Fire Detection and Suppression Chapter 2 Fire Detection and Signaling Systems.

Fire Detection and Suppression

Chapter 2

Fire Detection and Signaling Systems


2-2


The early detection of a fire and the signaling of an appropriate alarm remain the most significant factors in preventing large losses from occurring.


2-3

Standards and Codes

• Component tests by nationally recognized labs— Underwriters Laboratories

— Factory Mutual

• Codes— NFPA 70, National Electrical Code

— NPFA 72, The National Fire Alarm Code

— Local codes and ordinances


2-4

Basic System Components

• System control unit (alarm panel)— Brain of system

— Processes alarm signals from actuating devices and transmits them to the local or other alerting system


2-5

Basic System Components (cont.)

• Power supply— Primary power supply

– Public electric utility

– Engine-driven generator

— Secondary power supply– Storage battery and charger

– Engine-driven generator and 4-hour storage battery

– Multiple engine-driven generators

— Trouble signal power supply


2-6

Basic System Components (cont.)

• Initiating devices: manual pull stations, heat detectors, smoke detectors, flame detectors, waterflow devices, tamper switches, and combination detectors

• Notification appliances: bells, buzzers, horns, recorded voice messages, strobe lights, speakers, and other warning appliances

• Auxiliary services


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Types of Fire Alarm Systems

• Selection factors— Level of life-safety hazard

— Structural features of the building

— Level of hazard presented by the contents of the building

— Availability of fire suppression resources

— State and local code requirements(Continued)


2-8

Types of Fire Alarm Systems (cont.)

• Local system— Noncoded local alarm

– Simultaneous operation of all alarm-indicating devices

– Only practical in small occupancies with limited number of rooms

— Master coded local alarm– Serves the premises as a local control unit and

receives input from other fire alarm control units

– Used in occupancies that use the alarm signals for other purposes

(Continued)


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Types of Fire Alarm Systems

• Local system (cont.)— Zoned/annunciated alarm

– Identifies fire location quickly and accurately

– Alarm-initiating devices arranged in circuits or zones

– Initiating device sounds alarm and lights corresponding lamp on control unit

– Annunciator panel remote from control panel

– Coded signals

— Presignal alarm(Continued)


2-10


• Auxiliary system— Facility that receives signals where personnel are

always present to respond– Initiation devices

– Local requirements and policies

— Types of auxiliary systems– Local energy system

– Shunt system

– Parallel telephone system(Continued)


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• Remote station system— Connected to dispatch center by means other

than municipal fire alarm box system

— Local alarm capability

— Monitoring options(Continued)


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• Proprietary system— Used to protect large buildings or facilities

— Systems for individual buildings or areas wired into common receiving point

— Wide-ranging capabilities(Continued)


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• Central station system— Similar to proprietary system but receiving point

is an outside, contracted central station

— Alarm activation information received by central station employees, who initiate emergency response

(Continued)


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• Emergency voice/alarm communications system— Supplements other systems

— Communicates detailed information to occupants and fire fighting personnel

— One-way/two-way


2-15

Manual Alarm-Initiating Devices

• General requirements— Mounting and distribution

— Generally not required in fully sprinklered structures

— Outmoded “broken glass” pull stations

• Coded versus noncoded pull stations

• Single-action and double-action pull stations


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Automatic Alarm-Initiating Devices

• Continuously monitor atmosphere

• Four basic types— Heat detectors

— Smoke detectors

— Fire-gas detectors

— Flame detectors


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Heat Detectors

• Fixed temperature heat detectors— Fusible links/frangible bulbs

— Continuous line detector

— Bimetallic detector

• Rate-of-rise heat detector— Pneumatic rate-of-rise spot detector (Fig. 2.34)

— Pneumatic rate-of-rise line detector (Fig. 2.35)

— Rate compensated detector (Fig. 2.36)

— Thermoelectric detector


2-18

Smoke Detectors

• Photoelectric smoke detector— Projected beam (Fig. 2.37)

— Refractory photocell (Fig. 2.38)

• Ionization smoke detector (Fig. 2.39)— Dual chamber

— Air-sampling smoke detectors– Cloud chamber (Fig. 2.40)

– Second type (Fig. 2.41)(Continued)


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Smoke Detectors (cont.)

