Electrostatic DischargeStatic control in carpetCommercial carpet is often installed where electrostatic properties may be of concern. There are usually two aspects of this concern. The first involves the threshold of human static discharge sensitivity. The second involves electronic sensitivity. When static shock and human comfort is predicted to be a concern, it is advisable to specify a permanent built-in static control system. It has been found that carpet that has been tested by the American Association of Textile Chemists and Colorists (AATCC) Test Method 134 and does not exceed a 3.5 kilovolt(kV) level is usually acceptable for general commercial areas. For more critical commercial areas, a 2.0 kV is an accepted upper limit. The AATCC Test Method 134, Electrostatic Propensity of Carpet, is a laboratory simulation that assesses the static-generating tendency developed when a person walks across a carpeted area. Static generation is influenced by humidity conditions; therefore, all testing is performed in highly controlled test chambers at 20 percent ± 2 percent relative humidity. A specification for a selected maximum kilovolt level of performance will satisfy the majority of commercial carpet applications. As carpet is considered for use in evolving and increasingly high-technology applications or electronic offices, a new specification characteristic has become a key consideration. The miniaturization of electronic devices has made them even more susceptible to electrostatic discharge (ESD) damage. The Electrostatic Discharge Association suggests that appropriate floorings, of any type, may also need to be static dissipative in addition to being low in their kilovolt performance levels. They have developed a commonly used test method, ESD-S7.1, to measure dissipation and to characterize floor coverings. An additional characteristic that may also be incorporated into an ESD performance specification is the static decay rate. It is suggested that Federal Test Method 4046 (101C) or NFPA 45-A be used for product evaluations. Carpet performance may be engineered, through the introduction of conductive filaments and other techniques, to meet specified static propensity requirements as well as specified resistive and charge decay rates. |
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