Emergency light
Encyclopedia
An emergency light is a battery-backed lighting device
that comes on automatically when a building experiences a power outage
. Emergency lights are standard in new commercial and high occupancy residential buildings, such as college dormitories
. Most building codes require that they be installed in older buildings as well.
s which could dimly light an area during a blackout and perhaps provide enough light to solve the power problem or evacuate the building. It was quickly realized, however, that a more focused, brighter, and longer-lasting light was needed. The modern emergency floodlight
provides a high-lumen
, wide-coverage light that can illuminate an area quite well. Some lights are halogen
, and provide a light source and intensity similar to that of an automobile
headlight.
Early battery backup systems were huge, dwarfing the size of the lights for which they provided power. The systems normally used lead acid batteries to store a full 120-volt
charge. For comparison, an automobile
uses a single lead acid battery as part of the ignition system. Simple transistor
or relay
technology was used to switch on the lights and battery supply in the event of a power failure. The size of these units, as well as the weight and cost, made them relatively rare installations. As technology developed further, the voltage requirements for lights dropped, and subsequently the size of the batteries was reduced as well. Modern lights are only as large as the bulbs themselves - the battery fits quite well in the base of the fixture.
s (LED). The emergency lighting heads are usually either PAR 36 sealed beams or wedge base lamps. All units have some sort of a reflector
to focus and intensify the light they produce. This can either be in the form of a plastic cover over the fixture, or a reflector placed behind the light source. Most individual light sources can be rotated and aimed for where light is needed most in an emergency, such as toward fire exits. Modern fixtures usually have a test button of some sort which temporarily overrides the unit and causes it to switch on the lights and operate from battery power even if the main power is still on. Modern systems are operated with relatively low voltage, usually from 6-12 volts. This both reduces the size of the batteries required and reduces the load on the circuit to which the emergency light is wired. Modern fixtures include a small transformer
in the base of the fixture which steps-down the voltage from main current to the low power required by the lights. Batteries are commonly made of lead-calcium, and can last for 10 years or more on continuous charge. U.S. fire safety codes require a minimum of 90 minutes on battery power during a power outage along the path of egress.
As a method of signaling a power outage, some models of emergency lights must be shut off manually after they have been activated. This is true even if the main building power comes back on. The system will stay lit until the reset button on the side of the unit is pressed.
Emergency lighting is often referred to as egress lighting. Emergency lights are used in commercial buildings as a safety precaution to power outages, so that people will be able to find their way out of a building. Exit signs are often used in conjunction with emergency lighting.
New York City requires emergency lights to carry a Calendar Number signifying approval for local installation, Chicago requires emergency lighting to have a metal face plate, and Los Angeles requires additional exit signs be installed within 18 inches (45.7 cm) of the floor around doors to mark exits during a fire, as smoke rises and tends to block out higher installed units.
As there are strict requirements to provide an average of one footcandle of light along the path of egress, emergency lighting should be selected carefully to ensure codes are met.
In recent years, emergency lighting has started to move away from the traditional two-head unit - with manufacturers stretching the concept of emergency lighting to accommodate and integrate emergency lighting into the architecture.
An emergency lighting installation may be either a central standby source such as a bank of lead acid batteries and control gear/chargers supplying slave fittings throughout the building, or may be constructed using self contained emergency fittings which incorporate the lamp, battery, charger and control equipment.
Self contained emergency lighting fittings may operate in "Maintained" mode (illuminate all the time) or "Non-Maintained" mode (illuminated only when the normal supply fails).
Codes of practice for emergency lighting generally mandate that wiring from the central power source to emergency luminaires is kept segregated from other wiring, and constructed in fire resistant cabling and wiring systems.
Codes of practice lay down minimum illumination levels in escape routes and open areas. Codes of practice also lay down requirements governing siting of emergency lighting fittings, for example the UK code of practice, BS5266 specifies that a fitting must be within 2 metres (6.6 ft) horizontal distance of a fire alarm call point or location for fire fighting appliances.
