A fire alarm system is a building system designed to detect, alert occupants, and alert emergency forces of the presence of fire, smoke, carbon monoxide, or other fire-related emergencies. Fire alarm systems are required in most commercial buildings. They may include smoke detectors, heat detectors, and manual fire alarm activation devices (pull stations). All components of a fire alarm system are connected to a fire alarm control panel. Fire alarm control panels are usually found in an electrical or panel room. Fire alarm systems generally use visual and audio signalization to warn the occupants of the building. Some fire alarm systems may also disable elevators, which are unsafe to use during a fire under most circumstances.[1]
Fire alarm systems are designed after fire protection requirements in a location are established, which is usually done by referencing the minimum levels of security mandated by the appropriate model building code, insurance agencies, and other authorities. A fire alarm designer will detail specific components, arrangements, and interfaces necessary to accomplish these requirements. Equipment specifically manufactured for these purposes is selected, and standardized installation methods are anticipated during the design. There are several commonly referenced standards for fire protection requirements, including:
There are national codes in each European country for planning, design, installation, commissioning, use, and maintenance of fire detection systems with additional requirements that are mentioned on TS 54 -14:
Across Oceania, the following standards outline the requirements, test methods, and performance criteria for fire detection control and indicating equipment utilised in building fire detection and fire alarm systems:
Fire alarm systems are composed of several distinct parts:
Initiating devices used to activate a fire alarm system are either manually or automatically actuated devices. Manually actuated devices, also known as fire alarm boxes, manual pull stations, or simply pull stations, break glass stations, and (in Europe) call points, are installed to be readily located (usually near the exits of a floor or building), identified, and operated. They are usually actuated using physical interaction, such as pulling a lever or breaking glass.
Automatically actuated devices can take many forms, and are intended to respond to any number of detectable physical changes associated with fire: convected thermal energy for a heat detector, products of combustion for a smoke detector, radiant energy for a flame detector, combustion gases for a fire gas detector, and operation of sprinklers for a water-flow detector. Automatic initiating devices may use cameras and computer algorithms to analyze and respond to the visible effects of fire and movement in applications inappropriate for or hostile to other detection methods.[13] [14]
See main article: Fire alarm notification appliance. Alarms can take many forms, but are most often either motorized bells or wall-mountable sounders or horns. They can also be speaker strobes that sound an alarm, followed by a voice evacuation message for clearer instructions on what to do. Fire alarm sounders can be set to certain frequencies and different tones, either low, medium, or 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 continuous or set to different codes. Fire alarm warning devices can also be set to different volume levels.
Notification appliances utilize audible, visible, tactile, textual or even olfactory stimuli (odorizers)[15] [16] to alert the occupants of the need to evacuate or take action in the event of a fire or other emergency. Evacuation signals may consist of simple appliances that transmit uncoded information, coded appliances that transmit a predetermined pattern, and/or appliances that transmit audible and visible information such as live or prerecorded instructions and illuminated message displays. Some notification appliances are a combination of fire alarm and general emergency notification appliances, allowing both types of emergency notifications from a single device.
Some fire alarm systems utilize emergency voice alarm communication systems (EVAC)[17] to provide prerecorded and manual voice messages. Voice alarm systems are typically used in high-rise buildings, arenas, and other large "defend-in-place" occupancies such as hospitals and detention facilities where total evacuation is difficult to achieve. Voice-based systems allow response personnel to conduct orderly evacuation and notify building occupants of changing event circumstances.
Audible textual appliances can be employed as part of a fire alarm system that includes EVAC capabilities. High-reliability speakers notify the occupants of the need for action concerning a fire or other emergency. These speakers are employed in large facilities where general undirected evacuation is impracticable or undesirable. The signals from the speakers are used to direct the occupant's response. The fire alarm system automatically actuates speakers in a fire event. Following a pre-alert tone, selected groups of speakers may transmit one or more prerecorded messages directing the occupants to safety. These messages may be repeated in one or more languages. The system may be controlled from one or more locations within the building, known as "fire warden stations", or from a single location designated as the building's "fire command center". From these control locations, trained personnel activating and speaking into a dedicated microphone can suppress the replay of automated messages to initiate or relay real-time voice instructions.[18]
In highrise buildings, different evacuation messages may be played on each floor, depending on the location of the fire. The floor the fire is on along with ones above it may be told to evacuate while floors much lower may be asked to stand by.
