If using ESD flooring for a flooring / footwear personnel grounding system (or a possibility in the future), we recommend conductive flooring.
A “Conductive ESD Floor” is defined by ANSI/ESD S7.1 (the flooring standard) as a floor that measures <1.0 x 106 ohm Rtg.
The ANSI/ESD S20.20 standard states that an ESD floor must measure <1.0 x 109, This same standard also states if the Footwear / Flooring grounding system (Operator to footwear to floor to ground) is <3.5 x 107 ohm Rtg, no additional testing is required. If the system measures >3.5 x 107, but less that 1.0 x 109 ohm Rtg, then Charge Generation tests with operator voltage of <100 volts must be preformed.
Since floors get dirty, which can raise floor resistance, it is good to start off with a floor that is Conductive <1.0 x 106 ohm Rtg.
The figure to the left is from ESD TR 20.20, the Handbook for ANSI/ESD S20.20. At 3.5 x 107, ohm (35 megohm), by straight resistance (testing done wrist strap grounding), an operator’s voltage will always be <100 volts. This also shows that the lower the resistance to ground, the lower the body voltage.
Therefore, in selecting ESD Flooring products, you would want that them to be <1.0 x 106 ohm Rtg, unless there were special circumstances, like cleanroom concerns, that do not allow you to achieve the lower resistance level of “conductive”.
Desco manufactures a number of conductive flooring products: