Prior to 2014, the standard for qualifying an ESD floor, based on ANSI/ESD S20.20, required testing electrical resistance to ground and system resistance, which includes the floor, adhesive, and test subject wearing ESD footwear. If the floor measured below 1.0 x 10E9 ohms and below 3.5 x 10E7 ohms for system resistance, it passed the qualification testing. If the floor passed both types of resistance tests, it was assumed to meet the standard for static generation – ≥ 100 volts. (Testing for static generation was required only if the floor failed these tests.)
However, certain types of conductive flooring passed both tests and still generated significant static charges on people wearing certain types of ESD footwear. In 2014, changes to S20.20 acknowledged this flaw and qualification requirements were modified to include tests for body voltage (charge generation).
Today, to properly qualify an ESD floor, you must test resistance to ground, point to ground resistance, and system resistance. You must also test for walking body voltage. Tests must be performed in a controlled environment at 12% RH +/- 3%.
- System resistance and charge generation tests must be conducted with the test subject wearing ESD footwear.
Because some flooring materials perform differently with different types of shoes, qualification tests must be conducted with every type of footwear allowed in the space. If employees will be required to wear ESD shoes and visitors will be given conductive heel straps, for example, the floor must be tested with ESD shoes and heel straps.
- Resistance tests alone do not predict the floor’s propensity to generate static. Some highly conductive floors generate a significant amount of static on people wearing certain types of footwear.
- To meet qualification standards outlined in ANSI/ESD S20.20 – 2014, you must perform three different resistance tests as well as testing for charge generation.
- Tests include: Point to point resistance (STM7.1); Point to ground resistance (STM 7.1); System resistance (STM97.1); Charge generation/body voltage generation (STM97.2)
- To properly qualify a floor, tests should be done in a controlled environment at 12% humidity +/-3%.
- Different floors perform differently depending upon the footwear used. System resistance and charge generation tests must be performed multiple times with the test subject wearing every type of footwear to be allowed in the space.
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