Electrostatic discharge (ESD) flooring qualification commonly uses controlled low-humidity conditioning, while installed-floor acceptance and certain footwear–floor procedures use ambient conditions. The applicable humidity, temperature and conditioning time depend on the test method and testing stage. A minimum conditioning period does not guarantee moisture equilibrium. The standard test methods (STM) cited here are ESD Association documents approved by the American National Standards Institute (ANSI). ASTM F150-25 is published by ASTM International.
Humidity, temperature and conditioning by test procedure
| Method and procedure | Testing purpose | Relative humidity (RH) | Temperature | Conditioning time |
|---|---|---|---|---|
| STM7.1-2020, section 6.1: low-humidity stage | Flooring product qualification | 12% ±3% RH | 23°C ±3°C | At least 72 hours before testing in this environment |
| STM7.1-2020, section 6.1: subsequent moderate-humidity stage | Repeat qualification measurements on the same specimens | 50% ±5% RH | 23°C ±3°C | At least another 72 hours after completing low-humidity testing |
| STM7.1-2020, section 6.2 | Acceptance of installed or applied flooring | Ambient humidity | No temperature setpoint stated in the cited acceptance provisions | No fixed conditioning duration stated in the cited acceptance provisions |
| STM97.1-2025, section 6.1 | Qualification using flooring samples and footwear | 12% ±3% RH | 23°C ±3°C | At least 72 hours after cleaning; specimens remain in the environment through testing |
| STM97.1-2025, section 6.2 | New footwear on a previously qualified flooring system | Ambient humidity | Ambient temperature | No fixed duration stated in the ambient-condition provision; see informative Annex B |
| STM97.1-2025, section 6.3 | Intended footwear on a newly installed, unevaluated floor or an installed floor with unknown history or manufacturer | Ambient humidity | Ambient temperature | No fixed duration stated in the ambient-condition provision; see informative Annex B |
| STM97.2-2016, section 5.2.2.2: product qualification | Voltage on a person using footwear and flooring together | 12% ±3% RH | 23°C ±3°C | At least 72 hours after cleaning; samples remain in the environment through testing |
| ASTM F150-25, section 7.1 | Resistance testing of resilient flooring | 50% ±5% RH | 23°C ±1°C (73.4°F ±1.8°F) | Whenever possible, condition for at least 24 hours and test in the same environment |
The table summarizes the method conditions. S20.20-2021 permits a facility-specific qualification humidity under the restrictions explained below. Ambient testing does not mean that testing should begin immediately after cleaning.
ANSI/ESD STM7.1-2020 flooring system resistance
Product qualification: low humidity, then moderate humidity
STM7.1-2020 product qualification (section 6.1.5) places cleaned specimens in the low-humidity environment of 12% ±3% relative humidity and 23°C ±3°C (section 6.1.1.1) for a minimum of 72 hours and performs the tests in that environment.
At the conclusion of the low-humidity testing, the specimens are placed in the moderate-humidity environment of 50% ±5% relative humidity and 23°C ±3°C (section 6.1.1.2) for a minimum of 72 hours, and the tests are repeated there.
The tests performed at each stage are resistance to groundable point (section 6.1.6) and resistance point-to-point (section 6.1.7), on the same specimens.
Product acceptance of installed or applied flooring: ambient humidity
For product acceptance of installed or applied flooring systems, STM7.1-2020 section 6.2 requires both resistance to ground (section 6.2.1) and resistance point-to-point (section 6.2.2) to be measured. Both tests are performed at ambient humidity (sections 6.2.1.3 and 6.2.2.3).
ANSI/ESD STM97.1-2025 resistance of a person with footwear and flooring
Qualification with a flooring sample and footwear
STM97.1-2025 section 6.1, the qualification procedure performed before a flooring system is installed, uses a humidity environment of 12% ±3% relative humidity and 23°C ±3°C (section 5.6).
After cleaning, the footwear and flooring system specimens are placed in that environment and preconditioned for at least 72 hours. They remain in it until all testing is completed (section 6.1.3.6).
New footwear on a previously qualified flooring system
Section 6.2, which evaluates a new type of footwear on a previously qualified flooring system, performs all of its tests at ambient temperature and humidity (section 6.2.2.6).
