Facility security: keeping them away
Protective lighting is a smart addition to any facility. Using light to deter intruders is cheaper and more effective than you might think.
With so many methods and strategies available to keep trouble away from your facility, it would seem you could achieve freedom from theft and vandalism. Although it may not be entirely possible, the ultimate goal of planning and security measures is to keep bad things from happening. Let's take a look at how protective lighting can help keep intruders away.
Security lighting You should design protective or security-lighting systems on a facility-by-facility basis. There isn't a one-size-fits-all approach. Each situation requires careful study to provide the best visibility, prevention of illegal entry and detection of intruders (outside and inside building structures).
You should not use protective lighting as a psychological deterrent only. Use it at a perimeter fence, but only where the fence is under continuous or periodic observation. Protective lighting may be unnecessary where a central alarm system is in place.
Security lighting is relatively inexpensive to maintain and, when properly employed, it may reduce the need for security. It may also provide personal protection for occupants by reducing the advantages of concealment and surprise from an intruder.
Protective lighting usually requires less intensity than working light, except for identification and inspection at authorized portals and in emergencies. Each area of an installation presents challenges specific to physical layout, terrain and climatic conditions.
Design issues Consider two key components when designing a security lighting system: security effectiveness and operational efficiency.
In general, it's best to first design for security effectiveness and find the best methods of lighting your facility for safety. Then, design the system for practical operation. Don't worry if you have to give up a little on the second "run-through" because having a system that's reliable and easy to operate is important. Overly complex systems tend to breakdown too often.
Principles of protective lighting Protective lighting should enable security personnel to observe activities at an installation without disclosing their presence. Adequate lighting for all approaches to an installation discourages attempted unauthorized entry and reveals people in the area. However, don't solely rely on lighting. You should use it with other measures, such as fixed security posts or patrols, fences, and alarms.
When planning protective lighting, a high brightness contrast between the intruder and background should be your first consideration. With predominantly dark, dirty surfaces or painted surfaces, you'll need more light to produce the same brightness around installations and buildings than when clean concrete, light brick and grass predominate. When the same amount of light falls on an object and its background, the observer must depend on contrasts in the amount of light reflected.
Types of lighting Choosing the best type of lighting system depends on the overall security requirements of the installation. Let's look at three types of lighting units that provide protective lighting.
- Continuous lighting (stationary luminary). This is the most common protective lighting system. It consists of a series of fixed luminaries arranged to flood a given area continuously during the hours of darkness with overlapping cones of light.
- Standby lighting (stationary luminary). The layout of this system is similar to continuous lighting. However, you set the luminaries to automatically or manually turn on only when the security force or alarm systems recognize suspicious activity.
- Emergency lighting. This system may duplicate any or all of the above systems. Its use is limited to times of power failure or other emergencies. It depends on an alternative power source, such as installed or portable generators, or batteries.
Lighting levels You should illuminate open yards (unoccupied land only) and outdoor storage spaces (material storage areas, railroad sidings, motor pools and parking areas) as follows:
- Illuminate an open yard adjacent to a perimeter (between guards and fences) in accordance with the illumination requirements of the perimeter. Where lighting is necessary in other open yards, illumination should not be less than 0.2 footcandles (fc) at any point.
- Place lighting units in outdoor storage spaces to provide an adequate distribution of light in aisles, passageways and recesses to eliminate shadowed areas where unauthorized people may hide.
- When designing protective fencing and lighting, first consider critical structures and areas. Power, heat, water, communications, pesticide storage facilities and areas holding valuable equipment need special attention. Make sure you light the surroundings to a height of 8 feet to facilitate silhouette vision and force an intruder to cross the lighted area.
Proper lamp selection and adherence to practical guidelines combine to create functional lighting installations.
The purpose of security lighting is to protect people and property usually between dusk and dawn. Additionally, security lighting should provide enough light over an area so that anyone moving in or around it can be seen easily. For such an application, where lamps will be burning for at least 12 hours continuously, economy of system operation is a major consideration.
Another point to remember is that although security lighting can double as safety lighting, the two do not serve the same purpose. For example, safety lighting can be considered as providing sufficient illumination on a stairwell so that a person can see steps and not trip and fall. Also, a person must be visually aware of possible hazards such as curbs, sloped walkways or a change of direction on a path.
