The LaVergne, TN Police Department handles all 9-1-1 calls for police, fire, and medical services for one of the fastest-growing municipalities in America. When their telephone consoles began crashing last year, the department was faced with a serious threat to their mission-critical operation. “At any given time, one of our consoles was down,” says Lieutenant Freida Cameron, Communications Supervisor for the LaVergne County Police Department. A large-scale, multi-console crash—a remote, though viable possibility—could have left the municipality’s 24,000 residents and 24,000-plus non-residents, working in the surrounding areas, with no access to emergency services. “Without the use of our phone system,” Cameron says, “citizens have no way to reach us.”

Assuming that the problem was in the telephone lines, Cameron contacted Bellsouth, the department’s telecommunications provider. Bellsouth technicians replaced modules and grounded and re-grounded the telephone systems—to no avail. The consoles continued to crash. Finally, Bellsouth sent in a technical specialist. After retesting all of the equipment, the specialist determined that the problem was caused by static electricity.

When evaluating a static control carpet, always keep the following points in mind: > Never rely on your sense of touch to tell you that you have a static problem. Static is invisible to the senses. It takes 3500 Volts of static before a human feels the discharge. A few hundred Volts will harm your electronic equipment or corrupt data. > An ounce of prevention is worth a pound of cure. It is better to prevent static than to ground static. > The floor should have both conductive and antistatic properties; > Grounded mats do not work in a call center. Static is accumulative, it builds as you walk. Mats cannot discharge static after it has accumulated on your body. > The static control floor must cover the entire call center. Otherwise, people can generate static and carry it over to the protected area. > The floor should never rely on special sprays or treatments. These are temporary and impossible to monitor. > Rolling casters destroy most conductive fibers and computer-grade floors. > Be sure your floor passes the “Roller Caster Electrical Test” or CET. The CET is the only predictor of what will happen to your floor’s electrical properties after normal abuse in the most critical area—under your chair and next to your console. > Be wary of lifetime warranties from suppliers who do not provide test data after accelerated life testing. > Select the flooring before you call installers. Static is not their area of expertise. Beware of manufacturers that claim they will supply and install your floor. You need local support in case you have problems or need repairs.

Static Electricity Problems
The police department dispatchers had never considered. However, Cameron learned from the Bellsouth technician that, “mats will prevent static in the place where they’re located, but they do nothing to eliminate the static that builds up when people walk across the floor.”

The problem LaVergne experienced is by no means unique. The electronics inside the current generation of computer hard drives are the single most sensitive components ever developed. In older model electronics, internal protective devices provided significant immunity to static events. The trade-off was that those devices slowed circuit speed, inhibiting production of faster, more advanced electronics. To produce today’s higher performance electronic components, manufacturers were forced to eliminate the internal protective devices. Today, a static discharge of only 20 Volts—a discharge too small for a human to feel—can damage or destroy a sensitive electronic component.

Why Computer-Grade Antistatic Carpet and Mats Don't Work

Computer-grade low kV carpet, designed during the infancy of the computer age, contains a high density of bi-component yarns and generates less static than regular carpeting. The term bi-component refers to the co-extrusion of two materials within the same yarn strand. The internal cross-section of the yarn contains carbon; the surrounding fibers are composed of standard insulative (static generating) yarn. Bi-component yarn provides an overall reduction in static generation, but does not discharge or conduct static and does not provide a path to ground. Low kV carpet is usually specified to establish a space that is free of static charges, or zaps. When first installed, most low kV carpets will prevent shocks, as long as the relative humidity (RH) is above 50%. Low kV computer-grade carpet will not reduce static electricity when the humidity drops, as it does in the winter or when air conditioning is used.

Static shocks and zaps are Electrostatic Discharge (ESD) events, but the voltage in these charges is more than 1,000 times greater than the static discharge necessary to damage an electronic component. In fact, it takes 3500 volts of static electricity before a human feels or is in any way aware of the discharge. As already mentioned, today’s lightning fast computers and telephony equipment can be damaged by a minute charge of just a few hundred volts.

Standard low kV carpets, designed to prevent people from getting shocked, are useless in areas where electronic components are used. The antistatic properties of low kV or computer-grade carpet are usually described by obsolete standards, such as the IBM/Burroughs standard that grades the carpet by its kV rating. A carpet specified for use in a mission-critical area or communications center should be rated by both triboelectric compatibility—antistatic properties—and resistance to ground, measured in ohms.

LaVergne personnel had realized that computer-grade carpet would not protect their components, which was the reason they bought and installed the antistatic mats. The mats were treated with an antistatic chemical similar to the antistatic coating on a fabric softener sheet. As with spraying a solution made with Downy fabric softener on the floor, antistatic carpets and mats do provide some initial benefit. As soon as the antistatic coating wears off—often within a few weeks—the carpet or mat loses its antistatic properties and can actually become a significant generator of static. The problem is, static is invisible: the only way to know that the antistat has worn off is when the console goes down for no explainable reason.