The most recent codes of practice require the designer to allow for both failure of the supply to the building and the failure of an individual lighting circuit. BS5266 requires that when Non Maintained fittings are used, they must be supplied from the same final circuit as the main lighting circuit in the area.
60598-2-22 Ed. 3.0: Luminaires - Part 2-22: Particular requirements - Luminaires for emergency lighting
IEC 60364-5-56 Ed. 2.0: Low-voltage electrical installations - Part 5-56: Selection and erection of electrical equipment - Safety services
ISO
30061:2007 (CIE S 020/E:2007): Emergency lighting (specifies the luminous requirements for emergency lighting systems)
Electric light
Electric lights are a convenient and economic form of artificial lighting which provide increased comfort, safety and efficiency. Most electric lighting is powered by centrally-generated electric power, but lighting may also be powered by mobile or standby electric generators or battery systems...
that comes on automatically when a building experiences a power outage
Power outage
A power outage is a short- or long-term loss of the electric power to an area.There are many causes of power failures in an electricity network...
. Emergency lights are standard in new commercial and high occupancy residential buildings, such as college dormitories
Dormitory
A dormitory, often shortened to dorm, in the United States is a residence hall consisting of sleeping quarters or entire buildings primarily providing sleeping and residential quarters for large numbers of people, often boarding school, college or university students...
. Most building codes require that they be installed in older buildings as well.
History
By the nature of the device, an emergency light is designed to come on when the power goes out. Every model, therefore, requires some sort of a battery or generator system that could provide electricity to the lights during a blackout. The earliest models were incandescent light bulbIncandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
s which could dimly light an area during a blackout and perhaps provide enough light to solve the power problem or evacuate the building. It was quickly realized, however, that a more focused, brighter, and longer-lasting light was needed. The modern emergency floodlight
High-intensity discharge lamp
High-intensity discharge lamps are a type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with both gas and metal salts. The gas facilitates the...
provides a high-lumen
Lumen (unit)
The lumen is the SI derived unit of luminous flux, a measure of the total "amount" of visible light emitted by a source. Luminous flux differs from power in that luminous flux measurements reflect the varying sensitivity of the human eye to different wavelengths of light, while radiant flux...
, wide-coverage light that can illuminate an area quite well. Some lights are halogen
Halogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
, and provide a light source and intensity similar to that of an automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
headlight.
Early battery backup systems were huge, dwarfing the size of the lights for which they provided power. The systems normally used lead acid batteries to store a full 120-volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
charge. For comparison, an automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
uses a single lead acid battery as part of the ignition system. Simple transistor
Transistor
A transistor is a semiconductor device used to amplify and switch electronic signals and power. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current...
or relay
Relay
A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal , or where several circuits must be controlled...
technology was used to switch on the lights and battery supply in the event of a power failure. The size of these units, as well as the weight and cost, made them relatively rare installations. As technology developed further, the voltage requirements for lights dropped, and subsequently the size of the batteries was reduced as well. Modern lights are only as large as the bulbs themselves - the battery fits quite well in the base of the fixture.
Modern installations
Modern emergency lighting is installed in virtually every commercial and high occupancy residential building. The lights consist of one or more incandescent bulbs or one or more clusters of high-intensity light-emitting diodeLight-emitting diode
A light-emitting diode is a semiconductor light source. LEDs are used as indicator lamps in many devices and are increasingly used for other lighting...
s (LED). The emergency lighting heads are usually either PAR 36 sealed beams or wedge base lamps. All units have some sort of a reflector
Mirror
A mirror is an object that reflects light or sound in a way that preserves much of its original quality prior to its contact with the mirror. Some mirrors also filter out some wavelengths, while preserving other wavelengths in the reflection...
