Regulation update

Stack Testing Standards in 2026: What Changed, What Didn't, and What to Verify Before You Sign

EPA's core stack testing methods haven't been overhauled, but the accreditation standard behind Air Emission Testing Body certification was just withdrawn, PFAS test methods are moving fast, and two more standards bodies are mid-revision. Here is what a procurement team should confirm before signing with a vendor.

By Inspection Vendor Index Editorial Team · Published 2026-07-11 · Updated 2026-07-11

Related category: Environmental Stack Testing Providers

The EPA method baseline hasn't moved, but the reporting rules have

The working core of stack testing is still the EPA reference method set in 40 CFR Part 60 Appendix A (with parallel methods in Part 61 Appendix B and Part 63 Appendix A): Methods 1 through 5 for velocity, moisture, molecular weight, and particulate, the 3-series for O2 and CO2, and the rest of the numbered methods that make up a standard performance test. Title 40 stays current through periodic Federal Register amendments (the eCFR shows amendments through mid-2026), and EPA folded a round of corrections and updates into the general testing provisions used across Parts 51, 60, and 63 through a final rule effective May 30, 2023. What has actually changed is how results get reported, and the direction is toward more digital submission rather than a single new mandate. Many individual NSPS and NESHAP subparts already require electronic submission of performance test data to EPA's Compliance and Emissions Data Reporting Interface (CEDRI) through the Electronic Reporting Tool (ERT), a requirement EPA has been building into new and revised subparts for roughly a decade. Separately, EPA signed a cross-media notice on September 17, 2024 that took effect September 25, 2024, and that notice allows, but does not require, entities regulated under 40 CFR Parts 59 through 63 to submit performance test reports, Notification of Compliance Status reports, and periodic reports that were previously paper-only in digital format to CEDRI as well; digital submission under this specific notice is optional. EPA keeps adding ERT report templates for specific rules, for instance templates for the Hazardous Organic NESHAP and the Synthetic Organic Chemical Manufacturing NSPS were added in May 2024. A vendor's proposal should say plainly whether they handle CEDRI/ERT submission as part of the scope of work for any subpart where it is required, because a technically sound test report that never makes it into CEDRI in an acceptable format is a compliance problem the buyer inherits. Separately, EPA issues a recurring Federal Register notice, 'Recent Postings of Broadly Applicable Alternative Test Methods,' cataloging alternative methods approved the prior year (the most recent one found for this piece is dated May 28, 2025 and covers methods approved in 2024). If a buyer's permit or subpart allows an alternative method for cost or logistics reasons, this notice is the place that gets checked, and a vendor who tracks it proactively is doing part of the buyer's compliance homework for them. Finally, 2026 brought subpart-specific test and monitoring changes worth checking against a facility's actual source category: a final rule on Large Municipal Waste Combustors (effective May 11, 2026) revised emission limits and streamlined recordkeeping and reporting, a January 2026 New Source Performance Standards review for stationary combustion turbines revised the nitrogen oxide best-system-of-emission-reduction determination and added new capacity-factor and efficiency-based subcategories on top of technical corrections to the older subparts, and an April 2026 reconsideration of the Oil and Natural Gas Sector rules changed vent gas net heating value continuous monitoring requirements and alternative performance test options for flares and enclosed combustion devices. None of these rewrite the Appendix A method library, but each one changes testing or monitoring detail for its specific source category.

PFAS testing is the fastest-moving edge of the method set

The one part of this space that is not standing still is per- and polyfluoroalkyl substances (PFAS) testing. EPA's Other Test Method 45 (OTM-45) uses liquid chromatography-tandem mass spectrometry to target several dozen polar, semi-volatile PFAS compounds, including PFOA and PFOS, from stationary source air emissions. EPA revised OTM-45 in July 2024, adding pre-sampling standards to improve measurement quality, clarifying when lab materials containing PTFE (a fluoropolymer) can be used without contaminating results, and modifying test conditions for GenX chemicals. More recently, EPA posted a draft companion method, OTM-50, for sampling and analyzing volatile fluorinated compounds from stationary sources using passivated stainless-steel canisters, extending PFAS air testing beyond the original LC-MS/MS scope. The procurement detail that matters here: OTM-45 and OTM-50 are 'Other Test Methods,' not codified Appendix A methods. A source cannot substitute one for a required method just because it exists. Using either one still runs through the same alternative-method approval pathway as any other substitute method, whether that is a site-specific waiver or reliance on a broadly-applicable approval already published by EPA. For a buyer in an industry facing PFAS scrutiny (landfills, chemical manufacturing, metal finishing, biosolids handling, and similar categories), the honest question to ask a prospective vendor is whether they have actually run OTM-45 in the field and on what instrumentation, not whether PFAS testing appears as a bullet point on their capabilities page. ASTM's Subcommittee D22.03, the same group that produced D7036, also lists PFAS and microplastics in air among the areas under active development, so more codified test methods in this space are plausible in the next few code cycles.

