Conductive vs Dissipative ESD Flooring

Informative Annex C of ANSI/ESD STM7.1-2020 describes the difference in actual static-control properties between 9.5 × 10⁵ and 1.5 × 10⁶ ohms as negligible. A small variation around 1 megohm can change the class name without a corresponding sharp change in performance.

These are flooring definitions. Other static-control materials, including packaging, use different resistance ranges for the same class names.

The measurement scope of ANSI/ESD STM7.1-2020 is greater than 1.0 × 10⁴ ohms and less than 1.0 × 10⁹ ohms. That scope does not create a lower boundary in the conductive definition, which states only an upper limit.

Antistatic usually describes a material’s ability to inhibit triboelectric, or friction, charging. MSFC-RQMT-2918 Revision E, effective 17 December 2015, uses this definition and notes that the property is not necessarily correlated with resistance or resistivity.

An antistatic label therefore does not identify a third fixed resistance band. It also does not establish whether the complete flooring assembly provides a path to ground. Ask for the measured resistance and assembly details instead of inferring them from the label.

With appropriate static-control footwear, lower flooring-system resistance generally accompanies lower body-voltage generation, according to informative Annex C of ANSI/ESD STM7.1-2020. Body voltage also depends on:

• The footwear used and its contact area
• Relative humidity
• Personnel weight
• Movement speed
• The flooring material

Lower resistance is a tendency toward lower body voltage, not a guarantee. Compare measured performance for the combination and conditions you will use.

ANSI/ESD STM7.1-2020 prohibits using its resistance measurements to determine the relative safety of personnel exposed to high AC or DC voltages. The foreword to ANSI/ESD STM97.2-2016 warns that a footwear/flooring system conductive enough to discharge a person may also pose a shock hazard. Testing under that method does not guarantee personnel safety.

The electronics ESD criteria discussed here do not supply an ignition-hazard flooring specification. ANSI/ESD STM7.1-2020 excludes facilities where ordnance, flammables, or explosives are stored or handled and refers those concerns to ASTM F150 (current edition ASTM F150-25). ANSI/ESD S20.20-2021 excludes electrically initiated explosive devices, flammable liquids, and powders.

Use the hazardous-area flooring and static-control guides to find the source-specific requirements for the operation. Do not select an ignition-control floor from the electronics class table alone.

Informative Annex C of ANSI/ESD STM7.1-2020 recommends specifying the required resistance range at a defined test voltage rather than relying on the words conductive or dissipative.

Some materials near 1 megohm can measure at or above 1.0 × 10⁶ ohms at 10 volts, but below that boundary at 100 volts. The label is ambiguous without its measurement conditions. The focused guide to voltage-dependent floor classification explains this distinction.

ANSI/ESD STM7.1-2020 defines a flooring system as the full combination of components that carries static charge to ground. These can include the surface material, adhesive, grounding mechanism, substrate, and other required materials.

Qualification specimens must represent the installation and include its system components. ANSI/ESD STM7.1-2020 and ANSI/ESD STM97.1-2025 both require this; changing components can change the test results.

Informative Annex B of STM7.1-2020 illustrates the problem with a conductive tile installed using a higher-resistance adhesive. The tile can measure below 1.0 × 10⁶ ohms while the resulting assembly measures at or above that value; the annex characterizes its example as a dissipative system. A tile rating cannot substitute for the complete assembly’s result.

For the material-format decision, compare ESD epoxy, tile, and vinyl options. Keep the required electrical performance attached to whichever assembly is proposed.

Resistance from the top surface to a groundable point or ground reference, and between top-surface locations.

Resistance through a person wearing footwear or foot grounders while standing on the flooring system.

Voltage generation in combination with a person.

Table 2 of ANSI/ESD S20.20-2021 requires a footwear/flooring system used for personnel grounding to meet both product-qualification limits:

• System resistance below 1.0 × 10⁹ ohms, measured by ANSI/ESD STM97.1
• Peak body voltage below 100 volts, measured by ANSI/ESD STM97.2

The organization must qualify every footwear and flooring type combination it uses. These are personnel-system qualification requirements; meeting them alone is not a determination of full ESD-program compliance.

Product qualification and recurring compliance verification serve different purposes. ANSI/ESD S20.20-2021 does not allow compliance-verification records to replace footwear/flooring product qualification.

Qualification follows the test methods’ environmental conditioning, with a permitted facility-specific route using annual minimum humidity when it exceeds the methods’ conditioning levels. Footnote 7 recommends using the qualification resistances that met the below-100-volt limit for recurring verification; the maximum allowed verification resistance remains below 1 gigohm. The guide to system-resistance and body-voltage qualification limits covers these conditions in detail.

For product acceptance of installed or applied flooring systems, ANSI/ESD STM7.1-2020 requires both resistance to ground and resistance point-to-point. Newly installed systems must receive the proper cure time, where applicable, following the manufacturer’s instructions. Measurements taken before coatings, finishes, or adhesives fully cure may differ from later results.

Keep the measured quantity clear: qualification resistance to a groundable point and installed resistance to ground are distinct, and point-to-point resistance measures a different path again.

For a useful comparison, request:

• Resistance values in ohms and the measurement quantity
• Test method, voltage, and date
• Temperature and relative humidity at testing
• Test equipment and the flooring-system components tested

For the detailed reporting requirements and testing services, see ESD floor testing.