What is the need for a Fire Alarm System?
What is the need for a Fire alarm system?
WHAT IS A FIRE ALARM SYSTEM?
A fire Alarm System is designed to warn in an emergency so that can take action to protect ourselves, staff, and the general public.
Fire alarms are found in Offices, Schools, Hospitals, Factories, and public buildings, they are a part of our daily routine but are often ignored until there is an emergency at which point, they might just protect our lives.
Whatever the method of detection is, if the alarm is activated, sounders will operate to alert people in the establishment that there may be a fire and to evacuate.
The fire alarm system may also incorporate a remote signal system which could then alert the fire brigade via a central station.
So, what is the need for a Fire alarm system? In this article, we will the need for a Fire alarm system? and the types of “Fire Alarm Systems”.
WHY DO WE NEED A FIRE ALARM SYSTEM?
All Fire Alarm Systems essentially work on the same procedure. If a detector detects smoke or heat, or someone operates a broken glass unit, then alarm sounders operate to alert others in the building that there may be a fire and to evacuate. For the system protecting property and life, it is additionally likely that the Fire Alarm will incorporate remote signaling equipment which would warn the fire brigade via a central station.
A fire alarm system comprises a central Control and Indicating Equipment with various types of detectors, manual call points, interface units, and sounders connected to it.
Wired Fire Alarm Systems can be into three categories: Conventional, Addressable, and Analogue Addressable.
ADDRESSABLE FIRE ALARM SYSTEM
ANALOGUE ADDRESSABLE FIRE ALARM SYSTEM
Intelligent Fire Alarm Systems are another name for analog fire alarm systems. The type of protocol analog systems utilize determines the many sorts of systems that are available. The Control Unit is in charge of determining whether there is a fire, malfunction, pre-alarm, or anything else.
However, compared to conventional or addressable systems, analog systems are fundamentally significantly more sophisticated and have a much greater number of facilities. Their main goal is to lessen the likelihood of false alarms.
It should be noted that the way of wiring to a detector base is different with Addressable and Analogue Addressable Fire Alarm Systems from the method of wiring to a Conventional Base.
CONVENTIONAL FIRE ALARM SYSTEM
In a typical fire alarm system, numerous call points, or multiple call points and detectors, are connected to the fire alarm control panel in zones. One circuit is often connected to each floor or fire compartment, which is what a zone is.
On the Fire Alarm Control Panel, there would be several Zone Lamps. Zones are used to give a basic idea of where a fire has occurred. How precisely we can locate where a fire has started depends on the number of Zones a Control Panel has, and consequently, the number of circuits that have been wired inside the structure. Then, wire at least two sounder circuits, which could be made up of bells, electronic sounders, or other devices to the control panel or other audible devices. Detection Zones and Sounder Circuits are wired in a star pattern. An end-of-line device would be present on each circuit for monitoring purposes.
The traditional system is typically utilized in smaller, less sophisticated installations since it is better suited to smaller spaces and lacks the addressable system’s intricacy and processing capability.
CONSULTATION FOR DESIGNING FIRE ALARM SYSTEM
Regarding the laws governing specific premises, it is always important to consult the local fire prevention officer early on. The Fire Officer will interpret the Fire Precautions Act and any other legislation that may apply to a specific building and provide guidance on the type of fire alarm system that may be needed.
It is important to keep in mind that the fire prevention officer is more concerned with LIFE than property.
We suggest speaking with a fire prevention officer only with the client’s permission.
It is crucial to interact with any other interested parties while developing a fire alarm system, such as:
- The Local Fire Authority
- The System Installer
- The Health and Safety Officer
- Any Consultant or Architect
- The Insurance Company
During early discussions it is necessary to establish the purpose of the Fire Alarm System, ie:
- To improve the safety of the occupants
- To minimize harm to the property
While insurance companies offer substantial discounts to customers who install sprinkler systems, installing complex fire detection systems rarely results in a decrease in rates significant enough to persuade a customer to install a fire alarm system for the protection of their property. The vast majority of installed fire alarm systems often serve to safeguard life.
