04 Aug

Managing Static and ESD in Call Centers

Managing Static and ESD in Call Centers

Thanks to movies and TV, no matter how old you are, you’ve probably seen the old switchboards – whether it’s on Agent Carter or reruns of the Andy Griffith Show – and computers  that barely fit inside a room – like in The Imitation Game or the TV show Manhattan.

Nowadays, of course, we carry the switchboard and the computer in a handy-dandy pocket device.

Likewise with emergency services. When we call 9-11, we expect a prompt response, and the person on the other end of the line assures us that police, fire, or ambulance are already in route as they continue to gather our information.

Computers help planes land, monitor traffic on the freeways, and even park your car for you.

But for all the advances in technology, there have been setbacks as well.

In the old days, phone and computer systems were built “solid-state.” Everything was confined within one unit and was protected from outside forces. Internally, they were defended from ElectroStatic Discharge (ESD) by microcircuit gate protectors.

Unfortunately, these gate protectors, while highly effective, tended to slow down the machines they were protecting – kind of like how some companies’ virus protection forces their machines to crawl.

As technology progressed, emergency services, military bases, and flight control centers started abandoning these more stringent preventative measures, in favor of speed.

The end result being, while these computers and call centers are protected in buildings made to withstand hurricanes, earthquakes and power outages, they can be disabled or even rendered completely useless by the tiniest static shock.

Which is why the proper ESD protection and protocols are so important in these mission critical locations.

Another factor to consider is that these facilities are typically open 24-hours a day and have hundreds of people pass through them on a regular basis. Some of them are trained and properly equipped with ESD shoes, heel grounders and even personal wrist straps, but certainly not all of them.

And when there’s a crisis and everyone needs to scramble to get the problem solved, the first thing to go is proper ESD procedures.

The answer is to make these facilities as static proof (or charge proof) as possible.

Like your skin (the largest organ in the human body), flooring is the largest and most vulnerable area for ESD buildup and discharge, if it’s not handled properly.

There are many options for ESD flooring, as we’ve discussed in prior posts, but in this instance, there are really only one option: carbon-fiber laced carpet.

The first thing you should know is that not all ESD carpet is created equal. Some companies promote and sell an ESD carpeting that is treated with a chemical to reduce static that disintegrates over time and must be reapplied.

Avoid these – you don’t want your static protection to be subject to a random timetable. Again, these facilities are always open. You’ll want to invest in a carpet whose static-prevention comes from the permanent physical composition of the materials.

For the same reason, you’ll want to invest in an ESD carpeting that is certified by ANSI/ESDA standards and reduces static regardless of the humidity levels or footwear worn by the personnel.

As an added bonus look for ESD carpet that is low maintenance, crush resistant, able to handle heavy foot traffic and comes with a lifetime warranty.

Contact us today for more information or to talk about your ESD flooring options.  We would love to be your full service, seamless ESD solution provider.

21 Jul

Can New Flooring Be Installed Over Old?

Can New Flooring be installed over Old Flooring?

Whether your company has just invested in a new to them facility or is upgrading their current locations due to time or elevated ANSI/ESD standards, one of the largest expenses they will face is replacing the existing flooring.

Based on the existing installation, this can be a very time consuming task – days to strip off the old flooring, etch or acid burn off any leftover adhesive residue.  Plus the very real possibility of damaging the concrete itself or a pre-existing moisture barrier.

Which leads to a popular question from facility and production managers – can new ESD flooring be installed over existing flooring?

And depending on who you talk to, the answer is: Yes. No. And, of course, Maybe.

Yes.

If an existing floor is well-bonded, ANSI/ESD 20.20 compliant and in reasonably good condition, theoretically, the answer is yes.

Certain flooring options pose a lower risk and are considerably easier to install over an older floor. Vinyl, for example, generally can be installed over top existing vinyl. Generally.

Problems arise when the old floor has become hard and stiff.  It may be harder to install over it, and if the initial bond doesn’t take, vinyl is unforgiving and may delaminate – requiring a complete stripping and reinstallation that is likely to cost more than the initial money saved, not to mention the time lost during the removal and reinstallation.

An additional choice to consider is installing carpet tiles over old vinyl. Carpet has become a popular choice to install over existing floors because the irregularities of the surface below the carpeting are virtually hidden behind its barely reflective surface.

