Automatic Fire Detectors

Do we really need a detector?

Kerosene Kerosene

Speed & Aftermath of Fire

YesFire Detectors detect fires at their earliest stages and sound a loud warning to help you get out safely

Detection

Typical room

Typical roomAlarm bellFire AlarmPanelBellStair pressurisation fanCorridorFire escape stair

Typical room in hotelDetectorSprinklerAlarm bellFire AlarmPanelBellStair pressurisation fanCorridorFire escape stair

Fire starts in room

Smoke detector activates alarmSmoke fills guest roomAlarm sounds in rooms and at lobbyStairway fan pressurisation begins

Occupants make way to stairwellSmoke slowly spills into corridorStairwell provides SAFE egress path to outside of building

Sprinklers in room operate, discharging water, controlling and extinguishing fireOccupants exit from building

Occupants leave building to safe areaSmoke is discharged from building

DetectionDetectors sense the existence of a fireFire Panels acknowledge the detectors,test the system, check for faults operate the alarmsAlarms inform the occupants of a fire and assist the evacuation

1. Concentration of energy2. Source of oxygen3. Spontaneous oxidation at surface of combustible material4. Release of particles into atmosphere5. Exponential propagation of chain reaction6. Release of energy in the form of light and heat

Ignition and fire growth

Fire GrowthSTAGE 4STAGE 1STAGE 2STAGE 3VISIBLE SMOKEINTENSE HEATFLAMING FIREINCIPIENT STAGE - NO VISIBLE SMOKETIMESMOKE DENSITY AND HEAT OUTPUT

DetectorsSmokeFlame HeatCO

Detects the presence of smoke particlesInexpensive, early detection for smouldering firesNo need for line of sightIndoor applications onlySubject to occassional false alarmsSmoke Detector

Ionisation OpticalBeamSamplingInstalled every 10mSmoke Detector

Ionisation

ION-CHAMBER SMOKEChamber coverCollectorAlpha sourceBatterySmoke Detector

Working of Ionisation Detector

Smoke DetectorDouble Chamber Ionization Detector

OPTICAL SMOKEInsect ScreenFinsInsect ScreenSmoke PathSamplingVolume

Optical DetectorLight Scatter Type

Optical DetectorObscuration Type

Sampling Detector

What is an Air Sampling System?

Air sample ismoved throughthe laser chamber via the aspiratorand filterInlet manifoldAspirator Air enters detectorLaserChamberDual Stage FilterUltra pure air is used to keep optical surfaces cleanDust is filtered outThe signal is then passed to the processor card for and onto the Display ModuleDisplayOperation of the VESDA Detector

Very Early Smoke Detection ApparatusVESDA

Radiation / Flame Detectors

Forms of radiant energy produced by a fire

Detects radiation from flameAnalyses one or more UV or IR frequenciesExtremely fast on flaming firesLong range, line of sightSophisticated and expensiveSuitable for high risk, liquid and gas hazardsFlame Detector

Infra-red (IR) Radiation Detector

Scanning Infra-red (IR) Radiation Detector

Ultra-violet (UV) Radiation Detector

Ultra VioletWeldingX-rayLens contaminationHigh power consumptionInfra RedsunlightFALSE ALARMS

Senses temperature or temperature change Immune to false alarms in most casesReliable, fairly slow detection Fire must be near detectorLow maintenanceInexpensive

Heat Detector

Fixed temperatureRate-of-riseHeat Detector

Heat DetectorExpansion of single metal strip

Heat DetectorExpansion of single metal strip

Heat DetectorExpansion of bi-metallic strip

Heat DetectorExpansion of gases

Heat DetectorExpansion of gases

Heat DetectorLinear Heat Detecting Cables

Technology provides continuous profiles of temperature using a single optical fibre as the sensing elementAn instrument containing an Optical Time Domain Reflectometer and signal processing softwareMonitors hundreds of points in seconds Sensor is insensitive to EMISensor is Intrinsically safe

Optical Fibre Distributed Temperature Sensing

Beam DetectorsEffects of Flame on IR BeamEffects of Smoke on IR Beam

CO is a toxic gasCO is the major cause of death in firesCO detectors sense slow smouldering fires before smoke detectorsBest option for hotels, hospitals, nursing homes

Carbon Monoxide Detector

CARBON MONOXIDE SOMETHING NEW IN FIRE DETECTION?

Carbon Monoxide GasProduced in firesOdourlessColourlessTravels more freely than smokeMakes victims lethargic, disorientedBrain damage, death at high ppmFACTS

Slow Smouldering Fires

Vast quantities of CO before flamingCause of many deathsDifficult to detect using traditional Ion- or Optical based detectorsCause of backdraft?FACTS

Fire GrowthSTAGE 4STAGE 1STAGE 2STAGE 3VISIBLE SMOKEINTENSE HEATFLAMING FIREINCIPIENT STAGE - NO VISIBLE SMOKETIMESMOKE DENSITY AND HEAT OUTPUTFLAMESPRINKLERPHOTOIONBEAMHEATVESDA

Allow manual alarm of fireDifferent types include:BreakglassPush buttonLeverLocated at exits and throughout risk

Call Points

PanelsPanels are the Brains that receive the detector inputs and decide the action or output responseThe panels and detectors are configured into SYSTEMSThere are two types of system configurations:CONVENTIONAL and ADDRESSABLE

Conventional systemsSimple installationDetectors and inputs are grouped into ZONES

Addressable SystemsEach detector and input is individually identifiedOne wire connects different types of inputs

OutputsAlarmsBellsSirensLightsEVAC systemsVoice commands for regulated evacuationDrivers for controlSuppression systemShutdown of air handlingControl of doors

SelectingDetectorsPrevention issuesLife safety, Business interruption, Asset protection, Explosion preventionTolerable damage levelsFire issuesSlow or rapid developmentSmouldering or flamingSolids or liquids?

Selecting DetectorsAnalyse relative importance of:Speed of responseRange of responseSensitivity and discriminationReliabilityGeneral immunity to false alarm sourcesImmunity to specific radiation sourcesElectronic interfaceCost

Early Detectionleads toLife Safety