A close-up shot of a person's feet walking across a factory or laboratory floor wearing dark safety shoes.
Walking the Line: The Interaction of Flooring and Footwear in Walking Body Voltage Generation
Considerations for Specifying Flooring/Footwear Systems
By Tom Ricciardelli
E

lectrostatic discharge (ESD) control programs often focus heavily on individual components, such as conductive flooring, ESD shoes, heel grounders, or wrist straps. Yet one of the most important lessons emerging from recent research is that no single component determines success. Instead, the interaction between footwear, flooring, environmental conditions, and human behavior ultimately dictates walking body voltage performance.

The ANSI/ESD S20.20 standard requires personnel grounding systems to maintain body voltages below 100 volts during normal movement. ANSI/ESD S20.20 also requires that the footwear/flooring system keeps body voltage below 100 volts when tested as a system per ANSI/ESD STM 97.2. While many facilities assume that installing an ESD floor or purchasing certified ESD footwear guarantees compliance, practical testing demonstrates that the reality is far more complex. Different combinations of floors and footwear can produce dramatically different results, even when each component independently satisfies specification requirements.

Electrostatic discharge (ESD) control programs frequently emphasize compliance with resistance specifications for flooring materials and personnel grounding devices while overlooking the dynamic interaction between those components during actual use. Walking body voltage generation, however, depends on the complete footwear/flooring system rather than any individual element.

Data of a variety of footwear/flooring systems demonstrated significant variability in body voltage generation among different footwear models, flooring types, humidity conditions, and resistance ranges, even when individual components satisfy conventional requirements. Systems exhibiting resistance to ground values below 1 × 108 ohms consistently produced lower and more stable walking body voltages, while higher‑resistance systems frequently exceeded the ANSI/ESD S20.20 threshold of 100 volts.

The findings reinforce the importance of qualifying complete flooring and footwear systems under actual operating conditions rather than relying solely on component specifications.

Some Background
Modern manufacturing increasingly depends on effective electrostatic discharge control. Semiconductor devices, automotive electronics, medical instruments, aerospace systems, and advanced battery technologies all contain components vulnerable to electrostatic events. As device geometries shrink and operating voltages decline, the margin for error continues to narrow.

Despite these technological advances, one of the most persistent misconceptions in ESD control remains surprisingly simple, that is, the belief that installing an ESD floor or purchasing ESD footwear automatically guarantees compliance. In fact, we’ve had some users think that they only needed an ESD floor or ESD footwear (not both) to have proper control.

In practice, electrostatic performance is not determined by any single component. It emerges from a complex interaction involving flooring materials, footwear design, environmental conditions, human movement, and maintenance practices. A floor that performs exceptionally well with one shoe may fail with another. A system that passes testing during humid summer months may exceed allowable body voltages during winter operation. A resistance measurement that appears acceptable on paper may not predict actual walking body voltage generation.

Our recent research and testing sought to investigate these interactions and quantify how flooring systems and footwear combinations influence walking body voltage generation under realistic conditions. We believe that our findings can provide important guidance for organizations designing, specifying, and maintaining ESD-protected areas.

The Physics of Walking Body Voltage Generation
Walking body voltage originates from the triboelectric effect, that is, the transfer of electrical charge between two materials brought into contact and then separated. Every step an individual takes creates friction between the sole of the shoe and the floor surface. Depending upon the materials involved, electrons migrate from one surface to another, leaving one positively charged and the other negatively charged.

In uncontrolled environments, this process can generate thousands of volts. A person walking across conventional carpeting in dry winter conditions may accumulate 20,000 volts or more. Sensitive electronic devices, however, can suffer damage at discharge levels well below 100 volts.

Yet resistance values alone tell only part of the story.

Dynamic body voltage generation depends upon multiple factors, including:

  • Contact area between shoe and floor
  • Material composition of flooring and soles
  • Moisture content and ambient humidity
  • Walking speed and gait characteristics
  • Contamination and maintenance conditions
  • Localized variations within flooring installations
Understanding these interactions requires testing methods that replicate actual human movement rather than static resistance measurements alone.
ANSI/ESD S20.20 and the Importance of Walking Body Voltage
ANSI/ESD S20.20 establishes requirements for ESD control programs designed to protect electrical and electronic components susceptible to electrostatic damage. Among its requirements is the expectation that personnel grounding systems maintain body voltages below 100 volts during normal activity.

