fire alarm systems chapter-8 smoke detector

7/25/2019 Fire Alarm Systems Chapter-8 Smoke Detector

1/35

Chapter-8 Initiating Devices: Smoke Detectors

8-1

Chapter-8

Initiating Devices: Smoke Detectors

Smoke detector Smoke-sensing fire detector fire alarm system smoke detector

Smoke d

etector

() (able to detect fire early)

() (allows emergency personnel to respond)

() ( life safety) () (highly reliable)

smokedetector ionization spot-type smoke detector photoelectric spot-type smoke detector liner beam-type smoke detector air-sampling smoke detector duct-typesmoke detector

- (smoke detector spacing with beams less than 0.1 H.)


2/35

Fire Alarm Systems

8-2

-() Smoke detector spacing with beamdepths greater than 0.1 H and spaced more than 0.4

H.

-() Smoke detector spacing with beamdepths greater than 0.1 H and spaced less

than 0.4 H.

- (smoke) (stratification)

-Air sampling detector smoke detector heat detector

-Smoke detector with protectivemechanical guard

-Ceiling jet formed by fire plume


3/35


8-3

..

smoke detector (ambient conditions exist)() () (temperature below 32F (0C))

() () (temperature above 100F (38C))

() (relative humidity above 93 percent)

() 300 ft/min(300 ft/min or 1.5 m/sec)

..

Smoke d

etector

Smoke detector (environmental conditions that influence smoke detector response)

Air Velocity Altitude Temperature

>300 ft/min >3000 ft Humidity 100F Color of

Protection (>91.44m/min) (>914.4 m) >93% RH (37.8C) SmokeIon X X X X O

Photo O O X X X

Beam O O X X O

Air sampling O O X X O

X: Can affect detector response. O: Generally does not affect detector response.

..

Smoke Detector

Smoke detector ()

() Photoelectric () Ionization

. Ionization Detectors

() Ionization detector ionization chamber ionizing radiation (source) Ionizing radiation Americium-241 Ionization chamber Alpha particles(helium nuclei) () (+ve plate) (-ve plate) () (+ve plate) (-ve plate)

() (ionizationchamber) () current smoke detector activate

Smoke detector heat detector alarm activate (very early in a fires development or incipient stage) Photoelectric smoke detector (smoldering fire)


4/35

Fire Alarm Systems

8-4

(flaming fire) (smoldering) reset

-() Multi-criteriadetector

() Projected beamtype smokedetector with reflector.

() Typical projected beamtypesmoke detector.

-Device programmingunit and smoke detector.

Addressable smoke detector

showing programming switches.

Typical spot type smoke detector.

-() Initiating device base showing

duplicate terminals.

-() Smoke detector with base showing incoming

and outgoing terminals.

Photoelectric smoke detector (1) optical chamber

(2) cover

(3) case moulding

(4) Photodiode (detector)

(5) infrared LED

-Photoelectric smoke detector


5/35


8-5

-Manufacturers calibrated test instruments

-Photoelectric smoke detectorSensing chamber in a photoelectric smoke

detector. Smoke particles deflect the light

beam and trigger the alarm.

-Circuit of an ion chamber detector.Combustion particles reduce electrical flow and

trigger the alarm.

-Typical single- station smoke alarm -Operation of an ionization smoke detector

-Technician removing wire from device -Aerosol smoke product for functional


6/35

Fire Alarm Systems

8-6

to check electrical supervision test of a smoke detector

-Functional test of a smokedetector

-Technician using aheat detector tester

-Compressed-airsmoke detector cleaner

Ionization smoke detector (sensing chamber/metal chamber) (ionization ) (radioactive material) (radioactive material) radiation

(low, and steady electrical current) Electrode current

(smoke particles) chamber (air molecules) (ionize) electrode conductivity Conductivity electronic circuit current fire alarm signal Conductivity (pre-set threshold) fire alarm signal

-Ionisation type smoke detector : Normal operation -Fire operation

Photoelectric optical smoke detector (smoulderingfire) (more sensitive to largeparticles) flaming fire (lesssensitive to small particles)


7/35


8-7

-Ionization smoke detector

-Ionization smoke detector

.

.

