Condensable Particulate Matter (CPM)

Condensible Particulate Matter (CPM) Testing Issues & Procedure

When testing particulate matter emission sources in North Carolina, you are required to include testing for condensible particulate matter when determining particulate matter emission rates. New rules were developed and promulgated to incorporate quantification of condensible emission testing and are located in Section .2600 of DAQ's rules. These rules became effective on June 1, 2008.

Specifically the rules are as follows:

(a) With the exception allowed under Paragraph (b) of this Rule, Method 5 of Appendix A of 40 CFR Part 60 and Method 202 of Appendix M of 40 CFR Part 51 shall be used to demonstrate compliance with particulate emission standards. The owner or operator may request an exemption from using Method 202 and the Director shall approve the exemption if the Director determines that the demonstration compliance with an applicable emission standard is unlikely to change with or without the Method 202 results included.

These rules may be found in 02D .2609.

Emission standards, with limits which have been established based upon filterable particulate matter emissions, may use the filterable results data to report compliance with those standards. This, however, does not mean that testing need not include both filterable and condensible particulate matter testing. As noted in the regulation, the Director will provide an exemption from the condensible testing requirement as long as a source owner or operator demonstrates that the condensible fraction is unlikely to change the result of the compliance determination. This exemption may be requested for individual sources or categories of sources.

EPA has promulgated fine particulate testing methods (PM₁₀ and, more recently PM_2.5) and condensible particulate matter emission measurement methods under 40 CFR 51, Appendix M. Reference Method 202 is the method specified in North Carolina's regulations for use in determining condensible particulate emissions. EPA made significant changes to the original Method 202 and retired the wet impinger method and replaced it with a split temperature controlled dry impinger method to address concerns with artifact formation in the impinger water. NC DAQ is currently approving only those testing protocols which use the latest version of Reference Method 202 (promulgated December 2010).

Background

Particulate matter is defined as: any material except uncombined water that exists in a finely divided form as a liquid or solid at standard conditions. Standard conditions are 20° C (68° F) and 760 mm Hg atmospheric pressure. By their nature, condensible particulate matter may exist as a liquid or solid at standard conditions in the ambient atmosphere, but not at some elevated temperature or significantly different pressure conditions. Since it is under standard conditions that the National Ambient Air Quality Standards (NAAQS) for particulate matter is set and is regulated by the states and territories under their state implementation plans (SIPs), the presence of condensible particulate can be a concern.

The original particulate source test methods proposed on August 17, 1971 included measurement of filterable particulate ("front-half" emissions) and condensible particulate emissions ("back-half" emissions) in part for New Source Performance Standards (NSPS) and for states developing their initial SIPs. The method included a filter maintained at a nominal 250° F for filterable particulate and a series of impingers to capture condensible particulate and moisture drawn into the sampling train. In addition,, the proposed test method included additional steps to extract condensible organics though a sequence of ethyl ether and methyl chloroform extraction of the captured liquids as well as drying of the remaining 'water catch" to be counted as inorganic condensible particulate matter.

Prior to June 1, 2008, North Carolina testing requirement referred to the use of this method for determining particulate matter emissions. Although EPA went on the define the particulate emission control standards of the NSPS by the filterable emission rate, EPA kept the requirements for states to include both front and back-half testing and emission standards for their initial SIP submittals.

Over time, less attention was placed upon the condensible particulate matter emissions and it became common practice to test and report the filterable emissions using the impinger catch only to determine stack moisture content. This changed when EPA changed the focus from total suspended particulate matter to PM₁₀ (more recently EPA has also added PM_2.5 as a pollutant of concern and established NAAQS for them). It is likely that condensible particulate matter occurs in these size ranges for the fine particulate matter and condensibles are, therefore, a greater concern.

EPA has subsequently promulgated fine particulate testing methods (PM₁₀ and, more recently PM_2.5) and condensible particulate matter emission measurement methods under 40 CFR 51, Appendix M. Reference Method 202 is the method specified in North Carolina's regulations for use in determining condensible particulate emissions. EPA made significant changes to the original method 202 and retired the wet impinger method and replaced it with a split temperature controlled dry impinger method to address concerns with artifact formation in the impinger water that were not "real" emissions but rather a reaction product that occurred as a result of the testing methodology. NC DAQ is currently approving only those testing protocols which use the latest version of Reference Method 202.

Historical information

Historical CPM memoranda on issues concerning condensible particulate matter emissions measurements.