How to Comply:
Specification for Ohms Resistance Measurement and Grounding Flooring in FAA flight Towers
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Staticworx ShadowFX SD Modular Carpet Tile for FAA STD 019e Grounding: Link to Specification
What you need to know before bidding or recommending static control
flooring for FAA Flight control areas:
Attention Government Contractors
Are you familiar with the grounding requirements for static control flooring written in the most recent revision of FAA STD 019e ?
There are several recommended steps you should follow:
Step One: Obtain a full copy of 019e here from the FAA website: https://faaco.faa.gov/attachments/STD-019e2.pdf
A close reading of FAA STD 019e will ensure that your bid meets the requirements of your FAA clients.
The FAA requires flooring that measures in the "static dissipative" ohms range. This means the FAA does not want flooring measuring in the “conductive range.” According to the electrostatic discharge association’s glossary of terms, static dissipative flooring materials are defined as having a resistance to ground between 1.0 x 106 and 1.0 x 109 ohms.
To make it easy, we have outlined the sections you need to reference:
4.1.3.3.2 Static Conductive Materials
4.1.3.4.3.5 Static Dissipative ESD Control Floor Coverings
4.1.3.4.8 ESD Control Flooring and Floor Coverings
4.1.3.4.8.1 Surface Resistance
4.1.3.4.9 ESD Requirements for Raised Floors
Electro Static Discharge (ESD) Can Harm Static Sensitive Electronics in Flight Control Areas
Number One: 4.1.3.3.2 Static Conductive Materials
Those materials with a surface resistivity less than 1.0 x 105 ohms/square when tested per ANSI/ ESD S11.11 shall be considered conductive. Conductive ESD control materials shall not be used for ESD control work surfaces, tabletop mats, floor mats, flooring, or carpeting where the threat of personnel contact with energized electrical or electronic equipment exists.
Number Two: 4.1.3.4.3.5 Static Dissipative ESD Control Floor Coverings
Static dissipative ESD control floor coverings shall include static dissipative tile, carpeting, static limiting floor finishes, and floor mats. Floor coverings in ESD special protection areas shall have a point-to-point resistance and surface-to-ground resistance of greater than 1.0 x 106 ohms and less than 1.0 x 109 ohms (ANSI/ESD S7.1). These floor coverings shall be bonded to any SRS in the area served in accordance with paragraphs 4.1.3.4.3.1 and 4.1.3.4.8 – except to a single point ground system.
Number Three: 4.1.3.4.8 ESD Control Flooring and Floor Coverings
All ESD control floors and floor coverings shall have a point to point resistance and a surface to ground resistance of greater than 1.0 x 106 ohms and less than 1.0 x 109 ohms (ESD STM7.1). ESD control flooring and floor coverings include vinyl tile, vinyl sheet, carpet, carpet tile, carpet tile with positioning buttons and others but not to include applied coatings.
Number Four: 4.1.3.4.8.1 Surface Resistance (Rtt)
Surface resistance (Rtt - Resistance top-to-top or surface-to-surface) of ESD control floors, carpets or floor mats shall be greater than 1.0 x 106 ohms and less than 1.0 x 109 ohms (ANSI/ESD S7.1). A minimum of five readings shall be taken at different locations on the floor surface and averaged together for each 500 square feet (or fraction thereof) of floor surface. These readings shall be recorded in the FRDF.
Number Five: 4.1.3.4.9 ESD Requirements for Raised Floors
4.1.3.4.9.1 Resistance from Carpet Surface to Pedestal Understructure
Carpet tiles shall have a resistance from the carpeted surface of the raised floor to the pedestal greater than 1.0 x 106 ohms and less than 1.0 x 109 ohms.
The dissipative ohms electrical resistance range of flooring is mentioned 6 different times between section 4.1.3.3.2 and section 4.1.3.4.9. In all but one case, the document states that the flooring shall measure greater than 1.0 x 106 ohms and less than 1.0 x 109 ohms. The only exception to this requirement can be found in a section involving extraordinary measures. Those measures are:
- It is part of a designed approach for ESD control for the equipment approved by the OPR of this document.
- This designed approach shall include all steps required to produce an electrically safe working environment.
Testing to prove an electrically safe working environment in a room equipped with conductive flooring is not the same as performing a simple set of resistance tests with a current limiting ohm meter. Definitively stating that an environment is "electrically safe" requires special licensing, extensive research and the testing would need to be performed after the flooring has been installed.
To be conclusive, this level of safety testing would need to capture AC leakage current measurements under conditions simulating an AC short circuit similar to the way electrical high voltage safety shoes are tested.
Why would a conductive carpet cause concern for safety?
In a recent white paper, Ronald Gibson, a retired ESD program manager from Celestica Corporation, pointed out that measurements from DC resistance meters should never be used to determine if a grounded floor is safe or unsafe. Gibson provided examples demonstrating that actual (as opposed to calculated) AC electrical currents can be much higher than one would predict by calculating current using ohm meter readings and inserting them into an Ohms Law equation. In Gibson’s example below, the true AC current (22 milliamps) is actually nine times greater than the calculated current of 2.4 milliamps.
Note: Calculated current is computed using Ohm’s Law. Current equals voltage divided by resistance. 120 volts divided by 50,000 ohms = .0024 or 2.4 milliamps. In theory this means that a 50,000 ohm material would only deliver 2.4 milliamps when subjected to 120 volts AC power.
Item |
Condition |
Voltage |
Current |
Resistance |
Conductive |
Current limited Resistance Meter Reading |
10 |
200 uA |
5.0 X 104 |
|
Calculated current based on Ohm’s Law |
120 |
2.4 milli Amps |
5.0 X 104 |
|
Actual AC current |
120 |
22 milliamps |
5.4 X 103 |
|
Increase in current |
|
Actual current 9 times higher than predicted |
|
View OSHA Safety Chart Here
In these tests, the amount of current delivered through a conductive carpet tile was measured above 50 milliamps. OSHA cites 16 milliamps as the level of current where a person’s muscles would contract and prevent them from letting go of the electrified object. The AC current measured across conductive carpet tile was over three times that amount. 50 milliamps is considered a “fatal current.” Since studies have shown that conductive carpet offers no performance advantage over static dissipative carpet, there is no incentive for its use.
Item |
Condition |
Voltage |
Current |
Resistance |
Conductive Carpet with PVC-Free Backing |
Current limited Resistance Reading |
10 |
200 uA |
18,000 |
|
Calculated current based on Ohm’s Law |
120 |
6.6 milliamps |
18,000 |
|
Actual AC Current |
120 |
50 milliamps |
18,000 |
Dissipative Carpet with PVC Backing |
Current limited Resistance Reading |
100 |
200 uA |
3.0 x 106 |
|
Calculated current based on Ohm’s Law |
120 |
.04 milliamps |
3.0 x106 |
|
Actual AC Current |
120 |
< .1 milliamp |
3.0 X 106 |
How to test AC current potential
The tile was placed on a large piece of aluminum foil. A 5 pound electrode was placed on top of the tile. The a.c. voltage was applied from the top electrode to the aluminum foil.
The voltage was controlled by a variac feeding a step up transformer. The voltage applied was measured with a standard multimeter. The a.c. current was measured with a clamp-on style ammeter.
The voltage was raised slowly and the volts recorded for several “milestone” currents .