The standard recognizes walking body voltage as one of the most meaningful indicators of real-world system performance. Meeting this requirement demands more than purchasing compliant components. It requires demonstrating that the combined flooring and footwear system functions effectively as an integrated whole. Unfortunately, many facilities continue to specify flooring materials primarily according to resistance to ground measurements without evaluating actual walking performance. The research highlights why such an approach can produce misleading conclusions.

ANSI/ESD STM97.2: Measuring Real‑World Performance
ANSI/ESD STM97.2 provides the accepted methodology for measuring walking body voltage generation in combination with a person. In fact, ANSI/ESD S20.20 requires that the footwear/flooring system measures below 100 volts when tested per ANSI/ESD STM 97.2. The procedure utilizes a charge plate monitor connected to a recording device while a test subject walks across a grounded flooring surface using specified footwear. A handheld probe measures the individual’s body voltage throughout the test sequence (see Figure 1).
Figure 1: ANSI/ESD STM97.2 walking voltage test setup
Figure 1: ANSI/ESD STM97.2 walking voltage test setup
Unlike simple resistance measurements, STM97.2 captures dynamic interactions occurring during actual movement. This methodology offers several important advantages:
  • First, it accounts for triboelectric charging mechanisms that static resistance tests cannot capture.
  • Second, it incorporates human variability, including differences in gait, stride length, and  body movement.
  • Third, it evaluates complete systems rather than isolated components.
Most importantly, it reflects the conditions workers experience every day inside manufacturing facilities.

For organizations pursuing robust ESD control programs, walking body voltage testing should therefore be considered an essential qualification tool rather than an optional exercise.

Study Overview
Our study examined several critical variables influencing walking body voltage generation, including:
  • Different footwear brands and models
  • Flooring and footwear resistance values
  • Various flooring materials and constructions
  • Distinct personnel grounding methods
  • Conventional street shoes
  • Relative humidity conditions
The objective was straightforward: identify which combinations consistently maintained body voltages below the ANSI/ESD S20.20 threshold and determine why others failed.

The results revealed substantial differences among seemingly comparable systems.

Footwear Variability: Not All ESD Shoes Are Created Equal
One experiment evaluated multiple brands and models of safety footwear using a single low-resistance floor exhibiting an RTG value of approximately 8 × 104 ohms. Environmental conditions remained constant throughout testing (see Figure 2).
Figure 2: The complete footwear/flooring system affects performance in body voltage generation.
Figure 2: The complete footwear/flooring system affects performance in body voltage generation.
The expectation might have been that all certified ESD footwear would perform similarly. However, certain footwear models generated minimal body voltages, while others exceeded 100 volts despite operating on the same conductive flooring system. Some individual measurements approached 350 volts. These findings demonstrate that footwear certification alone cannot guarantee acceptable walking performance.

Potential causes include:

  • Sole compound formulation—Different manufacturers utilize varying conductive additives, carbon loadings, and polymer systems. Small formulation changes may significantly influence triboelectric behavior.
  • Contact geometry—Tread patterns affect the effective contact area between shoe and floor. Reduced contact can increase localized charge generation and impede dissipation pathways.
  • Conductive path placement—The location and continuity of conductive elements within footwear designs vary among manufacturers. Interruptions in these pathways can degrade overall performance.
  • Wear characteristics—Footwear performance evolves over time. Abrasion, contamination, and sole degradation may alter resistance and charge generation behavior.
For ESD program managers, the implication is unavoidable: specific footwear models should be qualified with the intended flooring system rather than assumed to perform adequately based solely on manufacturer claims.
Resistance: A Useful Indicator, But Not a Complete Answer
We then took a slightly different look at the data, comparing system resistance (combined resistance of footwear and flooring) versus the peak voltage measured in the walking body voltage test (see Figure 3). The relationship between flooring/footwear resistance and walking body voltage exhibited a clear trend. As combined resistance values increased toward 109 ohms, body voltages generally increased as well.
Figure 3: Peak body voltage generation increases with footwear/flooring system resistance.
Figure 3: Peak body voltage generation increases with footwear/flooring system resistance.
The research identified a practical benchmark: systems exhibiting resistance-to-ground values below approximately 1 × 108 ohms consistently demonstrated superior compliance with ANSI/ESD S20.20 requirements, while higher‑resistance systems frequently exceeded the 100-volt limit.