FIRE ALARM SYSTEM DESIGN
Before starting the design, you must ensure that necessary information is available. It may need to be confirmed or it may be stated in the specification. In addition to the buyer, there can be a requirement to communicate with other interested parties. The Fire Prevention Officer of the local Fire Brigade will probably be the most significant.
A FIRE ALARM SYSTEM'S USE OF MANUAL CALL POINTS
SITTING OF SOUNDERS IN A FIRE ALARM SYSTEM
CHOICE OF DETECTORS FOR FIRE ALARM SYSTEM
Heat detectors typically detect a fire far later than smoke detectors do. Therefore, installing smoke detectors is preferred unless there is a chance of false or unwanted alarms. Installing a smoke detector in a kitchen, for instance, is not advised since it would scare someone who was toasting toast. Boiler rooms, generator rooms, garages, and dusty places should all have heat detectors. A boiler’s combustion products, a generator’s leaky exhaust, or exhaust gases from a car could all set off a smoke detector and result in an unwelcome alarm. In places like kitchens and boiler rooms, where one may typically anticipate a sudden temperature rise, Fixed Temperature Heat Detectors should be fitted.
Rate of growth Where Smoke Detectors would not be appropriate but where a sudden rise in temperature is not anticipated, such as in garages, parking lots, dusty workshops, etc., Heat Detectors should be installed.
There are two basic types of Point Smoke Detectors:
- Emissions chamber Small particle smoke, such as that produced by burning paper and alcohol, as well as new cellulosic smoke, are extremely detectable by smoke detectors. They are not very susceptible to smoke that contains big particles, such as smoke from burning plastics or stale smoke.
- Optical Smoke Detectors are sensitive to optically dense smoke ie: and smoke with large particles and they are relatively insensitive to optically thin smoke.
Only optical smoke detectors are used in some nations, including Italy, Japan, and Qatar, while only ionization detectors are utilized in some regions of the Middle East and the Far East. Systems inside the UK may include a combination of the two. Most individuals are killed by thick, dense smoke, which is typically a bigger danger than getting burned. Because of this, optical detectors are typically utilized on exit routes like hallways and stairwells. Offices and other common areas typically have ionization smoke detectors installed.
SITTING OF FIRE ALARM DETECTORS
The most enclosed portions in a building will typically have the largest concentration of smoke and heat, so this is where the detectors should typically be placed. Smoke Detectors Smoke Detectors should be placed so that the detecting element is not 600mm or more below the ceiling or roof, whichever is lower. Smoke Detectors should be fitted in each apex of protected space with a pitched or northern light roof. The following guidelines should be followed for the maximum horizontal distance between any location in the protected area and the closest detector:
The maximum distance for Point Type Smoke Detectors should not be greater than 7.5m in areas with horizontally flat ceilings and hallways wider than 5m. A Point Smoke Detector may provide coverage up to 100 square meters.
A row of detectors should be placed inside the apex of a pitched or north-facing roof if detectors are to be installed there. At the tallest point, one row of detectors should be placed at least 0.5 meters away from a vertical wall. For every degree of slope, up to a maximum of 25%, the maximum horizontal distance is increased by 1%.
For example, The maximum distance between detectors, for a Point Type Smoke Detector 20-degree slope is as follows: 20% of 7.5m = 1.5m.
Therefore, the maximum distance between detectors is 7.5 + 1.5 = 9m. Additionally, the maximum coverage area may be correspondingly increased.
The horizontal distance shall be decreased by twice the depth of the obstruction where a ceiling obstruction, such as a beam with a depth greater than 150mm but less than 10% of the height of the ceiling, is expected to hinder the flow of smoke or hot gases from a position to a detector.
For instance, for a Point Type Smoke Detector obstructed by a 200mm depth beam then the maximum distance between detectors = 0.2m x 2 = 0.4m.
7.5m – 0.4m = 7.1m.
The region on either side of a ceiling impediment, such as a beam, should be treated as a separate room if it is greater than 10% of the height of the ceiling. Ceiling beams with a depth of less than 150 mm can be disregarded. For detecting smoke in expansive, unobstructed roof regions, such as those found in most warehouses, optical beam smoke detectors are helpful. As one smoke beam can offer the coverage of numerous separate point detectors, they can be highly cost-effective. A projector, receiver, remote manual reset unit, and local power supply with battery standby are the standard components of a smoke beam.