Another option is Zero Stat Crete – a state of the art water-based epoxy coating – which can, after proper testing, be applied over an area that has had the previous vinyl or carpeting tile removed – often without needing to strip off any leftover adhesive.

No.

Some experts caution that you should NEVER install a new floor covering over an old one. Along with the warnings above, the old flooring might hide structural defects, might not be properly bonded or might result in a plasticizer contamination of the new flooring, which could radically affect the quality and effectiveness of its ESD prevention.

Also, by not removing the old flooring, moisture concerns that need to be addressed may not be discovered.

Additionally, depending on the age of the old flooring, it might have been made with asbestos, a manufacturing material that causes severe respiratory problems and may lead to death.

Maybe.

Experts say that almost any floor can be installed over an old floor as long as the old floor is in good condition and well-bonded to the sub floor. BUT…

There are just too many variables to accurately consider or discuss every flooring replacement or recovering option in a single posting.

Even if your scenario is similar one of the ones we’ve elucidated above, there may be additional factors in your specific facility that are not taken into account in our hypothetical illustrations.

Which is why we always recommend speaking to a qualified flooring professional before making any final decisions. There is not usually a financial cost associated with their consultation and/or site visit, but the preventative savings far outweigh any nominal up front cost.

For a free consultation – or any other questions you may have, please contact us.  We would love to be your full service, seamless ESD solution provider!

07 Jul

Is Bare Concrete Really the Best “Anti-Static” Flooring?

Is Concrete Really Anti-Static?

There used to be an old wives’ tale that standing on bare concrete for too long caused varicose and spider veins.  In the 60’s, that idea was largely supplanted by the hippie movement that believed standing shoeless on bare concrete allowed the body to become more grounded.

Unfortunately, it seems that the once-held hippie belief has permeated into the world of electrostatic discharge (ESD) prevention.  But nothing could be further from the truth. Because while bare, unsealed concrete floors that are allowed to ‘breathe’ have anti-static tendencies, they are definitely NOT grounded.

Nothing to Cling To

While the lower expense of a bare concrete floor makes it appear like a desirable remedy, there are several reasons it is not classified as a true ESD flooring solution.

First there’s that word – tendencies. Bare concrete floors tend to be anti-static, but they are not reliably so. That’s because anti-static characteristics are not inherent in concrete like they are in a carbon-filled material or a poured ESD epoxy.

To further complicate the issue, the measure of how anti-static concrete is, is dependent on many variables – the most significant of which is its permeability to moisture. If you’ve explored our website at all, that should immediately raise a red flag.  In an earlier post, we talked about why moisture is the #1 enemy to your ESD flooring.

A Shift in Standards

If that doesn’t scare you away, we discussed in this post about how anti-static is not an adequate measure for ESD flooring. To summarize, the term “anti-static” refers to a material that resists generating a charge. And bare, sealed concrete does do that – most of the time. But over the past 30 years or so, ANSI and the ESD Association made the effort to remove the term from their professional industry standards because it was so overused and misunderstood.

Those standards are discussed in this post.

And for good measure, we discuss in another post the dangers of cutting corners to save money when building your ESD Protection Area (EPA). Some up front expenses are definitely worth the long-term benefits.

Fully Charged

So, let’s assume that the concrete floor you’ve just installed is as anti-static as it can get. You can walk across it to any other part of the room and there will be no static buildup, aka triboelectric effect.

But what happens when the CEO comes down to inspect the area, and as he’s walked from his office to the EPA area, he’s built up a static charge. It’s on his body, on his clothes; we know that even the slightest movement in a conductive area builds a charge that can damage sensitive electronics.

When he hits that concrete floor, the charge doesn’t just disappear. It stays with him. Because while concrete has the tendency to avoid building up a static charge, it does nothing to dissipate an existing charge. And this is the biggest problem with the use of concrete as an ESD floor. It cannot act as a ground.

The CEO touches a circuit board, it gets the electrostatic discharge, ruining it – and he blames you. And then you have to install a true ESD floor anyways. Why not just do it right the first time?

We would love to be your full service, seamless ESD solution provider.  Contact us today for more information.

15 Jun

Conductive, Dissipative, or Anti-Static Flooring?

Conductive, Dissipative, or Anti-Static Flooring

You’re hard at work at your latest assignment. Your boss wants you to put together a complete plan for creating a large-scale electrostatic protection area (EPA) for a client who will be assembling various sensitive electronics and they want to avoid any risk of losing their investment due to electrostatic discharge (ESD).

