No industry standard rates ESD (static-control) floors based on levels or classifications of static control.
You may have heard a sales or customer service rep (or flooring contractor) refer to ESD flooring by level, rating the floor Static Control Level 1, 2 or 3. Smart marketing strategy! A system of levels or classifications simplifies the scientific data used for standards and specifications. As psychological research shows, Easy = True.
If you’re an ESD buyer or specifier who has not mastered or doesn’t care to wade through complex technical data, defining static control by level is a welcome strategy. And why not? It makes your job easier. There’s no shame in choosing a quicker, easier option when it’s offered.
Some engineers we meet don’t know much more than the average Jane or Joe about the electrical resistance properties of an ESD floor. And don’t care to know.
We get it. It’s time consuming to learn and digest new, unfamiliar concepts. The problem is, for static control floors, levels and classifications are manufactured terms. People certainly don’t use those terms with any malicious intent. The goal is simply to make static-control flooring easier to understand; therefore, their ESD floor an easier sell.
What are “levels” of static control anyway?
Marketing terms. That’s all they really are.
While, in some cases, a conductive floor is a superior option – for example, EC (electrically conductive) rubber outperforms static dissipative rubber; that’s because the conductivity in dissipative rubber comes from a liquid additive that leaches out over time. With ESD carpet, depending upon the actual resistance readings, the opposite is often true. In critical applications – such as FAA flight towers, E-9-1-1 call centers, telecom spaces, for example – industry standards require dissipative flooring and, in fact, don’t allow for resistance readings below 1.0 x 10E6.
To claim that more conductivity is better or that a conductive floor provides greater – or a higher level of – static protection than a static-dissipative floor is an oversimplification, and – as shown above – can be misleading. (Despite perceptions, easy is not always true.) Properly evaluating/specifying an ESD floor is more complicated than that.
Depending upon the material and how it’s manufactured, a floor can be more or less conductive—have higher or lower electrical resistance. Higher conductivity does not mean the floor is more static protective. In fact, some highly conductive floors are static generators. More on this later.
The required electrical resistance – how conductive the floor should be – varies by industry. In some cases, it depends upon whether or not people in the space are required to wear static-protective shoes. In others, it depends upon the application or type of equipment in use.
Certain applications—explosives manufacturing, for example—prefer conductive flooring; that is, flooring materials that measure in the lower range of electrical resistance (below 1.0 x 10E6 or 1,000,000 ohms).
Applications such as FAA flight towers, telecom, and E-9-1-1 call centers—require flooring materials to measure in the mid to upper range of electrical resistance: above 1.0 x 10E6 (1,000,000 ohms) and below 1.0 x 10E9 (1 billion ohms). These standards are meant to ensure the safety of the people working with or around electrified equipment.
- Please note: conductivity is the opposite of electrical resistance.
- A floor with higher resistance (measuring in the upper range) would be less conductive, therefore correlating to a “lower level” of static control.
We’re not telling you a less conductive (“lower level” or static dissipative) floor is better for mission-critical environments.
What we’re telling you is: the people who write the industry standards and specifications for flight towers, telecom, E-9-1-1 call centers and other mission critical spaces require the use of less conductive flooring.
As we hinted above, conductivity/resistance is only one of the parameters necessary for specifying an ESD floor. The other crucial factor—having no relationship to conductivity or electrical resistance—is charge (or body voltage) generation.
How to Rate or Evaluate an ESD Floor
Let’s be clear: ESD (Static-control) floors are neither rated nor specified by levels.
ESD flooring should be tested and evaluated using industry-specific standards and universal test methods. Flooring should be selected and specified based upon these electrical metrics:
Resistance, measured in ohms
Charge generation, measured in volts
Electrical resistance readings are taken with an ohmmeter and measure the electrical resistance of flooring material from point to point or point to ground. Electrical resistance tests tell you how fast a static charge can be expected to travel across the floor and how quickly (or slowly) static electricity will bleed from the surface of the floor to ground.
This information is important because if static charges bleed – or dissipate – too slowly, the floor may be incapable of preventing random ESD events from damaging electronic components. If charges bleed too quickly, under certain circumstances the floor could pose a safety risk.
Resistance tests follow the specific procedures outlined in ANSI/ESD S20.20-2014, test method STM 97.1. The diagram below shows how the test should be performed.
Note: though measurement requirements differ by industry, every industry uses the identical – universal – test to measure the electrical resistance of static-control flooring materials.
Resistance Measurements – or Facts About Conductivity
As previously noted, electrical resistance requirements vary from industry to industry.
Electronics manufacturing and handling environments—which follow standards and specifications outlined in ANSI/ESD S20.20-2014—require resistance readings below 1.0 x 10E9 (less than 1 billion ohms). The use of ESD footwear accounts for this wide range of acceptable resistance readings. ESD footwear bonds electrically with the ESD floor and helps to control charges and dissipate static to ground, and the built-in resistor helps to prevent electrical shocks to the person wearing the ESD footwear or shoes.
