Static Electricity Professionals

Pending changes to the flooring requirements in ANSI/ESD S20.20

We have recently learned that the flooring requirements in the 2007 revision of ANSI/ESD S20.20 will be changing. This should be good news for everyone. According to our source, the new requirements should allow any conductive or static dissipative floor as long as the system resistance measures below 1.0 x 10 E9 AND the body voltage generation measures below 100 volts. These changes in ESD standards place heightened importance on identifying low generating flooring materials like rubber and dissipative carpet.

In anticipation of this change we strongly recommend testing your existing flooring and footwear combinations for system resistance and body voltage generation. The test method for system resistance is ANSI/ESD 97.1 and the method for measuring body voltage is S97.2. You can purchase these test standards from the ESD Association at this link. We see this as good news because it will reduce the use of overly conductive materials by placing more value on a floor's charge generation properties. For example, this independent lab study shows that a static dissipative carpet tile measuring between 1 million and 10 million ohms controls charge generation as well as an overly conductive carpet tile measuring close to 25,000 ohms to ground.

 

If you are unsure about the safety of your floor or wonder if your exisiting system will meet the new changes, contact Staticworx at info@staticworx.com to arrange a free GroundSafe flooring evaluation. You can also visit www.staticworx.com to learn more about ESD standards, safety and flooring material performance.

Based on these as well as other pending changes, Staticworx is excited to announce a soon to be published revision of an old article from the May 2005 edition of Conformity Magazine titled Choosing the Right ESD Flooring for Laboratory and Technical Environments. The revised and expanded article will be published in early 2012. The original article has become obsolete due to numerous industry changes since its publication in 2005:

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Read more about the changes below:

The original article Choosing the Right ESD Flooring for Laboratory and Technical Spaces was published in the May of 2005 of Conformity Magazine. In its published form, the article targeted specifiers interested in establishing a comprehensive ESD prevention program for electronics manufacturing in the factory and laboratory environment. Factory ESD programs require controlled footwear, special static free packaging, employee training about electricity, frequent scheduled testing of the electrical properties of work surfaces, carts, floors and packaging as well as a comprehensive grounding strategy for all conductive and dissipative materials.

The original article was not intended as an advisory for specifiers of grounded flooring for use end user environments where the flooring might be installed around telecommunications equipment, flight control electronics, operational electrical appliances and operational computer equipment.

At the time of publication, the article favored conductive flooring materials over static dissipative alternatives exclusively for controlled factory environments. This stand was made because, in 2005, most static dissipative materials were manufactured with too much electrical resistance to meet the requirements of ANSI/ESD S20.20 for factory environment.  The new version of S20.20 will raise the resistance limits, eliminating this concern with compliance. The bias towards conductive materials for factory environments gave many architects and designers the false impression that a highly conductive floor might be the better choice for any static control flooring application including end user spaces. This could not be further from the truth. A floor's conductivity is not a predictor of low charging properties. As has been well documented, highly conductive flooring should never be used in end user environments where electrical appliances are in operation. Recent testing of several different types of ESD carpet tile has proven that static dissipative carpet is safer and offers equal or better performance than the conductive carpet tiles used in the original study.

Go here to read the White Paper about conductive versus static dissipative carpet

 

A follow-up article incorporating the new versions of the standards referenced in the original article had been intended for some time. For example, ANSI/ESD S20.20-1999 was revised shortly after the original publication of the article, as were many other grounding documents. Unfortunately, Conformity Magazine dissolved before any revision could be submitted.

The original research and testing of all ESD flooring was performed on a limited number of samples in a warehouse in Wilmington, Massachusetts under uncontrolled humidity conditions.  The effects of relative humidity on the performance of static control flooring are well documented in the public domain.