You’ve selected the grounding cables, the workstations, the custom cut matting, containers and furniture, all designed to minimize or eliminate the slightest chance of ESD damage. But a curious thing happens when you research the proper flooring.

A simple Internet search for ESD flooring yields numerous options, more than you expect and you start to notice they all fall under 3 categories.  In an instant, you’re faced with a decision, just like the game show, “Let’s Make a Deal.”

Suddenly, Monty Hall (or Wayne Brady, the current host!) is staring at you, asking do you want to choose door number one, number two, or number three: conductive, dissipative, or anti-static? The clock is ticking… How do you decide?

Door #1

For starters, let’s eliminate one of your options. Much like the ‘ZONKS’ of the game show, ‘anti-static’ is a worthless term in your ESD vocabulary.  By strict definition, anti-static refers to a material that resists generating a charge.  At one time it did designate a level of resistance, but was so overused and misunderstood, the term was removed from the ANSI/ESD standards.

So likewise, eliminate the term ‘anti-static’ from your discussion.

Deciding between the other two doors requires a closer look at the specific needs of the area for which the flooring is intended.

We’ve talked in another article about Ohms (Ω) and how they are the unit of measurement for resistance to electrical current.

Door #2

Because of the size and scope of most areas where it is necessary, the most common form of ESD flooring is referred to as ‘Static Conductive.’ Conductive flooring is at the low end of the electrical resistance scale.

Conductive carpeting may even be laced with carbon lines or metallic yarn fibers to encourage the flow of electricity. Because of the low electrical resistance, electrons flow easily across and through the surface, and can be grounded safely and quickly. This carpeting or vinyl tile is laid down with a conductive adhesive and grounded through the use of conductive tape or copper strips that run to a common ground.

This type of flooring is also generally a little more cost-effective than a dissipative solution.

Door #3

On the higher end of the resistance scale falls ‘Static Dissipative’ flooring. The higher resistance of these materials keeps the electrical charge more under control as it slowly flows over the surface and into a ground. Dissipative flooring is much more common in shared office environments where everyday shoes are more common, as opposed to a location where every element, from furniture to footwear, is controlled.

In our example above, the client will be assembling sensitive electronics like circuit boards and such in a large-scale environment. In this instance, a vinyl tile, or a poured epoxy flooring with conductive properties would most likely be the best option.

In an office setting where a company has their own IT department that fixes and assembles computers within the same facility, a dissipative, static resilient tiled floor would be a better fit.

But the fact is, these are very simplified examples of the myriad of variables that you can encounter when selecting the proper ESD controlled flooring. Your best option is to talk to an expert.

We’d love to be the experts you can count on for your full service, seamless ESD solutions. For more information or advice on your specific ESD flooring needs – or any other ESD questions, contact us today.

25 May

What Are the Standards for Electrostatic Protection?

Standards for Electrostatic Protection

So, you’ve just been tasked with building or designing your first Electrostatic Protection Area (EPA). You’ve started doing your research, but there are so many choices, from so many different companies. Suppliers, manufacturers, third party providers… If only there was some established standard for judging the efficacy and reliability of all those pieces and parts.

Well, you’re in luck! In 2007, the American National Standards Institute (ANSI) in cooperation with ElectroStatic Discharge Association (ESDA) released a unified set of standards for the design, implementation and maintenance of ElectroStatic Discharge control programs.

In the midst of World War I, five engineering organizations recognized the need to develop standards that could eliminate confusion and could be adhered to across all disciplines, without regard to politics, profits or personal preferences. These groups reached out to the U.S. Departments of War, Navy, and Commerce to form an impartial third party non-profit organization, then known as the American Engineering Standards Committee.

Following the war, the organization spent the next 20 years establishing several safety protocols still observed today, like eye protection, hard hat standards and in-house electrical safety while at the same time reaching out to other similarly tasked international organizations.

When the United States entered World War II, the organization, which would eventually come to be known as ANSI, helped to accelerate the war effort and productivity, created more effective quality control measures, as well as helping to advance photography, radio, and even the development of Velcro.

In 1970’s, ANSI established a public review process and began the herculean effort of moving the United States to the metric system. While the general public never really connected with the metric system, the effort did bring ANSI to the forefront of private sector companies who discovered standardization was a way to stay more competitive in an increasingly global economy.

