Fire alarm system


A fire alarm system has a number of devices working together to detect and warn people through visual and audio appliances when smoke, fire, carbon monoxide or other emergencies are present. These alarms may be activated automatically from smoke detectors, and heat detectors or may also be activated via manual fire alarm activation devices such as manual call points or pull stations. Alarms can be either motorized bells or wall mountable sounders or horns. They can also be speaker strobes which sound an alarm, followed by a voice evacuation message which warns people inside the building not to use the elevators. Fire alarm sounders can be set to certain frequencies and different tones including low, medium and high, depending on the country and manufacturer of the device. Most fire alarm systems in Europe sound like a siren with alternating frequencies. Fire alarm electronic devices are known as horns in the United States and Canada, and can be either continuous or set to different codes. Fire alarm warning devices can also be set to different volume levels.

Design

After the fire protection are established – usually by referencing the minimum levels of protection mandated by the appropriate model building code, insurance agencies, and other authorities – the fire alarm designer undertakes to detail specific components, arrangements, and interfaces necessary to accomplish these goals. Equipment specifically manufactured for these purposes is selected and standardized installation methods are anticipated during the design.
Last version 2019; Status, Published.
This code is part of a family standard NFPA
There are national codes in each European country for planning, design, installation, commissioning, use and maintenance of fire detection system with additional requirements that are mentioned on TS 54 -14
As per NFPA 72, 18.4.2 Temporal Code 3 is the standard audible notification in a modern system. It consists of a repeated 3-pulse cycle. Voice Evacuation is the second most common audible in a modern system. Legacy systems, typically found in older schools and buildings have used continuous tones alongside other audible schemas.
Mass notification systems often extend the notification appliances of a standard fire alarm system to include PC based workstations, text-based digital signage, and a variety of remote notification options including email, text message, RSS feed, or IVR-based telephone text-to-speech messaging.

Building safety interfaces

Fire alarm systems in non-domestic premises are generally designed and installed in accordance with the guidance given in BS 5839 Part 1. There are many types of fire alarm systems each suited to different building types and applications. A fire alarm system can vary dramatically in both price and complexity, from a single panel with a detector and sounder in a small commercial property to an addressable fire alarm system in a multi-occupancy building.
BS 5839 Part 1 categorizes fire alarm systems as:
Categories for automatic systems are further subdivided into L1 to L5 and P1 to P2.
MManual systems, e.g. handbells, gongs, etc. These may be purely manual or manual electric, the latter may have call points and sounders. They rely on the occupants of the building discovering the fire and acting to warn others by operating the system. Such systems form the basic requirement for places of employment with no sleeping risk.
P1The system is installed throughout the building – the objective is to call the fire brigade as early as possible to ensure that any damage caused by the fire is minimized. Small low-risk areas can be excepted such as toilets and cupboards less than 1m².
P2Detection should be provided in parts of the building where the risk of ignition is high and/or the contents are particularly valuable. Category 2 systems provide fire detection in specified parts of the building where there is either high risk or where business disruption must be minimized.
L1A category L1 system is designed for the protection of life and which has automatic detectors installed throughout all areas of the building with the aim of providing the earliest possible warning. A category L1 system is likely to be appropriate for the majority of residential care premises. In practice, detectors should be placed in nearly all spaces and voids. With category 1 systems, the whole of a building is covered apart from minor exceptions.
L2A category L2 system designed for the protection of life and which has automatic detectors installed in escape routes, rooms adjoining escape routes and high hazard rooms. In medium-sized premises, a category L2 system is ideal. These fire alarm systems are identical to an L3 system but with additional detection in an area where there is a high chance of ignition or where the risk to people is particularly increased.
L3This category is designed to give early warnings to everyone. Detectors should be placed in all escape routes and all rooms that open onto escape routes. Category 3 systems provide more extensive cover than category 4. The objective is to warn the occupants of the building early enough to ensure that all are able to exit the building before escape routes become impassable.
L4Category 4 systems cover escape routes and circulation areas only. Therefore, detectors will be placed in escape routes, although this may not be suitable depending on the risk assessment or if the size and complexity of a building are increased. Detectors might be sited in other areas of the building, but the objective is to protect the escape route.
L5This is the "all other situations" category, e.g., computer rooms, which may be protected with an extinguishing system triggered by automatic detection. Category 5 systems are the "custom" category and relate to some special requirements that cannot be covered by any other category.

Zoning

An important consideration when designing fire alarms is that of individual zones. The following recommendations are found in BS 5839 Part 1:
Also, the NFPA recommends placing a list for reference near the FACP showing the devices contained in each zone.