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An alarm device is a mechanism that gives an audible, visual, combination, or other kind of alarm signal to alert someone to a problem or condition that requires urgent attention.
The word alarm comes from the Old French a l'arme meaning "to the arms", or "to the weapons", telling armed men to pick up their weapons and get ready for action because an enemy may have suddenly appeared. [1]
The word alarum is an archaic form of alarm. It was sometimes used as a call to arms in the stage directions of Elizabethan dramas. [2] The term comes from the Italian all'armi and appears 89 times in Shakespeare's first folio. [3] Often explained as the off-stage sounds of conflict or disturbance, [4] recent research suggests a bell or drum may have been used to rouse soldiers from sleep. [3]
Early alarm devices were often bells, drums, other musical instruments, or any items which made unusual loud noises that attracted the attention of the surrounding population.
Whistles were used by police in the 19th century. Steam whistles have been used on locomotives, ships, and in factories as alarm devices.
With the advent of electricity, a variety of other alerting devices have been invented, such as buzzers, klaxons, sirens, horns, flashing and coloured lights, and other all-purpose alarms.
Alarm devices can be fitted to buildings as well as vehicles. Many buildings are fitted with fire alarms, ranging from a self-contained domestic smoke detector to a sophisticated alarm system that can operate building fire fighting systems automatically to extinguish fires with water or inert gases.
Many industries have developed standards for alarm devices, and the colours red, blue and amber are generally recognized as alarm device-related colours, with flashing lights often indicating urgent conditions.[ citation needed ]
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Human reactions to an alarm will often depend on upbringing, psychological training, or the behavior of others in the environment. Consequently, the ability to test an alarm and hold regular drills to practice an appropriate response may be provided as part of an alarm system.
Alarm devices that are intended to cause the evacuation of an occupied building, such as fire alarms, may be deliberately designed to make remaining in the space difficult or even painful in order to encourage occupants to leave.
Some alarms may startle and cause a fight-or-flight response in humans; a person under this mindset will panic and either flee the perceived danger or attempt to eliminate it, often ignoring rational thought in either case.[ citation needed ] A person in such a state can be characterized as "alarmed".[ according to whom? ]
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With any kind of alarm, you must balance between the danger of false alarms (called "false positives") — the signal going off in the absence of a problem — or an alarm failing to signal an actual problem (called a "false negative"). False alarms can waste resources expensively and can even be dangerous. For example, false alarms of a fire can waste firefighter manpower, making them unavailable for a real fire, and risk injury to firefighters and others as the fire engines race to the alleged fire's location. [5] In addition, false alarms may acclimatise people to ignore alarm signals, and thus possibly to ignore an actual emergency: Aesop's fable of The Boy Who Cried Wolf exemplifies this problem.
A false alarm is one of the most significant issues with conventional alarm systems. They can be triggered for several reasons, such as the movement of pets, [6] typing in the wrong security codes, or loud sounds from windows or doors. In the case of fire alarms, aerosol sprays, smoking, or burning food can all lead to a false alarm. [5]
Many avoid the risk of false alarms by ensuring their alarms are secured in an appropriate location, such as placing a smoke detector or fire alarm away from the kitchen where smoke from burned food or large quantities of steam which may trigger a false alarm are common occurrences. In the case of a security alarm, an additional monitoring station which assesses whether there is a legitimate need for help can reduce false alarms.
There are many kinds of alarm devices. The most common types include:
Alarm devices, by category, include[ citation needed ]:
A civil defense siren, also known as an air-raid siren or tornado siren, is a siren used to provide an emergency population warning to the general population of approaching danger. It is sometimes sounded again to indicate the danger has passed. Some sirens, especially within small municipalities, are also used to alert the fire department when needed. Initially designed to warn city dwellers of air raids during World War II, they were later used to warn of nuclear attack and natural disasters, such as tornadoes. The generalized nature of sirens led to many of them being replaced with more specific warnings, such as the broadcast-based Emergency Alert System and the Cell Broadcast-based Wireless Emergency Alerts and EU-Alert mobile technologies.
A smoke detector is a device that senses smoke, typically as an indicator of fire. Smoke detectors are usually housed in plastic enclosures, typically shaped like a disk about 150 millimetres (6 in) in diameter and 25 millimetres (1 in) thick, but shape and size vary. Smoke can be detected either optically (photoelectric) or by physical process (ionization). Detectors may use one or both sensing methods. Sensitive alarms can be used to detect and deter smoking in banned areas. Smoke detectors in large commercial and industrial buildings are usually connected to a central fire alarm system.
A fire alarm notification appliance is an active fire protection component of a fire alarm system. A notification appliance may use audible, visible, or other stimuli to alert the occupants of a fire or other emergency condition requiring action. Audible appliances have been in use longer than any other method of notification. Initially, all appliances were either electromechanical horns or electric bells, which would later be replaced by electronic sounders. Most of today's appliances produce sound levels between 70 and 100 decibels at three feet.
