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Does the %RH need to be at a certain level to get the maximum benefit and if so, how can that level be determined? - Rick Dibble, Palmyra, NY

Answer

There is a definite and noticeable difference in the ability to generate static electricity when the air gets dryer (the % RH decreases). The event of walking across a carpet can yield a charge of 35kV at 10% RH [very dry air], but will drop significantly to 7.5kV at 55% RH. A good range for working humidity would be between 25%RH and 70%RH. This range depends on your working environments. Some clean rooms are kept at a constant RH (~50%), other environments want lower %RH due to corrosion susceptibility to humidity sensitive parts. Check with the manufacturer of your devices and ESD control products for the optimum humidity range. Some ESD control products are humidity dependent such as floor finish and topical antistats.