Fire alarm system

A fire alarm notification appliance that is used in the United States and Canada, the (Wheelock MT-24-LSM) with a strobe light

A fire alarm system is 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 sounders in the United States and Canada can be either continuous or set to different codes such as Code 3. Fire alarm warning devices can also be set to different volume levels. Smaller buildings may have the alarm set to a lower volume and larger buildings may have alarms set to a higher level.


After the fire protection goals 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. In the United States, NFPA 72, The National Fire Alarm Code is an established and widely used installation standard. In Canada, the ULC is the standard for the fire system. The equivalent standard in the United Kingdom is BS 5839 Part 1.

EN 54 is a mandatory standard for fire detection and fire alarm systems in the European Union, aiming to establish harmonized technical standards against which products in the field should be benchmarked and certified by a qualified testing house known as a Notified Body. Every product for fire alarm systems must achieve the standards laid out in EN 54 in order to properly carry a CE mark, which is in turn required if the product is to be delivered and installed in any country of the EU. It is a standard widely used around the world.[1]

Pull station


A Honeywell DeltaNet FS90 fire alarm control panel
A publicly accessible alarm box on a street in San Francisco

Initiating devices

Notification appliances

A Honeywell speaker and a Space Age Electronics V33 remote light

As per NFPA 72, 18.4.2 (2010 Edition)Temporal Code 3 is the standard audible notification in a modern system. It consists of a repeated 3-pulse cycle (.5s on .5s off .5s on .5s off .5s on 1.5s off). Voice Evacuation is the second most common audible in a modern system. Legacy systems, typically found in older schools and building have used continuous tones alongside other audible schema.

Emergency voice alarm communication systems

Mass notification systems/emergency communication systems

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

S.H. Couch F5GX non-coded fire alarm pull station below a Couch 10" bell.

UK fire alarm system categories

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:[7]

Categories for automatic systems are further subdivided into L1 to L5, and P1 to P2.

M Manual systems, e.g. hand bells, 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.
P1 The system is installed throughout the building – the objective being 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.
P2 Detection 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.
L1 A category L1 system is designed for the protection of life and which has automatic detectors installed throughout all areas of the building (including roof spaces and voids) 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.
L2 A 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 (sleeping no more than ten residents), 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 (e.g., kitchen) or where the risk to people is particularly increased (e.g., sleeping risk).
L3 This category is designed to give early warning 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.
L4 Category 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 is increased. Detectors might be sited in other areas of the building, but the objective is to protect the escape route.
L5 This 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 requirement that cannot be covered by any other category.


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.

See also


  1. CEN – European Committee for Standardization :: Standards. Retrieved on 2013-02-02.
  2. Chenebert, A.; Breckon, T.P.; Gaszczak, A. (September 2011). "A Non-temporal Texture Driven Approach to Real-time Fire Detection". Proc. International Conference on Image Processing (PDF). IEEE. pp. 1781–1784. doi:10.1109/ICIP.2011.6115796. Retrieved 8 April 2013.
  3. "Chapter 3 Fundamental Fire Protection Program and Design Elements". NFPA 805 Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants. National Fire Protection Association. February 2001. standard: Gaseous Fire Suppression Systems 3.10.7. |first1= missing |last1= in Authors list (help)
  4. "Chapter 4 Annex A". NFPA 12 Standard on Carbon Dioxide Extinguishing Systems. National Fire Protection Association. 2011. standard: A. |first1= missing |last1= in Authors list (help)
  5. Cote, Arthur E. (March 2000). Fire Protection Handbook eighteenth edition. National Fire Protection Association. pp. 5–8. ISBN 0-87765-377-1.
  6. NFPA 72 – National Fire Alarm and Signaling Code – 2010 Edition. National Fire Alarm Association, 2009, Page 118, Subsection 24.4.1
  7. "Fire Industry Association Fact File 0058". the Fire Industry Association ("FIA"). Retrieved 2015-02-20.
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