The updated article will include several revisions and additional conclusions based on independent lab testing at low humidity in a controlled environment. For example, conductive carpet generates over 1kV at low humidity. In the original study this fact was not revealed due to high humidity conditions. As a result of recent changes in grounding and safety standards, the edited version will include NFPA 99 test results on several flooring materials. NFPA 99 testing was added to evaluate the safety and liability exposure of grounded carpet used in the vicinity of school computer labs, electrical appliances in switch rooms, call centers and dispatcher areas, networked offices and other uncontrolled public access spaces. Using the NFPA 99 test method we discovered that most carpet measuring in the conductive range (between 25,000 ohms and 1,000,000 ohms) would likely not meet NFPA 99. The updated article will also include commentary by consultants and engineering experts in the field. There will be a collection of pdfs containing relevant language from grounding standards, a commentary on the upcoming revision (again) to ANSI/ESD S20.20 and a reference chart designed to help specifiers match suitable ESD flooring options with the safety standards and requirements of specific types of work spaces. The chart will include a checklist on whether or not a particular type of floor meets the following safety and grounding standards:

•   ATIS 030062-2005
• Motorola R56- 2005
• FAA STD 019e-2005
• ANSI/ESD S20.20-2007 and pending changes in 2012

• IBM Data Center Recommendations
• NFPA 99
• DoD Manual 4145.26-M for explosives

Learn more about static watching short videos

 

Conductive Carpet Tile Cannot Meet NFPA 99 Healthcare Standard

Testing ESD Carpet Tile Resistance:  Exposing the Facts

As many have noticed, Staticworx recently generated major industry news with our launch of ShadowFX, the first anti-static carpet tile that meets the latest national safety requirements and provides lifetime static control. 

Based on standards and specifications from organizations like NFPA, Motorola, ATIS, FAA, and IBM, carpet that is too conductive is not approved for use in healthcare, telecommunication, electronic equipment, and end-user environments like networked offices, data centers, dispatch centers and hospitals. 

The need for a new product was clear, since previous options—like conductive, mission-critical, ESD-grade carpet tiles—are made with excessively conductive yarns and backings.  We recognized this need and responded with ShadowFX.

While ShadowFX has been touted as a breakthrough product, it has caused some carpet distributors and manufacturers to feel anxious.  They point out that older, conductive carpet lines have been installed in many facilities for many years.  This is true, but it misses the point:

If conductive carpet doesn’t comply with the recommended range of electrical resistance required by third-party standards organizations, it exposes workers and the facility owners to risk and unnecessary liability in the event of an accident.

 The Facts Speak for Themselves

 As part of our due diligence during the development of ShadowFX carpet tile, we reviewed numerous grounding and safety standards. This was essential to the project because grounding standards differ depending on the environment where the floor will be used. Since our goal was to build one product for all applications, we scrutinized standards in great detail. For example, NFPA 99 is well known because it is the key grounding document used for defining flooring in healthcare environments. Many flooring manufacturers cite the NFPA minimum resistance of 25,000 ohms in their specifications for conductive flooring.  Some flooring manufacturers and distributors assume this low minimum resistance permits the use of highly conductive flooring.

However, upon closer examination, section E6.6.8.2.7 in NFPA 99 stipulates that resistance testing must be performed using a 500 volts applied test voltage. Understanding the physics surrounding this specific requirement is essential to understanding ESD flooring and electrical safety. As voltage is increased, resistance will decrease. The opposite is also true. As voltage is decreased, resistance increases.  How does this relate to an architect or designer? This means that they should always cite the details of the appropriate grounding standard and test method for a particular type of space when they write a specification. Since most marketing collateral for ESD carpet tiles reference an ANSI/ESD test method that tests floors using 10 volts – not 500 volts – it is quite possible that the floor could appear to meet an approved conductivity range when in fact it is not even safe for use in explosives handling environments.

To make the implications of the preceding paragraph more easily understood, we have measured the resistance of three conductive ESD carpet tiles using two applied voltages: 10 volts and 500 volts.