In the United States, fire alarm evacuation signals generally consist of a standardized audible tone, with visual notification in all public and common-use areas. Emergency signals are intended to be distinct and understandable to avoid confusion with other signals.
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 three-pulse cycle (0.5 s on, 0.5 s off, 0.5 s on, 0.5 s off, 0.5 s on, 1.5 s off). Voice evacuation is the second most common audible notification in modern systems. Legacy systems, typically found in older schools and buildings, have used continuous tones alongside other audible notifications.
In the United Kingdom, fire alarm evacuation signals generally consist of a two-tone siren with visual notifications in all public and common-use areas. Some fire alarm devices can emit an alert signal, which is generally used in schools for lesson changes, the start of morning break, the end of morning break, the start of lunch break, the end of lunch break, and when the school day is over.
New codes and standards introduced around 2010, especially the new UL Standard 2572, the US Department of Defense's UFC 4-021-01 Design and O&M Mass Notification Systems, and NFPA 72 2010 edition Chapter 24, have led fire alarm system manufacturers to expand their systems voice evacuation capabilities to support new requirements for mass notification. These expanded capabilities include support for multiple types of emergency messaging (i.e., inclement weather emergency, security alerts, amber alerts). The major requirement of a mass notification system is to provide prioritized messaging according to the local facilities' emergency response plan, and the fire alarm system must support the promotion and demotion of notifications based on this emergency response plan. In the United States, emergency communication systems also have requirements for visible notification in coordination with any audible notification activities to meet the needs of the Americans with Disabilities Act.
Mass notification system categories include the following:
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.
Residential fire alarm systems are commonplace. Typically, residential fire alarm systems are installed along with security alarm systems. In the United States, a residential fire alarm system is required in buildings where more than 12 smoke detectors are needed.[19] Residential systems generally have fewer parts compared to commercial systems.
A poorly designed system may result in erroneous alarms. The repetitive incidence of false alarms could potentially lead individuals to underestimate the significance of fire alarms, thereby posing the risk of severe consequences.
To minimize potential risks, it is important to entrust the installation of alarm systems to certified technicians. Additionally, maintaining a consistent schedule for servicing and testing these systems is crucial for their optimal functionality and reliability. Regular inspections not only contribute to the early detection of malfunctions but also enhance the overall effectiveness of the alarm system, ensuring a prompt and accurate response when needed.
Various equipment may be connected to a fire alarm system to facilitate evacuation or to control a fire, directly or indirectly:
In the United Kingdom, 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 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:[21]
Categories for automatic systems are further subdivided into L1 to L5 and P1 to P2.
| M | Manual 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; e.g., a fire cannot occur while occupants are asleep. | |
|---|---|---|
| P1 | The system is installed throughout the building—the objective is to automatically call the fire brigade as early as possible to minimize any damage caused by the fire. Small low-risk areas can be excepted from the system, such as toilets and cupboards less than 1sp=usNaNsp=us. | |
| P2 | Detection should be provided in parts of the building where the risk of ignition is high and/or the contents are precious. 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) to provide 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 is designed for the protection of life and 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), category L2 system are often used. These fire alarm systems are identical to an L3 system but with additional detection in areas with a high chance of ignition (e.g., kitchens) or where the risk to people is particularly increased (e.g., sleeping risk). | |
| L3 | This 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 can 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 are increased. Detectors might be located in other areas of the building, but the objective of an L4 system 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 special requirements that other categories cannot cover. |
An important consideration when designing fire alarms is that of individual "zones". The following recommendations are found in BS 5839 Part 1:
The NFPA recommends placing a list for reference near the fire alarm control panel showing the devices contained in each zone.