Q. Looking for some guidance regarding the use of ESD flooring.
1) Between static dissipative or static conductive is one considered better than the other?
2) How is it determined which product is more appropriate for a given use?
3) Are the protocols associated with either type? (Footwear grounding , straps, etc?)
4) Is there an ideal surface resistance range that covers a majority of projects?
5) What are the advantages and disadvantages between rubber and vinyl?
A. These are fairly often asked questions. There are lots of choices in flooring materials today, you do need to be careful in the selection since it is an expensive purchase. For those that want to use the floor as either the main grounding path for the personnel or as a back-up in an ANSI/ESD S20.20 compliant or certified facility, the combination of floor and footwear becomes the primary quantity to measure.In the current release of S20.20 (2007) two methods are used to qualify the floor and footwear system. In the first, the resistance to ground from a person, through their footwear while standing on the floor has to be less than 35 megohms (<3.5 x 10E7 ohms). If the floor and footwear combination is greater than 35 megohms but the floor resistance to ground is less than 1 gigohm( <1 x 10E9 ohms) then a walking test according to ANSI/ESD STM97.2 must be used to qualify the floor and footwear combination. The result of the walking test must be less than 100 volts (or other user defined value).
In order to have a combined floor and footwear resistance of <35 megohms, the floor itself has to be just about 10 megohms or less to ground. This means that in almost every case, a conductive range floor is needed. The vast majority of floors being installed today are considered conductive and are in range of (2.5 x 10E5 ohms) to (1 x 10E6 ohms) when measured according to ANSI/ESD S7.1(soon to be STM7.1 without significant content change) A 1 megohm floor +/- 10% would be considered ideal by most today.
We cannot get into details regarding features and advantages of the various materials but it can be stated that there are both vinyl and rubber based flooring materials that will meet the requirements for grounding of personnel as stated above. There are also vinyl and rubber materials that will not meet the requirements as stated above so it is necessary to thoroughly review product literature before purchase.
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