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STANDALONE FIRE ALARM
Standalone Fire, Heat Alarm is designed for Domestic Usage such us a house, villa and apartment,etc,.
Toxic smoke and fumes kill. In a house fire, it is the flames that do the structural damage, but smoke is the main danger to people. The majority of deaths in fires come from smoke poisoning.
Modern homes contain many materials, such as wood, wool, nylon and plastics, which when burning, produce heavy smoke and toxic fumes such as carbon monoxide. These materials can smolder for extended periods of time, producing substantial smoke and fumes before they burst into visible flames.
If you are asleep when a fire starts, you could suffer from smoke inhalation before you wake up. In fact, the combination of toxic smoke and gases and reduced levels of oxygen in the air can make waking up extremely difficult and in some circumstances, tragically impossible. So, it is essential to install and maintain working smoke, heat alarms that will detect the smoke, heat and sound an alarm.
SMOKE ALARM
Self contain Optical Smoke detector and alarm sounder
Photoelectric Output, Sound level : 80dB, Detection Area: 40m2
FEATURES
1. With test and reset button
2. 9v operated
3. Low battery indication
4. Battery removable will inhabit cover from closing ( as per UL standard)
5. Easy installation
6. LED indicator for 360º vision
7. Connection port to link up to 30 detectors in a single network
8. Output to interface with other security equipment
CONVENTIONAL PANELS
A Conventional Fire Alarm System normally consists of a control panel linked to a number of lines of fire detectors and manual call points, normally called detection zones, and a number of sounder or alarm circuits.
Control Panel
The Control Panel drives the detection zones and sounder circuits, provides LED indications of fire, fault or normal conditions and contains switches to allow the sounders to be activated or silenced and the detectors to reset following and alarm. The control panel is powered from the mains (230VAC) and will contain back-up batteries to allow the system to function for a minimum of 24 hours, dependent on the application, in case of main failure.
Fire Detection and Alarm Zones
Most conventional fire alarm panels have several detection zones comprising a mixture of automatic fire detectors and manual call points. In order to limit the effect of faults, and to limit the search area in the case for fire, the size of fire detection zone is limited to 2000 m², with a maximum travel distance within the zone to locate a fire of 60m. In addition, zones should not cover more than one floor, unless the total floor area of the building is less than 300m². As a result unless the site is very small, the system will comprise several detection zones.
A fire alarm (or sounder) circuit may cover more than one detection zone, but it must follow the boundaries of the relevant detection zones, and the boundaries should be of fire resisting construction.
FIRE ALARM DEVICES
Fire alarm systems have devices connected to them to detect the fire/smoke or to alert the occupants of an emergency. Below is a list of common devices found on a fire alarm.
Manual pull stations/manual call points - Devices to allow people to manually activate the fire alarm. Usually located near exits. Also called "manual pull boxes". Other countries have different devices as standard, for example the UK uses 'break-glasses', when people break a small pane of glass to activate the alarm.
Smoke detectors - Spot type: Photoelectric and Ionization; Line type: Projected Beam Smoke Detector; Air-Sampling type: Cloud Chamber
Water Flow Switches - Detect when water is flowing through the fire sprinkler system
Rate-of-Rise and Thermostat (heat) Detectors - Detect heat changes
Valve Supervisory Switch - Indicates that a fire sprinkler system valve that is required to be open, is now closed (off-normal).
Carbon Monoxide Detectors - Detects poisonous carbon monoxide gas and usually only connected to household fire alarm systems. Very rarely seen in commercial systems.
SMOKE DETECTOR
How Optical Smoke Detector Work
An optical smoke alarm (also called photo-electric smoke alarm) works using the light scatter principle,. The alarm contains a pulsed Infra red LED which pulses a beam of light into the sensor chamber every 10 seconds to check for smoke particles.
When a fire breaks out smoke will enter the optical chamber through the opening vents. Smoke alarms from quality manufacturers have the chamber protected with insect screens to stop bugs entering and causing false alarms.
As the smoke enters the optical chamber, its particles cause the Infra red light to be scattered onto the photo-diode light receptor.
Once the scattered light hits the photo-diode light receptor a signal is sent to the integrated circuit which causes the alarm to sound alerting the occupants to the fire.
An optical smoke alarm uses the principle of light sensors to identify the smoke and hence, detect fire. It consists of LED lights (light emitting diode), a lens and a photo-diode. Let's know how light helps to detect a fire. A light emitting diode is a semiconductor device that operates on the principle of a diode. When the diode is forward biased, recombination of holes and electrons take place, thereby releasing energy in the form of light.
In normal conditions (when there is no fire or smoke), light from the light emitting diode passes the detector in a straight line and so the alarm is not triggered. A lens is provided in the optical smoke alarm device to direct the light source in the form of a light beam. In the events of a smoke, the smoke particles fill the smoke alarm and due to the presence of the smoke particles, the light beam gets deflected from the straight line path. The deflected light beam strikes the photoelectric sensors (photo-diodes) and thus the alarm is triggered. You must be thinking what is a photo-diode? Well, a photo-diode is another form of diode that become active when a light beam (photons) falls on it. These alarms are also called photoelectric alarms.
When mounted on a flat ceiling, smoke detection devices have an individual coverage of 7.5m radius. However these radii must overlap to ensure there are no “blind spots”. Therefore individual coverage can be represented by a square measuring 10.6 X 10.6m giving an actual coverage area of 112 m² per device
HEAT DETECTOR
How Heat Detectors Work
A heat alarm is designed to detect heat instead of smoke, the alarm contains a thermistor which is set to respond to temperatures above 58°C.
When a fire breaks out hot air from the fire will rise and enter the sensor chamber.
