Regulatory Update   |   Jun 7th, 2018 New EPA Method Improves Measurement of Condensable Particulate Matter

Trc Epa Otm 37

After extensive collaboration with the emissions measurement community, the Environmental Protection Agency last month unveiled a new, improved method for measuring condensable particulate matter (CPM) using dilution sampling – Other Test Method 37 (Measurement of PM2.5 and PM10 Emissions at Low Concentrations by Dilution Sampling). CPM forms after the plume exits the emissions source and is very difficult to measure.  The dilution approach mimics particulate formation after exiting the stack by mixing the sampled stack gas with cool, dry air and allowing a residence time for the particles to form and grow.

OTM-37 incorporates the dilution sampling approach established in Conditional Test Method 39 (Measurement of PM2.5 and PM10 Emissions by Dilution Sampling) and applies more sensitive ambient air gravimetric sampling and analysis methods to the diluted and cooled source gas sample to achieve greater sensitivity.

Importantly, OTM-37 overcomes the problems associated with the formation of artifact particulate matter in the Method 202 (Dry Impinger Method for Determining Condensable Particulate Matter Emissions from Stationary Sources) sampling train.  Artifact formation in CPM measurements has long been identified as an important source of bias in these measurements and modifications to Method 202 has reduced, but not eliminated the bias.  OTM-37 takes an entirely new approach to sampling and collecting condensable particulate that removes this bias.

Improving Measurements at Lower Levels

The proper application of OTM-37 enables sources to measure and report emissions at lower levels without the positive bias associated with Method 202.  Improved CPM measurement is a significant development for sources looking to expand operations or renew Title V operating permits.

Since 2011, regulatory agencies have been required to account for CPM when establishing emission limits for both PM2.5 and PM10 in Prevention of Significant Deterioration (PSD) and New Source Review (NSR) permitting.  Further, Title V permits require counting of CPM for PM2.5 and PM10 emissions. OTM-37, with improved measurement sensitivity and the ability to overcome the positive bias of Method 202, may yield CPM measurement data that simplifies and streamlines new source permitting and Title V permit renewals.

Lower CPM measurements mean that it is easier to meet previously established particulate matter emission limits. Further, lower CPM measurements mean that when obtaining a new permit (PSD, NSR, or Title V), calculated emission rates will be lower, making it easier to model National Ambient Air Quality Standards (NAAQS) compliance at the fence line or beyond. TRC has provided valuable field-based feedback to the EPA to assist the agency in developing the new sampling methodology and to the OTM-37 equipment manufacturer to help them design and operate the sampling equipment. We would welcome the opportunity to discuss the application of our OTM-37 measurement experience to your CPM measurement or permitting challenge. Visit to learn more about our air emissions testing services.

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