With the advancement of personal computers in the late 70’s and early 80’s, engineers at several companies recognized a need for more understanding of electrostatic discharge and its prevention. They formed the ESD Association, a non-profit, voluntary professional organization that for almost 35 years has sponsored educational programs and developed standards to help eliminate losses due to electrostatic discharges.

Together, leaning on the historical experience of both military and several commercial organizations, ANSI and ESDA developed the definitive standard for ESD protection, the very cleverly named ANSI/ESD S20.20-2007.

Covering about every conceivable area of ElectroStatic Discharge, the ANSI/ESD S20.20-2007 utilizes both the human body model and the machine model to provide a broad set of guidelines for ESD protection.

The Human Body Model is the military standard that defines and rates the vulnerability of an electronic device to the ESD generated by a human being touching it. The Machine Model works similarly, except it rates the vulnerability of a device receiving a machine discharge into ground. It was originally developed by car manufacturers as their plants moved to more mechanized production technology.  The Human Body Model is about 10 times more sensitive than the Machine Model.

There is a lot to explore in the ANSI/ESD S20.20-2007 guidelines, but for the purpose of this primer, the document highlights 3 fundamental ESD control principles:

  1. All conductors should be grounded. This includes the personnel and the surfaces they are working on.  We recommend, at a minimum, personal grounding wrist straps, ESD table or bench mats, and a common ground cord.
  2. Necessary non-conductors – certain circuit board materials, device packaging, etc. – cannot lose their electrostatic charge by being grounded and appropriate precautions must be implemented.
  3. Static protective materials, such as ESD shielding bags or ESD totes and boxes must be utilized when transporting sensitive electronics outside a properly prepared EPA.

There are slightly less stringent standards that apply to floors and bench mats, but ANSI/ESD S20.20-2007 is the highest and most comprehensive guideline so far. So when you’re shopping for the parts needed to establish your EPA area, always look for companies that maintain that standard in their products and services.

We would love to be your full service, seamless ESD solution provider; contact us today for more information.

17 Dec

Do You Need Static Control Flooring?

Do You Need Static Control Floors?

Does your business have a substantial investment in electronics or computers?

Have you ever experienced an unexplained failure? Perhaps one of your critical systems went down with no warning at a critical time (there’s never really a convenient time for that, is there?), or perhaps a component was working beautifully one minute and performing erratically the next.

One of the most nefarious—and hardest to detect— culprits behind failures of this kind is electrostatic discharge. By some estimates, it could be responsible for more than fifty percent of hardware failures, costing upwards of $5 billion each year.

So, if you have devices, people, and floors, then you face risks from the devastating effects of static electricity—specifically electrostatic discharge (ESD).

How Can Floors Protect Equipment from ESD Damage?

Since static control flooring provides an attractive “escape route” for static electricity that builds up in the most common of circumstances, it can be a relatively simple and inexpensive way to protect your valuable data & devices from getting zapped.

Aren’t specialized static control floors ugly?

If the thought of specialized protective flooring conjures up images of server rooms, data centers, or ugly hospital wards, then we’ve got good news!

Today, ESD floors come in an amazing array of materials, styles, and colors. Sure… we install rubber floors. We epoxy concrete.

But we also have attractive broadloom carpet that provides decent ESD protection for your sensitive electronics in beautiful designs—so beautiful, in fact, that no one would ever suspect that the carpet is actually serving a valuable purpose beyond that of ordinary carpet!

In addition to broadloom carpet, we also carry carpet tiles and vinyl tiles and sheet flooring. Each is suitable for different situations, and they are available in configurations that provide varying degrees of protection depending upon your specific situation.

Which Static Control Floor is Right for You?

Whether you run a manufacturing facility or a cubicle farm, a call center or a clean room, the fantastic assortment of options available today means that you can find a flooring solution that meets your needs. Obviously, there are a number of factors involved in making the right decision.

Some of the considerations you’ll need to include in your decision-making process include:

  • Durability: Will the floor be in a high-traffic area? The volume of foot traffic will certainly affect how long your floor will last, and therefore should be considered as part of the overall cost of ownership.
  • Maintenance: Since your floor contains components—from conductive carpet fibers to embedded veins of specialized materials—to give static electricity a place to go, you’ll want to weigh out the maintenance needs of the flooring.
  • Static Control Performance: ESD flooring comes in various levels of effectiveness (measured by its “conductivity”). How conductive or dissipative your floor needs to be depends upon the nature of your equipment, the installation environment, and the nature of the usage.
  • Other Factors: Does the floor need to help absorb sound to help control the noise in the environment? Do you need slip protection? What chemicals might be spilled on your floor?