• Limitations— May not provide early warning of a fire

developing on another level of a building

— May not detect fire developing on the other side of a closed door

— May not be effective when fire is caused by explosions resulting from careless housekeeping


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Flame Detectors

• Types— Ultraviolet (UV) Fig. (2.42a)

— Infrared (IR) Fig. (2.42b)

• Fast to respond

• Frequent false alarms


2-21

Fire Gas Detectors

• Monitors levels of gases released by combustion— Carbon dioxide

— Carbon monoxide

• Faster than heat detectors but slower than smoke detectors


2-22

Combination Detectors

• Various possible combinations— Fixed rate/rate-of-rise detectors

— Heat/smoke detectors

— Smoke/fire gas detectors

• Offer benefits of both systems and increase responsiveness to fire conditions


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Acceptance Testing• Should be observe by representatives of

building owner, fire department, system installer, and system manufacturer.

• All functions of the fire detection and signaling system should be operated:— All alarm-indicating and alarm-initiating devices

— Restorable heat detectors

— Response of outside entities responsible for monitoring the system


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General Inspections

• Fire department participation

• Checkpoints— Condition of wiring and batteries

— All equipment free of foreign materials

— Adequate clearance around system control units, recording instruments, and other devices


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Inspecting and Service Testing Initiating Devices

(cont.)• Manual alarm-initiating devices

• Automatic alarm-initiating devices— Detectors must not be damaged or painted.

— Replace or send the following detectors to a recognized testing laboratory for testing:– Detectors on systems that are being restored to

service after a period of disuse

– Detectors that are obviously corroded(Continued)


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(cont.)• Automatic alarm-initiating devices

— Replace or send the following detectors to a recognized testing laboratory for testing (cont.):– Detectors that have been painted over, even if

attempts were made to clean them

– Detectors that have been mechanically damaged or abused

– Detectors on circuits that were subjected to current surges, overvoltages, or lightning strikes

(Continued)


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(cont.)• Automatic alarm-initiating devices

— Replace or send the following detectors to a recognized testing laboratory for testing (cont.):– Detectors subjected to foreign substances that might

affect their operation

– Detectors subjected to either direct flame, excessive heat, or smoke damage

— Testing– Nonrestorable

– Restorable


2-28

Inspecting System Control Units

• Control panel switches and functions

• Auxiliary devices

• Receiving signals


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System Testing Timetables• Local systems: local guidelines

• Central station systems: monthly

• Auxiliary systems: monthly (noncoded fire alarm boxes: monthly)

• Remote station and proprietary systems: authority having jurisdiction

• Emergency voice/alarm systems: quarterly

• NOTE: In all cases, check the most current edition of NFPA 72, National Fire Alarm Code.


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Record Keeping

• Maintaining Files and Records— Documents:

– Inspection reports, forms, and letters

– Violation notices

– Summonses

– Plans review comments, approvals, and drawings

– Fire reports

– Investigations

– Permits and certificates issued(Continued)


2-31

Record Keeping

• Maintaining Files and Records (cont.)— Occupancies:

– Those that have been issued a permit, certificate, or license

– Those that contain automatic fire suppression or detection systems

– Those that conduct hazardous operations or routinely house hazardous materials

— Duration: life of structure

— Public record(Continued)


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Record Keeping (cont.)

• Written records— File for each inspected property

— Cataloging and storage

• Electronic records— Two primary methods of entering data:

– Inspectors use laptop computers or handheld electronic data recording equipment during the inspection.

– Inspectors use written forms during the inspection and then enter the information upon returning to the office.

(Continued)


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Record Keeping (cont.)

• Electronic records (cont.)— Considerations in computer system management

– How will the information be filed?

– How can the information be retrieved?

– What portion of the information will be stored in a read-only format?

– What personnel will be given access to retrieve information from the system?

– What information can be released to the public?

Fire Detection and Suppression Chapter 2 Fire Detection and Signaling Systems.

Documents

alarm systems local

zonedannunciated alarm

appropriate alarm

alarm code local codes

alerting system slide

alarm control units

early detection

local control unit