 Testing of Conductive Carpet Tiles with Black PVC-free Backing

                                10 volts                500 volts

                                ANSI/ESD              NFPA 99:

 

Color 1                   7.5 x 10e4            1.6 x 10e4 = 16,000

                              7.2 X 10E4            1.4 X 10E4 = 14,000

Color 2                   7.5 x 10e4             1.4 x 10e4 = 14,000

                              6.9 X 10E4             1.3 X 10E4 = 13,000

Color 3                    5.0 x 10e4            1.4 x 10e4 = 14,000

 

Please note: A more conductive reading below 25,000 ohms is not an indication of a floor's ability to perform better than the standard requires. To pass NFPA 99, the resistance must measure above 25,000 ohms when tested at 500 volts using the NFPA 99 test method. These tiles would not pass a certification in any ESD application including those specified using: Motorola R56, ATIS 0600321, FAA 019e.

Conclusions:

1. Conductive carpet tiles with black carbon loaded backing do not meet the safety requirements of NFPA 99 when they are tested using the NFPA 99 test method.

2. A floor measuring at or above 25,000 ohms using NFPA test methods would likely measure over 100,000 ohms (10 E5) using ANSI/ESD test methods.

3. 25,000 ohms is an inadequate lower parameter for commercial floor resistance specifications.

4. Conductive carpet tile should not be used in health care or clinical applications.

5. Always require certification to ATIS-0600321 (or equivalent) and NFPA 99 after installation for equipment environments.

 

 

Further:

The requirements for ESD carpet tile installed in telecommunications environments, call centers, dispatcher rooms, radio broadcasting areas, FAA flight towers and data centers are more conservative than NFPA 99. The grounding standards for all of these environments require a resistance greater than 1,000,000 (1.0 X 10 E6) ohms.

See this link:http://www.staticworx.com/articles/MotorolaR56-ATIS-0600321_flooring_dissipative_not_conductive.php

Download Chart-Comparison-Staticworx SDC-vs-PVC-free Conductive

Motorola R56 And Static Dissipative Recommendations for Antistatic Flooring?

What is Motorola R56 and why is it important?
Communication network downtime significantly impacts daily operations and much of potential downtime can be the result of non-compliance to minimum communication site standards. If the equipment isn’t properly grounded and incorporates surge suppression, it can significantly jeopardize your network, and it also puts those who maintain the site at significant risk. Originally developed by Motorola in 1987 to provide internal guidelines and requirements for the installation of communication equipment, infrastructure and facilities, the “Standards and Guidelines for Communication Sites” (R56) form the minimum standards required to provide expected system performance, reliability and equipment longevity. The Motorola guidelines have since become the recognized standard in the industry and serve as the most complete and rigorous specification for the protection of communication system equipment installed at public safety and commercial wireless communication sites. 

What type of antistatic flooring is recommended for communications application in R56?

Motorola R56 recommends static dissipative flooring - not conductive flooring. Static dissipative flooring is defined as having an ohms resistance between 1.0 X 10 E6 and 1.0 X 10 E9. Conductive flooring is defined as having an ohms resistance between 2.5 X 10 E4 and 1.0 X 10 E6.

The excerpt below is taken directly from page 469: Full R56 document is available at this website: http://www.radioandtrunking.com/downloads/motorola/R56_2005_manual.pdf

"Carpeting or floor tiles within an equipment room or dispatch center, including raised flooring, should have a resistance to ground measurement of between 10 E6 and 10 E9 ohms when measured using the test method of ANSI/ESD STM7.1-2001 or later. Existing flooring that does not meet this requirement should be treated with a topical solution such as an antistatic floor wax or spray solution. The effectiveness of antistatic solutions is temporary and varies with floor material and relative humidity.

Use the following language in an RFQ to ensure contractors are bidding the proper antistatic flooring for a dispatch area?

1. Flooring must comply with electrical resistance range noted in Motorola R56 and ATIS-0600321-2010
2. Flooring must measure over 1 million ohms from any point on the floor to ground using an ohm meter based on test method ANSI/ESD S7.1-2005
3. At the completion of the project the floor must be tested and certified by a trained individual. A certification letter must state compliance with the static dissipative electrical resistance range outlined in Motorola R56 and ATIS-0600321-2010.

This video helps explain these concepts:

   

Mission Critical Anti Static Flooring for Public Safety Emergency Communications Applications: Which Resistance Range is Correct – Static Dissipative or Conductive?

