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Stack test method OTM-50 announced to measure PFAS in air emissions

Stack test method OTM-50 announced to measure PFAS in air emissions

There is now a way to measure nonpolar volatile fluorinated compounds (VFCs), including per- and polyfluoroalkyl substances (PFAS), in air emissions. In late January, the Environmental Protection Agency (EPA) posted Other Test Method 50 (OTM-50), which addresses sampling and analysis methodologies to measure VFCs and short-chain PFAS compounds in air emissions from stationary sources. This long-awaited new test method can be used to collect and analyze samples in passivated stainless-steel (SUMMA®) canisters. The method is intended to complement OTM-45 (which measures polar semi-volatile organic compounds) and increase the type and number of PFAS compounds that can be measured in air.

What are the implications of this new test method?

You may be wondering what implications this new testing method will have on your facility. Here are a few key considerations:

  • A significant driver in developing OTM-50 was to determine a more complete picture of PFAS emissions from stationary sources. The targeted constituents of this method may be the products of incomplete combustion (PICs) or incomplete destruction (PIDs) of PFAS compounds targeted by OTM-45.

  • While OTM-50 is not an EPA-approved test method and has not been subject to federal rulemaking, it can be considered for use in determining PFAS emissions from stationary sources. The test method is intended to assist the EPA, states, and industry in gathering more comprehensive data on PFAS air emissions, which are expected to inform future rulemaking.

  • With the recent release of OTM-50, the analytical laboratory industry is rapidly developing needed procedures and analytical standards to commercialize routine validation of data for fluorinated compounds detected using OTM-50.

How important is it to verify the data collected from this test method?

Based on our experience with OTM-45, comprehensive data analysis and data review are imperative to successfully implement OTM-50 and produce valid results. Barr’s longstanding practice of validating data from our partner labs has consistently produced reliable, verified results. As the use of OTM-50 becomes commonplace, it becomes even more critical to work with a consultant that not only understands the testing protocol but also has the experience providing quality control and assurance from reported data.

What was Barr’s role in influencing testing method development?

Since the early 2000s, Barr has been at the leading edge of PFAS stack testing method development, with our research influencing the development of OTM-45. During recent PFAS stack tests, Barr collected and provided samples to the EPA’s Office of Research and Development (ORD) to assist in developing OTM-50, providing us with insights into the nuances that come with implementing this method. Barr has used SUMMA® canisters to sample ambient air for decades and has been engaged by numerous clients across industries and around the world for our PFAS stack testing expertise. We continue to contribute to and monitor the development of test methods for PFAS measurement.

Contact our team of PFAS experts for additional information or learn more about Barr’s PFAS services.

About the authors

Tim Russell, vice president and senior chemical engineer, has more than 30 years of consulting industry experience. He established Barr’s air-quality testing practice in the early 1990s and now oversees projects involving stack testing and ambient air monitoring, as well as wind-resource assessments and meteorological monitoring. He has managed or participated in hundreds of stack tests encompassing the full range of EPA test methodologies for clients in the mining, power, forest-products, manufacturing, pharmaceutical, and agricultural sectors. Tim participated in numerous research and engineering test projects, including one in which multimedia testing was used to measure emissions of PFAS; the data were then incorporated into mass balance calculations to characterize emissions across an entire industry. By providing stack-testing training to Barr staff and clients, he creates a shared understanding of methodologies and responsibilities that fosters successful projects.

Adam Driscoll, vice president and senior environmental engineer, has more than 15 years of experience with environmental permitting and compliance, primarily involving petroleum refining, mining, power generation, and manufacturing. He spent three of those years working for a global manufacturing corporation, where he acquired critical experience with environmental permitting, led cross-functional EHS audits, and negotiated issues of noncompliance with regulatory agencies. Adam serves as leader for Barr’s PFAS service offerings and monitors pertinent regulatory updates to inform clients of significant changes and how they apply to them. Adam has also assisted clients in negotiating conditions related to PFAS emissions into Title V air quality permits.

Related projects

PFAS stack testing services for a manufacturing client

A confidential manufacturing client hired Barr to perform compliance testing to evaluate the performance of thermal oxidation as a best available control technology (BACT) to control PFAS emissions from its processes. Barr conducted stack testing for EPA OTM-45, Method 25A hydrocarbons, 26A hydrogen fluoride, and EPA 204 capture efficiency. We wrote the test plan, performed testing, and prepared the report. The test results satisfied all permit requirements. The determination of BACT and incorporation of PFAS emission limits in the permit was among the first such instances in the U.S. and was based on the potential to cause or contribute to surface or groundwater contamination. Our work contributed to the development of OTM-45, published in January 2021 through submission of a separate and complete set of stack samples to EPA-ORD to further method development. Barr’s stack test emissions data has been used as input to air, soil, and hydrogeologic modeling to understand PFAS fate and transport as well as the impact of air emissions on surface and groundwater.

Capture-efficiency testing for ethanol production facility

An ethanol production facility was required to demonstrate that the coarse particulate (PM10) and fine particulate (PM2.5) emissions from its grains-receiving and loadout building were at or below the ambient air quality standards. To meet this requirement, the facility decided to undertake a first-of-its-kind capture-efficiency-testing program rather than face potentially severe operational restrictions. Barr was hired to develop a combined testing and air-dispersion-modeling approach and worked with the client and the regulatory agency to gain approval of the methodology. Our stack testing specialists measured the PM10 and PM2.5 emissions from the building over several days under various operating and weather conditions. The measurements were used to develop site-specific and wind-dependent (speed and direction) emission factors for operations occurring in the building. These factors were then incorporated into an air dispersion model, which demonstrated the facility’s compliance with ambient-air-quality standards.

Air-quality services for steel company

Barr has been testing a confidential steel client’s stack emissions at multiple facilities in Minnesota for a quarter century. In part because of our longstanding service to client, Barr was hired to perform a demanding stack test project at a coke oven works to gather data in response to an EPA Coke Ovens Information Collection Request (ICR). Barr helped the client scope the project in agreement with EPA and industry collaborators and undertook testing at coke oven battery combustion and quench tower sources. We wrote the test plan, performed testing, and prepared the report. Barr mobilized a 10-person team comprising two 14-hour daily shifts in order to test around the clock for 11 consecutive days. According to the EPA, our work product was the sole test report submitted by the industry on time with project deadlines set by the agency.


Tim Russell, Vice President, Senior Chemical Engineer
Tim Russell
Vice President, Senior Chemical Engineer


Adam Driscoll, Vice President, Senior Environmental Engineer
Adam Driscoll
Vice President, Senior Environmental Engineer
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