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

by David H. Long

Within the A&D community, unnecessary confusion exists over which ohms resistance rating is correct for grounded static control flooring used in end user operational* equipment, communication and data storage environments. The root cause of this confusion is the misapplication of ESD flooring standards used in ESD protected areas (EPAs) in electronics manufacturing and explosives handling. The telecommunications and data center industries have their own set of grounding and surge protection standards focused on the unique needs of a 24/7 mission critical environment.

The purpose of this article is to bring clarity to this important subject by providing vetted 3rd party information and links to respected 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 The research yielded information that lays to rest outdated assumptions about the proper electrical specifications of floors - particularly carpeting - installed in environments where static sensitive operational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:

IBM Publications Center

• 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 - 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"

ATIS 0600321-2010

• Alliance for Telecommunications Industry Solutions
  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 from Page, 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."
• ATIS publishes standards for the information, entertainment and communications industries 

FAA STD 019e

• Link to FAA STD 019e Lightning and Surge Protection, Grounding, Bonding and Shielding
• Excerpt from 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.

Produced by UNINETT

• Working group on physical infrastructure
  (No UFS103) Author: Stein Nygaard: May 2010 
• Link to: Requirements for the Design of ICT Rooms - Best Practice Document
  European Requirement
• Recommended range:
  The resistance between any point in the floor covering and earth shall be from 1,0 X 10 E6 to 1,0 X 10 E7_, cf. NEK EN 50174-2009
  Section 3 - Subsection 9 General Requirements
   

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

1. All organizations cited in this article approved the use of materials measuring in the static dissipative range.
2. When evaluating an ohms rating expressed in scientific notation, keep in mind that the difference between each ascending exponent is a multiplier of 10.  For example 1.5 X 10 to the 4th = 15,000 ohms --- 1.5 X 10 to the 5th = 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.

*Operational equipment is the same as energized equipment.

 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 would be modifying their electrical resistance range for acceptable static control carpet in the near future. 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.