 Understanding Grounding Standards: Motorola R56 and ATIS-0600321-2010

Unnecessary confusion exists over which ohms resistance rating is correct for grounded static control flooring used in end user operational equipment environments. The root cause of this confusion is the misapplication of flooring requirements used in electronics manufacturing and explosives handling with the recommendations of compliance/standards organizations overseeing telecommunications and data center environments. The purpose of this post is to clear up this confusion by providing information and links to appropriate industry resources and standards organizations. (Please note: ESDA document ANSI/ESD S20.20-2007 is not referenced.  S20.20 is intended for program managers involved with the design and implementation of a static control process in ESD protected areas as part of a comprehensive program in electronics manufacturing environments.) This article focuses on non-factory, end user operational equipment concerns like networked offices, data centers and emergency dispatch call centers.

  During research for an article to be published by The Construction Specifier in their September issue, we examined FAA, telecommunications and computer industry grounding, lightning, electrical surge and safety standards. The research yielded information that lays to rest outdated assumptions about the proper electrical specifications of floors – particularly carpeting - installed in environments where static sensitive operational equipment is used. Many ESD flooring distributors incorrectly assumed that conductive flooring measuring between 2.5 X 10 E4 and 1.0 X 10 E6 was acceptable for end user environments. This static prevention strategy was borrowed from unrelated requirements involving the mandatory use of conductive flooring when handling explosives and flammable materials. This assumption and the applicability of explosives grade flooring for installation in end user environments – spaces often accessible to the public - is incorrect and poses unnecessary risks. Conductive flooring does not comply with the pertinent grounding standards for telecommunication equipment end user spaces. According to five different authorities/standards organizations, there is consensus in the recommended ohms resistance range for the type of flooring discussed here. The overlap or consensus opinion consists of a recommended ohms range above 1.0 X 10 E6 and below 1.0 X 10 E9 for end user spaces like server rooms, 911 call centers and data centers.

Specifically we looked at standards and recommendations from the following organizations:

 Link to IBM site recommendation and physical planning

IBM's Recommended range of flooring 1.5 X 10 E5 – 1.0 X 10 E10 ohms

A common document referenced by data center designers

 

Motorola R56: The Motorola guidelines have become the recognized standard in the industry and serve as the most complete and rigorous specification for the protection of communication system equipment installed at public safety and commercial wireless communication sites

Link to Motorola R56 See pages 468-470

Excerpt from Appendix C 3.3 of 2005 - 68P81089E50-B
9/1/05 — UP Version:

"Carpeting or floor tiles within an equipment room or dispatch center, including raised flooring, should have a resistance to ground measurement of between 106 and 109 ohms when measured using the test method of ANSI/ESD STM7.1-2001 or later"

 A new revision will be coming soon. This information was provided directly to Staticworx by the current working R56 committee.The excerpt from the new version is pasted into the bottom of this post

This standard should be cited when defining grounding parameters in public safety 911 communication centers

 

Alliance for Telecommunications Industry Solutions (ATIS) ATIS-0600321-2010

ATIS publishes standards for the information, entertainment and communications industries 

Electrical Protection for Network Operator-Type Equipment Positions

Link to ATIS-0600321-2010  Protection for Network Operator-Type Equipment Positions

Available for purchase: Digital Edition available from www.engineers.ihs.com

 Excerpt: Page 5, Section 4.2 Flooring

"Any carpeting or floor tiles should have a resistance to ground between 10 E6 and 10 E10 ohms when measured using the method of ESD-S7.1."

A telecommunications standard overseen by most telecommunications manufacturers

Applicable to numerous environments

 

Link to FAA STD 019e Lightning and Surge Protection, Grounding, Bonding and Shielding

Section 4.1.3.4.3.5 Static Dissipative ESD Floor Coverings

Recommended range of flooring 1.0 X 10 E6 – 1.0 X 10 E9 ohms

The 019e document supersedes a previous document (019d) where conductive flooring was considered acceptable.

