How to Read an ESD Mat Test Report: STM4.1, Rtt, Groundable-Point Resistance, and Test Conditions

A supplier may send an ESD mat report showing:

Resistance: 2.5 × 10⁷ Ω
Result: PASS

That number alone is not enough for a purchasing decision.

Before approving an ESD worksurface, buyers should know which product was tested, which resistance measurement was used, which ANSI/ESD STM4.1 edition was referenced, the test conditions, the individual readings, the applicable acceptance limit, and whether the report can be connected to the material being supplied.

This is especially important for bulk orders, OEM projects, and controlled electronics workstations where the test report becomes part of supplier qualification.

The key rule is simple:

Do not approve an ESD worksurface from one resistance number or a “PASS” statement. Review the test method, measurement type, test conditions, actual data, acceptance criteria, and product traceability together.

Quick Answer: Read the Report in the Right Order

When reviewing an ESD mat test report, check these items in sequence:

1. Product identity
2. Standard and edition
3. Resistance measurement type
4. Test equipment and setup
5. Temperature and relative humidity
6. Sample preparation and conditioning
7. Individual resistance readings
8. Minimum, maximum, and average results
9. Acceptance criteria
10. Report and product traceability

ANSI/ESD STM4.1 is a worksurface resistance measurement method used for qualification testing. The current EOS/ESD Association publication is ANSI/ESD STM4.1-2026, titled Worksurfaces – Resistance Measurements. The Association lists it as the current worksurface standard test method and states that its purpose is to provide qualification test methods for worksurfaces, including shelving and mobile equipment.

If you need the practical measurement process rather than report interpretation, see our guide on how to test an ESD mat.

First Confirm That the Report Tests the Product You Are Buying

A technically correct test method does not compensate for the wrong test sample.

Before reviewing resistance values, compare the report with the quotation.

Check:

• Product model
• Material
• Rubber, NBR, vinyl, or other construction
• Single-layer, two-layer, or multilayer design
• Thickness
• Color
• Surface finish
• Groundable-point design
• Sample identification
• Manufacturer or applicant
• Test date
• Report number

For example, suppose your quotation is for:

2 mm two-layer ESD rubber mat

but the submitted report identifies:

3 mm vinyl worksurface

The resistance result may be valid for the tested sample, but it is weak evidence for the product you are purchasing.

The buyer should be able to build this connection:

Quoted product → tested sample → test report → production product → delivered batch

This is similar to reviewing material-compliance documents. Our ESD mat material compliance checklist explains how RoHS, material declarations, product identity, and supporting documents should also match the purchased product.

Check the Exact STM4.1 Edition

Do not accept:

Tested according to ESD standard.

Even this is incomplete:

Tested according to STM4.1.

The report should identify the actual edition.

As of 2026, EOS/ESD Association lists ANSI/ESD STM4.1-2026 as its current worksurface resistance-measurement test method. The 2026 document replaced the older STM4.1-2017 reference now found in many supplier reports and existing product documents.

An older 2017 report should not automatically be rejected.

Instead, ask:

• Is the currently supplied mat still the same construction?
• Has the compound changed?
• Has the layer structure changed?
• Has the groundable-point design changed?
• Does the buyer or project accept the older edition?
• Has the supplier reviewed the report against the current requirement?

The important issue is not report age alone.

It is whether the evidence remains technically relevant to the supplied product.

Rtt, Rpp, Rtg, and Rpgp: Do Not Approve from the Abbreviation Alone

One of the most confusing parts of ESD mat reports is terminology.

Suppliers may write:

• Rtt
• Rtg
• RTG
• Rpp
• Rpgp
• RTGP
• Point-to-point
• Point-to-ground
• Point-to-groundable point
• Surface-to-ground

These terms should not be treated as automatically interchangeable.

EOS/ESD Association’s current acronym list distinguishes:

• Rpp — resistance point-to-point
• Rpgp — resistance point-to-groundable point
• Rtg — resistance top-to-ground
• Rtt — resistance top-to-top

More importantly, the ANSI/ESD STM4.1-2026 worksurface qualification structure specifically identifies:

• Resistance – Point to Groundable Point
• Resistance – Point to Point

Therefore:

Do not approve a report because the supplier writes “Rtg PASS.”

First determine what was actually connected and measured.

