It provide sufficient illumination or light for an emergency situation such as Fire or Power failure. In case of Fire it helps to locate the fire fighting equipment quickly and identify exit routes from the premises. Or in power failure it provide sufficient light to get rid of the break in the normal lighting supplies leading to sudden darkness and the resultant hazard to human life, either through physical danger or panic. Emergency lighting is normally required to operate fully automatically and give illumination of a sufficiently high level to enable persons of all ages to evacuate the premises safely.
Type of systems:
1) Self-contained : There are conventional and Addressable systems consists luminaires with built in battery and charging unit. In the conventional system there is no monitoring and testing facility for the luminaires where as in addressable there is Control panel with loop and radial circuits and monitoring and testing facility.
2) Central battery: Consist the batteries for a number of addressable luminaries housed in some specific, central and remote locations with control panel.
Most emergency lighting schemes fall into one of the following categories:-
1) Non-maintained - The emergency light units only illuminate in the event of a mains failure.
2) Maintained - The emergency light units are illuminated at all times using the same lamps for both normal and emergency operation.
3) Sustained - The emergency light units are fitted with 2 No. Lamps or 2 No. Sets of lamps, one of which operates on mains 240V a.c.supply, the other which operates from the battery supply in the event of mains failure. It is basically a non-maintained system with the addition of mains lamps which should be illuminated whenever the premises are occupied.
The type of system and emergency duration is often expressed in abbreviated form as per the following
examples:-
M3 - Maintained System,emergency duration 3 hours.
NM2 - Non-maintained System,emergency duration 2 hours.
S1 - Sustained System,emergency duration 1 hour.
Lumen (lm): is the SI unit of luminous flux, a measure of the power of light perceived by the human eye.
Lux (lx):is the SI unit of illuminance and luminous emittance. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. One Lux is equal to one lumen per square meter, where 4π lumens is the total luminous flux of a light source of one candela of luminous intensity: 1 lx = 1 lm/m2 = 1 cd·sr·m–2.
Brightness: is an attribute of visual perception in which a source appears to be radiating or reflecting light In other words, brightness is the perception elicited by the luminance of a visual target. This is a subjective attribute/property of an object being observed.
Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12,000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.
Lux versus foot-candle: One footcandle ≈ 10.764 lux. The footcandle (or lumen per square foot) is a non-SI unit of illuminance like the BTU. Lux and footcandles are different units of the same quantity, it is perfectly valid to convert footcandles to lux and vice versa. The name "footcandle" conveys "the illuminance cast on a surface by a one-candela source one foot away. In practical applications, as when measuring room illumination, it is very difficult to measure illuminance more accurately than ±10%, and for many purposes it is quite sufficient to think of one footcandle as about ten lux.
Type of systems:
1) Self-contained : There are conventional and Addressable systems consists luminaires with built in battery and charging unit. In the conventional system there is no monitoring and testing facility for the luminaires where as in addressable there is Control panel with loop and radial circuits and monitoring and testing facility.
2) Central battery: Consist the batteries for a number of addressable luminaries housed in some specific, central and remote locations with control panel.
Most emergency lighting schemes fall into one of the following categories:-
1) Non-maintained - The emergency light units only illuminate in the event of a mains failure.
2) Maintained - The emergency light units are illuminated at all times using the same lamps for both normal and emergency operation.
3) Sustained - The emergency light units are fitted with 2 No. Lamps or 2 No. Sets of lamps, one of which operates on mains 240V a.c.supply, the other which operates from the battery supply in the event of mains failure. It is basically a non-maintained system with the addition of mains lamps which should be illuminated whenever the premises are occupied.
The type of system and emergency duration is often expressed in abbreviated form as per the following
examples:-
M3 - Maintained System,emergency duration 3 hours.
NM2 - Non-maintained System,emergency duration 2 hours.
S1 - Sustained System,emergency duration 1 hour.
Lumen (lm): is the SI unit of luminous flux, a measure of the power of light perceived by the human eye.
Lux (lx):is the SI unit of illuminance and luminous emittance. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. One Lux is equal to one lumen per square meter, where 4π lumens is the total luminous flux of a light source of one candela of luminous intensity: 1 lx = 1 lm/m2 = 1 cd·sr·m–2.
Brightness: is an attribute of visual perception in which a source appears to be radiating or reflecting light In other words, brightness is the perception elicited by the luminance of a visual target. This is a subjective attribute/property of an object being observed.
Lux versus lumen: The difference between the lux and
the lumen
is that the lux takes into account the area over which the luminous flux is
spread. A flux of 1,000 lumens, concentrated into an area of one square metre,
lights up that square metre with an illuminance of 1,000 lux. However, the same
1,000 lumens, spread out over ten square metres, produces a dimmer illuminance
of only 100 lux.
Achieving an illuminance of 500 lux might be possible in a home kitchen with a single fluorescent light fixture with an output of 12,000 lumens. To light a factory floor with dozens of times the area of the kitchen would require dozens of such fixtures. Thus, lighting a larger area to the same level of lux requires a greater number of lumens.
Lux versus foot-candle: One footcandle ≈ 10.764 lux. The footcandle (or lumen per square foot) is a non-SI unit of illuminance like the BTU. Lux and footcandles are different units of the same quantity, it is perfectly valid to convert footcandles to lux and vice versa. The name "footcandle" conveys "the illuminance cast on a surface by a one-candela source one foot away. In practical applications, as when measuring room illumination, it is very difficult to measure illuminance more accurately than ±10%, and for many purposes it is quite sufficient to think of one footcandle as about ten lux.
