In addition to the challenges of protecting and maintaining interior spaces, some facility managers are also responsible for securing exterior spaces that can sometimes span hundreds of acres. Fortunately, there are some excellent technologies that can help facility professionals stay on top of the challenge presented by "the great outdoors."

Protecting the perimeter of a large area can be extremely costly and difficult. Hiring an adequate number of security staff members may be cost prohibitive, and even under the best circumstances, an intruder who has nothing more than a good set of tools and the patience to learn the security guard's watch routines can easily gain entry. However, there is good news: new technology can be leveraged for better perimeter security with lower costs.

Exterior security is very different from interior security. Inside a facility, the controlled environment and physical barriers of walls and doors make it relatively simple to control the flow of traffic and detect suspicious intruders. But in the outdoors, changing weather, roaming animals, and large, unpartitioned areas make it extremely difficult to secure an area effectively.

These same challenges mean any intrusion detection systems will never be absolutely perfect, but the right technology will give facility professionals far more security than traditional approaches and manual methods.

For securing the perimeter (also known as the fence line), the two most common approaches are to use sensors on the fence itself or use in ground sensors. Fence mounted devices tend to use either individual vibration sensors mounted on the fence or a continuous cable-or "ribbon"-that reacts to an intruder. Vibration sensors are similar to those used in interior applications that send an alert when the fence is moved or struck. Ribbon devices detect movement or tampering (such as when the fence is cut) by sensing the effect on the cable. Some of these ribbon systems use metal cabling that registers changes in continuity, capacitance, or resistance. Others use fiber optic technology to detect activity based on the affect these undesirable actions have on the light waves inside the cable.

Ribbon and fiber optic systems have their own set of advantages and disadvantages, and no single one can be called the best. For example, the mounting requirements, susceptibility to false alarms (due to weather or animals), and other characteristics are different for each system and need to be carefully considered.

The other type of perimeter security device is in ground sensors. These systems use the same principles as fence-mounted sensors, with the addition of cables or tubes buried just below the surface of the ground. These tubes react to ground pressure or interference with electrical fields.

What happens if there is no fence line to secure? Many facility managers are in charge of areas that are not fenced and frequently have wild animals that roam the premises. These areas are especially difficult to secure.

There are two main approaches to this challenge: volumetric sensors and video sensors. Volumetric sensors capture modifications in an area based on changes in a detection field. The most common volumetric devices are infrared sensors that detect light in this spectrum (otherwise invisible to the naked eye). Active infrared uses a transmitter and receiver and sets up a beam of light between the two. Interference with this beam triggers an alarm.

Passive infrared detects the heat from human bodies by sensing a change from the temperature of the background. Passive infrared does not need a receiver, so it can scan a wider area than active infrared. Unfortunately, when the outside temperature is almost equal to that of a human body, these systems can have trouble distinguishing people from scenery; larger animals can also trigger false alarms. Other systems use radio signals or microwaves rather than infrared but essentially use the same basic concepts.

Video sensors use cameras that detect intruders by comparing the image they see with established parameters. The simplest (and oldest) type compares the current scene with a stored scene and looks for differences. When the system sees a change in the scene, it triggers an alarm. This works successfully if an area is very well controlled and nothing moves. However, an area where there is movement (such as trees blowing in the wind) may cause many false alarms.

In more dynamic areas, the latest video detection systems can use sophisticated computer programs to distinguish between movement that is normal for the area and movement that is suspicious. The video image is fed to a computer system that analyzes the specific characteristics of the image and can recognize distinct objects as they move through the scene. These systems can recognize a person or vehicle moving through the scene, and some can even distinguish between people and animals.

Video cameras today are a far cry from what they were just a few years ago. Today, cameras are affordable and widely available, and they can use a wide variety of spectrums including infrared, extremely low light, and normal visible light. The range of lenses available is staggering, and extremely powerful lenses allow one camera to scan many acres.

No matter what your facility's grounds are like, one of these new technologies should allow you to keep your grounds secure without breaking the bank.

Condon, a Facility Technologist and former facility manager, is one of the contributing authors for BOMI Institute's revised Technologies In Facilities Management textbook. He works for System Development Integration, a Chicago, IL-based firm committed to improving the performance, quality, and reliability of client business through the use of technology.

Send your questions about this column to tcondon@sdichicago.com.