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Spring 2005 - Article 3

From The Lab
Anti-Stat Floor Finishes

Static electricity is electricity at rest, or the accumulation of electrical charge, as opposed to an electrical current which is the movement of electricity. As you walk across a floor (insulator), negative electrons are drawn from the flooring onto your body. Because electrons are accumulating, you are becoming statically charged.

An Electrostatic discharge (ESD) occurs when the electrostatic charge that has accumulated on your body is transferred to an electrostatic sensitive material such as a light switch (conductor). When touched, you are "shocked" since the imbalanced charge (negative versus positive) gets shared between you and the object.

Electrostatic discharges can be very damaging to sensitive
electrical equipment as well as other industrial, commercial and consumer products. As far back as the 1400's, military forts implemented static control procedures to prevent the ignition of black powder from ESD's.

Standard floor finishes can be considered antistatic or insulative. Since the finish has no dissipative qualities, any electrons transferred to the floor will tend to stay there. If the conditions are right, (low humidity and a susceptible electrostatic sensitive material being two key elements) you may produce an ESD after walking across this finish. The surface resistivity of these finishes is very high, usually measuring at 1 x 10^¹² ohms/sq.

Static dissipative finishes will allow the transfer of electrons to grounded objects or to other conductive materials, thereby reducing the formation of static electricity. If the relative humidity is very low (10-25%), the effectiveness of these finishes is compromised. The surface resistivity of these finishes usually measures between 1 x 10⁶ to 1 x 10^¹² ohms/sq.

Conductive materials have an extremely low surface resistivity (1 x 10⁵ ohms/sq) and allow for the free flow of electrons across a surface. Floor finishes do not fall into this category even though the term conductive floor finish is used by many industry professionals.

As mentioned above, humidity levels have a huge impact on ESD. Below is a chart showing how relative humidity (RH) affects static electricity formation.

Even though Essential does not carry a static dissipative finish, keeping the relative humidity in the 40 to 60% range in a room will produce suitable results in many static-sensitive areas.

*Chart courtesy of Electrostatic Discharge Association