As you can see, the flooring choices available to you can be a bit of a dizzying maze. But there’s good news: we’re here to help you navigate! Reach out today, and let our team of experts help you find the most effective solution at the right budget to match your situation perfectly!

14 Sep

Dissipative vs. Static Conductive Flooring: Which Works Best?

Dissipative vs. Static Conductive Flooring: Which Works Best?

Previously, we talked in greater detail about how ESD flooring works. But when it comes to choosing what type of static control flooring to use, the biggest question you need to answer is this:

Should I use static dissipative flooring or static conductive flooring?

Perhaps the most important factor you’ll need to consider in making this decision is safety.

Shouldn’t I Always Choose the Fastest Pathway to Ground?

At first glance, it might seem like a no-brainer: just put in the flooring that has the lowest resistance so that electrostatic discharge is carried most quickly and efficiency to ground. If that’s true, then static conductive flooring is an obvious choice.

But if the floor is too conductive, then we introduce another set of risks to personal safety.

This is where we start to get into safety standards developed by OSHA and the National Fire Protection Association (NFPA), among others.

Put simply, “static dissipative” flooring and “static conductive” flooring are two very specific classifications based upon levels of conductivity which is measured in terms of the materials’ resistance to electricity.

Resistance of ESD Flooring Options

Resistance, or impedance, is measurable, and is expressed in ohms. The ohm is a unit of measurement named after Georg Ohm, the German physicist who discovered Ohm’s law. In specifications documents, schematics, and other materials, the ohm is represented by the symbol Ω (the Greek letter omega).

Put simply, higher resistance = lower conductivity.

A substance with resistance measured at zero ohms (0 Ω) would highly conductive conductive (carbon, silver, and copper all have resistance measured in a fraction of an ohm). On the opposite end of the spectrum, a substance with 1 billion ohms (1 × 109 Ω) would have very low conductivity (rubber, which is so resistive that it’s used as an insulator, has a resistance in the 1.00×1013 Ω range, or 10,000,000,000,000 Ω, AKA ten trillion ohms).

In general terms defined by the ESD Association, “conductive” is describes any flooring with a resistance of up to 1 million ohms. “Dissipative” is used for anything greater than 1 million ohms and up to 1 billion ohms. 

ESD Flooring Type Resistance (Ω) Range (Low End) Resistance (Ω) Range (High End)
Static Conductive 1 × 106
Static Dissipative 1 × 106 1 × 109

Unfortunately, these categories are so broad that they aren’t entirely useful.

Thankfully, the ANSI 20.20 specification helps clarify things for us. It indicates that the maximum resistance of the flooring and the person (measured together) should be less than 3.5 × 10ohms.

The NPFA has also specified that flooring should have no less than 25,000 ohms resistance. Below this number, the conductivity of the floor is considered to be too high and therefore unsafe due to risk of electric shock and other hazards.

As you can see, neither the minimum resistance specified by the NFPA nor the maximum specified by ANSI 20.20 lines up perfectly with our terms for “static conductive” or “static dissipative” flooring.

So… we’re left with making a selection based upon the specific needs of your industry. What is the application of the flooring? Will it be used in a clean room? Will it be used in electronics manufacturing? What are the considerations around flammable materials?

Other factors will affect the decision as well. Will the humidity and temperature of the environment be maintained within specific parameters? Both will affect conductivity, not just in the floor, but in the environment as a whole. What other building materials will be used?

Additionally, when specifying the levels of conductivity in flooring, there is a diversity in testing and measurement that exists which will cause test results to vary widely depending upon the methodologies used. It’s important to understand how these measurements will affect the final outcome where conductivity is concerned.

The Bottom Line?

There are a number of factors involved in the decision when you’re selecting between static conductive or static dissipative flooring. Our ESD control experts will be more than happy to help walk you through the decision-making process and the range of options available to you — both from a performance standpoint and from an aesthetic one. Contact us today!

07 Jul

Can we make our own ESD tools?

Q: Can we make our own ESD Tools?

A: Perhaps.  Since common hand tools can be at risk of creating an ESD event via CDM, what do we do about it?  I was able to treat the screw driver in my last installation with our ESD anti-stat chemical Shock Stop.  We also have Ultra Spray which lasts for a good deal longer than gimmicky products on the market, which are probably based on a fabric softener.