The accreditation standard behind AETB certificates was just withdrawn

ASTM D7036, Standard Practice for Competence of Air Emission Testing Bodies, is the quality management system standard against which stack testing firms (Air Emission Testing Bodies, or AETBs) have been accredited for roughly two decades. The Stack Testing Accreditation Council (STAC) began accrediting AETBs against it in 2007. In 2014, STAC signed a memorandum of understanding with A2LA (the American Association for Laboratory Accreditation): A2LA administers the actual assessment process, conforming to ISO/IEC 17011 (the standard that governs accreditation bodies), while STAC retains technical oversight, sets requirements for assessors, and participates in A2LA's Accreditation Council through its own Technical Assessment Board. Certificates are issued jointly. A2LA's AETB program, run in partnership with the Source Evaluation Society (SES), lets a firm be assessed to D7036 alone, or combine that assessment with ISO/IEC 17025:2017 for ILAC-endorsed accredited status under A2LA's environmental field of testing. Here is the twist a lot of capabilities pages have not caught up with: ASTM's own product listing shows D7036-16, the last active edition (from Subcommittee D22.03), as withdrawn in 2025. A search of public sources for this piece did not turn up a confirmed successor standard. This creates a real compliance gap, not a paperwork footnote. D7036-04, an earlier edition, is incorporated by reference into 40 CFR 75.6, tied to the Part 75 continuous emissions monitoring quality assurance provisions referenced in 75.21 and Appendix A. A withdrawn ASTM standard sitting inside a still-active federal incorporation-by-reference is exactly the kind of gap that creates ambiguity for accreditation bodies and for sources that lean on AETB accreditation to satisfy Part 75 QA obligations. Until that gap gets formally resolved, the safest move for a buyer is to not take 'STAC/A2LA accredited' at face value on a vendor's website. Ask which edition and framework the current certificate is actually issued against, and confirm directly with A2LA or STAC that the accreditation is active and recognized by the buyer's permitting authority.

ISO/IEC 17020 and TNI are mid-revision on the lab and field-sampling side

Two more standards relevant to this category are also moving right now, on a different track from D7036. ISO/IEC 17020, the international standard covering the competence, impartiality, and consistent operation of inspection bodies, was revised and published in March 2026, replacing the 2012 edition. The headline change is a simplification of the old three-tier independence classification (Type A, B, and C) down to two tiers, Type A and Type non-A, alongside more risk-based thinking, added flexibility in requirements, and new provisions on data and information control. The revision is also being aligned in structure and terminology with ISO/IEC 17025 and 17065. A roughly three-year transition window, 2026 to 2029, applies before the 2012 edition is fully retired. This matters here because A2LA runs a separate Inspection Body Accreditation Program under ISO/IEC 17020, alongside its AETB program, so any firm or accreditation body using the 17020 route for part of its scope has a transition assessment to plan for inside that window. On the laboratory side, TNI (The NELAC Institute) is mid-revision on its own standards. The Environmental Laboratory Sector Volume 1 standard, modeled on ISO/IEC 17025 and the basis for NELAP lab accreditation, had a draft revision to Module 5 (Microbiological Testing) out for public comment as of January 2025, with a separate draft revision to Module 2 (Quality Management System) posted for public comment later, in 2026. TNI has also been finalizing a new standard, Field Sampling and Measurement Organization (FSMO) Volume 1 General Requirements, the NEFAP accreditation route for field sampling and measurement organizations. A response-to-comments on the FSMO Volume 1 draft was posted March 19, 2026, and TNI then posted a new FSMO accreditation standard in mid-April 2026, so the standard moved from draft to newly issued within the same year. A2LA and other accreditation bodies already list FSMO accreditation programs, and a buyer should confirm with TNI or the relevant accreditation body which edition a specific FSMO accreditation is currently issued against. Why this matters for a stack testing buyer specifically: a single field crew is often doing sample collection and, depending on the pollutant, handing samples off for laboratory analysis. That means a testing firm's overall qualification picture can span three separate accreditation lanes at once, AETB accreditation for the stack test itself, NELAP lab accreditation for any samples sent out for analysis, and FSMO accreditation for the field sampling portion under TNI's newly issued standard, each governed by a different standards body on its own revision schedule.