For facility designers, this threshold offers an important guideline when selecting flooring technologies. Most flooring systems marketed as “dissipative” have resistance that measures closer to 1 x 109 ohms and so have a higher likelihood of not providing an adequate footwear/flooring system. Flooring systems sold as “conductive” will measure below 1 x 106 ohms and will generally provide a higher likelihood of producing a footwear/flooring system that meets the requirements of ANSI/ESD S20.20.

Conductive and Dissipative Flooring: Practical Differences
The industry often categorizes ESD flooring as either conductive or dissipative. While both classifications can satisfy resistance requirements, their practical behavior may differ substantially.

We then compared three visually distinct interlocking floor products under extremely dry conditions of 12 percent relative humidity. Each product was available in both conductive and dissipative formulations.

Figure 4 plots the peak voltage measured in the walking body voltage test on the various flooring samples. As shown, the conductive grades exhibited remarkably consistent performance regardless of product type. Dissipative grades showed greater variability and higher peak voltages.

Figure 4: Conductive flooring grades had lower and more consistent peak body voltage generation.
Figure 4: Conductive flooring grades had lower and more consistent peak body voltage generation.
This finding has important implications for advanced manufacturing sectors. Semiconductor fabrication facilities, lithium battery plants, and electronics assembly operations frequently operate in low‑humidity environments where static generation becomes increasingly problematic. Under such conditions, conductive flooring may provide valuable performance margins unavailable from higher‑resistance dissipative systems.

The choice between conductive and dissipative materials should therefore consider environmental conditions, process sensitivity, and reliability of maintaining low body voltage rather than relying solely upon initial cost comparisons.

Footwear Systems in Comparison
In another comparison test, we evaluated four common personnel grounding methods:
  • ESD shoes
  • ESD booties
  • Heel grounders
  • Sole grounders
All were tested on both conductive interlocking flooring and dissipative glue‑down tile at 12 percent relative humidity.

Figure 5 plots the peak voltage measured in the walking body voltage test using the different footwear on both conductive and dissipative flooring samples.

Figure 5: Different footwear types produced different peak body voltage on the same floor.
Figure 5: Different footwear types produced different peak body voltage on the same floor.
The results were unequivocal:
  • Every footwear category performed better on the conductive flooring system; and
  • Many exceeded 100 volts when used on the dissipative flooring system.
This observation highlights an important systems-engineering principle. The effectiveness of personnel grounding devices cannot be evaluated independently from the floor upon which they operate.

Facilities frequently debate whether premium ESD shoes justify their higher cost. The research suggests that optimizing flooring performance may produce greater improvements than upgrading footwear alone. The best outcomes occur when both components are designed and qualified as a unified system.

The Problem with Street Shoes
We often hear the misconception that some ESD floors don’t require ESD footwear. So, we put this concept to the test. Figure 6 shows the results of testing conducted with conventional athletic shoes. As shown in this test, body voltages approached 1,800 volts on dissipative flooring and more than 400 volts on conductive flooring.
Figure 6: Street shoes on ESD floors produced peak body voltages above the ANSI/ESD S20.20 100 volt limit.
Figure 6: Street shoes on ESD floors produced peak body voltages above the ANSI/ESD S20.20 100 volt limit.
These voltages remained below the level of human perception thresholds (approximately 2,000 to 3,000 volts), but exceeded acceptable levels for sensitive electronics by wide margins. So, one might get the false assumption that the floor alone is providing adequate protection since shocks are generally not felt.

The findings demonstrate two important points:

  • First, conductive flooring significantly reduces charge generation even for non-ESD footwear. This can be helpful to protect enclosed electronic products, like computers and data tablets, and to prevent painful shocks to personnel.
  • Second, flooring alone will not provide compliance with the requirements of ANSI/ESD S20.20. Without a proper footwear/flooring system, human body voltage will generally not be maintained below 100 volts and will therefore not provide protection to sensitive electronic components.
Visitors, contractors, maintenance personnel, and temporary workers require appropriate grounding devices whenever they enter ESD-protected areas. Disposable heel straps and booties remain inexpensive insurance against potentially costly product failures.
Humidity: The Hidden Variable
Humidity influences nearly every aspect of electrostatic behavior.

