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U.S. EPA Proposes Changes to Condensable Particulate Matter Test Methods

04.01.2009

By Andy Bowman, Attorney, Bingham Greenebaum Doll LLP

On March 25, 2009, the U.S. EPA published notice of a proposed rule to modify the methods for measurement of condensable particulate matter (CPM) during stack testing. 74 Federal Register 12969 (March 25, 2009). CPM is material that is in vapor stage at stack conditions but which condenses upon cooling and dilution in the ambient air to form particulate matter (PM) immediately after discharge from the stack. U.S. EPA is proposing to change Method 201A to include the capability of measuring fine particulate matter (PM2.5) and to modify Method 202 to provide for more accurate measurement of the condensable component of PM2.5 and course PM (PM10). A particle-sizing cyclone will be added to the sampling train under Method 201A. Method 202 will be changed to make certain currently optional procedures mandatory. U.S. EPA believes that the revised Method 202 will reduce the formation of sulfuric acid artifacts by at least an additional ninety percent, allow greater consistency among testing contractors, improve precision of the method and provide for more accurate quantification of direct PM emissions.

During the promulgation of the Clean Air Fine Particle Implementation Rule (72 Federal Register 20586) in 2007, U.S. EPA acknowledged problems with the current Method 202. U.S. EPA found that some stack testing contractors were inappropriately applying sampling hardware and optional analytic procedures which could lead to inaccurate CPM measurements. In addition U.S. EPA determined that SO2 could be absorbed during use of Method 202 resulting in sulfuric acid artifacts being erroneously counted as CPM. As a result, U.S. EPA established a transitional period for States to develop emission limits for condensable PM2.5 which ends January 1, 2011. After January 1, 2011 States are required to consider inclusion of CPM emissions in new or revised emission limits. U.S. EPA allows each State to determine whether or not and at what time it is appropriate to revise existing facility emission limits or operating permits to incorporate information from the revised CPM test method once it becomes final.

U.S. EPA believes that the use of the proposed changes to Method 202 will likely result in reduced levels of CPM emissions measured at a source compared to the existing method. However, there may be cases where the revised test method results in higher measurements of condensable particulate matter due to changes in the way sample water is evaporated.

Key changes to Method 202 include replacing the wet impingers with dry impingers and requiring the use of an out-of-stack low-temperature filter. A one-hour nitrogen purge of the impinger water is now required to remove SO2 before it can form sulfuric acid artifacts. In the event the revised test methods are finalized, sources will need to evaluate whether their operating permits will require modification.

U.S. EPA is taking comments on the proposed changes to the test methods through May 26, 2009. Comments can be submitted at www.regulations.gov under Docket ID No. EPA-HQ-OAR-2008-0348. U.S. EPA is also taking comments on whether the transition period should end earlier than January 1, 2011 for purposes of new source review.

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