sources of
interference can cause these
square wave pulses to round
off. This makes an accurate
reading very difficult.
?

Most manufacturers that
utilize a non-digital protocol
will specify special
requirements such as
twisted or shielded wire to
counteract this problem.
?

Digital Protocol
Using a digital protocol the
panel looks for for a series
of “1” or “on” bits that are
detected by looking for
voltage rather than the
length of a pulse.
0
1 1 1 1
0 0
24v

Digital Protocol
Even if a source of
interference causes
rounding off of the digital
pulses the voltage is still
present for the panel to
determine the digital value.
0
1 1 1 1
0 0
24v

Digital Protocol
Digital protocol panels do
not typically require special
cabling since interference
does not pose any
substantial signal problems.
Retrofits can be done using
existing cable.
0
1 1 1 1
0 0
24v

Non-digital Loop Response
• When an alarm occurs on many non-digital protocol
systems, some panels must continue polling until it
reaches the alarming device, before an alarm is initiated.
– Larger systems with hundreds of points can cause
delays initiating an alarm.

Non-Digital Loop Response
FIREFIRE
SILENT KNIGHT
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
Addressable
Relay Module
(Fan Shutdown)

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
FIRE!
A fire erupts at the Heat Detector (Point 001)
while the system is polling the Smoke
Detector (Point 002).
FIREFIRE
SILENT KNIGHT
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
Addressable
Relay Module
(Fan Shutdown)

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
An alarm is not initiated. The
system continues polling until it
reaches the point in alarm.
FIREFIRE
SILENT KNIGHT
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
An alarm is not initiated. The
system continues polling until
it reaches the point in alarm.
FIREFIRE
SILENT KNIGHT
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
An alarm is not initiated. The system
continues polling until it reaches the
point in alarm.
FIREFIRE
SILENT KNIGHT
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)

ALARM
POINT 001
HEAT DETECTOR
15-Jan-00 3:10 PM
ALARM!
FIREFIRE
SILENT KNIGHT
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)

ALARM
POINT 001
HEAT DETECTOR
15-Jan-00 3:10 PM
Systems with hundreds of points
can take 15 -20 seconds or
longer to respond to alarm
conditions.
FIREFIRE
SILENT KNIGHT
Addressable
Relay Module
(Fan Shutdown)
Addressable
Heat Detector
Addressable
Smoke Detector
Addressable
Input Module
(Waterflow)
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Detector
006
FIRE!

Digital Loop Response
• When an alarm occurs on most digital protocol systems,
an interrupt request from the device sensing the alarm
interrupts the polling sequence to immediately handle
the alarm.
– Systems with hundreds of points will respond to
alarms in the same amount of time that they would to
smaller systems with very few points.

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
Addressable
Heat Sensor
Addressable
Smoke Sensor
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
Addressable
Relay Module
(Fan Shutdown)
Addressable
Input Module
(Waterflow)

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
A fire erupts at the Heat sensor (Point
001) while the system is polling the
Smoke Detector (Point 002).
Addressable
Heat Sensor
Addressable
Smoke Sensor
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)
Addressable
Input Module
(Waterflow)

ABC FIRE SYSTEMS
ALL SYSTEMS NORMAL
15-Jan-00 3:10 PM
The Heat Sensor (Point 001) interrupts
the polling process to handle the alarm
immediately.
Addressable
Heat Sensor
Addressable
Smoke Sensor
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)
Addressable
Input Module
(Waterflow)

ALARM!
ALARM
POINT 001
HEAT SENSOR
15-Jan-00 3:10 PM
Addressable
Heat Sensor
Addressable
Smoke Sensor
001 002
003
004
005
Addressable
Pull Station
Addressable
Smoke Sensor
006
FIRE!
Addressable
Relay Module
(Fan Shutdown)
Addressable
Input Module
(Waterflow)

THE END

fire detection system

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