An upgrade or retrofit security-lighting project can be a factor in reducing the overall cost of security services, or it can be an important adjunct to increased security effectiveness. After a decision to upgrade is made, the first task is to conduct an audit of the building's security-lighting needs. Parking lots are the most commonly lighted areas, then walkways and building perimeters. For parking lots and walkways, the key is to have uniform footcandle (fc) levels with maximum efficiency at ground levels. Often, the area surrounding a parking lot is neglected. A building perimeter can be illuminated for architectural enhancement, and in most cases, building accent or facade lighting can double as security lighting.
It's best to light as large an exposed area as possible, such as an expanse of wall, driveway or paved ground surface; this will help to reflect and spread the light, creating a background or plane of low-level light against which an intruder can be seen.
The Illuminating Engineering Society lighting handbook offers some general guidelines for the illumination level in an area. One to 3 fc may be sufficient for a suburban facility, but 5 fc may be better for an urban-area office building. Other factors, such as traffic patterns, may cause local or IES guidelines to be exceeded.
You should select the most appropriate light source and wattage. Generally, the higher the wattage, the greater the efficacy (lumen per watt output) of the lamp. Additionally, high-wattage lamps usually allow high spacing-to-mounting-height ratios, permitting the fixtures to be well-elevated on a pole or structure, out of reach of vandals.
High-pressure-sodium (HPS) or metal-halide (M-H) sources are the two preferred lamp types. HPS lamps are available in ratings from 35W to 1000W, with efficacy ranges from 54 to 130 lumens per watt, including ballast losses. HPS lamps have an average rated life of 24,000 hours, plus excellent lumen maintenance (they still emit a high proportion of their rated lumens even near the end of lamp life).
M-H lamps are available in rating from 50W to 1500W. The single-ended lamp comes in three different outer bulb finishes: clear, phosphor-coated and diffuse coated. The M-H lamp's lumen maintenance is not as good as an HPS lamp because of its construction. Also, the particular lamp design and burning position determines average rated life.
Exterior fluorescent fixtures may be used in certain applications, such as covered walkways or overhangs. Lamps and ballasts should be specified for cold-weather application, if necessary.
Factors you should consider in selecting a light source are its luminous efficacy, color properties, restrike and run-up times, and performance at temperatures likely to occur on the site. The color properties are important for accurate rendering of people and objects, though not necessarily for the detection of their presence. (Restrike is important in the event utility power is interrupted. Restrike refers to the ability of an HID lamp to regain full output after the arc has been extinguished.) Additionally, the lamp should start reliably in cold temperatures.
No single lamp type is the best for all applications. It's generally advisable not to mix lamp types, unless two or more lamp types (and colors) are used as part of a specific lighting design. In addition, the color characteristics of a light source can be modified by inserting a filter in the lamp compartment.
Important points to consider The following are important application parameters you must consider for security lighting.
- Excessive direct or reflected glare and harsh shadows can hamper your vision. Generally, the use of fixtures with cut-off optics that direct the light downward is recommended. Many municipalities in the United States have ordinances or laws requiring cut-off optics on exterior fixtures to avoid light "trespass" onto adjacent properties.
- Use equipment that can be shielded after installation if necessary. Many fixtures have an optional louver installed behind the lens so that the Effective Projected Area (EPA), the wind loading of the fixture, is not increased.
- Use fixtures that are easy to mount and secure. The wiring (or ballast) compartment should have convenient openings or knockouts for conduit entry. Frequently, HID fixtures replace old incandescent PAR lamps in bullet-type fixtures installed on a building wall. Plan for easy access of conduit runs.
- Use fixtures with tamper-resistant hardware and vandal-resistant polycarbonate refractors. Fixtures with electrical components mounted to a diecast aluminum housing provide proper transfer of heat generated by the ballast.
Fixtures can be selected that serve for both landscape and security lighting. Light only those objects in the landscape that are pleasant to look at, such as certain trees, shrubs, statuary and fences.
A useful design technique is to provide layering of light in an urban setting. General illumination can be provided by standard roadway/street lighting luminaires with poles ranging in height from 20 to 30 feet. A second layer can be provided by fixtures on poles ranging in heights from 8 to 15 feet, with the spacing planned to provide a design feature. This fixture can have a decorative element such as edge-lit acrylic lens added at the top. A third layer of light can be provided by small scale fixtures, such as bollards, to provide physical as well as psychological cues to a specific locale, such as a walkway. Multifunction bollards are also available, with one side having a controlled downlight component while the other side may have one or more accent or adjustable assemblies for highlighting plantings or buildings. Some bollards are made of heavy gauge cast aluminum and use 18W to 150W HID lamps.
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