Ionization Smoke Detector

Advantages)

() (detects invisible products of combustion)

() (aerosol) (detect other aerosol)

() (quick acting)

() Clean room computer room

.

.

Ionization Smoke Detector

Disadvantages)

() (detects the

Ionisation type smoke detector (fast flaming fires) reset (automatically resets when the atmosphere clears)


8/35

Fire Alarm Systems

8-8

presence of smoke only, not toxicity)

() False alarm (high false alarm rate)

() (radioactive material) (hazardsfor ionization detection)

-Operation of a photoelectric light obscuration smoke detector

-Photoelectric light-scattering smoke detector

.Photoelectric Light-Scattering Smoke Detector

.

.

Light-Scattering Smoke Detector

Photoelectric light-scattering smoke detector (light source) (photosensitive sensor) Light Emitting Diode(LED)(light source) Dark chamber (beam of light) photo diode chamber

photosensitive sensor Light source (rays)photosensitive sensor

-Operation of a photoelectric light-scattering smoke detector


9/35


8-9

(smoke particle) (chamber) photo cell (smoke particle) (light path) (reflection) (scattering) Photo cell photo cell current current

firealarm signal

-Circuit of photoelectric smoke detector

-Ionization smoke detector -Projected-Beam smoke detector

ionization smoke detector photoelectric smoke detector System smoke detector Ionization smoke detector Photoelectric smoke detector Photoelectric smoke detector smoldering fire sensitive


10/35

Fire Alarm Systems

8-10

-Light-Scattering smoke detector -Reflected type beam smoke detector

-Photoelectric smoke detector

-Smoke detector Smoke alarm Intelligent smoke detector

..Photoelectric Smoke Detector

Advantages)

() (sensitive to visual particles of smoke)() (detects smothering low heat fires)() (provide early warning)

..Photoelectric Smoke Detector

Disadvantages)

() (early contamination by dust causing reduced sensitivity)

() (detects presence of smoke, not toxicity)() (must be cleaned on a regular basis)() False alarm (high false alarm rate)

.

.

Photoelectric Detectors

Locations)

(office) clean rooms raised floor spaces (computer rooms) (telecommunications rooms) (electrical equipment rooms)(sleeping rooms) smoke detector


11/35


8-11

-Photoelectric type smoke detector : Normal operation

-Photoelectric type smoke detector : Fire situation

-Beam detector deflection characteristics (Vertical plane view)

.Beam Smoke Detector

Photoelectric device (light beam) Photocell activate

-Photoelectric linear projected beam smoke detector(Light obscuration smoke detector)


12/35

Fire Alarm Systems

8-12

(diffusing the projected light beam by a specified percentage of obstruction)beam detector alarm Beam blockage trouble signal Optical Beam Detectors

-Beam detector coverage characteristics (Horizontal Plane View)

-Beam Detector Spacing

-Sitting of supplementary optical beam detectors


13/35


8-13

Optical Beam Detector Difficult access for detector installation, maintenance, testing and replacement

Exposure to direct sunlight

Multiple reflective surfaces causing false alarms

Building movement

Multi-level detection Aesthetics

Smoke detector false alarm () Cooking smoke () Spray paint() Steam from a hot shower () Sanding dust() Dust stirred up while cleaning () Solder smoke

.Ion Smoke Detector Photo Smoke Detector Sensitivity)

) Ion Detectors

Ion smoke detector sensing chamber (ionizes) (smaller smoke particles) smoldering fire (large

particles) smoldering fire sensitivity (smaller smoke particles) oversensitive

(ionization )

) Photo Detectors

Photo smoke detector chamber smoke particle (reflection) Photo smoke detector smoldering fire (larger smoke particle) (flaming fire) (small particles) smoldering fire sensitivity (large particles) oversensitive

Flaming fire (small particles) Smoldering fire (large particles)

Smoke detector


14/35

Fire Alarm Systems

8-14

smoke detector Ion Photo combined smoke detector (enclosure) ion smoke detector photo smoke detector Combinedsmoke detector smoldering fire (largeparticles) flaming fire (small particles)

Combination smoke detector less sensitive false alarm

-Pendant-mounted air duct installation. Inlet tube orientation.

