“I am a monster, hiding in the darkness – the intruder had whispered.”
Undoubtedly, artificial lighting is a vital component of urban life; and well-designed lighting is not only energy efficient but also minimizes the negative effects on human life. Over a period of time, artificial lighting has been developed in a manner that people may continue to perform their routine activities, even in the absence of the natural light provided by the Sun.
Purely from a security perspective, the basic purpose of protective lighting is to amicably help in shielding the organization’s assets 24/7. The crime data from around the world indicates that about 90% (with slight variations) of all the crimes occur after dark; hence the importance of well-designed and properly placed exterior/interior protective lighting becomes quite essential.
Some of the main advantages associated with a properly designed protective lighting system are that it deters and discourage potential adversaries, enhances observation to detect intruders, and reduces legal liabilities during an incident’s litigations process. Disadvantages are that it may attract undue attention, lightings are generally not aesthetically pleasing, lighting trespassing/pollution is taken quite seriously in advanced countries, and lastly, the cost of running a proper protective lighting is generally high.
Lighting – important terms
Before proceeding further, it is necessary to go through some important terms and definitions, which are frequently used while discussing the subject:-
• Brightness: Intensity of the sensation from light, as seen by the human eye.
• Color Rendering Index (CRI): Measures the ability of a light source to reveal the colors of various objects faithfully in comparison with a natural light source.
• Contrast: Relationship between the brightness of an object and its immediate background.
• Correlated Color Temperature (CCT): Measures the warmth/coolness of light.
• Foot-candle: Measures the light on a surface of 1 square foot, in an area on which one unit of light (lumen) is distributed uniformly.
• Foot-lambert: Measure of brightness.
• Glare: Excessive brightness of light.
• High-intensity Discharge (HID): Four types of lamps – mercury vapor, metal halide, high-and low-pressure sodium are known as HID lamps. HID lamps take several minutes to produce full light output. If they are turned off, even more time is required to reach full output because they first have to cool down. Before taking any decision, manufacturers can be asked to provide more information regarding the characteristics of lamps including the “strike” and “restrike” time. This in-built defect, most obviously, keeps them away from certain security usage.
• Illuminare: Intensity of light that falls on an object.
• Lumen: Unit of light output from a lamp.
• Lamp: Light sources that are also called bulbs.
• Lux: Measurement of illumination.
• Watts: Measures the amount of electrical energy used.
Types of lamps
The selection of the right type of lamps is the most important decision, as it will determine the future health of the whole night security operation. In the succeeding paragraphs, the key features associated with each type of lamp are briefly described.
Incandescent lamps are the most common lamps which are used in a household. Passage of electrical current through a tungsten wire makes it white-hot, which in return produces light. These lamps produce 10 to 20 lumens per watt, which are the least efficient/most expensive to operate, and have a short lifetime of about 1000 to 2000 hours. On the other hand, Incandescent lamps provide excellent CRI. Incandescent lamps have the advantage of providing instant light once electricity is turned on.
Halogen and Quartz-Halogen lamps are Incandescent bulbs filled with halogen, for example sealed beam auto headlights; and it provides about 25% better efficiency and life than ordinary Incandescent bulbs. Halogen and Quartz-Halogen also have the advantage of providing instant light once electricity is turned on.
Fluorescent lamps pass electricity through a gas, which is enclosed in a glass tube, to produce light; yielding 40 to 80 lumens per watt. They create twice the light and less than half the heat of an Incandescent bulb of equal voltage, and cost 5 to 10 times less. The life is about 10,000 to 15,000 hours. They are not being extensively used outdoors, except for signage. Fluorescent lamps provide excellent CRI.
Mercury Vapor lamps also pass electricity through a gas tube to create light. The output is 30 to 60 lumens per watt, and the life is about 20,000 hours. Mercury vapor lamps provide good CRI, but are heavy on blue color.
Metal Halide lamps are also of the gaseous type. The output is 80 to 100 lumens per watt, and the life is about 10,000 hours. They often are used at sports stadiums because they imitate daylight conditions and have better CRI. Consequently, these lamps complement CCTV systems, but they are the most expensive to install and maintain.
High-pressure Sodium lamps are gaseous type. The output is about 100 lumens per watt; have life of about 20,000 hours, and are energy efficient. These lamps are often installed on streets and parking lots, and are designed to allow the eyes to see more details at greater distances, e.g. through fog. High-pressure Sodium lamps, which are used extensively outdoors, provide poor CRI, making things look yellow.
Low-pressure Sodium lamps are also gaseous type. They produce 150 lumens per watt; have a life of about 15,000 hours, and are even more efficient than High-pressure Sodium. These lamps are expensive to maintain. Low-pressure Sodium lamps provide poor CRI, while making colors unrecognizable and produce a yellow-gray color on objects.
On many occasions, when people park their vehicles in a parking lot during the day, and return to find their vehicle at night, they are often unable to locate it because of poor CRI from Low & High sodium lamps; while another problem is the inability of witnesses to describe offenders, accurately.