What to verify before you sign

None of the above is a reason to stall a procurement decision, but it is a reason to ask sharper questions than 'are you accredited.' Before contracting with a stack testing provider: ask for the firm's current AETB accreditation certificate and confirm directly with A2LA or STAC that it is active, given the D7036 withdrawal noted above. Ask which individual field team leads hold SES QSTI or QSTO certification, and in which methods group (manual particulate and isokinetic sampling, manual gaseous pollutants, instrumental gaseous methods, hazardous metals, or Part 75 CEMS RATA), since that is a person-level credential distinct from the firm's own accreditation. SES publishes a $200 per-methods-group exam fee for QSTI/QSTO candidates, who must show at least a year of relevant experience or ten field tests performed or observed in that method area, so it is a real, checkable credential rather than a marketing claim. Confirm CEDRI/ERT reporting capability as part of the scope of work: many subparts already mandate electronic submission, and a September 2024 EPA notice separately allows, without requiring, digital CEDRI submission for Parts 59 through 63 reports that were previously paper-only. If the facility's processes touch PFAS-relevant pollutants, ask specifically about OTM-45 field experience and whether OTM-50 is on the vendor's roadmap. And if any part of the scope touches Part 75 CEMS quality assurance, ISO/IEC 17020-based inspection body accreditation, or TNI's newly issued FSMO standard, ask how the vendor's accreditation body is handling the 2026-2029 ISO 17020 transition and the open D7036 question together, since a permitting authority may eventually ask for documentation on both. This is procurement information, not compliance or legal advice. Confirm applicability to a specific facility, permit, and jurisdiction with environmental counsel or the agency that holds permitting authority before making a testing decision.

Key takeaways

EPA's core Part 60/61/63 Appendix A stack testing methods remain the working baseline. Many individual NSPS/NESHAP subparts already require electronic performance-test submission to EPA's CEDRI portal via the Electronic Reporting Tool, and a September 2024 EPA notice (effective September 25, 2024) separately made CEDRI submission an optional path, not a new mandate, for Parts 59 through 63 reports that were previously paper-only. EPA also issues a recurring Federal Register notice cataloging newly approved alternative test methods.
PFAS air testing (EPA's OTM-45, revised July 2024, plus a newer draft companion canister method, OTM-50) is the fastest-moving part of the method set, and both remain case-by-case 'Other Test Methods' rather than blanket-approved Appendix A procedures.
ASTM D7036, the quality management standard the Stack Testing Accreditation Council (STAC) and A2LA have used to accredit Air Emission Testing Bodies since 2007, shows as withdrawn in ASTM's own catalog as of 2025, with no confirmed successor standard turning up in public sources.
ISO/IEC 17020, the standard behind A2LA's separate inspection-body accreditation route, was revised in March 2026 with a roughly three-year transition window (2026 to 2029). TNI's new Field Sampling and Measurement Organization standard for field crews was still in a response-to-comments stage as of March 19, 2026, but TNI posted a new FSMO accreditation standard in mid-April 2026, so buyers should confirm current status directly rather than assume it is still in draft.
Firm-level accreditation (AETB/D7036) and individual-level certification (SES QSTI/QSTO) are two different things. A buyer should confirm both before assuming a vendor is qualified for a specific method group.

FAQ

Is ASTM D7036 still required for a stack testing firm to call itself accredited?

D7036 (Standard Practice for Competence of Air Emission Testing Bodies) is the quality management standard STAC and A2LA have used to accredit Air Emission Testing Bodies since 2007. ASTM's own product catalog lists the last active edition, D7036-16, as withdrawn in 2025, and a search of public sources for this piece did not turn up a confirmed successor standard. Ask A2LA or STAC directly what standard backs a specific vendor's current certificate rather than assuming the old citation still applies.

Does a stack testing vendor need to prove PFAS testing capability?

Only if the facility's processes or permit conditions put PFAS air emissions in scope. EPA's current PFAS air methods are OTM-45 (revised July 2024) and a newer draft companion method, OTM-50, for canister-based sampling. Both are 'Other Test Methods,' meaning they require case-specific or broadly-applicable alternative-method approval rather than blanket use under 40 CFR 60.8, 61.13, or 63.7(f). Ask for actual field experience with OTM-45, not just a line item on a capabilities list.

What is the difference between a firm's AETB accreditation and an individual tester's SES certification?

AETB accreditation, historically assessed against ASTM D7036 through STAC and A2LA, certifies the testing company's quality management system as a whole. The Source Evaluation Society's QSTI/QSTO program certifies an individual field team leader's competence in a specific methods group: manual particulate and isokinetic sampling, manual gaseous pollutants, instrumental gaseous methods, hazardous metals, or Part 75 CEMS RATA work. A firm can hold accreditation while a specific crew lead lacks QSTI certification in the exact methods group your test requires, so ask about both levels separately.

Editorial process Compiled from primary standards, codes, and regulatory sources, then adversarially fact-checked against those sources. Not written or reviewed by a licensed engineer or safety professional. Procurement education, not safety or legal advice.

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