.. Smoke Detector Location)

Beam (affect air flow) () smoke detector beam (underside) (open areas) flat ceiling smokedetector (distance between smoke detectors)(.)

.Air-sampling Smoke Detector

Air-sampling smoke detector (tubing) (samplingport) (protected space) (smoke particles)

detection chamber (particle)detector fire alarm signal

-Aspirating detector ceiling mounted pipework


15/35


8-15

.Air Sampling Smoke Detectors

air-sampling system Air sampling aspirating type fire detection system ()(fiveprimary components)

() Air-sampling system () Detector

() Aspiration system () Control system () Filter assembly

-Use of Sampling Tubes to Convey Smoke-Laden Air to the Central Detection Unit of an Air-Sampling Detector.

-Air SamplingType SmokeDetectors

-Air Sampling Smoke Detector with CoverRemoved

-Internal View of a Duct-Type Smoke Detector.


16/35

Fire Alarm Systems

8-16

.Air Duct-type Smoke Detector

Air ductsmoke detector (detect) duct (air outlet) Heating, ventilation and AirConditioning (HVAC) system

Air duct smoke detector () (area smoke detection)()(early warning)() (buildings regular fire detection system)

-Duct detectors -Duct-type smoke detector

..Duct Detectors

() Duct detector photoelectric detector Duct (outside the ductwork) Duct (sample the air

inside the duct) ductprobe () Smoke control device duct

(control the flow of air in ductwork)Air Handling Unit(AHU)

Table 8-1 Environmental Conditions that Influence Smoke Detector Response

Detection

Protection

Air Velocity

>91.44 m/min

(>300 ft/min)

Altitude >

9.4.4 m (>

3000 ft)

Humidity >

93% RH

Temperature

37.8C

(100F)

Color of

Smoke

Ion X X X X OPhoto O O X X X

Beam O O X X O

Air sampling O O X X O

X = Can affect detector response.

O = Generally does not affect detector response.


17/35


8-17

. Smoke Detector Placement)

smoke detector nationaland local standard manufacturers specification Smoke detector NFPA 72 () feet(9m) apart Firedetection and fire alarm systems for buildings(BS 5839-1:2013) () ()

-Smoke detector with listed heatdetection

-Duct probe unit installed in return air duct

-Partitions extending higher than 85 percent of the floor-to ceiling height (thickness of the ceiling jet)

()()(approximately one-tenth the floor-toceilingheight.) () (8 ft (2.4 m ceiling) ceiling jet thickness

()9.6 in. (244 mm) () joist heat detector ceiling jet

(Locating a heat detector on the bottom of a 4

Spot-type smoke detector (area of coverage) 21 feet(6.5m) Detector (L) (W)() (9.1m) (diagonal measurement) 42feet (13m) detector


18/35

Fire Alarm Systems

8-18

in. (100 mm) joist would place the detector in the center of the ceiling jet, an ideal location for

undelayed response.)

detector () (space is not accessible

for storage purposes)

() (steam pipes) (electric wiring)(conveyors) equipment

() (floor over the space is tight)

() detector (No flammable liquids are processed,handled, or stored on the floor above)

-Detector coverage and spacing under flat ceilings

-Detector coverage for pitched


19/35


8-19

-Ceiling Obstructions Treated as Walls

-Proximity of Detectors to Ceiling Fittings

-Horizontal ceiling comprising a series of small cells (Honeycomb Ceilings)

.Detector Coverage)

Detector (constructioncharacteristics) () Corridors () Pitched ceilings() Flat ceilings () Shafts/Flues

() Honeycomb ceilings () Stairways

Detector detect (range) Smokedetector heat detector detect smoke detector coverage heat detector detector


20/35

Fire Alarm Systems

8-20

Spacing and Siting of Detectors for Honeycomb Ceilings(Horizontal ceiling comprising a series of

small cells)

.Detector

Conventional addressable analog addressable fire alarm system detector (fullcoverage) detector (environment) (potential fire hazards)

detector

-Joists: 3 ft (0.9 m) or less on center, more than 4 in. (100 mm) deep Beams: More than 3 ft(0.9 m) on center, more than 4 in. (100 mm) deep Effect of Joists and Beams on the Ceiling Jet.

.