What Point-to-Point Resistance Tells the Buyer

Point-to-point resistance evaluates resistance between defined locations on the worksurface.

From a purchasing perspective, it helps answer:

Does the surface provide reasonably consistent resistive behavior across the tested area?

Do not focus only on one average value.

Look for:

• Number of samples
• Number of measurement positions
• Individual readings
• Minimum result
• Maximum result
• Average or mean, where reported
• Unexpected outliers

For example:

An average may still look acceptable while one area behaves very differently from the rest.

That is why:

Individual readings are more useful than an average alone.

For a broader explanation of how a dissipative worksurface and grounding path work together, see how ESD mats work.

What Point-to-Groundable-Point Resistance Tells the Buyer

Point-to-groundable-point measurement asks a different question.

Instead of comparing two areas of the mat, it evaluates the resistance path between the worksurface and its designated groundable point under the defined test setup.

That groundable point might be related to:

• A snap
• A terminal
• A grounding connection
• Another designed groundable feature

The report should identify what was used.

This matters because the production mat may have:

• One snap instead of two
• A different snap location
• Different hardware
• A different conductive bottom layer
• A custom-cut configuration
• A different grounding design

A report on one configuration should not automatically be treated as proof for every custom version.

If your project involves custom cutting or moving the grounding point, our guide on what changes after cutting an ESD mat explains why the finished configuration still needs verification.

Test Conditions Matter as Much as the Resistance Number

Two suppliers may send these results:

Supplier A: 4 × 10⁷ Ω
Supplier B: 8 × 10⁷ Ω

It is tempting to compare the numbers directly.

That can be misleading if the test conditions are different.

ANSI/ESD STM4.1-2026 includes specific sections covering test equipment, electrodes, resistance-measurement apparatus, specimen preparation and conditioning, cleaning, and low-humidity environment requirements.

A useful report should therefore identify enough test information for the reader to understand how the result was obtained.

Check:

• Temperature
• Relative humidity
• Conditioning
• Sample preparation
• Cleaning condition
• Test voltage used
• Measurement equipment
• Electrode configuration
• Test locations

A resistance value without its test conditions is weaker evidence.

Why Relative Humidity Deserves Special Attention

Humidity can influence the resistive behavior of many materials and surfaces.

For that reason, a buyer should not compare two supplier reports only from the final resistance values if the tests were performed under different environmental conditions.

Ask:

Were both products tested at comparable temperature and relative humidity?

The STM4.1-2026 document explicitly includes a low-humidity environment within specimen preparation and conditioning, which confirms that environmental conditions are part of worksurface qualification methodology rather than a minor reporting detail.

For bulk purchasing, a good report should state the actual test environment rather than only:

Room condition.

Check Sample Conditioning and Cleaning

Another common omission is sample condition.

Ask whether the tested sample was:

• New
• Cleaned before testing
• Conditioned before testing
• Tested after a defined environmental exposure
• Tested immediately after manufacturing
• Tested after storage

Why does this matter?

A worksurface covered with:

• Flux residue
• Oil
• Cleaner film
• Dust
• Process contamination

may behave differently from a clean qualification sample.

STM4.1-2026 includes specific sections for cleaning and specimen preparation/conditioning.

If your workstations regularly use IPA, flux remover, oils, or solvents, this becomes even more important. See our ESD worksurface chemical resistance guide for how chemical exposure and post-exposure resistance verification should be treated separately.

Test Voltage, Meter, and Electrodes Should Be Identified

Buyers do not need to become laboratory technicians.

However, the report should show that the measurement setup is controlled.

Useful fields include:

• Resistance meter manufacturer/model
• Test voltage used
• Electrode type
• Electrode identification
• Calibration status
• Calibration date
• Laboratory or testing organization
• Test procedure reference

EOS/ESD Association guidance notes that resistance measurement equipment used in ESD programs must cover the relevant high-resistance ranges and that ESD resistance measurements commonly use controlled test voltages.

The procurement question is not:

Which meter brand is best?

The better question is:

Can the buyer identify the instrument, electrodes, setup, and calibration control behind the reported result?

Test Method and Pass Limit Are Not the Same Thing

This is one of the most important points in the entire report.

ANSI/ESD STM4.1 tells you how the worksurface resistance is qualified.

It should not automatically be treated as the source of every project pass/fail resistance limit.