 

Requirements for the Design of ICT Rooms - Best Practice Document

European Requirement

Recommended range of flooring 1.0 X 10 E6 – 1.0 X 10 E7 ohms per a European resistive properties test method.

Section 3 – Subsection 9 General Requirements

 

As you review these organization’s recommended parameters keep in mind 3 factors:

1.   Research has shown that conductive flooring offers no advantage over static dissipative flooring in end user environments.  

2.   When evaluating the ohms ratings, keep in mind that the difference between each ascending exponent is a factor of 10.  For example 1.5 X 10 to the 4^th = 15,000 ohms --- 1.5 X 10 to the 5^th = 150,000 ohms

3. A floor measuring between 2.5 X 10 E4 and 1.0 x 10 E6 is defined as a conductive floor. A floor measuring between 1.0 X 10 E6 and 1.0 X 10 E9 is defined as a static dissipative floor.

 Addendum: As part of our research we contacted a member of the Motorola committee overseeing Motorola R56. The purpose of contact was to determine if Motorola might be expanding their electrical resistance range for acceptable static control carpet. The published range since 2005 has been 1.0 X 10 E6 to 1.0 X 10 E9 ohms. There is currently a new draft of R56 in the works. As with other grounding and electrical standards organizations like ATIS and FAA 019e, we were told that Motorola’s acceptable resistance range will remain in the static dissipative range from 1.0 X 10 E6 to 1.0 X 10 E9.

Below is an excerpt of the flooring section as it will appear in the new draft:

Motorola R56 Appendix C

PROTECTING AGAINST ELECTROSTATIC DISCHARGE (ESD) IN EQUIPMENT ROOMS AND DISPATCH CENTERS

C.3.3 FLOORING

Carpeting or floor tiles within an equipment room or dispatch center, including raised flooring, should have a resistance to ground measurement of between 106 and 109 ohms when measured using the test method of ANSI/ESD-S7.1-2005 or later. Existing flooring that does not meet this requirement should be treated with a topical solution such as an antistatic floor wax or spray solution. The effectiveness of antistatic solutions is temporary and varies with floor material and relative humidity. Flooring resistance should be monitored every two weeks minimum to verify conformance to the above requirements. See ATIS-0600321.2010, section 4.2 and ANSI/ESD-S7.1-2005 for more information.

When ESD protective flooring is used, the following should be observed:

• ESD protective flooring shall be installed per the manufacturer's recommendations.

• ESD protective flooring and floor coverings should be installed, grounded, and tested by trained installers.

• Personnel entering the equipment room or dispatch area should wear ESD dissipative footwear or dissipative foot straps. The footwear should provide dissipative resistance values of less than 3.5 ´ 107 ohms as measured according to the measuring requirements within ANSI/ESD STM97.1-2006 or later. The footwear should also provide dissipative resistance values of less than 1.0 ´ 109 ohms as measured according to the measuring requirements of ANSI/ESD STM97.1-2006 or later.

 When ESD protective flooring is not installed at a dispatch position or equipment room, an ESD protective floor mat should be installed at the work areas. When ESD protective floor mats are installed, the following should be observed:

• The floor mat should provide dissipative resistance values between 106 and 109 ohms when measured using the test method of ANSI/ESD-S7.1-2005 or later.

 

Next blog:

We will investigate the grounding parameters required by medical electronic manufacturers for end user clinical environments.

 

What We Knew About Static Generation Was A Myth

 

Every once in a while a study, a new piece of information, a laboratory experiment, completely erases a previous model of scientific understanding. Newton did it to Aristotle. Einstein did it to Newton. But, who would have thought that the prevailing model for the basics of static charge generation would go the way of the Precopernican Geocentric model of the universe? Well according to a recently published paper, we now have a completely new theory on how static charges are generated when two materials contact and then separate. This will certainly have an impact on 8th grade science curricula but it also shows us how little we know about the most basic aspects of our environment.