Environmental and Fire Type Considerations

detector smoke detector

heat detector flame detector smoke detector activate


21/35


8-21

(areas with materials that overheat, smolder, or

ignite) (electrical equipment) ( paper) (wood) (visible smoke is the first indicator a fire has started) optical(photoelectric) smoke detector (best protected)

ionization smoke detector detector

.

Selection of Detectors for Different Area

S.No Plant Area Type of Detector

1

Main control room, Computer

room, Electronic cubicle

room and control rooms in

outlying areas.

Combination of - Ionisation smoke detector and Optical

type smoke detector

2

Switchgear rooms in main

Plant and outlying areas,

battery charger room, record

and shift-in-charge engineers

room

Ionisation type smoke detector.

3 Office rooms / storage rooms Ionisation type smoke detector

4Battery rooms and

chemically corrosive areas.

Corrosion resistant, Rate of rise of temperature heat

detector with fixed temperature setting.

5 Cable gallery

Combination of Optical type smoke detectors and Linear

heat sensor running above all HV and LV power cable trays.

Unless the vertical distance between cable tray is less than

500 mm in which case alternate trays (in addition to the top

and bottom trays). The optical smoke detector and LHS

detectors along with necessary number of interface units in

the cable gallery will be cross zoned to actuate the water

spray system

6 Station building / Plant area Infrared flame detectors (where oil tanks are located),spray tanks rate of rise of temp. detector with fixed element

( combustible materials) detector (combustible materials) detector

flame detector


22/35

Fire Alarm Systems

8-22

. Smoke Detector

Smoke detector (power sources)() (can be batteries or household power)

() smoke detector (battery operated are easy to install and are economical to purchase)

() (independent of housepower so they will operate during power failures)

()British Standard fire code smoke detector (British Standard fire code will permit battery operated units (existing buildings))

() hard wired smoke detector (British Standard building code requires hard wired smoke alarms for new construction)

() (should install both on every level of homeplus in the sleeping rooms.)

() smoke alarm (British Standardfire code (British Standard fire code requires hard wired smoke alarms fornew construction)

() (lack of maintenance (ie. not replacing batteries) is greatestconcern)

.

Fire Detector

Criteria to Determine Layout)

() operation (design, construction and operational features of all types ofdetectors shall be in accordance with relevant standards.)

()fire detector

() (total area to be protected)() (type of building construction)

() (air movement & air velocity)() (ceiling obstructions)() equipment (concentration of equipment in the area covered)()sensitivity

() (area is divided into zones to be protected)

() detector detector (the zones of individual detectors should overlap and no blind zone shouldbe left. )

() (Areas above false ceiling and below false flooring shall be considered as


23/35


8-23

separate zones.)

() detector (Under ideal conditions of smooth ceiling and average roomsize, one detector is recommended to protect the area.)

() (largest combustible gas concentration) ionisation detector

() (air conditioned areas) ionization optical typesmoke detectors

()Detector (highest point of the ceiling) (manufacture) minimum coverage

()Complete coverage detector (location)

()smoke detector () () () (35to 40 sq.m per detector for general application.)

()Main control room electronic cubicle room computer room ()()(20 to 25 sq.m per detector)

() IS/NFPA (the exact requirementshall calculated based on relevant IS/NFPA standard)

Table 8-5 Common sources of aerosols and particulate matter moisture

Moisture Humid outside air

Humidifiers

Live steam

Showers

Slop sink

Steam tables

Water spray

Atmospheric

contaminants

Corrosive atmospheres

Dust or lint

Excessive tobacco smoke

Heat treating

Linen and bedding handling

Pneumatic transport

Sawing, drilling, and grinding

Textile and agricultural

processing

Combustion

products

and fumes

Chemical fumes

Cleaning fluids

Cooking equipment

Curing

Cutting, welding, and

Engine

exhaust

Diesel trucks and locomotives

Engines not vented to the

outside

Gasoline forklift trucks


24/35

Fire Alarm Systems

8-24

brazing

Dryers

Exhaust hoods

Fireplaces

Machining

Ovens

Paint spray

Heating

element with

abnormal

conditions

Dust

accumulations

Improper

exhaust

Incomplete combustion

Smoke detector (sources of electrical and mechanicalinfluences on smoke detectors)

Electrical Noise and Transients Airflow

Vibration or shock

Radiation

Radio frequency

Intense light Lightning

Electrostatic discharge

Power supply

o Gusts

o Excessive velocity

- Smoke detector with protective plasticcover.

