ESD Library

Managing Static: The Invisible Threat to Call Centers

By Dave Long — Vice President of New Business Development, Julie Industries, Inc.

Designers of mission critical spaces such as 911 call centers, mission control command centers and flight control towers routinely design their spaces to withstand external threats—weather, power outages, earthquakes and, in some cases, even biological threats. While clearly all of these external threats must be addressed, an invisible threat, inside the call center, is sometimes overlooked. Electrostatic discharge (ESD) can wreak havoc inside the mission critical command center. Dropped calls, blown headsets, PC lockup and lost or corrupted data represent just a few of the problems caused by random static discharge.

Microcircuits inside electronic equipment perceive a static discharge as an overwhelming burst of energy. Older, more rugged components, though still prone to ESD failure, contained special microcircuit "gate protectors," capable of diverting the random charge away from the heart of the device. These interior shields, while protecting the circuitry, slowed the performance of the devices. Today, many designers of the new breed of electronics have done away with these cumbersome internal protection devices. This progress in design translates into a world of faster, more capable computers and telephony equipment. Without the internal shields, however, devices are far more susceptible to the invisible threat of static electricity, a phenomenon even more ubiquitous than the common cold. Most people, having experienced the nuisance of static cling or felt the zap of a shock, assume that static is something that can be seen and felt. Yet it takes 3500 Volts of static electricity for human beings to perceive the effects of a static discharge. To put that number in perspective, sensitive electronic components can be damaged or destroyed by a discharge of under 25 Volts. Random static discharge and field effects caused by such common events as sliding a chair, rising from a seated position or walking across a floor can wreak havoc on computers and sophisticated telephone systems. Last year, Palm, the manufacturer of the Palm Pilot, was engaged in a class action suit after low levels of static inside their PDA caused lost and corrupted data during transmission to PCs.

Defining Antistatic
In almost all cases, the floor is the primary site of ESD generation. Fortunately, it is also the easiest place to mitigate the problem. At one time, conductive vinyl was the only choice for a static control flooring material. Today, almost every conceivable floor covering can be manufactured with some sort of static protective properties. Products ranging from ergonomically-friendly conductive carpets to super hard carbon-filled epoxies are used everywhere, from networked office spaces to circuit manufacturing facilities that require maximum static protection along with a tough, durable surface. Resilient materials such as rubber and vinyl are also available in static-free versions.Selecting the right static control floor can be confusing, particularly when people toss around terms such as "static dissipative" or "conductive," words that are unfamiliar and often meaningless to architects and facilities managers. Most flooring materials currently on the market claim to have some "antistatic" properties. Almost every carpet product produced in the U.S. contains some form of antistatic ingredient, with companies often advertising their products as "computer-grade" or "3kV." For the call center facilities manager, these terms may be misleading. As with any industry, the static control field has its own technical jargon. In fact, relative to the selection of flooring, the word "antistatic" is too broad to be useful. By antistatic, people usually mean that the floor will reduce the generation of static between footwear and the floor. But which footwear? What type of floor? Some shoe soles produce low levels of static when they rub against certain flooring materials and high levels of static when they interact with others. When the resultant charge measures in the low range, we call the condition "antistatic." When the charge is high, we call the condition static-generating. The important distinction is that "antistatic" is a snap shot condition that will easily change if any parameter—from humidity to surface hardness to footwear composition—is altered.As for computer-grade, the term means only that the floor will suppress static charges to a level of 3.5 kilovolts—so you won't feel a discharge. As we know, call centers and other mission critical command centers house some of the most sophisticated electronics and telephony equipment available today. What good is a "computer-grade" flooring product that will reduce static charges to under 3.5 kV when sensitive equipment can be destroyed by a static charge of less than 1/100 of that? And how will an antistatic or computer-grade floor tested in the summer at 50% humidity fare in dry winter conditions when the RH drops to 10%? The keys are finding a product that requires no special sprays or coatings, provides a low static rating at all humidity levels and one that also provides a verifiable path to ground.

Two Objectives—One Solution
To ensure electrical performance, the static control floor must meet two basic objectives:1) The floor must not contribute to static generation;2) It must be groundable after it is installed. Many static control floors are capable of meeting one of these objectives, but not the other. A computer-grade carpet, for example, might marginally address the first objective, but it cannot be grounded. An ungrounded floor can allow a person to remain charged just as an electrical capacitor stores energy. And because electricity is always looking for the path of least resistance, as soon as the charged person makes contact with equipment or some other item in the room – unwanted rapid discharge will take place.What is to be gained from a floor that prevents shocks if it cannot be grounded, so will not reduce charges below the threshold of damage to the mission critical equipment it was intended to protect? That type of floor could provide false security and contribute to the very problem it is supposed to eliminate.

*This article originally appeared in the May '04 issue of Emergency Number Professional Magazine.