 

Using Kelvin force microscopy scans, the authors show that charges are not transferred uniformly between materials when they are rubbed together. They state that interacting materials actually pick up a random combination of both positive and negative charges when they contact and separate; Previously, we assumed that each material would either charge negatively or positively because that is the net effect. However, their study shows that each material actually picks up pockets of each polarity where some of the isolated pocket charges measure almost 100 times greater than the net charge on the overall surface. They also opine that this is not the result of an exchange of electrons but the result of an actual chemical transfer. We'll comment on this more later including what we believe may be some implications to the control of electrostatic discharge (ESD) with ionization and static dissipative flooring. In the meantime you can access the full study,The Mosaic of Surface Charge in Contact Electrification or you can read a well sythesized synopsis called What You Learned About Static Electricity is Wrong in WIRED Magazine at this link.

How will this impact static prevention stategies like ESD flooring used in facilities where people handle  ESD sensitive electronic parts? This may explain the phenomena of tribocharging and why rubber flooring charges shoe soles less than conductive and static dissiaptive vinyl and epoxy floors. It may provide insight into why old shoes charge up more than new plasticizer rich shoe soles and why conductive carpet offers charge generation adavantage compared to safer, static dissipative carpet tiles like Staticworx ShadowFX. More to come!

 

Don't Get Stuck Referencing The Wrong ESD Flooring Test Methods

ANSI/ESD Test Methods Are Different than EU Standards

ANSI/ESD S7.1 versus EN 1081

 

A military electronics company trying to meet static control requirements in ANSI/ESD S20.20-2007 contacted us about a problem they were having with their new floor. The new floor was purchased under the assumption that it would meet all the requirements of Table 2 in the S20.20 document. The caller explained that the floor wasn’t meeting any of the requirements even though the manufacturer assured them nothing was wrong with it. They described the floor as a static conductive linoleum sheet floor. After reviewing the clients test data I agreed to meet with and help them find out why the floor wasn’t doing what it was supposed to do.

 

Immediately after I arrived, I was asked to measure the floor with my meter, a Prostat megohm meter. After several tests, we concluded that the floor was incapable of meeting any of the S20.20 requirements; it was far too resistive The resistance to ground exceeded 1 billion ohms (1.0 X 10 E9.) The system resistance exceeded 3.5 X 10 E7. The building representative was extremely agitated because they knew it would be difficult to shut down the facility and replace the floor. They told me they were guaranteed that this floor would do everything they required. After a quick review of the floor manufacturer’s documents we discovered the real problem with the floor. The manufacturer’s specifications referenced a resistive test method call EN 1081. Unlike North American method ANSI/ESD S7.1, the European method tests floors using a much higher applied voltage. EN1081 actually references an applied voltage of 500 volts. Higher applied voltages cause the resistance to drop. Using our methods, the floor measured extremely high. Unfortunately for this end user, they were probably stuck with the floor without recourse because no one in their organization had picked up on the test method used by the European manufacturer. It was clearly printed on their spec sheet.

 

A word of advice: Always ask for domestic independent test data when qualifying any kind of static control flooring. Additionally, require a post installation certification demonstrating that the flooring meets Method One in ANSI/ESD S20.20 for Personnel grounding. Method One utilizes ANSI/ESD S97.1 System resistance testing. An acceptable system resistance measures below 3.5 X 10 E7 ohms. You might also take a look at this video for further understanding.  

Short Videos Provide Overview on ESD Flooring and Testing

Hello Flooring Professionals,

For months you have been asking for an alternative to reading all the technical articles on www.staticworx.com. Here's a link to 5 videos that cut to the chase on testing and evaluating ESD flooring. Please keep in mind that the video content is highly condensed. If you need more detail on ESD safety, grounding or how to write a specification, don't hesitate to e-mail me at dave@staticworx.com.

 

Which ESD Standards Are Easiest for Evaluating ESD Flooring?

ESD Standards

Question

Our company currently adheres to the same ESD standards as the ones you recommend on your website: The total system resistance of the person, footwear, walking surface and ground must be less than or equal to 3.5 x 107 or 35 meg-ohms maximum.

