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Question Hello, Thank you for the opportunity to attend the presentation today about the basics of ESD controls. I have just around 10 years of experience in the industry, but I've seen a few phenomenon in this time about which I would like to get you advice. Do you think it is a major or a low risk from ESD standpoint if operators have cooling fans switched on during hotter summer days on their workbenches? Do you agree that these should be replaced by ionizers? Some operators have to make long moves with their hands and find the wrist straps obstructing in their work. Is it acceptable to have their wrist straps attached to their ankles or is it a must to have it as close as possible to their palms so any charge created by their hands is neutralized through the shortest distance? Thank you! Best Regards, Zoltan Szoke
Answer Virtually all materials, including water and dirt particles in the air, can be triboelectrically charged. If the air is relatively clean there should be no ESD control issue with operators using regular cooling fans which generally would have the airflow directed towards the operator.
Ionisers will neutralize charges on insulators and isolated conductors; when used the airflow should be directed towards the ESD sensitive items.

Per EN 61340-5-1 operators are to be grounded using a wrist strap system or a Person/footwear /flooring system. There is no requirement that the wristband contact the skin of the person’s wrist. 

For example, see Vermason Statshield ESD Smocks at; on page 1 of its Technical Bulletin TB-7516 it says:“The Vermason Statshield® premium smock incorporates our “hip-to-cuff” grounding feature which allows for hands-free grounding with no coil cord tugging at the operator’s wrist This feature allows connection of a ground cord to a 4mm snap stud on the smock at the hip”

Vermason Statshield Smocks meet EN 61340-5-1 Personnel grounding requirements Table 2 Note a “For situations where an ESD garment is used as part of the wrist strap grounding path, the total system resistance including the person, garment and grounding cord should be less than 3,5 x 10^7 ohm.”

If the wrist strap system wristband is attached to the operator’s ankle, it should be tested that way while worn using a standard wrist strap tester.
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