A fire alarm system, often just called a fire alarm, 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.
Design 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:
ISO 7240-14, the international standard for the design, installation, commissioning, and service of fire detection and fire alarm systems in and around a building. This standard was published in August 2013. NFPA 72, The National Fire Alarm Code, an established and widely used installation standard from the United States. In Canada, the Underwriters' Laboratories of Canada or ULC provides fire system installation standards. TS 54 -14 is a technical specification (CEN/TS) for fire detection and fire alarm systems (Part 14: Guidelines for planning, design, installation, commissioning, use, and maintenance). Technical Committee CEN/TC72 has prepared this document as part of the EN 54 series of standards. This standard was published in October 2018. 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: Germany, VdS 2095 Italy, UNI 9795 France, NF S61-936 Spain, UNE 23007-14 United Kingdom, BS 5839 Part 1 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: Australia AS 1603.4 (superseded), AS 4428.1 (superseded), and AS 7240.2:2018.
Parts
Fire alarm systems are composed of several distinct parts:
Fire alarm control panel (FACP), or fire alarm control unit (FACU): This component, the hub of the system, monitors inputs and system integrity, controls outputs, and transmits information. Remote annunciator: a device that connects directly to the panel; the annunciator's main purpose is to allow emergency personnel to view the system status and take command from outside the electrical room the panel is located in. Usually, annunciators are installed by the front door, the door the fire department responds by, or in a fire command center. Annunciators typically have the same commands as those available from the panel's LCD screen, although some annunciators allow for full system control. Primary power supply: Commonly, a commercial power utility supplies a non-switched 120 or 240-volt alternating current source. A dedicated branch circuit is connected to the fire alarm system and its constituents in non-residential applications. "Dedicated branch circuits" should not be confused with "Individual branch circuits" which supply energy to a single appliance. Secondary (backup) power supplies: Sealed lead-acid storage batteries or other emergency sources, including generators, are used to supply energy during a primary power failure. The batteries can be either inside the bottom of the panel or inside a separate battery box installed near the panel. Initiating devices: These components act as inputs to the fire alarm control unit and are manually or automatically activated. Examples include pull stations, heat detectors, duct detectors, and smoke detectors. Fire alarm notification appliance: This component uses energy supplied from the fire alarm system or other stored energy source to inform the proximate persons of the need to take action, usually to evacuate. This is done using a variety of audio and visual means, ranging from pulsing incandescent lights, flashing strobe lights, horns, sirens, chimes, bells, loudspeakers, or a combination of these devices. Building safety interfaces: This interface allows the fire alarm system to control aspects of the built environment, prepare the building for fire, and control the spread of smoke fumes by influencing air movement, lighting, process control, human transport, and availability of exits.
Initiating devices
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.
Notification appliances
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) 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. In addition to pre-recorded and predetermined messages and instructions, some systems also support the live broadcasting and recording of voice announcements to all or certain parts of the property or facility, including customized instructions for the situation for each area, such as by emergency or facility management personnel. Outdoor appliances (such as large-scale speaker/horn/strobe poles to effectively reach outdoor occupants over potentially larger distances or areas), lighting control, and dynamic exit signage may also be used in certain circumstances.
Emergency voice alarm communication systems Some fire alarm systems utilize emergency voice alarm communication systems (EVAC)NFPA 72 – National Fire Alarm and Signaling Code – 2010 Edition. National Fire Alarm Association, 2009, Page 118, Subsection 24.4.1 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.
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 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 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.
Emergency communication systems