ch03 fire alarm system components and functions

Chapter 3Fire Alarm System Components and Functions

Objectives• Describe a fire alarm system.• List five functions fire alarm systems provide.• List and describe the three types of fire alarm

signals.• Discuss the characteristics of conventional

fire alarm system technology.• Discuss the characteristics of addressable

fire alarm system technology.

Objectives• Discuss the functions of a fire alarm

control panel and annunciation panel.• List and describe the different components

that make up a fire alarm system.• List and describe devices that interface

with a fire alarm system to supervise the condition of other fire protection systems.

Introduction • Fire alarm systems provide notification of

fire emergencies.– Survival depends on time from recognition to

evacuation.• Three main system components of

systems:– Initiating device– Notification device– Control panel

Introduction • Some systems can send signals in

addition to occupant notification.– To locations where trained staff receive and

act– To other fire and life safety systems

Introduction • Many system components ensure

functionality and operational capabilities.– Some systems are basic; others perform

complex tasks.– All components have a purpose and must be

evaluated and tested by a nationally recognized lab.

Fire Alarm Control Panel/Unit• History of system

“brain”– Older systems used

conventional technology to link manual fire alarm boxes and bells.

• 2-wire circuits• A break in a wire could

down entire system.

© A. Maurice Jones, Jr./Jones & Bartlett Learning

Fire Alarm Control Panel/Unit• History (cont’d)

– Next generation of panels featured:

• Smaller electronic components

• Logic or circuit relays• Two- and four-wire

circuits• Expanded performance

and monitoring


Fire Alarm Control Panel/Unit• History (cont’d)

– Today’s panels use:• State-of-the-art electronics• Microprocessors• Intelligent software

– Technology supports all system sizes and makes information available immediately to first responders and others.


Fire Alarm Control Panel/Unit• The panel has multiple functions:

– Monitors integrity of system circuits and devices– Processes input signals from initiating devices– Drives notification appliances– Provides an interface with other system– Powers power supply

• Two independent sources of power are used:– Power utility and backup source

Fire Alarm Control Panel/Unit• Types of fire alarm signals

– Not all information communicated by alarm system means there is a fire.

– Alarms alert occupants to a fire emergency.– Trouble signals sound when there is a problem

with system integrity. – Supervisory signals sound when there is a

change in normal ready status of other fire protection systems or devices connected to the control panel.

Initiating Devices• Manual initiating devices

– Manual fire alarm box is the only kind (manual box, manual pull box, manual pull station).

– A person pulls a handle to activate the alarm.

– Device must be accessible and visible.


Initiating Devices• Manual initiating devices (cont’d)

– NFPA 72, National Fire Alarm and Signaling Code, lists requirements for boxes.

– Boxes must be within 5ʹ of exit, 42–48″ above the floor, colored red unless environment precludes use of color.

– Boxes must be listed and approved for moist, damp, or wet conditions.

• Protect from corrosion, rust, electrical shorting, grounding


– Protective covers:• Protect from environment• Protect from physical damage• Deter individuals from pulling to create false alarm


– Operational characteristics create categories:• Non-coded• Coded• General alarm• Pre-signal• Break-glass• Non-break-glass• Single-action• Double-action

– Once fire alarm box is pulled, it requires resetting.

Initiating Devices• Automatic initiating devices

– Classified by fire signature component they detect: heat, smoke, flame, or gas

– Also classified by class and size of hazard they protect

• Spot detectors: specific area• Line detectors: area along an uninterrupted linear

route• Air sampling detectors: pull air from a protected

area and check for products of combustion

Initiating Devices• Automatic initiating devices (cont’d)

– Heat detectors (general info)• Installed when environmental conditions and

temperatures fluctuate, heat output is high, or speed of fire detection is not of concern

• Not prone to false alarms• Low cost• Slower at detection because rely on heat (not life

safety devices)


– Heat detectors (types)• Fixed-temperature heat detectors • Rate-of-rise heat detectors• Fixed-temperature/rate-of-rise detectors• Rate-compensation heat detectors


– Smoke detectors (general info)• Rely on smoke particles, not heat generation

– Smoke is developed and detected faster than heat.

• Considered life safety devices• Some limitations (cover small areas, must be

appropriately sensitive, only as good as upkeep)• Selection of type is based on multiple factors.• Correct type and location are critical to quick

response.


– Smoke detectors (types)• Ionized smoke detectors• Light-scattering photoelectric smoke detectors• Light-obscuration photoelectric smoke detectors

(beam detectors)• Air sampling smoke detectors• Duct smoke detectors• Video smoke and flame detectors• Multiple-parameter, low-false-alarm fire detectors


– Radiant energy sensing fire detectors• Also called flame or spark/ember detectors• Look for specific portions of the light spectrum

produced by flames, sparks, and embers• Used especially in industrial/manufacturing • Installed where hazard level is high, rapid and

sensitive detection is critical, and remote detection of small fires is critical

• Right type of detector based on environment and fuel type, and sources of non-fire radiant energy

Initiating Devices• Automatic initiating

devices (cont’d)– Radiant energy sensing

fire detectors (categories):

• Ultraviolet (UV)• Infrared (IR)• Ultraviolet/infrared (UV/IR)• Infrared/infrared (IR/IR)



– Gas sensing fire detectors• Utilize multiple sensing technologies (infrared,

semiconductor, electrochemical, catalytic bead)• Detect gas and vapors• Protect high hazard environments (e.g., offshore

oil and gas rigs, HVAC air intakes, oil and gas wells)


– Signal processing/alarm verification• Most modern alarms/detectors can validate

conditions before sounding an alarm.• Signal processing checks the smoke in the detector

at specified intervals, initiating an alarm when threshold is exceeded for a certain amount of time.