EOS/ESD Association describes STM4.1 as a qualification test method for worksurfaces. ANSI/ESD S20.20, the organization’s ESD control-program standard, remains a separate document; its current listed edition is ANSI/ESD S20.20-2021.

Think about it this way:

ESD Association guidance commonly describes protective worksurfaces in a controlled resistance-to-ground range and S20.20 qualification requirements set defined upper resistance requirements for relevant worksurfaces. Those requirements should be read from the applicable program/specification rather than invented from the test-method title alone.

Therefore, this statement is weak:

STM4.1 PASS: 5 × 10⁷ Ω.

A better report identifies:

Measurement method + actual reading + acceptance requirement + result.

Do Not Assume “Lower Resistance Is Better”

An ESD worksurface is intended to support controlled static management.

The objective is not simply to achieve the lowest possible ohm value.

EOS/ESD Association describes protective worksurfaces as providing an electrical path for controlled charge dissipation and discusses worksurface resistance in the context of an ESD control system.

The correct question is:

Does the worksurface meet the resistance requirement defined by the applicable ESD control program?

Not:

Which supplier has the lowest resistance number?

This is why resistance data should always be compared against the same:

• Requirement
• Measurement type
• Test conditions
• Product construction

Individual Results Are More Valuable Than “Average: PASS”

A weak report may show:

Average resistance: 6.8 × 10⁷ Ω
PASS

That hides several important questions.

Ask:

• How many specimens were tested?
• How many locations were measured?
• What was the lowest reading?
• What was the highest reading?
• Were all readings within the requirement?
• Was one unusual result excluded?
• Were different samples taken from the same production batch?

For supplier qualification, request individual values whenever practical.

A useful format looks like:

This allows the buyer to see consistency rather than only a summary.

Qualification Report vs Installed Workstation Verification

A supplier test report and a site verification record perform different jobs.

Supplier qualification report

It helps show that the product design performed as a worksurface under defined qualification conditions.

Installed workstation verification

It checks the actual system after installation, including:

• Mat
• Groundable point
• Ground cord
• Common point ground
• Bench configuration
• Contamination
• Actual environment

Therefore:

A supplier qualification report does not replace your site’s ESD compliance-verification program.

Your existing ESD workbench mat guide explains why mat selection, grounding, workstation setup, and ongoing verification should be managed as one system.

ESD Mat Test Report Review Table

Common ESD Test Report Red Flags

“PASS” Without Actual Values

The buyer cannot judge consistency or margin to the requirement.

STM4.1 Without an Edition

The report does not show which version of the test method was used.

Old STM4.1 Report Presented Without Explanation

A 2017 report may still be useful, but current product equivalence and project acceptance should be checked against the current 2026 publication.

Rtg Is Not Defined

The buyer does not know whether the supplier means top-to-ground, point-to-groundable-point, or another internal test setup.

Humidity Is Missing

Environmental conditions cannot be compared with another supplier’s report.

Test Voltage Is Missing

The measurement setup is incomplete.

Only an Average Is Provided

Local variation may be hidden.

Product Thickness or Construction Is Missing

The report may not prove the quoted mat.

Groundable-Point Design Is Different

The electrical path in the tested configuration may differ from the supplied product.

No Equipment or Calibration Information

Measurement control cannot be evaluated properly.

STM4.1 Is Used as a Universal Pass Range

The test method and the project acceptance requirement have been confused.

Weak Report vs Better Report

Weak Report

Product: ESD Mat
Standard: STM4.1
Resistance: 10⁷ Ω
Result: PASS

This leaves too many unanswered questions.

Better Report

A stronger report identifies:

• Product model
• Material
• Layer construction
• Thickness
• Groundable-point configuration
• ANSI/ESD STM4.1 edition
• Measurement type
• Sample quantity
• Test locations
• Temperature
• Relative humidity
• Conditioning
• Test voltage
• Meter
• Electrodes
• Calibration status
• Individual readings
• Minimum result
• Maximum result
• Average result
• Applicable acceptance criterion
• Report number
• Test date
• Issuing organization

This is a procurement-content example, not a substitute for the actual standard or laboratory report format.