Water molecules adsorbed onto surfaces enhance conductivity and facilitate charge dissipation. As humidity declines, insulating behavior increases and triboelectric charging intensifies. The data in our testing clearly illustrated this relationship.

Figure 7 plots the peak voltage measured in the walking voltage test for five different footwear/flooring systems under both 12% and 50% relative humidity. Systems exhibiting marginal performance at 12 percent relative humidity often achieved compliance at 50 percent humidity. Systems already producing low voltages showed comparatively little change.

Figure 7: Low humidity generally produces much higher peak body voltages.
Figure 7: Low humidity generally produces much higher peak body voltages.
This creates an important challenge for manufacturers. Seasonal variations can transform compliant systems into failing systems without any changes to equipment or procedures. Facilities relying upon ambient humidity as an unintentional component of their ESD strategy may experience unexpected failures during winter months. The most robust systems maintain compliance regardless of environmental conditions.

That objective typically requires:

  • Lower resistance flooring
  • Proper footwear qualification
  • Comprehensive maintenance procedures
  • Routine walking body voltage verification
Best Practices for System Qualification
Our research supports several recommendations for organizations establishing or upgrading ESD programs, as follows:
  • Test complete systems—As required by ANSI/ESD S20.20, qualification should always include actual flooring and footwear combinations rather than individual products evaluated separately.
  • Test under worst-case conditions—Low-humidity environments provide the most meaningful performance data. Product qualification testing, as prescribed by ANSI/ESD S20.20, generally requires testing at low humidity.
  • Establish resistance targets—Systems below 1 × 108 ohms consistently demonstrated superior performance. Most flooring systems marketed as “dissipative” have resistance that measures closer to 1 x 109 ohms and so have a higher likelihood of not providing an adequate footwear/flooring system. Flooring systems sold as “conductive” will measure below 1 x 106 ohms and will generally provide a higher likelihood of producing a footwear/flooring system that meets the requirements of ANSI/ESD S20.20.
  • Monitor performance over time—Wear, contamination, and maintenance practices influence long-term effectiveness.
The Economics of Better ESD Systems
Investments in conductive flooring and qualification testing may initially appear expensive. Yet the economics overwhelmingly favor prevention. A single electrostatic event can destroy high-value semiconductor devices, create latent failures, compromise automotive electronics, or interrupt production schedules. The costs associated with field failures, warranty claims, and customer dissatisfaction far exceed the incremental investment required to optimize flooring-footwear systems.

Organizations evaluating ESD infrastructure should therefore consider lifecycle risk reduction rather than initial installation costs alone. Robust systems deliver value through consistency, reliability, and reduce operational uncertainty.

Conclusions
The evidence leads to a clear conclusion: combinations matter. Flooring type, footwear selection, resistance characteristics, environmental conditions, and human behavior collectively determine walking body voltage performance.

Our research demonstrated that:

  • Footwear/flooring systems with resistance to ground values below 1 × 108 ohms generally maintained compliance with
    ANSI/ESD S20.20 requirements.
  • Higher-resistance systems frequently exceeded the 100-volt threshold.
  • Different ESD footwear models produced dramatically different results on identical floors.
  • Conductive flooring consistently outperformed dissipative alternatives under challenging conditions.
  • Humidity can mask deficiencies in otherwise inadequate systems.
  • Street shoes remain incompatible with protected manufacturing environments.
Perhaps the most important lesson is that ESD control cannot be achieved through isolated specifications. Successful programs qualify complete systems. They test under realistic conditions. They recognize that every step a worker takes represents a dynamic interaction between person, footwear, flooring, and environment. In the end, effective electrostatic control requires more than compliant products. It requires understanding how those products work together.

Only by walking that line can organizations ensure reliable protection for the increasingly sensitive technologies upon which modern industry depends.

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The Author
Tom Ricciardelli founded SelecTech in 1993 to create products from recycled materials and invented an adhesive‑free, interlocking static-control flooring system. He joined the ESD Association in 2013 and currently chairs multiple working groups. Ricciardelli can be reached at tricca@selectech.com.
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