However, at a recent ESD conference, attendees were told that an ESD floor can have a maximum resistance of 1 G Ohm (1 billion ohms), as long as the voltage generated in the walking test does not exceed 100V.

Could you please provide your input to the pros and cons for this seemingly excessive resistance to ground?

Answer

From a purely technical perspective, a floor’s ESD properties can be evaluated:

1) by measuring the floor’s resistance to ground;
2) by measuring the total resistance ground of the system including the person and the floor;
3) by using a walking test to measure voltage generation on a person;
4) or by testing some combination of the above.

According to the recommendations of ANSI/ESD S20.20, it is acceptable to install a floor with a resistance to ground (RTG) that is ≤1.0 X10E9. But, to comply with ESD standards, the floor must not allow body voltage generation over 100V.

A static control floor with high RTG values up to 1Gohm may—or may not—prevent 100V generation. For example, despite its higher resistance values, rubber flooring, used in conjunction with ESD footwear, will usually prevent high body voltages. Vinyl in the higher resistance range, on the other hand, will not reduce body voltage spikes to below 100V.

In order to certify that a highly resistive floor is ANSI/ESD S.20.20 compliant, the ESD program manager must test the body voltage generation caused by the interaction between the floor, the person walking across the floor, and the footwear. Bear in mind that a floor’s voltage generation characteristics are affected by multiple variables, including maintenance procedures and humidity—even spills or contamination can have an effect—so the amount of body voltage a floor generates can change overnight. For that reason, body voltage tests must be monitored regularly and must also be conducted during routine auditing.

ANSI/ESD S.20.20 also recommends a “system resistance” of ﻛ 35 meg-ohms. Simple, easy-to-implement system resistance tests measure the entire static control system: the ESD footwear; the person wearing ESD footwear; and the floor’s resistance to ground. Significant research has proven that it is mathematically impossible for a floor with a system resistance below 35 meg-ohms to generate more than 100V of static electricity. Verifying readings below 35 megohms using this simple test eliminates the need for testing body voltage.

Test Methods Must Be Reliable When Used In Active Factory Environments

Weighing the technical advantages of one test method over another is only part of the answer. One must also consider which test is simplest, less expensive and most practical and provides the most reliable date when used in an active factory environment.

Complicated tests requiring the use of complex equipment and procedures should be performed by people with special skill or knowledge and are best suited for use in laboratory environments. The test methods that work best in active factory environments are those that use simple equipment, rely on simple procedures, and can be performed by less skilled individuals. Scientific validity and reliability (Reliability refers to the consistency of a measure. A test is considered reliable if we get the same result repeatedly.) become skewed when a test method relies too heavily upon a test method that relies upon too much human intervention.

Body voltage tests are expensive, time consuming, highly dependent on environmental conditions and, because of all the variables, require a much larger statistical sampling to gather meaningful data. Remember: the mere act of connecting people to a body voltage meter and recording data is neither scientifically reliable nor statistically valid. Because Body voltage tests should conducted by a skilled individual and should be performed exactly the same way, using a specific type of body movement each time the test is performed, ESD program managers usually find it unrealistic and cost prohibitive to monitor body voltage on a regular basis.

Body voltage tests, like system resistance tests, check the whole system, but voltage tests are tougher to duplicate because of the increased influence of multiple variables. If a tester wears a slip resistant shoe, for instance, the way the tester moves her feet will provide different data than the same test performed with smoother shoe soles. The tester can drag his or her feet, generating greater than normal voltage; walk in a way that the heel straps make poor contact with the floor; shuffle while lifting the shoe heels slightly above the floor; or even jump off the floor, breaking contact altogether. The official instructions describe a specific walking patter that is to be used for the test; unfortunately most people fail to follow the instructions, and, even when they do, the methods used by different people will always differ slightly.

Conclusion

For this reason, I highly recommend sticking with the 35 meg-ohms upper limit system resistance limit. The test is simple and inexpensive. One lead of the ohm-meter is connected to ground and the second lead is connected to a probe held by a test subject standing still. The test subject simply holds a the probe  and presses a button, and the meter tests the resistance between the tester and ground. Because a floor with a total system resistance of below 35 meg-ohms cannot generate body voltages above 100V, this simple test provides fast, inexpensive and reliable verification of the entire esd flooring/footwear system.

