Fire Detection and Alarm Systems Flashcards
Need for Fire Alarm Systems in
Buildings
- In event of fire outbreak, any delay in activation of the fire alarm system & notifying of fire service will contribute to danger to life & heavy property losses.
Fire detection in small premises
- In small premises like open-air areas & single-storey buildings, all exits
are visible & escape travel distances are small.
*Therefore, any fire can be quickly detected by occupants present & shouts of ‘fire!’ may be all that is needed.
Fire detection in larger premises
- Fire could start & develop to extent that escape routes may become affected before fire is discovered
- Thus need automatic fire warning system
*Hence, an effective means for early detection of any fire outbreak is necessary.
Functions of a Fire Detection and
Alarm System
- Active fire protection system for the purpose of early detection & raising an alarm of a fire outbreak within building.
- Consists of detection devices working together to detect & warn people thru visual & audio appliances when smoke, fire or other emergencies are present.
- Alarms may be activated automatically from detection devices such as smoke detectors & heat detectors or manual call points or pull stations.
- Alarms can come from either electrically operated alarm bells or visual strobes.
Provision of Fire Alarm Systems in
Buildings
- Most Purpose Groups buildings must be provided with a fire detection & alarm system.
- Provision of automatic fire detection and alarm systems & type of fire alarm system is dependent on height of building & total floor area per storey.
- Home fire alarm device (HFAD) must be installed for individual residential units under PG I or II.
- Operation of HFAD must be based on smoke detection technology, with indicator lights to inform occupants
Manual Fire Detection System
- Consists of manual call points, that is wired together with alarm system with normally open contacts.
- Usually of the break-glass type & bright red in colour.
- In event of fire, breaking of glass will close electrical contacts and activate alarm system.
- Only effective in premises when people are present to raise alarm in event of a fire.
Code Requirements for Manual Call Points
- Provided on every storey of building or part of building and located so that no person need travel more than 30m from any position within building to activate alarm.
- Located on exit routes preferably next to hose reels & on floor landings of exit staircases and at exits to street.
- Located between 0.8m and 1.2m above floor level & should be located at easily accessible and noticeable positions free from obstructions.
Audible Alarm Sounders or Alarm Bells
- Should generate a continuous tone.
- Sound should be readily distinguishable from other forms of alarm systems.
- In places of entertainment / areas where sound & special effects lighting systems are installed such as karaoke booths, sound systems must be electronically interlocked with fire alarm system such that these systems will be automatically cut-off when fire alarm system is activated.
Visual Alarm Devices
- Signals should be provided to alert people who are hearing-impaired
or where hearing protection is likely to be worn. - Signals should not be used in place of audible alarm signals.
- Intensity of light must be sufficient to draw attention of people in vicinity.
- Should be mounted at height of 2m to 2.5m above floor level, such that it is visible from all corners of floor.
- Visual alarms can be in form of a flashing beacon or strobe light.
- Visual alarms must be located tgth with manual alarm call points.
Automatic Fire Detection Systems consist of…
- smoke detectors
- heat detectors
- flame detectors
- video imaging fire detector
- maybe manual call points
- maybe fire suppression systems like automatic fire sprinkler system
Components of Automatic Fire Detection Systems are wired together for…
Providing continuous surveillance & early detection of any fire outbreak.
Automatic Fire Detection Systems are useful where?
- Particularly useful in places where few people will ever visit such as storage areas / at night where people are not around.
Why are Automatic Fire Detection Systems effective?
do not rely on people to raise an alarm.
Functions of Main Alarm Panel
- Main alarm panel (MAP) is ‘brains’ of fire alarm system.
- Responsible for monitoring various alarm ‘input’ devices like signals from manual call points & automatic detection devices & then activating alarm ‘output’ devices like sounding of audible alarm sounders / alarm bells, visual alarm devices to notify occupants that there is a fire outbreak so that evacuation procedures can begin.
DECAM stands for…
Decentralised Alarm Monitoring Station
what is DECAM?
- private organisation certified by SCDF to provide Central Alarm Monitoring service to monitor fire alarm signals linked to SCDF Operations Centre.
- acts as an intermediary between building and SCDF Operations Centre.
Function of Decentralised Alarm
Monitoring Station (DECAM)
- MAP transmit alarm signal to DECAM and thence to SCDF/Fire service
- Fire alarm system will automatically be placed in alert state.
- After alarm signal has been transmitted, FSM will verify if alarm signal comes from a fire outbreak.
- FSM need affirm w DECAM if got fire or is false alarm
- If is false, DECAM will communicate w Fire Service & signal will be cancelled
- If got fire, DECAM will convey to Fire Service, Fire service send ppl.
- If no reply to DECAM within 2 min, Fire Service still send ppl.
- If Fire Service go and is false alarm, got penalty on building owner
Activation of secondary systems:
- Homing of lifts to designated floors, usually first floor so can use to transport firefighters to fight fire & conduct rescue.
- Shut down air-handling units to prevent smoke spread.
- Activate smoke exhaust systems to remove smoke from fire.
- Activate air pressurisation systems to keep smoke out of evacuation routes such as lobbies & staircases.
- Lowering of smoke curtains to keep smoke out of occupied areas.
- Deactivating doors held open by electromagnetic devices to prevent smoke travelling afar.
- Others
Precautions against Failure: Fire Detection
- Main Alarm Panel must have means to ensure that automatic detection system is in working order.
- Must be capable of detecting failures, such as loss of power supply to system
or faulty detectors. - Such failures will normally be registered visually by the lighting up of an amber fault lamp and audibly by the sounding of the fault buzzer.
- Battery system has to be used for backing-up for 24 hours when the main
power supply fails. - Regular inspection, testing & maintenance of the system on daily, weekly and monthly basis.
Siting of Main Alarm Panel
(a) Fire command centre
or
(b) Main entrance of building if a Fire Command Centre is not available.
Use of Sub-Alarm Panel
- Located remotely from the Main Alarm Panel.
- Has alarm zone facilities or alarms to show the location of the alarm signal and transmits such alarm signal to the Main Alarm Panel.
- Normally located on every floor at fire lift lobbies, smoke stop lobbies, or at the main point of entry to the alarm zone.
Zoning for Fire Detection and
Alarm Systems: Consideration
- Area & accessibility
- By ensuring that each zone is accessible from main corridors leading from where the Sub-Alarm Panel is sited.
Zoning for Fire Detection and
Alarm Systems is carried out as follows:
- allocate one zone for each floor & each fire compartment.
- divide large floor areas into smaller ones, each not exceeding 2000 m2.
- provide separate protection zones for concealed areas, areas with difficult
access & high hazard areas such as fuel storage rooms.
Weekly Checks and Tests on Fire
Detection and Alarm System
- Carry out simulation & transmission of fire alarm signal & fault signal
to monitoring station & confirm that it is functioning correctly. - Necessary to contact decentralised monitoring station & inform them of test before transmitting simulated fire alarm & fault signal
- Necessary to check w monitoring station after completion of test to ensure fire alarm & fault signal were received and to advise them when
system has been placed back to normal. - Check the battery voltage and battery condition.
- On completion of the test, take corrective action immediately on any
abnormality or faults encountered within the system. - Enter the test results and follow-up actions, if any, in the log.