to focus and intensify the light they produce. This can either be in the form of a plastic cover over the fixture, or a reflector placed behind the light source. Most individual light sources can be rotated and aimed for where light is needed most in an emergency, such as toward fire exits. Modern fixtures usually have a test button of some sort which temporarily overrides the unit and causes it to switch on the lights and operate from battery power even if the main power is still on. Modern systems are operated with relatively low voltage, usually from 6-12 volts. This both reduces the size of the batteries required and reduces the load on the circuit to which the emergency light is wired. Modern fixtures include a small transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
in the base of the fixture which steps-down the voltage from main current to the low power required by the lights. Batteries are commonly made of lead-calcium, and can last for 10 years or more on continuous charge. U.S. fire safety codes require a minimum of 90 minutes on battery power during a power outage along the path of egress.
As a method of signaling a power outage, some models of emergency lights must be shut off manually after they have been activated. This is true even if the main building power comes back on. The system will stay lit until the reset button on the side of the unit is pressed.
Emergency lighting is often referred to as egress lighting. Emergency lights are used in commercial buildings as a safety precaution to power outages, so that people will be able to find their way out of a building. Exit signs are often used in conjunction with emergency lighting.
New York City requires emergency lights to carry a Calendar Number signifying approval for local installation, Chicago requires emergency lighting to have a metal face plate, and Los Angeles requires additional exit signs be installed within 18 inches (45.7 cm) of the floor around doors to mark exits during a fire, as smoke rises and tends to block out higher installed units.
As there are strict requirements to provide an average of one footcandle of light along the path of egress, emergency lighting should be selected carefully to ensure codes are met.
In recent years, emergency lighting has started to move away from the traditional two-head unit - with manufacturers stretching the concept of emergency lighting to accommodate and integrate emergency lighting into the architecture.
An emergency lighting installation may be either a central standby source such as a bank of lead acid batteries and control gear/chargers supplying slave fittings throughout the building, or may be constructed using self contained emergency fittings which incorporate the lamp, battery, charger and control equipment.
Self contained emergency lighting fittings may operate in "Maintained" mode (illuminate all the time) or "Non-Maintained" mode (illuminated only when the normal supply fails).
Codes of practice for emergency lighting generally mandate that wiring from the central power source to emergency luminaires is kept segregated from other wiring, and constructed in fire resistant cabling and wiring systems.
Codes of practice lay down minimum illumination levels in escape routes and open areas. Codes of practice also lay down requirements governing siting of emergency lighting fittings, for example the UK code of practice, BS5266 specifies that a fitting must be within 2 metres (6.6 ft) horizontal distance of a fire alarm call point or location for fire fighting appliances.
The most recent codes of practice require the designer to allow for both failure of the supply to the building and the failure of an individual lighting circuit. BS5266 requires that when Non Maintained fittings are used, they must be supplied from the same final circuit as the main lighting circuit in the area.
Relevant standards
IECInternational Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
60598-2-22 Ed. 3.0: Luminaires - Part 2-22: Particular requirements - Luminaires for emergency lighting
IEC 60364-5-56 Ed. 2.0: Low-voltage electrical installations - Part 5-56: Selection and erection of electrical equipment - Safety services
ISO
International Organization for Standardization
The International Organization for Standardization , widely known as ISO, is an international standard-setting body composed of representatives from various national standards organizations. Founded on February 23, 1947, the organization promulgates worldwide proprietary, industrial and commercial...
30061:2007 (CIE S 020/E:2007): Emergency lighting (specifies the luminous requirements for emergency lighting systems)
External links
- ICEL Industry Committee for Emergency Lighting (UK)
- NEMA Emergency Lighting Section National Electrical Manufacturers AssociationNational Electrical Manufacturers Associationis the association of electrical and medical imaging equipment manufacturers. Founded in 1926 and headquartered near Washington, D.C., its approximately manufacture products used in the generation, transmission, distribution, control, and end use of electricity. These products are used in utility,...
(US)