- Concealed Smoke Detector(SD) inLocked Room with Remote Indicator(RI).

detector (predicting detector response)

(anticipated fires) system(intended respond) ()(ceiling shape and surface)

()(ceiling height)

() (configuration of contents in the protectedarea)

() (combustion characteristicsand probable equivalence ratio of the anticipated fires involving the fuel loads within the

protected area)

()(compartment ventilation)


25/35


8-25

() (ambient temperature, pressure,altitude, humidity, and atmosphere)

Table 8-x Comparison of combination, multi-criteria, and multi-sensor detectors

Detector Type Features

Combination

Multiple sensors

Does not utilize a mathematical evaluation principle, just a simple or functionMultiple listings

Multi-criteria

Multiple sensors

Mathematically evaluated

Only one alarm signal

Single listing

Multi-sensor

Multiple sensors

Mathematically evaluated

Capable of generating multiple alarm signals

Multiple listings

.Mounting

-Mounting installations permitted (top) and not permitted (bottom).

.Detector Spacing)

beam detector (for sloping ceilings with beams running perpendicular across slope, the fol-lowing shall apply)


26/35

Fire Alarm Systems

8-26

() Spot-type detector beam (bottom of the beams)() (average height over slope)(ceiling height)

() (spacingshall be measured along a horizontal projection of the ceiling)

() Beam (smooth ceiling spacing shall be permitted within beam pockets)

() % beam spot type detector (For beam depths less than or equal to 10 percent of theceiling height (0.1 H), spot-type detectors shall be located with smooth ceiling spacing.)

() 0.4H % % beamspot-type detector (For beam depths greater than 10 percent of theceiling height (0.1 H), spot-type detectors shall not be required to be located closer than (0.4 H)

and shall not exceed 50 percent of smooth ceiling spacing.)

beam (for sloping ceilings with beams running parallel up slope, the following shall apply)() Spot-type detector(s) shall be located on the ceiling within beam pocket(s).

() The ceiling height shall be taken as the average height over slope.

() Spacing shall be measured along a horizontal projection of the ceiling.

() Smooth ceiling spacing shall be permitted within beam pocket(s) parallel to the beams.

() For beam depths less than or equal to 10 percent of the ceiling height (0.1 H), spot-type detectorsshall be located with smooth ceiling spacing perpendicular to the beams.

() For beam depths greater than 10 percent of the ceiling height (0.1 H), the following shall applyfor spacing perpendicular to the beams.

() For beam spacing greater than or equal to 40 percent of the ceiling height (0.4 H), spot-typedetectors shall be located in each beam pocket.

() For beam spacing less than 40 percent of the ceiling height (0.4 H), spot-type detec-tors shall notbe required in every beam pocket but shall be spaced not greater than 50 percent of smooth

ceiling spacing.

beam (for sloped ceilings with beam pockets formed by intersectingbeams, the following shall apply)

() Spot-type detector(s) shall be located at the bottom of the beams.

(

) The ceiling height shall be taken as the average height over slope.

() Spacing shall be measured along a horizontal projection of the ceiling.

() For beam depths less than or equal to 10 percent of the ceiling height (0.1 H), spot-type


27/35


8-27

detectors shall be spaced with not more than three beams between detectors and shall not

exceed smooth ceiling spacing.

() For beam depths greater than 10 percent of the ceiling height (0.1 H), spot-type detectors shallbe spaced with not more than two beams between detectors, but shall not be required to be

spaced closer than (0.4 H), and shall not exceed 50 percent of smooth ceiling spacing.

-High Air Movement Areas (Not to Be Used for Under-Floor or Above-Ceiling Spaces).

Smoke Detector Spacing Based on Air Movement

Smoke Detector Spacing Based on Air

Movement

Minutes per

Air Change

Air

ChangesSpacing per Detector

per Hour ft2 m2

1 60 125 12

2 30 250 23

3 20 375 35

4 15 500 46

5 12 625 58

6 10 750 70

7 8.6 875 81

8 7.5 900 84

9 6.7 900 84

10 6 900 84

-Ceiling height limits (general)


28/35

Fire Alarm Systems

8-28

-Remote Indicator Used for Concealed

Detectors.