• With alarm verification, when the panel receives a signal it delays to see if the condition clears before sounding an alarm.


– Water flow initiating devices• Also known as a water flow switch• Use a flexible round paddle or vane that inserts into

the wet sprinkler piping• The paddle can activate a switch, which sends a

signal to the panel and activates the alarm• Installed by sprinkler contractor but wired to fire alarm

system by fire alarm or electrical contractor• Switches have built-in adjustable time delay;

compensate for fluctuations in water pressure


– Alarm pressure switch initiating devices• Installed by fire sprinkler contractor; wired by fire

alarm or electrical contractor• Screw into a fitting in the sprinkler system’s pipe

components package• Operate when pressure setting rises above/drops

below a certain threshold• No time delay• May require manual reset

Notification Appliances• Overview

– Notifying occupants is the most important function of the fire alarm system.

– Many different notification appliances are used.

– System type and device location depend on multiple factors.

Notification Appliances• Public mode/private mode notification

– Public mode notification alerts occupants visually or audibly.

• Most common• Appropriate for locations where people can make

decisions and take action– Grocery stores– Schools– Office buildings

Notification Appliances• Public mode/private mode notification

(cont’d)– Private mode is used when sounding a general

alarm is impractical.• When occupants are not physically or mentally

capable or when their movement is restricted– Nursing homes– Hospitals– Jails

• Trained individuals receive signal and implement emergency procedures.

Notification Appliances• Coded, non-coded, and textual signals

– Coded signals: Generate a predetermined number of visual or audible patterns for a specific duration to identify the location of the initiating device

– Non-coded signals: Provide a constant visual or audible signal until reset

– Textual signals: Voice message over speakers, text message on an annunciation panel, or symbol flashing on a screen

Notification Appliances• Audible appliances (general info)

– Must be loud enough to be heard over regular noise level of the area

• NFPA 72 requirements– Must make a distinctive sound

• ANSI S3.41, three-pulse temporal pattern– Must relay information intelligibly

• Clear and understandable

Notification Appliances• Audible appliances

(types)– Horns– Speakers– Bells – Chimes, buzzers,

sirens, piezos– Exit-marking audible

notification appliances© A. Maurice Jones, Jr./Jones & Bartlett Learning

Notification Appliances• Visible appliances (general info)

– Produce flashing lights seen when the fire alarm system activates

– Necessary in case audible alarms are not heard– Required by adopted building, fire accessibility,

and life safety codes– Installed in public/common areas, employee work

areas, high-ambient-noise-level areas, sleeping rooms in institutional/residential occupancies

Notification Appliances• Visible appliances

(types)– Strobe lights are the

most common.– Other options include:

• Quartz lamps• Solid-state lamps• Fluorescent lamps• Incandescent


Notification Appliances• Combination appliances

– Audible and visible devices combined to originate from a single appliance

– Combinations: horn/strobe, speaker/stroke, bell/flashing incandescent lamp


Notification Appliances• Addressable notification appliances

– New appliance that can interact with software via microprocessor-based fire alarm control panel to:

• Program candela rating• Determine and adjust power levels• Perform tests• Print status reports

Annunciation Panels• Overview

– First, fire fighters respond to the main entrance and initiate operational activities; then they look for the annunciation panel.

– The panel provides valuable information on initiating device, involved system(s), and location of fire.

– Some panels are simple (handwritten); others incorporate LCD textual messaging or touch screens.

Annunciation Panels• Components

– Some panels provide a graphic representation of a building footprint.

– Different colored lights, lenses, or light-emitting diodes identify the type of signal being generated by the initiating device.

– Panels serve multiple functions, from system reset to control features that assist first responders.

Annunciation Panels• Graphic panels

– Provide info about building layout, fire protection systems, and related systems

– Immediate visual info– Display locations

(“You are here”)– Info must be kept up to

date and be accurate.


Annunciation Panels• Computer touch

screen– Most advanced type of

annunciation panel– Provides info about

the status of the building fire protection systems and integrates with other systems


Power Expander Panels• When buildings are

renovated, it is common to find that existing control panels cannot support additional notification devices.

• Power expander panels provide supplemental power.


Other Components and Systems

• Other components associated with fire alarm systems include:– Electronic valve supervisory devices

• Tamper switches can send supervisory signals.– Pressure switches

• Switches can initiate alarm/generate supervisory signal

– Air and water temperature sensors/water level sensors

• Sensors can send supervisory signals.

Summary• One of the most important functions of the

fire alarm system is to notify building occupants that there is a fire condition. The fire alarm system is also capable of sending different signals to an on- or off-site location where trained staff take the appropriate action.

Summary• Over the past 40 or so years, fire alarm

control panel technology has evolved from very simple to very complex. The most sophisticated and newest systems use microprocessor-based software-driven systems that interface with building and life safety systems.

Summary• Some fire alarm systems have the capability

of sending signals to other building systems to perform life safety functions such as capturing elevators, recalling elevators to a particular floor, turning off the power to elevators, unlocking exit doors, starting fans, closing smoke dampers, pressurizing stair towers and elevator shafts, and closing smoke doors to compartmentalize an area of a building.

Summary• The fire alarm system provides critical

information to first responders by identifying alarm type and location, and supervising other fire and life safety systems and components.

• Many different components are necessary to ensure full system functionality and operational capability during a fire emergency.

Summary• Fire alarm panels monitor and control all

system devices and initiate the appropriate type of signal, which includes alarm, trouble, or supervisory.

• Initiating devices provide manual or automatic means of activating fire alarm and supervisory signals.

Summary• Notification appliances provide audible,

visual, and textual signals to begin evacuation or relocation of occupants.

• The annunciation panel provides visible and valuable information concerning the device signaling an alarm and area of the building where the fire is located.

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