110 INTERIORS & SOURCES MAY 2015
presented in this section, ESD hazard assessments should be conducted
under the advisement of a qualified and certified professional. Further, many
flooring products are designed to be used in conjunction with other wearable
Generally speaking, any floor with a level of conductivity that minimizes
static charge generation and drains charges to the ground from personnel
wearing conductive footwear falls under the category of ESD flooring. Static
control floors may be “conductive” or “static-dissipative,” or may have
insulative properties. Understanding the differences between these terms is
critical in the process of selecting the right flooring product for environments
in which ESD events may occur. According to the Electrostatic Discharge
Association, these terms are defined as follows (for more definitions, see
related sidebar on preceding page):
w Insulative Materials. A material that prevents or limits the flow of
electrons across its surface or through its volume is called an insulator.
Insulators have an extremely high electrical resistance, and insulative
materials are defined as “materials with a surface resistance or a volume
resistance equal to or greater than 1 × 1011 ohms.” A considerable
amount of charge can be generated on the surface of an insulator.
w Conductive Materials. A conductive material, because it has low
electrical resistance, allows electrons to flow easily across its surface or
through its volume. Conductive materials have low electrical resistance,
meaning less than 1 × 104 ohms (surface resistance) and 1 × 104 ohm
(volume resistance). When a conductive material becomes charged,
the charge (i.e., the deficiency or excess of electrons) will be uniformly
distributed across the surface of the material. If the charged conductive
material makes contact with another conductive material, the electrons
will be shared between the materials quite easily. If the second conductor
is attached to AC equipment ground or any other grounding point, the
electrons will flow to ground and the excess charge on the conductor will
w Static Dissipative Materials. Static dissipative materials have an
electrical resistance between insulative and conductive materials (1 ×
104 < 1 × 1011 ohms surface or volume resistance). There can be electron
flow across or through the dissipative material, but it is controlled by the
surface resistance or volume resistance of the material. As with the other
two types of materials, charge can be generated triboelectrically on a
static dissipative material. However, like the conductive material, the static
dissipative material will allow the transfer of charge to ground or other
There are a variety of ESD flooring types that can minimize static charge
generation and drain static electricity from personnel working in areas where
an ESD event may cause damage to products or people. ESD flooring
products fall within a range of categories each with distinct characteristics
1. “No wax” vinyl tile /sheet: Available in “conductive” and “dissipative”
ranges, no-wax vinyl tiles can be installed with conductive adhesives
to address electrostatic charges. Its uniform size makes for easy installation, and waxing is not required to maintain ESD properties, making
this an especially attractive option for many commercial applications.
Further, the tiles are easy to repair and offer exceptional durability.
2. Standard vinyl tile/sheet (wax needed): Although vinyl tiles offer a
low initial cost, ESD polish or wax is required for appearance, electrical
performance, or both. As a result, maintenance costs tend to be high
for this type of product.
3. ESD wax on VCT: Vinyl composition tile can be applied with special
ESD wax that serves as a temporary solution to ESD issues. It has
a very low initial cost but is limited in its control properties to static-dissipative only. This means its effectiveness is dependent upon the
application, and is also characterized by high maintenance costs.
4. Rubber: Rubber ESD flooring can be very effective in dissipating static
electricity. However, the use of some types of paper/fabric footwear covers
(booties) or similar footwear covers used in hospital or clean room
applications may inhibit the slip resistance properties of the flooring.
Initial costs are relatively high, but floor finishes, waxes, or sealers are not
recommended12, so maintenance costs are low while durability is high.
5. Carpet: Whether installed as tile or broadloom, carpet offers limited
ESD conductivity range and moderate maintenance costs. It provides light
noise reduction and a softer walking surface, but it is not typically used for
heavy production traffic where many ESD events are likely to occur.
Conductive and static dissipative vinyl tiles are typically manufactured as a
solid, homogeneous tile using first quality, virgin raw materials. Special ingredients
are added to provide light stability, chemical resistance, and to ensure an
aesthetically pleasing finish without the need for waxing. The major benefit of
no-wax tiles is that the conductive or static dissipative properties are inherent
within the tile and will not wear out, unlike those that require waxing or coatings
The National Safety Council notes
that high ESD voltages are often
found in and around high-speed web-processing equipment, seen here,
necessitating ESD flooring products.