-Beam Measurements for predicting

effects on detection

-Four-Wire Smoke Detectors Supervised for the Absence of Operating Power by an End-of-Line Power Supervision Relay.


29/35


8-29

-Alarm verification timing diagram.

ASmoke detector goes into alarm.ABRetard-reset period (control unit)

Control unit senses detector in alarm and retards (delays) alarm signal, usually by de-

energizing power to the detector. Length of time varies with design.

BCRestart period (detector power-up time)Power to the detector is reapplied and time is allowed for detector to become operational for

alarm. Time varies with detector design.

ACRetard-reset-restart periodNo alarm obtained from control unit. Maximum permissible time is 60 seconds.

CDConfirmation periodDetector is operational for alarm at point C. If detector is still in alarm at point C, control unit

will alarm. If detector is not in alarm, system returns to standby. If the detector re-alarms at

any time during the confirmation period, the control unit will alarm.

DEOptional region

Either an alarm can occur at control unit or restart of the alarm verification cycle can occur.

ADAlarm verification period

Consists of the retard-reset-restart and confirmation periods.


30/35

Fire Alarm Systems

8-30

-Inclined Manometer for Velocity Pressure Readings in Low Velocity Ducts, 400 ft/min to 2000ft/min (2.0 m/sec to 14.2 m/sec).

-Smoke Alarm with IntegralNotification Appliance for the Hearing

Impaired.

-Single-Station Smoke Alarm with RemoteNotification Appliance.

If appropriate, the Plans and Specifications addressed in D.3.3 should be updated based on the resultsof the test.


31/35


8-31

-Hard-Wired Multiple-Station(Interconnected) Smoke Alarms.

-Multiple- Station Smoke Alarm AuxiliaryRelay Module for Remote Notification Appliance.

-Wireless Interconnected Multiple- StationSmoke Alarm Device.

-AC-Powered Ionization Smoke Alarm withBattery Backup.

-Fixed- Temperature Combination SmokeAlarm and Heat Alarm.

-Low-Profile Rate-of-Rise Heat Detector.


32/35

Fire Alarm Systems

8-32

-Wireless Interconnected Multiple- Station Smoke Alarms.Table 8-5 Ceiling height limits (general).

Table 8-6 Ceiling height limits (category P systems and 5 minute fire service attendance).


33/35


8-33

Table 8-7 Ceiling height limits (category P systems and 5 minute fire service attendance).

-End-

Contents

.. ...........................................................................................

..Smoke detector .........................................................

..Smoke Detector ...............................................................................................

.Ionization Detectors ....................................................................................................... 3

..Ionization Smoke Detector (Advantages) .................................................


34/35

Fire Alarm Systems

8-34

..Ionization Smoke Detector (Disadvantages) .........................................................

.Photoelectric Light-Scattering Smoke Detector .................................................................. 8

..Light-Scattering Smoke Detector .................................................................................

..Photoelectric Smoke Detector (Advantages) .....................................................

..Photoelectric Smoke Detector (Disadvantages) ..................................................

..Photoelectric Detectors (Locations) ...........................................

.Beam Smoke Detector .................................................................................................. 11

.Ion Smoke Detector Photo Smoke Detector(Sensitivity) .................... 13

..Smoke Detector(Location) ..............................................................................

.Air-sampling Smoke Detector ......................................................................................... 14

.Air Sampling Smoke Detectors ....................................................................................... 15

.Air Duct-type Smoke Detector ........................................................................................ 16

..Duct Detectors .............................................................................................................................

.Smoke Detector (Placement) .................................................................... 17

.Detector (Coverage) ................................................. 19

. Detector ................................................................................................... 20

.Environmental and Fire Type Considerations ................................................................. 20

.Selection of Detectors for Different Area ....................................................................... 21

.Smoke Detector .............................................................. 22

.Fire Detector (Criteria to Determine Layout) ......... 22

.Mounting ................................................................................................................... 25

.(Detector Spacing) ................................................................. 25


35/35


fire alarm systems chapter-8 smoke detector

Documents