Dig deeper at this link: http://www.staticworx.com/articles/index.php

ShareThis

Type of Test	Body voltage	35 Meg-ohm System Resistance
Instrument	Charge Plate Monitor	Ohm Meter
Unit of Measure	Volts/kV	Ohms/Meg-Ohms
Test Method	ANSI/ESD STM97.2-1999	ANSI/ESD STM97.1-1999
Skill Level	Knowledgeable Tester	Anyone can perform test
Difficulty factor	Complex equipment	Simple equipment
Interpretation	Affected by variables	No Interpretation Necessary
Consistency	Voltages can spike	Measurements are consistent

Anti Static Interlocking Flooring in a Data Center?

Hi Dave,

We are thinking about using some interlocking flooring in our data center. The flooring is made with a recycled content vinyl material.

The salesman is telling us to use the static dissipative version. Which one - "static dissipative" or "static conductive" - do you recommend?

Ed from California

 

Hi Ed,

This is a critical question. The right choice for your application is not predicated on whether the floor is static dissipative or static conductive. The right choice involves knowing what happens when a person wearing ordinary everyday footwear walks on the floor. Any vinyl floor - static dissipative, static conductive anti-static - requires special static control footwear in order to prevent static. Unfortunately, all vinyl floors _ anti static etc -are static generators when they are frictioned by a person wearing regular footwear. The reason this happens is due to an effect called triboelectrification. In layman's terms, triboelectrification is the generation of static resulting from two materials rubbing together. From tribolectrification theory we know that vinyl is very antagonistic in interactions with most of the materials that are used to manufacture shoe soles. If you must employ a removable interlocking floor, you should install one with an EC rubber walking surface - not a vinyl one. Based on studies from groups like MIT Lincoln Labs we know that EC rubber will prevent static generation over 200 volts regardless of footwear. Static control vinyl will allow charges as high as 4000 volts. The right floor needs to prevent charges above 500 volts regardless of temperature or humidity or footwear!

Here is a link to an article from the Data Center Journal

 

 

Static Dissipative Interlocking Flooring: 4 Things You Must Know

Hi Dave,

We are considering an antistatic interlocking vinyl floor for our new call center. Should we use a static dissipative or static conductive one?

Over the past couple of years, interlocking floors have become a very popular choice. The idea of buying a floor that can be installed with no adhesive and then moved and reinstalled in a new location is very enticing - and quite legitimate. When it comes to static control, there are a few things you need to know before choosing an interlocking version. 

1. Static control vinyl floors do not reduce static on people walking on them wearing standard everyday footwear. Static control vinyl (PVC) is actually a static generator when it contacts most shoe sole materials. Research shows that static control vinyl will only reduce static if a person is wearing special static control shoes or special heel straps and shoe covers. If people will be wearing ordinary shoes, you might as well save your money and skip the purchase of a vinyl interlocking floor.

2. Choose a fooring material that prevents static regardless of footwear. Inerlocking flooring isn't just available with PVC - vinyl. You can also get an interlocking floor with EC rubber or carpet tile attached to the top. Both EC rubber and static control carpet will provide excellent static controls regardless of what composition of shoes people wear when they walk on the floor.

3. Interlocking floors are expensive. They are not the only solution for a buyer looking for flexibility and mobility. Carefully compare the real cost of a glue down solution before assuming you will save money by taking the floor with you. In many cases, you can buy "dry adhesive" systems that will provide the stability of a hard set adhesive but you will also have the ability to remove and reinstall the tile in a new location. Some floors like EC rubber are available in rolls making them the ideal solution for long-term but temporaty installation.

4. Static dissipative floors do not perform as well as static conductive floors. Recently there has been a very strong push to eliminate the use of static dissipative flooring when conductive versions are also available. If you are getting steered in the direction of static dissipative, ask if there is a cost difference for the same floor in the static conductive range. There should not be any cost difference.