Under ANSI/ESD STM7.1-2020, laboratory product qualification measures a flooring system’s resistance before installation. Qualification requires at least five representative flooring samples (referred to as specimens in STM7.1), each containing the intended installation components and two groundable points. Both resistance measurements are performed on every sample after conditioning at low humidity and again after conditioning at moderate humidity. The report must identify the system tested, the equipment and test conditions, every resistance reading, and the minimum and maximum values.
ANSI/ESD STM7.1-2020 is an ESD Association standard test method (STM) for electrostatic discharge (ESD) flooring, approved by the American National Standards Institute (ANSI). The ASTM methods cited below are published by ASTM International.
Flooring samples
Number and size
Product qualification requires at least five flooring samples, labeled 1 to 5 (section 6.1.3.2). Each flooring sample must be large enough to define a 300 mm by 600 mm test area laid out as in the standard’s Figures 1 and 2 (section 6.1.2.2).
What each flooring sample must include
Each flooring sample must be representative of the flooring system and include all of its components as they would be used in an installation (section 6.1.2.2.2). A tile installed with an adhesive is therefore tested as the tile, the appropriate adhesive, the grounding system, and the substrate that would be used. Each flooring sample must have two groundable points that simulate end-user grounding methods (section 6.1.3.3). If the installed product has seams, the flooring sample must include a seam.
Why the assembly must match the installation
The standard’s foreword explains that when the test evaluates a system composed of several materials, interactions among those materials can affect the overall resistance measured. Its informative Annex B adds that adhesives can be affected by the moisture or mineral content of the substrate on which they are applied. That can change the adhesive resistance and with it the resistance of the flooring system, most significantly when the adhesive is the main controlling element of the system.
Support surface under the flooring sample
A planar (flat) surface used for flooring sample support must have a surface resistivity greater than 1.0 × 10¹¹ ohms/square when measured per ASTM D257 (section 6.1.2.1). The alternative criterion is a surface resistance greater than 1.0 × 10¹⁰ ohms when measured per ANSI/ESD STM11.11.
Preparing and cleaning the flooring samples
Mounting
Mount each flooring-system sample on the defined substrate using the manufacturer’s recommendations, including cure time, pressure applied, rolling direction, adhesive thickness or application method, and grounding location (section 6.1.3.1). When a floor finish or similar product requires an alternative substrate for the test, mount the manufacturer’s recommended substrate on the support material of section 6.1.2.1 according to the manufacturer’s instructions (section 6.1.2.2.1). If the flooring sample is a floor finish, apply or coat the recommended substrate according to the manufacturer’s instructions.
Cleaning before conditioning
Clean the flooring samples before humidity conditioning according to their material (section 6.1.4):
- Flooring, mats, or other hard-surface materials: follow the manufacturer’s instructions.
- Carpet or similar textile materials: clean with standard hot-water extraction procedures such as those described in ANSI/IICRC S001 or AATCC 171 and AATCC 138, or follow the manufacturer’s recommendations.
- Floor finishes: remove any surface contamination by wiping with a clean, dry, low-linting cloth.
IICRC is the Institute of Inspection, Cleaning and Restoration Certification; AATCC is the American Association of Textile Chemists and Colorists.
Equipment for qualification measurements
Meter
For product qualification, the meter must measure from 1.0 × 10³ ohms to 1.0 × 10¹⁰ ohms (STM7.1-2020 section 5.1.1). The required circuit voltage depends on the resistance being measured.
| Measurement range | Circuit voltage |
|---|---|
| 1.0 × 10⁶ ohms and above | 100 volts (± 5%) under load |
| 1.0 × 10⁴ ohms to less than 1.0 × 10⁶ ohms | 10 volts (± 5%) under load |
| 1.0 × 10³ ohms to less than 1.0 × 10⁴ ohms | 10 volts (± 5%), open circuit or under load |
The standard recommends battery-powered equipment, because alternating-current (AC) line-powered resistance measuring devices may give erroneous results due to undefined ground paths.
Electrodes
Product qualification uses conductive rubber electrodes (section 5.2). Each is a cylindrical electrode of 2.27 kg ± 0.06 kg with a diameter of 63.5 mm ± 5%. Its contact of electrically conductive material has a Shore-A durometer hardness between 50 and 70 per ASTM D2240. The resistance between two electrodes must be less than 1.0 × 10³ ohms when measured on a metallic surface.
