Fire alarm system is a system that monitors situations of fire and provides instant communication to the occupants and security personnels about fire or the incident that may lead to fire.
A complete fire alarm systems constitutes
- Fire Detection System
- Notification / Alarm System
Fire, considered to be a worst disaster that spreads rapidly to destroy properties and life can be difficult to overcome at later stages of growth. With timely warnings, intensity of occurrences of any calamity can be drastically minimised.
Fire alarm system that consists of automatic fire detectors, manual call points, sounders etc. is designed for the purpose of providing early fire warning. With these signs, occupants can take the opportunity to leave and also immediately take necessary action in suppressing the fire at its very early stage.
Fire detection part of complete fire alarm system is responsible for detecting or sensing the presence of fire alone. The process of warning the occupants through audio visual utilities such as sirens, hooters etc. are taken care by the alarm system.
The fire detection and alarm system function together to provide timely fire warnings to those in emergency zones.
Fire detection can either be
Automatic Fire Detection:
Automatic fire detection is achieved by fire sensors/ detectors. Smoke or heat are considered the best indicators of fire. Hence, fire detectors use these parameters to sense the presence of fire.
Fire detectors such as smoke detector, heat detectors etc. act only as measuring instruments to measure values of smoke/heat in their surveillance. They automatically declare fire when the level of smoke/heat in its surveillance is beyond its pre programmed threshold/upper limit value.
Once the detectors declare fire, the alarm sounders begin to operate automatically.
Manual Fire Detection:
Manual fire detection occurs when the manual call points or call stations are triggered manually by those who confirm fire or other situations of emergency.
By actuating the fire call points, the sirens, beacons etc. will begin to sound warning the occupants of fire.
Fire Alarm system constitutes fire detection system and alarm/notification system. Fire detection is achieved automatically with fire detectors such as smoke detector, heat detector, multisensors(smoke+heat sensors) etc. Fire detection can also be achieved manually through manual call points/call stations etc.
All the devices that initiate fire warning such as fire detectors or manual call points etc. are regarded as alarm initiating devices.
The devices that respond to fire initiation and warn the occupants with audio visual utilities such as sirens, sounder beacons, speakers etc. are called as notification/ alarming devices.
All of the initiating(detectors, call points etc.) and notifications devices(sounder beacons, speakers etc.) are all together connected to one central and control unit called the Fire Alarm Control Panel. This the central unit that control and monitors the whole fire alarm system.
Fire detectors such as smoke detector, heat detectors etc. act only as measuring instruments to measure values of smoke/heat in their surveillance. The detectors send the measured values to the fire alarm control panel and it is the panel that compares the live values with the pre programmed threshold values of smoke/heat. It then provides the instruction to the sounders to sound only when the level of smoke/heat is beyond its threshold/ fixed upper limit.
Fire alarm systems are of various types as listed below that differ in the suiting the size, complexity or type of application/building the system needs to be installed in
- Addressable fire alarm system
- Wireless Addressable fire alarm system
- Conventional fire alarm system
A Zone is a specific area of a full building. Buildings are split into zones for identification purpose. For example, first floor of a building can be identified as a zone. Similarly, second floor the same can be another zone.
Zones are kept small enough for easy identification of the area. Buildings of large size and increased complexity can have multiple zones and a very small building can even be a single zone.
For example, In case a building is large sized and complex, the zones can be split as below
- Left side→ Zone 1
- Right side→ Zone 2
- Left side→ Zone 3
- Right side→ Zone 4 etc.
We can now identify zone 3 as the left side of the second floor. By increasing the number of zones or reference for splitting the building, location identification can be made easier. Architecture of the building can also influence the number of zones.
In fire alarm system, all devices such as fire detectors, call points, sounders etc. will be wired together zone wise to a common fire alarm control panel. In case of fire detected by any detector/ call point in the network, the zone that the initiating device is wired in will be indicated in the control panel.
As per the above example, if a smoke detector in the left side of the second floor has detected fire, the control panel will indicate fire emergency at Zone 3. With this information, the area in emergency can be identified with ease.
Conventional system is an old technique to construct a fire alarm system. All devices such as detectors, MCPs etc. are wired zone wise and is connected to the Conventional Fire Alarm Panel that has LED as indicators for each zone.
If a device detector goes into alarm, the control panel will be able to identify which zone has gone into alarm, but will not have the exact location of the fire or which device that triggered the alarm.
Such a system keeps up to the basic necessities of an alarm system and is preferred for small applications or projects that work on a tight budget.
Large and complex applications may require finer diagnostic details of location in fire as it can be difficult to locate the spot with details of just the zone. With Addressable type system, the location can be pinpointed for enabling immediate attention.
Every device in the Addressable fire alarm network will have a unique ID. When the alarm is raised, the control panel will be able to pin-point the device that has raised alarm keeping its ID as reference.
|Location Detailing||Exact details of location fire specified along with device ID and type of device initiating alarm||Only the area/ zone is indicated|
|Wiring||All the devices in the fire alarm system can be connected using the same wire in a loop with its one terminal arising from the control panel, running all through the location to connect all the devices, and then brought back to the panel.||Wiring in a building has to be exclusive to zones. Meaning, the wire has to cover all devices in one zone and should be brought back to the panel. Similarly, for the next zone, new set of wires have to arise from the panel to connect the next set of devices and then be brought back to the panel.|
|Reliability||More reliable in terms of information delivery and functionality.||Less reliable.|
|Cost||Little expensive due to high reliablity and advanced features.||Less expensive. However, cost for long term maintenance and cables would be more compared to addressable type.|
|Overall recommendation||More recommended due to its advancement in features and information capability that makes operation during fire more easy.||Recommended only for very small sized applications that function under a tight budget.|
|S.No||TRADITIONAL PA SYSTEM||ADDRESSABLE DIGITAL VOICE SYSTEM|
|1.||100V AC signal and analog communication.||12/24V DC signal bus and digital communication.|
|2.||With 100V AC as power cables or instrument cables cannot be laid, a separate conduit will be required.||Simple and low cost cabling can be done.|
|3.||Audio power amplification at main equipment.||Audio power amplification at individual speaker unit.|
|4.||No indivdual speaker control is possible.||Every speaker unit has a unique ID. Control of individual speaker from panel or from multiple remote control units is possible.|
|5.||Indivdual speaker unit is not electrically supervised. No reliability of devices available at circuit at all times.||Indivdual speaker devices are electrically supervised. Reliability of devices available at circuit at all times.|
|6.||Protection or Detection is not available for cable short circuit or open circuit.||Cable short circuit or open circuit detection and protection is available in the display unit.|
|7.||Low sound reproduction quality.||High sound reproduction quality.|
|8.||Consumes more cable at a high cost.||Consumes less cable bringing down the cost.|