In FAA flight towers, telecom facilities, and E-9-1-1 call centers, where people do not wear static-control footwear, standards require ESD flooring to measure 1.0 X 10E6 to 1.0 X 10E9 ohms. This higher range of electrical resistance – or more controlled rate of static dissipation – protects personnel who work with or around electrified equipment.
To adhere to safety protocols, any floor installed in the above applications should be verified – after installation – that it does not measure above or below this resistance range. Floors with resistance readings higher than 1.0 x 10E9 may not dissipate static quickly enough to prevent damaging ESD events; under the right circumstances, floors with resistance readings below 1.0 x 10E5 could pose a safety risk.
Charge Generation, also called Body Voltage Generation
Many specifiers don’t realize this: a floor can be electrically conductive (or dissipative) and still generate enough of a static charge to damage or destroy sensitive electronics.
In most work environments, static is primarily generated when people walk on the floor. That’s because walking creates friction (between the shoe sole and the floor) and friction generates static electricity. That’s why it’s so important to test charge generation.
Charge generation tests, performed with a voltmeter, measure the static charge generated by a person walking on a flooring surface, wearing a particular type of footwear. (The test should be performed multiple times with subject wearing every type of footwear that may be worn in the space.)
Body voltage tests predict how much static a person will generate – and accumulate on his or her body – as he or she walks across the floor wearing a particular type of footwear.
As noted above, this is important because a floor that generates static can be the source of damaging static events – even if the floor measures in the highly conductive range.
Charge Generation Test
Charge generation—or body voltage—tests are performed according to the procedures outlined in ANSI/ESD S20.20-2014, test method ANSI/ESD STM 97.2.
Body Voltage Measurements
ESD flooring should be chosen to address critical operations based on the sensitivity classification of the electronic components, assemblies and systems. That is, tests should be performed to predict charge generation and measurements should align with the static-control needs of the electronic equipment that’s to be protected.
How much static a component can tolerate depends upon various factors, such as its speed and sensitivity, the way it’s manufactured, or environmental factors it’s subject to.
Here are the basic requirements:
|Class of Electronics||Voltage Range|
|Class 0||< 250 volts|
|Class 1A||250 volts to <500 volts|
|Class 1B||500 volts to <1,000 volts|
|Class 1C||1,000 volts to <2,000 volts|
|Class 2||2,000 volts to <4,000 volts|
|Class 3A||4,000 volts to <8,000 volts|
|Class 3B||≤ 8,000 volts|
ESDS Component Sensitivity Classification for the Human Body Model (Per ESD-STM5.1)
* Note: Sensitivity increases as Class number decreases
Bottom Line: What’s Wrong with Levels or Classifications of Static Control?
Nothing. there is absolutely nothing inherently wrong with describing a floor by level or classification – assuming the terms correspond directly to industry standards.
To have any relevance to standards or specifications, “levels” or classification must refer to very specific electrical resistance readings. Level 1, for example, would need to mean that this particular flooring material measures between X number and Y number of ohms – for instance, from 1.0 x 10E8 to 1.0 x 10E9 ohms.
Even then, to say a particular “level” of static control – or degree of resistance or conductivity – is “better” than or superior to another is meaningless.
What is wrong is using marketing terms as an easy shortcut for specifying an ESD floor.
Because no legitimate industry standard or specification refers to levels or classifications. Every standard and specification, in every industry, refers to specific electrical resistance parameters measured in ohms.
Furthermore, conductivity tells only part of the story. To ensure your ESD floor will protect your equipment, the material must also be tested for charge generation.
This may not be what you wanted to hear. If not, we apologize. We don’t like making your job any more complicated or time-consuming than it needs to be. But – if you’re specifying a floor with electrical properties, you need to reference metrics. This is the only way to be sure your new floor meets the code, parameters and specifications defined by your industry. And to do the job right, you’ve got to put in the time.
Excerpt from FAA 019f, governing flight control towers and flight support:
From FAA 019f
5.8.9 Electrostatic Discharge (ESD) Control Flooring and Floor Coverings
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 10E6 ohms and less than 1.0 x 10E9 ohms (ANSI/ESD STM7.1). ESD control flooring, floor coverings, and floor tile laminates include materials such as vinyl tile, vinyl sheet, carpet, carpet tile, and carpet tile with positioning buttons, but not the applied coatings on the material.
To find electrical specifications by industry, visit our standards and specifications hub.
For objective, evidence-based advice on selecting and specifying an ESD floor, visit our hub, Selecting and Specifying an ESD floor.
With Staticworx ESD flooring, you never have to choose between performance and aesthetics. Our beautiful, high quality ESD carpet tile, vinyl, EC rubber tile and sheet goods, and ESD epoxy floors are as beautiful as they are functional.