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 The research yielded information that lays to rest outdated assumptions about the proper electrical specifications of floors – particularly carpeting - installed in environments where static sensitive operational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

 

How to discuss and recommend the right static control flooring with a client

A guide for architects working within client environments and applications that require conductive flooring

I recently visited with an architect who asked me how to best discuss and guide a client interested in using static control carpet in their application and environment.

There are two main question areas to begin the client discussion and help determine the right static control flooring recommendation:

1. What is the electronic industry supplier environment? Are they actively handling static sensitive electronic parts and sub-assemblies (as opposed to using them)?
   
2. What is the end user environment? Is the organization reliant on electronic systems that may be affected by static discharge events?

Specifying for electronic industry supplier environments handling static sensitive electronic parts and sub-assemblies

Electronic industry supplier environment organizations make, handle, test, store and repair electronic parts. A static event in these types of spaces would damage or destroy the part, assembly or final system. Grounding is achieved by wearing conductive heel straps or special shoes in conjunction with a grounded static control floor. In other words, personnel need to be grounded in any operation in this environment.

Generally, organizations handling and producing static sensitive parts designate certain areas as “ESD safe areas” or static free zones; an ESD safe area requires vigilant compliance with personnel grounding procedures as well as numerous other protocols for preventing the generation and accumulation of static electricity. The processes in these environments are usually governed by international standards like ANSI/ESD S20.20-2007.

Best flooring solutions for electronic industry supplier environments

Staticworx works with the architect to help narrow down which flooring to specify for the client for this type of application:

• EC ESD Rubber
• ESD Carpet Tile
  (not the same as low kV or computer grade carpet)
• ESD Vinyl Tile
  (Also called static conductive and static dissipative tile)
• Conductive Epoxy Coatings

For more information on conductive flooring solutions for electronic industry supplier environments, read the article, “Taking the Mystery Out of Selecting ESD Flooring” which is part of the Staticworx Knowledge Center.

Specifying for electronic industry end user environments: operations reliant upon electronic systems

The term “reliant upon electronic systems” means that the operation does not involve active handling, testing or assembly of electronic sub assemblies. These operations are electronic systems end user environments requiring sophisticated electronic equipment to accomplish their mission.

These spaces are often called Mission Critical Environments: examples include data centers, R & D labs, 9-1-1 call centers, hospital ERs, MRI suites, communication centers, flight towers, control rooms. These spaces utilize operational electronic systems which are manned by personnel who will not use special footwear. A static problem in these spaces would lead to an event that would impact either the equipment, operational mission or both. Examples of these types of problems include: data corruption, system lock-up, dropped phone call, unintended signals in a system.

In these applications, the static control floor must be fault tolerant. (See my recent blog entry on fault tolerant design.) The flooring must prevent the generation of static without the added benefit of special footwear; conversely the anti static floor must prevent static despite the use of static generating footwear.

Best flooring solutions for electronic industry end user environments

Most static control flooring will not inhibit static without the use of special footwear. That said, there are two flooring materials that perform very well despite this obvious deficiency and that Staticworx recommends for electronic industry user environment applications:

• EC ESD Rubber
  (with carbon chip conductors)
• ESD Carpet Tile
  (with conductive fibers wrapped around nylon tuftsand conductive backing.
  Not the same as low kV or computer grade carpet)

For more information on conductive flooring solutions for electronic industry end user environments, read these articles, part of the Staticworx Knowledge Center:

• Static Control in a 9-1-1 Call Center: City of Lowell Case History
• Static Control Flooring for Data Centers (featured in The Data Center Journal)

Processor Magazine feature examines data center flooring selection with focus on maintenance

Recently, I was interviewed as a static flooring expert for an article in Processor magazine. That article went live today. Read it here >

The article entitled, "Maintain the Ground You Walk On: Flooring is an Important Yet Often Neglected Part of Your Data Center," focuses on the maintenance required for flooring selected for data centers. It describes how the flooring selected for a data center will determine what is required for the cleaning/maintenance process in that space: vacuums, steam cleaners, waxing, professional vs. in-hosue cleaning staff, and more are explored.

What are the differences between ESD rubber mats and vinyl mats for work surfaces?

As we launch our new product, ESD Rubber Mats for benches and tabletops, I realized there is confusion in the marketplace about the difference between rubber mats and vinyl mats in static sensitive settings. The difference between the two is critical especially when being written into a spec. See my latest article, comparing the difference in performance between the two mat types and let me know if you have comments. I can be reached at dave@staticworx.com

 

Why specify different static control parameters for tabletops than flooring?

Question:
I was recently told to install “static dissipative” table covering on our work benches in conjunction with “static conductive” flooring. Why would I specify different static control electrical parameters based on whether the material would be used as a table covering versus a flooring installation? Shouldn’t we use the same material on the benches and the floor ?

Answer:
The advice you were given was correct: Table coverings and flooring materials, because they perform different functions, require different electrical parameters.

Table coverings solve CDM (charged device model) problems—that is, they prevent static from building on and discharge static from sensitive electronic parts. The static on sensitive electronics must be discharged slowly—or the rate of discharge could fry the internal circuitry.

Static control flooring solves HBM (human body model) problems—it prevents and eliminates static on people, carts and moving fixtures. Static charges on the human body must be discharged rapidly—before the person comes into contact with static-sensitive parts.

Further information on static control terms CDM and HBM provided below.

Rules of thumb for electronic parts handling:

Table coverings

1. Table coverings should be static dissipative – not conductive.

2. Static control table coverings should provide static dissipation in any environment, regardless of the relative humidity.

Hard laminates eliminate static by pulling moisture from the air; the moisture collects on their top layer. This reliance on relative humidity inhibits the ability of hard surfaces to control static when the air is dry. For this reason, hard materials are less desirable as table coverings.

Flooring materials

1. Flooring materials should be conductive – not static dissipative.

           

The floor should discharge static from moving people—regardless of activity level—rapidly, faster than new charges can accumulate. When mobile people wear static control footwear, a good conductive floor will prevent the accumulation of static above 20 volts. Effective floors also exhibit anti static properties—in other words, they prevent excessive static charges from accumulating on people who are wearing standard footwear. (Read my recent article explaining the difference between conductive and dissipative static flooring.)

2. As with table coverings, the floor should work at all humidity levels.

The difference between CDM and HBM failures

CDM or charged device model failures occur when charged parts – like circuit boards – discharge to conductive objects. Example: an ungrounded person holding a circuit board places the board on a metal plate. The static passed (from the person) to the board will discharge rapidly to the plate. Under the right circumstances this rapid discharge will result in a CDM failure.

Static dissipative table coverings are the first line of defense in the prevention of CDM problems.

HBM or human body model failures occur when charged people touch sensitive electronic parts. Example: A person walks on a static generating floor (or a highly resistive static dissipative floor). The charged person touches a circuit board. If contact occurs between the person’s hand and a sensitive electronic part, the resulting discharge – called a human body model discharge– could harm or destroy the circuit board.

Static conductive flooring is a key element in controlling HBM problems.

Why specify phthalate-free flooring?

Over the last few years, the U.S., Canada and the EU have banned the use of phthalates, such as DEHP, di (2-ethylhexyl) phthalate (also known as DOP), in children’s toys. This blogger believes that it is equally important to specify phthalate-free and PVC-free ESD flooring as well.

To avoid SICK Building Syndrome, we recommend specifying DOP-free flooring that will not outgas VOCs and that passes California 1350 indoor air quality testing.

Read my recent article on this topic to learn more >