Static Electricity Professionals

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 The research yielded information that lays to rest outdated assumptions about the proper electrical specifications of floors – particularly carpeting - installed in environments where static sensitive operational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.

 

Choosing the Right ESD Flooring for Data Center Applications

Random static discharge will wreak havoc inside your call center--lost or corrupted data, dropped calls, PC lookup, and blown headsets are only a few problems that can be caused by static.

The most important factors to consider when choosing data center flooring are required maintenance and the type of footwear people will wear when they walk on the floor. Flooring selection must prevent static regardless of shoe sole composition worn in the workplace. Rubber ESD flooring is most appropriate for data centers as it is unaffected by aging, traffic, humidity, or footwear choice.

With so many options, choosing the right static control floor can be a challenge for architects, designers, and facilities managers. The most important criteria to remember are these:

1. The floor must be compatible with the environment
2. The material should require a minimal amount of maintenance
3. The floor must meet the electrostatic requirements of the facility.

Learn more about the importance of ESD, anti static flooring in call centers. Read my recent article here >

Appropriate Applications for Static Control Table Covering vs. Static Control Flooring

Question

I am confused about the applicability of static dissipative floors versus static conductive flooring. Most literature says that we should specify a static dissipative and never a conductive work surface on our tables. If this is true, why shouldn’t we use the same logic when we select an ESD flooring solution? I have read most of the ESD articles on your web site.

--Tim, QA Director, Arcai International Electronics

Answer

The unwritten rule is that table covering (mats, laminates) should always measure in the static dissipative range and ESD flooring (carpet, tile and epoxy) should always measure in the static conductive range.

This rule stems from the fact that static control table coverings and ESD floors serve two entirely different functions:

• Table covering is intended to discharge objects like ESD sensitive part as well as tools and fixtures.
• Flooring is used to ground and remove static on people while they move around the work area. (Incidentally, wrist straps serve the same purpose for grounding people when they are stationary.)

Table Coverings

A static control work surface is specifically designed to eliminate charges on any item that either contacts or rests on the surface including: tools, test equipment, electronic parts, static shielding bags, circuit boards, assemblies, material handling fixtures and ESD safe packaging etc.  

ESD sensitive parts can be safely charged and discharged--as long as the work surface has a sheet resistance greater than 100,000 ohms--a charged sensitive part can be discharged without negative consequences. A resistance above 100,000 ohms allows a slow and controlled voltage ramp-down within the charged part. Conversely, any table top surface with a sheet resistance below 100,000 ohms could enable a discharge that is too fast. In layman’s terms, rapid discharges will “fry the internal circuit” because the discharge will overwhelm the part.

A good analogy of damage from “too rapid static discharge” might be the physical effect on our bodies from sudden changes in atmospheric pressure. A controlled depressurization system would be the equivalent of a static dissipative table top – slow and easy.

Floor Coverings vs. Wrist Straps

The main purpose of a static control floor is to duplicate the performance of a wrist trap. Wrist straps, unlike table tops, are worn to prevent and eliminate static charges on people. Wrist straps connect people to a ground connection. But, wrist straps are cumbersome and impractical if the person needs mobility to do his job. The wrist strap cord ties down the person and greatly limits their range of motion.

For safety reasons, wrist straps are equipped with a current limiting resistor. The purpose of the resistor is the prevention of dangerous electrical shocks in the event that the person contacts live voltages while they are wearing the wrist strap. Resistors do not improve the performance of the wrist strap; they are there for safety reasons only. Properly designed ESD flooring also has built-in resistance. ESD flooring is made with static conductive materials that disperse static charges safely but rapidly. This is completely different than the function of a table top.

Why do floors need to be more conductive than a table top work surface?

Properly designed and installed ESD flooring has built-in resistance. ESD flooring is made with static conductive materials that disperse static charges safely but rapidly.(See “How Does ESD Flooring Work?) This is completely different than the function of a table top. The table top should remove static slowly; the floor needs to remove static rapidly or a charged person could discharge to a static sensitive assembly like a circuit board or a computer.

Wrist Straps

Wrist straps are worn to prevent and eliminate static charges on people, by connecting to a ground connection. For safety reasons, wrist straps are equipped with a current limiting resistor. The purpose of the resistor is the prevention of dangerous electrical shocks in the event that the person contacts live voltages. Resistors do not improve the performance of the wrist strap; they are there for personnel safety reasons only.