Our industrial products mentioned above will last longer, but need to be re-applied depending on usage.

I was brainstorming and came up with a more permanent solution to the ESD Screw Driver.  Pretty effective, huh?

1-measuring-resistance-of-non-esd-screw-driver3

1-measuring-resistance-of-non-esd-screw-driver3

2-esd-chemical-shock-stop

2-esd-chemical-shock-stop

3-treating-non-esd-screw-driver-with-anti-stat-shock-stop

3-treating-non-esd-screw-driver-with-anti-stat-shock-stop

4-remeasuring-screw-driver-resistance

4-remeasuring-screw-driver-resistance

5-looking-for-a-more-permanent-esd-screw-driver

5-looking-for-a-more-permanent-esd-screw-driver

6-ground-zero-esd-modified-screw-driver

6-ground-zero-esd-modified-screw-driver

6.5 esd-modified

6.5 esd-modified

7-measuring-resistance-of-gz-esd-modified-sd

7-measuring-resistance-of-gz-esd-modified-sd

Until I can work out a deal with Western Forge in Colorado Springs (dreaming a bit here), ESD Finger Cots!  Ground Zero ElectroStatics, Inc. has got them.  We’ve also got GZ-Shock Stop and GZ Ultra Spray for industrial uses in the EPA.

www.gndzero.com

1-719-676-2548

Order a sample today.

18 Jun

We don't need no stinking wrist straps, do we?

Q: I have read the White Paper 1: A Case for Lowering Component Level HBM/MM ESD Specifications and Requirements and found the ESD Control Programs and Resulting Data (Chapter 1, Page 20-23) particularly interesting.

Assuming a production environment with ESD flooring, footwear (and clothing), by the time a person walks to a workstation and sits down, the voltage of this persons should not exceed 500V (or even 100V as seen in Figure 3). That would mean even a seated operator in this case would not need to wear wrist strap, that theory would be correct right? After sitting down and this person sits on a stool (feet off the floor) with resistance to floor < 1.0x10exp9ohms, any HBM risk would be further reduced wouldn’t it?

A: Hello ****.  Nice try.  Even if you have an ESD flooring system and even if you have ESD footwear and even if you have an ESD task chair with ESD casters or an ordinary task chair with an ESD chair cover (very effective as well), ESD smock on… you STILL have to wear the wrist strap when seated at an ESD workstation.

The only time, per ANSI/ESD S20.20-2007 page 4, 8.2 Personnel Grounding, that personnel in the EPA (ESD Protected Area) should be without a wrist strap is when doing standing or walking about operations, and then two conditions must be met;
·         “When the total resistance of the system (from the person, through the footwear and flooring to the grounding / Equipotential bonding system) is less than 3.5E7 Ω…”
·         “When the total resistance of the system (from the person, through the footwear and flooring to the grounding / Equipotential bonding system) is greater than 3.5E7 Ω and less than 1.0E9 Ω and the BVG is less than 100 v per 97.2…”

This is what is said about seated personnel:

“When personnel are seated at ESD protective workstations, they shall be connected to the grounding / Equipotential bonding system via a wrist strap system.”

Hope this helps.   I guess you could say redundancy is good in the realm of ESD.  It’s the weak link in the chain that will cause an ESD event.  If someone lifts their ESD footwear from the ESD flooring system while seated, they can tribocharge to above 100 volts.  It takes only 0.3 seconds of charge time to exceed 20.20 requirements.  If personnel is seated and getting up to go to break, it seems best to stand up, remove the wrist strap from the wrist, carefully set it down and walk away from the ESD workstation.  Worst case is to take the wrist strap off while still seated, set it down, put your hand on the ESD workstation and near ESDS devices, then stand up out of the task chair before leaving the work station.  Under proper conditions and with good bench mats, clean ESD floors, ESD task chairs, etc. in place, no ESD event.  The problem with ESD events is that we cannot see, hear, feel them.

The only alternative to not wearing a wrist strap while seated may be the used of a smock with a grounding coil cord attached to it.  You can see the footnotes on the 20.20 document at the bottom of page 4 for further details.

 We adhere to and meet or exceed requirements put forth in ANSI/ESD S20.20-2007 or IEC 61340-5-1, which assumes a target HBM of 100 volts and less.