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PLANNING CONSIDERATIONS First, while studies have shown that adequate lighting around a physical structure can significantly reduce the risk of an intrusion, it is important that the lighting be designed carefully as poorly arranged lighting can create Glare which actually obstructs vision, and other studies have shown that many criminals are aware of this effect and actively exploit it. The optimal design will also depend on whether the area will be watched directly by humans or by Closed-circuit Television , and on the location of the observers or cameras. Security lighting may be subject to Vandalism , possibly to reduce its effectiveness for a subsequent intrusion attempt. Thus security lights should either be mounted very high, or else protected by Wire Mesh or tough Polycarbonate shields. Other lamps may be completely recessed from view and access, with the light directed out through a Light Pipe or reflected from a polished aluminium or stainless steel Mirror . For similar reasons high security installations may provide a Stand-by Power Supply for their security lighting. Some typical considerations include:
USE Security lighting can be used in residential, commercial, industrial, institutional, and military settings. Some examples of security lighting include Floodlight s and Low Pressure Sodium Vapour Light s. Most lights intended to be left on all night are High-intensity Discharge Lamp s as these have good energy efficiency, thus reducing the cost of running a lamp for such long periods. A disadvantage of low pressure sodium lamps is that the colour is pure yellow, so the illuminated scene is seen without any colour differentiation. Consequently high pressure sodium vapour lamps (which are still yellowish, but closer to golden white) are also used, at the cost of greater running expenses and increased light pollution. High pressure sodium lamps also take slightly longer to restrike after a power interruption. Other lights may be activated by sensors such as Passive Infrared Sensors (PIRs), turning on only when a person (or other mammal) approaches. PIR activated lamps will usually be incandescent bulbs so that they can activate instantly; energy saving is less important since they will not be on all the time. PIR sensor activation can increase both the deterrent effect (since the intruder knows that he has been detected) and the detection effect (since a person will be attracted to the sudden increase in light). Some PIR units can be set up to sound a chime as well as turn on the light. Most modern units have a Photocell so that they only turn on when it is dark. RECENT DEVELOPMENTS A recent addition to the field of security lighting is the blue outdoor lamp (Similar to Mercury-vapor Lamp s), used to illuminate areas which have been used by Drug Addict s to inject drugs. The idea is that the blue lighting makes it impossible to identify veins, thus discouraging the addicts from using that location to "shoot up" and then discard needles. LIMITATIONS An important limitation to the usefulness of security lighting is the simple fact that it is only useful at night. This is particularly significant for home owners because, contrary to a widespread myth, most household Burglaries occur during the day, when the occupants are away at work or shopping. SEE ALSO |
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