HEAT DETECTORS IN FIRE ALARM SYSTEM
Heat detectors should be placed such that the heat-sensitive element is not less than 25mm below the ceiling or roof and not more than 150mm below it. The following guidelines should be followed for the maximum horizontal distance between any location in the protected area and the closest detector:
The maximum distance between any heat detector and any wall or partition shall be 5.3m when there are horizontally flat ceilings present and when the hallway is wider than 5m. 50 square meters is the largest area that a heat detector can cover.
FIRE ALARM SYSTEM CONTROL EQUIPMENT
The following location should typically be used for the fire alarm control equipment:
Preferably on the bottom level at the Fire Brigade’s entrance, preferably in a low-fire risk area, and ideally visible from the outside of the building. When automatic detection is in use, the Control Panel should be in a protected place that is accessible to all building users. Although it shouldn’t be too close to the phone position, an alarm sounder should be placed next to the control unit. Normally, a sufficient zone map of the building should be mounted close to the control panel.
FIRE ALARM SYSTEM POWER SUPPLIES
The Fire Alarm Control Panel typically includes both the mains power supply and the battery power supply, which are the two power sources needed. In addition to supporting the sounders for an additional half-hour, standby batteries must allow the system to run without power for 24 hours longer than the likelihood that the building will be vacant. Six hours of standby time + 30 minutes of the alert load is enough if the mains supply is backed by an emergency generator. There are 24 volts in every modern fire alarm system.
The backup batteries on medium-sized and bigger fire alarm systems frequently do not fit inside the control panel. If standby batteries are housed in a separate housing, the main Fire Alarm Control Panel should be as close to this housing as practicable. Serious volt drop issues may occur if the power supply or battery housing is placed more than 10 meters from the primary fire alarm control panel. Lead-acid sealed batteries are always used as standby batteries. Automobile batteries should not be installed since using nickel-cadmium batteries is not cost-effective.
FIRE COMPARTMENTS IN FIRE ALARM SYSTEM
To prevent the spread of fire from one compartment to another, buildings are typically divided into fire compartments. In a building, each level and stairwell often serve as a distinct fire compartment. To stop the spread of smoke and fire within a small factory, the factory unit is typically divided from the offices by “firewalls.” As a result, the manufacturing and offices will have distinct fire compartments. Typically, a zone should only cover one fire compartment.
ZONING IN FIRE ALARM SYSTEM
Buildings are typically divided into fire compartments, each of which is built in such a way as to stop a fire from spreading to adjacent compartments. A building typically has a separate fire compartment for each story and stairs. To prevent the spread of smoke and fire from one area to another within a small facility, the factory unit is typically divided from the offices by “firewalls.” This will result in distinct fire compartments for the plant and offices. Typically, only one fire compartment should be covered by a zone.
There are two exceptions:
- If the building is divided into fire compartments, any compartment communicating with other compartments only on the ground floor of the building can be treated as if it were a separate building. For example, if a floor area is not greater than 300 square meters, it can all be one zone, regardless of the number of stories.
- If the building is divided into fire compartments, any compartment that only communicates with other compartments at the lowest level of the building can be treated as if it were a separate building; in other words, if the floor area is not greater than 300 square meters, it can all be one zone, regardless of how many stories the building has.
Regardless of the size of the building, there are two limitations on the maximum size of a zone.
- It should have a maximum floor space of 2000 square meters.
- The search area shouldn’t be larger than 30 meters. This means that, even if the fire is only visible from the end of the searcher’s path, the searcher entering the zone by the typical route shouldn’t have to go more than 30 meters after entering the zone before seeing a fire large enough to operate a detector. Remote indicators can be fitted to allow bigger areas to meet the search distance criteria and display an alarm in a closed space.
No matter how big or small a zone is, there are two limits to its design.
- The zone borders should follow compartment boundaries if the area includes more than one fire compartment.
Each occupancy should be located within a separate zone (or collection of zones) if the building is divided into several occupancies; no zone should be divided into more than one occupancy.