It's EASY to generate a static charge! Static electricity is generated (in most cases) by contact and separation. Whether it's the technician's clothes rubbing against their skin, their shoes contacting and separating against flooring or the action of them pushing a cart with casters across a room it's EASY to generate a charge! A person's skin is moderately conductive allowing the static charge to flow around the human body but to eliminate this charge the skin needs to be grounded. An ESD Wrist Strap contacts the skin while the attached cord provides a pathway for the static charge to go to a ground point.
Yes! It's THAT simple!
But what if the Technician is Mobile or hates a cord dangling from their wrist?
Shoe soles are insulative! ESD Heel Straps have a conductive ribbon that tucks into the technician's shoes and makes contact with the skin via the moisture in the socks. The static charge flows from the technician's skin, through the moisture laden socks, to the conductive ribbon, around the insulative shoe sole and to the conductive heel strap cup where it is grounded by the conductive floor (or esd floor mat). Let's look at a case study. This client has an ESD tile floor but the technician's aren't wearing heel straps! They have a carpeted area they walk across before entering the ESD area. They wear Tennis shoes. They've generated around 3,900 volts on the carpet. How long does it take for the charge to decay to an acceptable limit of under 100 volts? Answer: 94 Seconds!
They decided to start wearing heel straps because it was EASY for a person to walk over to an assembly bench and grab a board in a minute or two. Next Question: How long does it take for a static charge of 5,000 Volts to dissipate to ZER0 when wearing ESD heel grounders? Answer: 1/10 of a second!
Question of the Day on Charge Generation While Walking: We have an ESD tile floor. When we purchased it the supplier said we'd be FINE without wearing heel straps. Answer: You were misled by your ESD flooring supplier. United is probably the Nation's most popular resource for 3rd party Certifications of ESD flooring. We test all types of ESD flooring and have done so for over 15 years.
Long and Short?
Without wearing Heel Straps you WILL create a static charge on ANY type or brand of ESD floor or floor mat.
The charge is much less than walking on standard flooring BUT it's at least 200 to 400 Volts (the maximum limit for compliance is less than 100). How much of a charge will you generate when walking on the floor while wearing ESD heel straps? Generally less than 50 and with some ESD floors you'll only generate 2 or 3 volts!
NOTE: It's important to wear a heel strap on each foot! When walking one heel is not touching the grounded floor (or mat) hence the charge needs to be dissipated by the other foot that's making contact. Tech Tip: For compliance, seated technicians should always wear a wrist strap - even if they are wearing heel grounders! Why? Many stools have a rail and the technician could possibly rest their shoes on the rail - disconnecting the connection of the heel strap to the grounded floor (or floor mat) thus negating the heel strap's effectiveness.
*NOTE for those working with static charged items. Some clients use processes that generate substantial amounts of static electricity. When a highly charged item contacts a human it HURTS and has the potential to cause harm! Examples of items that may generate intense amounts of static include isolated rolling robotics, man lifts, the manufacturing and spooling of plastic laminates, sheeting, printing, etc. ESD heel straps are NOT recommended in or around high voltage static. Why? The discharge will be massively more powerful when it transfers into the grounded technician. Hint: Reduce or eliminate the static generation at the source, not through your body. Please call us for suggestions.
All ESD straps are NOT created equal! OUR straps are professional grade and achieve the perfect balance of price, longevity, performance and ULTIMATE Static Control. Comments, questions, opinions? Contact the author.
*Republished with revision adding high voltage static discharges on 9/9/2019