A car alarm is an electronic device installed in a vehicle in an attempt to discourage theft of the vehicle itself, its contents, or both. Car alarms work by emitting high-volume sound when the conditions necessary for triggering it are met. Such alarms may also cause the vehicle's headlights to flash, may notify the car's owner of the incident via a paging system, and may interrupt one or more electrical circuits necessary for the car to start. Although inexpensive to acquire and install, the effectiveness of such devices in deterring vehicle burglary or theft when their only effect is to emit sound appears to be negligible.
A security alarm is a system designed to detect intrusions, such as unauthorized entry, into a building or other areas, such as a home or school. Security alarms protect against burglary (theft) or property damage, as well as against intruders. Examples include personal systems, neighborhood security alerts, car alarms, and prison alarms.
An emergency population warning is a method where by local, regional, or national authorities can contact members of the public to warn them of an impending emergency. These warnings may be necessary for a number of reasons, including:
A fire alarm control panel (FACP), fire alarm control unit (FACU), fire indicator panel (FIP), or simply fire alarm panel is the controlling component of a fire alarm system. The panel receives information from devices designed to detect and report fires, monitors their operational integrity, and provides for automatic control of equipment, and transmission of information necessary to prepare the facility for fire based on a predetermined sequence. The panel may also supply electrical energy to operate any associated initiating device, notification appliance, control, transmitter, or relay. There are four basic types of panels: coded panels, conventional panels, addressable panels, and multiplex systems.
"Inspector Sands" is a code phrase used by public transport authorities in the United Kingdom, including Network Rail and London Underground, to alert staff to a fire alarm without needing to evacuate the station. The exact wording depends on the station and the nature of the incident. For example: "Would Inspector Sands please report to the operations room immediately." or "Would Inspector Sands please report to Platform 2."
A false alarm, also called a nuisance alarm, is the deceptive or erroneous report of an emergency, causing unnecessary panic and/or bringing resources to a place where they are not needed. False alarms may occur with residential burglary alarms, smoke detectors, industrial alarms, and in signal detection theory. False alarms have the potential to divert emergency responders away from legitimate emergencies, which could ultimately lead to loss of life. In some cases, repeated false alarms in a certain area may cause occupants to develop alarm fatigue and to start ignoring most alarms, knowing that each time it will probably be false. Intentionally falsely activating alarms in businesses and schools can lead to serious disciplinary actions, and criminal penalties such as fines and jail time.
A passive infrared sensor is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors are commonly used in security alarms and automatic lighting applications.
Manual fire alarm activation is the process of triggering a fire alarm through a call point, pull station, or other device. This usually causes the alarm to sound the evacuation signal for the relevant building or zone. Manual fire alarm activation requires human intervention, as distinct from automatic fire alarm activation such as that provided through the use of heat detectors and smoke detectors. It is, however, possible for call points/pull stations to be used in conjunction with automatic detection as part of the overall fire detection and alarm system. Systems in completed buildings tend to be wired in and include a control panel. Wireless activators are common during construction.
A panic alarm is an electronic device that can easily be activated to request help during an emergency where danger to persons or property exists. It is designed to contact assistance quicker, easier, and simpler than a conventional phone call.
A motion detector is an electrical device that utilizes a sensor to detect nearby motion. Such a device is often integrated as a component of a system that automatically performs a task or alerts a user of motion in an area. They form a vital component of security, automated lighting control, home control, energy efficiency, and other useful systems.
An aspirating smoke detector (ASD) is a system used in active fire protection, consisting of a central detection unit which draws air through a network of pipes to detect smoke. The sampling chamber is based on a nephelometer that detects the presence of smoke particles suspended in air by detecting the light scattered by them in the chamber. ASDs can typically detect smoke before it is visible to the naked eye.
Emergency vehicle equipment is any equipment fitted to, or carried by, an emergency vehicle, other than the equipment that a standard non-emergency vehicle is fitted with.
A heat detector is a fire alarm device designed to respond when the convected thermal energy of a fire increases the temperature of a heat sensitive element. The thermal mass and conductivity of the element regulate the rate flow of heat into the element. All heat detectors have this thermal lag. Heat detectors have two main classifications of operation, "rate-of-rise" and "fixed temperature". The heat detector is used to help in the reduction of property damage.
A fire alarm system is a building system designed to detect and alert occupants and emergency forces of the presence of smoke, fire, 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, all of which are connected to a Fire Alarm Control Panel (FACP) normally found in an electrical room 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 under most circumstances, are unsafe to use during a fire.
A medical alarm is an alarm system designed to signal the presence of a hazard requiring urgent attention and to summon emergency medical personnel. Other terms for a medical alarm are Personal Emergency Response System (PERS) or medical alert. It is especially important to recognize the need to respond to situations where the person is unable to summon help.
An annunciator panel, also known in some aircraft as the Centralized Warning Panel (CWP) or Caution Advisory Panel (CAP), is a group of lights used as a central indicator of status of equipment or systems in an aircraft, industrial process, building or other installation. Usually, the annunciator panel includes a main warning lamp or audible signal to draw the attention of operating personnel to the annunciator panel for abnormal events or condition.
A bell box is an audible device, often electric, which when activated, emits a chime, bell, or buzzer sound.