Conditioning and test order
After cleaning, place the flooring samples in the low-humidity environment for at least 72 hours and perform both the resistance-to-groundable-point and point-to-point tests in that environment (section 6.1.5). At the conclusion of the low-humidity testing, place the flooring samples in the moderate-humidity environment for at least 72 hours and repeat both tests in that environment.
| Stage | Environment | Minimum preconditioning |
|---|---|---|
| Low humidity (section 6.1.1.1) | 12% ± 3% relative humidity and 23°C ± 3°C | 72 hours |
| Moderate humidity (section 6.1.1.2) | 50% ± 5% relative humidity and 23°C ± 3°C | 72 hours |
How each reading is taken
Every reading in both configurations starts at 10 volts, and the value recorded depends on the resistance the meter indicates.
- If the indicated resistance is less than 1.0 × 10⁶ ohms, record the value after 5 seconds.
- If the indicated resistance is equal to or greater than 1.0 × 10⁶ ohms, de-energize the equipment, energize it at 100 volts, and record the resistance after 15 seconds or as defined by the meter electrification period.
- De-energize the measurement equipment after the reading.
The standard notes that if switching to 100 volts gives a reading below 1.0 × 10⁶ ohms, the reading made at 100 volts is the one used.
Measurement configurations and flooring sample coverage
Resistance to groundable point
STM7.1-2020 measures resistance between a flooring sample’s groundable point and an electrode on its surface (section 6.1.6). The qualification plan must cover both groundable points and all prescribed electrode positions on every flooring sample.
Point-to-point resistance
STM7.1-2020 point-to-point qualification measures between two surface electrodes on the same flooring sample, leaving its groundable points unconnected (section 6.1.7). Use the insulating support and cleaned, air-dried electrodes, and complete the prescribed electrode-pair sequence for every flooring sample.
What a reviewer should find in the report
STM7.1-2020 section 6.3.1 requires the report to give all resistance-to-groundable-point and point-to-point values in ohms, together with:
- the test voltage
- the test date
- the temperature and relative humidity at the time of testing
- the actual duration of conditioning
- the test equipment used
- all components of the flooring system tested
- the substrate to which the flooring sample is applied
The test data must be summarized by reporting the minimum and maximum values obtained. If conditions other than those specified in the test method are used, such as a flooring system installed to a stainless steel substrate, they must be reported (section 6.3.3).
Before arranging laboratory qualification
Before arranging laboratory qualification, confirm the flooring assembly and substrate to be tested, provide the manufacturer’s preparation instructions, and agree on a schedule that accommodates both conditioning stages.
For installed-floor projects, Craftsman Concrete Floors provides a project closeout package with documented test results, mapped test locations and meter calibration records, prepared in accordance with ANSI/ESD STM7.1 reporting requirements where applicable.
Frequently Asked Questions
STM7.1-2020 requires at least five flooring samples, labeled 1 to 5, each large enough for a 300 mm by 600 mm test area. Each must represent the intended flooring system, have two groundable points simulating end-user grounding, and include a seam if the installed product has seams. For adhesive-installed tiles, the flooring sample includes the tile, appropriate adhesive, grounding system, and substrate.
Yes. Under STM7.1-2020, cleaned flooring samples are conditioned for at least 72 hours at 12% ± 3% relative humidity and 23°C ± 3°C, and both resistance-to-groundable-point and point-to-point tests are performed in that environment. After low-humidity testing, flooring samples are conditioned for at least 72 hours at 50% ± 5% relative humidity and 23°C ± 3°C, and both tests are repeated there.
No. STM7.1-2020 point-to-point qualification uses two surface electrodes on the same flooring sample used for resistance-to-groundable-point testing, with the flooring sample’s groundable points left unconnected.
The report must give every resistance-to-groundable-point and point-to-point value in ohms, the test voltage and date, temperature and relative humidity at testing, actual conditioning duration, equipment, flooring-system components, and the substrate used for the flooring sample. It must summarize the minimum and maximum resistance values and report any conditions that differ from the specified method.