Newly installed or unknown-history floors
Section 6.3 applies to a newly installed floor that was not evaluated under section 6.1 before installation, or to an installed floor whose history and/or manufacturer is unknown.
It evaluates a set of footwear intended for use with that flooring system, and all of its tests are performed at ambient temperature and humidity (section 6.3.2.6).
Testing immediately after cleaning
Sections 6.2 and 6.3 refer to Annex B for their ambient conditioning. That annex is informative rather than part of the test method, and it cautions that moisture or water introduced from the environment or the cleaning process may lead to misleading resistance values if testing is done immediately after cleaning.
When 72 hours may not be enough
STM97.1-2025 informative Annex B also notes that some materials are hygroscopic (able to absorb moisture from the air) and may show widely varying resistance at different relative humidity levels or with moisture from cleaning. The time needed for the surface to equilibrate may be longer than 72 hours; the annex gives no replacement duration.
ANSI/ESD STM97.2-2016 voltage on a person with footwear and flooring
For STM97.2-2016 product qualification testing, the floor material and footwear are cleaned and then placed in a low-humidity environment set to 12% ±3% RH and 23°C ±3°C and conditioned for a minimum of 72 hours (section 5.2.2.2).
The samples must not be removed from that environment until all testing has been completed.
ASTM F150-25 resistance of resilient flooring
ASTM F150-25 section 7.1 directs that, whenever possible, the test specimen be conditioned for at least 24 hours at 73.4°F ±1.8°F (23°C ±1°C) and 50% ±5% relative humidity and tested in the same environment.
F150 also notes (section 8.3.1) that areas with lower ambient relative humidity could have resistance readings that vary from readings at higher ambient relative humidity.
ANSI/ESD S20.20-2021 facility minimum humidity
When a facility’s annual minimum RH may replace the method level
Under ANSI/ESD S20.20-2021 section 7.3, an organization whose facility has an annual minimum relative humidity above the environmental conditioning level identified in the product qualification test method can use that minimum value to qualify each item used within that facility.
The allowance covers only items that stay at that facility. It does not apply across multiple sites or to materials that leave the site.
Footwear/flooring personnel-grounding qualification
When a footwear/flooring system is selected as the personnel grounding method, S20.20-2021 requires it to be qualified using the environmental test conditioning specified in the test methods identified in its Table 2, or at the facility’s annual minimum RH when that minimum is above the method’s conditioning level and the items stay within that facility.
Compliance verification records cannot be used for that qualification.
Recording qualification conditions
S20.20-2021 requires product qualification test data to include the environmental conditioning used during testing as defined within the test method.
Standards basis: ANSI/ESD STM7.1-2020; ANSI/ESD STM97.1-2025, including informative Annex B; ANSI/ESD STM97.2-2016; ASTM F150-25; ANSI/ESD S20.20-2021. Confirm the governing editions and project requirements before testing.
Frequently Asked Questions
STM7.1-2020 uses ambient humidity for both resistance-to-ground and point-to-point acceptance tests of installed or applied flooring. STM97.1-2025 uses ambient temperature and humidity in section 6.2 for new footwear on a previously qualified floor, and in section 6.3 for intended footwear on a newly installed floor not evaluated under section 6.1, or an installed floor with unknown history and/or manufacturer. STM97.1’s informative Annex B cautions that testing immediately after cleaning can produce misleading resistance values because of moisture.
No. STM97.1-2025 informative Annex B says some hygroscopic materials may need longer than 72 hours for the surface to equilibrate. It gives no fixed replacement duration, and warns that moisture from the environment or cleaning can make immediate resistance tests misleading.
S20.20-2021 permits a facility’s annual minimum relative humidity for qualification only when it is above the applicable method’s environmental conditioning level and the items stay within that facility. The allowance does not extend across multiple sites or to materials leaving the site. A footwear/flooring system selected for personnel grounding must still be qualified using the Table 2 method conditioning or this permitted facility minimum; compliance verification records cannot replace that qualification.
No. ASTM F150-25 section 7.1 says, whenever possible, to condition specimens for at least 24 hours at 23°C ±1°C (73.4°F ±1.8°F) and 50% ±5% relative humidity, then test in that environment. STM7.1-2020, STM97.1-2025 section 6.1 and STM97.2-2016 specimen qualification require at least 72 hours; STM7.1 has separate low- and moderate-humidity stages.
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