In response to my answer about rodents chewing cable (see "Rodent damage to cable," April 1997, page 44), I received the following information. Many thanks to David Cox, chief engineer of telecommunications for gte (Columbia, MD), for taking the time to educate all of us on the fine art of rodent eradication. I would caution you that, working in commercial office buildings, we do not have the same latitude in terms of options as is available in central-office buildings. And, while in the heat of the hunt, do not forget the Occupational Safety and Health Administration (osha--Washington, DC).
Dave explains that rodents chew to keep their front teeth short. So, as a first line of defense, we should give them something other than cable to chew on while we plan our major offensive. Debarked, split hardwood logs are recommended for this purpose.
To protect subground inside cabling plant, seal emt conduit for laterals and risers to at least the second story. Cable trays in the subground levels can be "rat raceways." After sealing all underground ducts, holes, and other openings, have the area "tented" with gas. Dave reports that this procedure is nearly 100% effective, and when performed every year, it also keeps all other pests safely under control. If gassing rodents is impractical, poisoned rodent bait should be used.
Another trick that has produced sure-fire results is running sealing current in every 25-pair binder group. This elevates the temperature of the cable by 4! or 5!. Dave reports that rodents hate the feeling of heat on their teeth.
Next, consider Underwriters Laboratories Inc. flame-proof coatings for exposed cable. It tastes bad, breaks little teeth, and causes internal bleeding and death within 24 to 48 hours. Also, some nonbiodegradable pulling compounds, which taste and smell unpleasant, have the same effect on the nervous system of rodents.
A more aggressive approach, sometimes used by the military for high-security areas, is to pressurize the riser cable with nitrogen gas, as if it were outside-plant cable. Nitrogen is a safety hazard to people in confined spaces, but it is also deadly to rodents in basement ladders, trays, and cable vaults. Dave does not recommend nitrogen in a building with confined or low airflow spaces.
Electrocution is also an option. Dave reports that some folks have gone to war with rodents by placing a cattle-yard fence charger on the inner cable sheath. He does not recommend this option either, however, since it can cause ac/dc noise on the line and electrical shock to cable-maintenance personnel.
gte uses live-catch traps in central-office cable vaults with rodent problems. The company also plugs every duct hole, both outside and inside the central office, and stoppers all riser duct holes. In addition, it places metal door stops, sweeps, hinge plates, and similar devices on all below-ground passage doors.
In major cities such as New York, Boston, Chicago, IL, or Cleveland, OH, rodents are a fact of life. At best, gte has been able to control them. Dave`s last suggestion was a time-honored one. "In several central offices," he said, "we have a `gte Co. cat` to help. I am told that these four-footed employees tend to work at night and get to eat all that they capture. Oh, yes: The cats have had all of their shots....We try to run a safe workplace."