When temperature inside the chamber reaches 58°C a signal is sent to the integrated circuit which causes the alarm to sound alerting the occupants to the fire
Heat Detectors are normally used in environments where a smoke detector might generate false alarms. Heat detectors can be situated in the kitchen and the garage, because heat alarms don't react to smoke they are not prone to false alarms from cooking and exhaust fumes.
Rate of Rise heat detectors will alarm if the temperature rises very quickly, or if the temperature reaches a set threshold. This type of detector would be the first choice in an environment where a smoke detector could not be used.
In some environments, such as boiler rooms, fast rates of rise of temperature can be expected normally, meaning that there would be a risk of false alarm when using a rat-of-rise device. In this case a fixed temperature detectors give an alarm once the temperature has reached a preset threshold, most commonly 58°C or 78°C for EN54-5 Class AS or BS respectively.
When mounted on a flat ceiling, heat detection devices have an individual coverage of 5.3m radius. However these radii must overlap to ensure there are no “blind spots”. Therefore individual coverage can be represented by a square measuring 7.5 X 7.5m giving an actual coverage area of 56.3m² per device
MULTI SENSOR DETECTOR
Multi Criteria Detectors Comprise of two or more sensors within the same housing, integrated by the detector electronics or software to give a rapid response to a broader range of fires and greater immunity to nuisance alarms. The most common type at present is a combination of optical and rate of rise heat sensors, which can give a response to fast flaming fires similar to that of ionisation detectors. Other sensor combinations are also available.
The new Multi-Sensor from EI combines the results of the heat and optical sensors and uses the combined data to give earliest fire protection while giving full protection against false alarms.
BEAM DETECTOR
Optical Beam Detectors work on the principle of projecting a beam of light across a room, which is attenuated when smoke is present thus allowing an alarm to be given.
There are two forms of beam detector: emitter and receiver separate (single path), requiring separate wiring both to the emitter and receiver, and reflective in which the emitter and receiver are mounted in the same box, and the beam is shone onto a reflective material at the far side of the room (dual path).
Since an optical beam detector senses smoke across the entire smoke plume, it tends to be less affected by smoke dilution as the ceiling height increases than point type smoke detectors. In addition a single beam detector can protect a large area; hence they are particularly suitable for protecting large high rooms such as sports arenas, warehouses and shopping malls.
Beam detectors are more complex to install than ordinary point smoke detectors and it is advisable to consult an application guide for the use of projected beam smoke detectors before considering the use of these detectors.
MANUAL CALL POINT
People can often still detect a fire long before automatic fire detectors; hence manual call points are important components of fire detection systems in occupied buildings to ensure timely evacuation in the case of fire. All call points should be approved to EN54-11, and should be of type A, that is once the frangible element is broken or displace the alarm condition is automatic.
Manual Call points should be mounted on all escape routes, and at all exit points from the floors of a building and to clear air. It should not be possible to leave the floor of a building without passing a manual call point, nor should it be necessary to deviate from any escape route in order to operate a manual call point. Call points mounted at the exists from a floor may be mounted within the accommodation or on the stairwell. In multiple storey buildings where phased evacuation is to be used call points should be mounted within the accommodation to avoid activation of call points on lower levels by people leaving the building.
In order to provide easy access, call points should be mounted between 1.2 and 1.6m from the floor, and should be clearly visible and identifiable. The maximum distance anyone should have to travel in order to activate a manual call point is 45m, unless the building is occupied by people having limited mobility, or rapid fire development is likely, in which case the maximum travel distance should be reduced to 20m. Call points should also be sited in close proximity to specific hazards, for example kitchens or paint spray booths.
FIRE ALARM SIREN
Audible Alarm Signals Audible fire alarm signals must provide a clear warning of a fire to all those for whom the signal is intended. For category M an L systems this would normally imply all occupants of a building, however in some sites this may not apply, for example in hospitals or rest homes, residents might need assistance to evacuate, in which case it may be sufficient to alert staff.
The general requirement for the volume of audible alarm signals is that they should provide a Sound Pressure Level (SPL) of at least 65dB(A), but not more than 120dB(A) throughout all accessible areas of building.
Exceptions to this general rule are as follows:
· In stairways the SPL may be reduced to 60dB(A)
· Enclosures less than 60m² may be reduced to 60dB(A)
· There is no minimum for enclosed areas less than 1 m²
· At specific points of limited extent the SPL may be reduced to 60dB(A)
Where a continuous background noise level greater the 60dB(A) is present the fire alarm signal should be 5dB above the ambient, but not greater than 120dB(A).
Where the alarm is intended to wake people, an SPL of 75dB(A) is required at the bed head. Generally this will require a sounder to be place within the room.
Where it is not possible to place a sounder within a room, there will be a loss of approximately 20dB(A) through a standard door, and 30dB(A) through a fire door.
Warning: Volumes greater than 120dB(A) will cause damage to hearing.
In Open Space, as the distance from a sounder doubles, the sound level will be reduced by 6dB(A).
It is Preferable to use multiple quieter sounders to achieve the required sound level, rather than a smaller number of loud devices. This is to prevent points of excessive volume, which may lead to disorientation or damage to hearing. Two sounder providing equal sound levels will combine to add 3dB(A) to the SPL.
Visual alarms are required in order to satisfy the Disability Discrimination Act (DDA) as well as being used in areas of high background noise where hearing protection is likely to be worn. Just as audible alarms should be placed through all accessible areas of a building, visual alarms should be placed such that they can be seen in order to alert the hearing impaired.
Visual alarms should be clearly distinguishable from other warning lights, preferably red and should flash at a rate of 30 to 130 flashes per minute. The recommended mounting height is above 2.1m; however they should not be mounted closer than 150mm from the ceiling. They should be positioned so that any alarm is clearly visible from all locations within the area protected.
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