Small Changes Affect Sampling Methods

A team effort determines the most accurate, efficient, cost-effective emission compliance testing.
By Edward “EJ” Juers | May 19, 2015

Particulate matter (PM) emissions are one of the six major criteria pollutants regulated by the U.S. EPA that are controlled and quantified from point sources at industrial facilities to meet air quality standards. While particulate testing is a routine sampling procedure performed during air emission compliance testing, it is important to stay abreast of changes that may affect test planning, pollution control operations and compliance status. As regulations have evolved, new methods used to measure PM have been introduced and modified in an effort to more accurately quantify emissions. Some of these changes may affect facility permit limits and compliance tests. It is important to understand the various types and classifications of particulate matter and the methodologies commonly utilized for PM measurements, as well as changes that may cause issues leading to costly compliance mistakes.

Regulation of particulate matter through the EPA, along with state and local governments, is directed by the federal Clean Air Act, with the goal of preserving and improving the ambient air quality that can affect human health as well as the public welfare through such things as PM’s impact on visibility, buildings, crops, vegetation. Over the course of time, as information on particulate matter and its effects has expanded, regulatory mechanisms have evolved to effectively target and control the more harmful forms of particulate matter (primarily very small particles) as well as total particulate matter measurements used as a surrogate to quantify and control hazardous air pollutants (HAPS).

Various terms and acronyms are used to describe particulate emissions and emission limits, which can vary across different regulatory agencies, so it is imperative that the exact intent of the language is defined and the methodology is clearly determined in the permitting process. PM, PM state, PM federal, PM filterable, condensable PM, TSP, PM10 and PM2.5 are all acronyms that are commonly used in the permitting process, and may imply that one or more test methods needs to be used to measure emissions. Careful navigation through the language and terminology within a facility’s air permit often requires a team effort consisting of facility personnel, test consultants and regulatory authorities, to determine the most accurate, efficient and cost effective means to completing emission tests and assuring compliance.

Dry mill emissions are vented from multiple sources and controlled using a variety of pollution control technologies. Dictated by the type of source, characteristics of the gas streams, required level of control, as well as cost. The table above shows common emission sources and various particulate control devices. Bear in mind that emission control requirements can vary widely between facilities depending upon regional air quality conditions and facility emission limits.

Testing Methods
In the most simplistic form, emission testing to measure particulate matter consists of extracting a known volume of gas through a filter from vents exiting an industrial process through a stack. The particulates collected on the filter are rinsed, dried, weighed and quantified to report the source’s emission rate, which is used to demonstrate compliance with allowable levels set forth in the facility’s air permits. In more complex methodology, additional components are introduced to the sample assembly, such as cyclones or glassware, which may allow for particle size fractionation or measurement of condensable (vapor form) particulate matter. Standard methodologies have been developed to sample specific source types, particulate sizes, and/or conditions present within a given gas stream.

Common test methods used to sample total particulate matter (PM or TSP) are EPA Methods 5 and 17. In addition, state agencies may require total or partial condensable particulate matter to be measured to quantify total PM using methods equal or similar to EPA Method 202. Fine particulate matter test methods targeting PM10 and PM2.5 (particulate with an aerodynamic diameter matter smaller than 10 and 2.5 microns, respectively) are typically measured using EPA Method 201A, when possible, coupled with EPA Method 202. When sampling limitations or test site constraints do not allow for sampling using EPA Method 201A, other arrangements need to be made, such as reverting to a total particulate method (such as EPA Method 5 or 17) and quantifying all particulate as PM10 or 2.5.
The primary points to consider when determining the proper PM sampling methods include the following:

• What needs to be quantified? (PM, PM10, PM2.5, condensable PM, etc.)

•  Does the facility air permit or associated rule(s) require specific methods?

•  Can new methods yield different results than those that were used to develop permit emission limits? If so, what if results are higher?

• Will the chosen method accurately quantify emissions, or are there conditions that may bias the results, prevent the method from being performed properly or meet required quality assurance standards? Examples include high moisture content, uneven flow distribution, high temperatures, improperly sized test ports or inadequate test site design.

• There may be allowable method modifications, but if implemented, how can the results and compliance status be affected?

• Can one single test be performed to meet all needs of a plant’s PM sampling requirements? If so, are there long term considerations and how could it potentially effect reporting and compliance status now and in the future?

All of these questions and points, among others, need to be carefully considered and navigated when determining a sampling strategy for particulate matter. Seemingly subtle changes in methodology or facility operations can have a major impact on test results. The ultimate goal is to complete the sampling in an efficient, accurate manner, in order to prove compliance with the regulatory requirements. This can all be accomplished by thoughtful planning and working with a competent test consultant who can help determine the proper testing methods and bridge communication between regulatory agencies and facility personnel.

Author: Edward “EJ” Juers
Stack Department Manager, Interpoll Laboratories Inc.