LED (Light Emitting Diode) lamps produce light up to 90% more efficiently than incandescent light bulbs. An electrical current passes through a microchip, which illuminates the tiny light sources and the result is visible light. The lifespans of LED is about 30,000+ hours, and has excellent CRI. As LEDs are comparatively newer technology, they are more expensive than conventional incandescent/fluorescent lamps.
Type of lighting
• Streetlights project downward beam of light; usually installed for footpaths, roads and streets of commercial and residential areas.
• Searchlights are very narrow high intensity beam of light, concentrating on a specific area; the waving searchlight beams can still be seen as a design element on the logo of the 20th Century Fox. Searchlights are also used by hovering helicopters to search for someone on the ground.
• Floodlights project medium-to-broad beam on a larger area, generally used during professional sports events at night.
• Fresnel projects a narrow horizontal beam for medium distance. It is unlike floodlight, which illuminates a larger and longer area. Fresnel can be used to illuminate escaping intruder, while keeping security personnel well-masked. Fresnel is also commonly used in theatres during dramas and musical concerts.
• High-mast projects downward beam of light, and generally are utilized where light is required at a larger area, like highways, main parking lots of airports etc. Height of high-mast varies between 70 to 150 feet.
Basic Principles of Lighting General
• During security lighting installations, it is recommended that only the most critical elements are to be dictated by the client, i.e. minimum Illumination, type of lamp etc., allowing the designer to have required freedom to optimize the best solution.
• Protective lighting should be installed in a manner that it must not pose a disadvantage for the guard force through strike/restrike gap, the direction of glare etc.
• Protective lighting should be safe, as many lamps contain toxic metals or other materials, which can be a hazard to personnel or environment, if not controlled.
• Protective lighting must not be the source of any hazard; particularly in case of outdoor lighting, where it may become a hazard for people driving in the vicinity.
• Protective lighting must not be a nuisance for its neighborhood. Trespassing of light has been comprehensively covered by law in advanced countries.
• Protective lighting should be cost effective, and any installed security measure must give back value for money and must be affordable to operate.
• Protective lighting should be reliable, as any system which is unreliable will soon be discredited.
• Protective lighting must comply with rules and regulations of local authorities and other legal requirements. In modern societies, clean neighborhoods and environment by-laws allow ‘Light’ to be treated in the same way as ‘Noise’.
In terms of application
• Direction of protective lighting should be down and away from the facility, which is to create glare for an intruder and not for the security staff.
• The intensity of light may vary, but there should not be any dark spaces between lighted areas for intruders to easily move-in, rather protective lighting should be designed to have overlapping and uniform illumination.
• Moreover, protective lighting should itself be protected. Lights should be located inside the barrier, protective covers should be placed on lamps, mount lamps should be of appropriate height and power lines should be underground.
• Photoelectric and Motion-activated apparatus will enable protective lighting to go ON and OFF automatically, while responding to natural light or any movement. As a back-up to this system, manual operation is always considered useful.
• Besides having a main supply for protective lighting, an auxiliary arrangement for emergency electrical supply to the whole system should always be placed. Moreover, protective lights should be checked for operation, daily – before darkness.
• If a clear view of an area/window is provided, that would enable security staff to see anyone moving around, easily.
• As a thumb rule, the illumination of protective lighting should facilitate security staff to do facial-identification from a distance of at least 9m (30ft).
• Internationally, a specific illumination level has been recommended for a precise area. Some figures are tabulated below, just to give an idea in relation to number of Lux for a specific place. Light meters are commercially available in market, which should be used to gauge the illumination of the area at night; even light-meters are available in mobile phones, in the shape of applications.
The cost and effort of installing protective lighting will be a waste, if the system is not properly and consistently maintained. Over a period of time, output from a lamp falls due to both – degradation of the lamp, and build-up of dirt around it. Figures are often quoted for reduction in output at 15% after 1 year, 20% after 2 years and 26% after 3 years.
Corrective Maintenance: Suitably qualified technicians should be available to respond for on-site emergency repair or replacement of lamps. Expected response time should depend solely on how critical the lighting is for the site. A log should be maintained about lamps which have been replaced, as this can also identify design issues, if some lamps fail more often than others.
Preventative Maintenance: Routine servicing and preventative maintenance of the system should be undertaken, typically annually. The length of this maintenance cycle will depend on the predicted life of the lamps, knowing that some lamps don’t develop a fault, but may suffer decreasing lumen output.
The subject of energy management is expected to become one of the most important considerations in future, as it is apparent that serious measures will be taken to reduce energy usage and waste. This will have an impact on protected lighting, and the way it is applied. Security professionals are supposed to be better educated on the issues of lighting design, which are effective and energy efficient.
Some other questions which require serious brainstorming include whether an offender looks more suspicious under a light or in the dark with a flashlight? Should motion-activated lighting be considered to save energy instead of continuous lighting? While doing exploration on the subject, many other such questions also come into one’s mind, which all are ripe for further research and debate.