What Buyers Should Request Before Bulk Purchase

Before approving a large ESD mat order, ask for:

• Product datasheet
• Exact product model
• Material and layer construction
• Thickness
• ANSI/ESD STM4.1 test report
• Standard edition
• Point-to-point results
• Point-to-groundable-point results where applicable
• Temperature and humidity
• Sample conditioning information
• Test equipment information
• Individual readings
• Acceptance criteria
• Report number and date
• Product marking or batch identification
• Material compliance documents where required
• Chemical-exposure data where relevant
• Certificate of Conformity for the approved order

For general product sourcing, buyers can review our ESD and anti-static mat product category.

How We Review an ESD Mat Test Report

When we receive a buyer requirement or review supplier evidence, we use a fixed sequence.

We Confirm the Exact Product

We match material, thickness, construction, surface, and grounding design.

We Check the STM4.1 Edition

We identify whether the evidence refers to the current 2026 edition or an older report.

We Identify the Measurement Type

We do not rely on Rtt or Rtg abbreviations without checking how the report defines them.

We Review Test Conditions

We check temperature, humidity, sample conditioning, and cleaning condition.

We Review Test Equipment

We look for the meter, electrodes, test voltage, and calibration information.

We Check Individual Readings

We review the actual values rather than only the reported mean.

We Confirm the Acceptance Requirement

We separate the measurement method from the ESD control-program or buyer acceptance limit.

We Compare the Report with the Quoted Construction

A report for another thickness, material, or layer structure should be clarified.

We Confirm the Groundable-Point Design

The tested electrical path should match the supplied worksurface configuration.

We Check Traceability Before Production

Report reference, sample identity, product specification, and order documents should form one evidence chain.

FAQ

What is the current ANSI/ESD STM4.1 edition?

EOS/ESD Association currently lists ANSI/ESD STM4.1-2026 as its worksurface resistance-measurement test method.

What does Rtt mean on an ESD mat report?

EOS/ESD Association defines Rtt as resistance top-to-top. For formal STM4.1 worksurface qualification, the current standard uses point-to-point terminology. Always check the report’s own measurement definition.

Is Rtg the same as point-to-groundable-point resistance?

Do not assume that it is. ESDA distinguishes Rtg, resistance top-to-ground, from Rpgp, resistance point-to-groundable point. The report should state the actual connection arrangement.

Does STM4.1 define the ESD mat pass limit?

STM4.1 is primarily the worksurface qualification measurement method. The applicable acceptance requirement should be identified from ANSI/ESD S20.20, the buyer’s ESD control program, or another project specification.

Why should humidity be shown on the report?

Environmental conditions are part of worksurface qualification. STM4.1-2026 specifically includes sample conditioning and a low-humidity environment within the test method.

Is an average resistance result enough?

It is better to review individual readings, test locations, and minimum/maximum values as well. An average can hide local variation across the material.

Should a 2017 STM4.1 test report be rejected?

Not automatically. Check whether the supplied product still matches the tested design, whether your project accepts the older edition, and whether any differences from STM4.1-2026 need additional evidence.

Can a supplier test report replace onsite ESD verification?

No. Supplier qualification evidence evaluates the product under controlled conditions. The installed workstation still includes its actual ground point, cord, common ground, environment, contamination, and operating conditions.

Should an ESD mat be retested after chemical exposure?

If IPA, flux cleaner, oils, or solvents are significant to the process, post-exposure resistance verification can help confirm that the worksurface still meets the required ESD performance.

Practical Buyer Summary

Do not approve an ESD mat because a report says:

10⁷ Ω — PASS.

Instead, confirm:

• Which product was tested
• Which STM4.1 edition was used
• Whether the measurement is point-to-point or point-to-groundable-point
• How Rtt or Rtg is defined
• Test voltage
• Temperature
• Relative humidity
• Conditioning
• Cleaning condition
• Number of samples
• Test locations
• Individual readings
• Minimum and maximum values
• Applicable acceptance limit
• Test equipment
• Calibration
• Groundable-point design
• Report number and date
• Product and batch traceability

The most useful evidence chain is:

Product identity → test method → measurement type → test conditions → actual results → acceptance requirement → traceability → bulk purchase approval

A professional ESD mat report should allow the buyer to answer all of these questions without relying on a single resistance value or a vague “ESD compliant” statement.

For the next stage after supplier qualification, use our ESD mat resistance and grounding verification guide to understand how the installed worksurface should be checked in the actual workstation.