It is possible, of course, to periodically spray the floor with an antistatic chemical, like Downy, and people who know little about static sometimes recommend doing so. The trouble with periodic maintenance is twofold: 1) you don’t always know when it’s time to reapply the antistat; 2) more importantly, surface additives do not work in dry conditions, such as in winter or in air conditioned spaces. Unless the static problem is minor—involving nuisance shocks, in places where no sensitive computers, electronic components or telephone systems are in use—or the solution need not be long-term, these types of solutions are not recommended and should never be used.

Solving the Problem
As with any purchasing decision, finding the correct antistatic solution requires doing some homework. Before deciding on a solution, it's always best to understand the cause of a problem. That way, any problems will actually be fixed rather than applying a band-aid. Buyers should have at least a rudimentary understanding of three things:

• What is electricity discharge?

• What conditions cause or increased the generation of static charges?

• What can be done to prevent static in the first place?

Static electricity is electricity at rest; amperes of electrical current do not apply to static electricity as they do to the electricity flowing through plugs, switches, and electrical outlets. While at rest, electricity cannot harm anything. However, when it discharges, the electricity that was once static becomes dynamic. That invisible, high-speed computers and telephony equipment. A seemingly insignificant signal from a static discharge can command a mainframe computer system to shut down or generate an unwarranted signal directing an unintended action.

Static generation, like any physical phenomena, requires certain conditions that will either promote or inhibit it. We know from birthday party experiences of rubbing balloons on our heads and watching hair stand on end that static is a good generator. We also know that static is more easily generated when the humidity is low. Since most communications centers are carpeted, which is essentially the same thing as coating a floor with plastic, the first condition for static generation has been satisfied. Until the advent of air conditioning, condition number two was only satisfied during the so-called heating months between November and April. However, today's 24/7 HVAC systems increase comfort by extracting humidity from the air whether they are heating or cooling, resulting in potential static problems on any given day regardless of the season or geographic location.

The most important thing to know about controlling static electricity in a 9-1-1 communications center is that it must be prevented. Because high humidity will reduce the possible generation of static, installing large humidification systems inside HVAC air ducts is an option to consider. Unfortunately, this solution usually backfires because most people become significantly less comfortable as relative humidity rises. Additionally, it is almost impossible to control static with humidity generators if the external humidity is already low as as it is in the wintertime.

This forces us to attack condition number two, the plastic or static-generating floor. Since most carpets contain millions of static generating nylon fibers, many facilities have tried replacing carpet with conductive mats and or special conductive tiles. Unfortunately, mats are clumsy and they only prevent static that might be generated after a person stands on them. They do nothing to the static that a person brings with him or her when walking across the rest of the floor.

Covering the entire area with conductive vinyl tiles might seem like a good solution, but recent research has shown that vinyl tiles will not reduce static on people unless they wear special conductive footwear. Without special footwear, conductive vinyl tiles actually generate static electricity. Fortunately, the same research has proven that conductive—not low kV, not computer-grade, and not 2 or 3 kV—carpet tiles not only eliminate static, but also actually prevent charge generation or what we call walking body voltage, in the first place.

Understanding Charge Generation: Walking Body Voltage
The generation of static electricity from contact and separation is a well documented phenomenon: any time two materials interact and then separate, there is an exchange of electrons between the two materials. In the case of people and floors, shoe soles interact with the floor’s surface, generating an electrical charge that accumulates on the person’s body. This is called walking body voltage. The minute the person touches something—a door knob, for example—the voltage that has accumulated on his body immediately discharges from him to whatever he touched. If the object happens to be an electronic component—a telephone console, for instance—the electrical signal from the static discharge interferes with the component’s internal circuitry, causing the sort of crash experienced by the LaVergne dispatchers and the military air traffic controllers.

Conductive Carpet Discharges Static to Ground
The floor is the central contact point in a dispatch center—everyone touches the floor. The floor is also the area where all static charges originate. The mats in the LaVergne PD didn’t work because static is an accumulative problem. People walking around a busy call center generate and store static before they ever set foot on a mat. Since an antistatic mat provides no electrical path between the shoe soles and itself—to dissipate static, you need a conductive, not an antistatic material—it cannot discharge static electricity. With static electricity, the proper solution is always preemptive: static must be prevented before it becomes a problem.

To solve the LaVergne Police Department static problem the old carpet and antistatic mats needed to be replaced with conductive carpeting, specially designed for use in mission-critical areas. To function properly, a conductive carpet must contain conductive fibers, have a conductive backing, be installed with conductive adhesive and be attached to a path to ground. The conductive floor must be installed throughout the center, not just in certain areas. When a person walks across a properly installed conductive carpet, the charge generated between his or her feet and the floor discharges to the carpet, then travels along the designated path to ground. A good-quality, high-performance conductive floor is the only fail-safe means of safely and effectively controlling static in a mission-critical environment or communications center.

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