Principles of Sampling and Analysis

The components of an air pollution monitoring system include the collection or sampling of pollutants both from the ambient air and from specific sources, the analysis or measurement of the pollutant concentrations, and the reporting and use of the information collected. Emissions data collected from point sources are used to determine compliance with air pollution regulations, determine the effectiveness of air pollution control technology, evaluate production efficiencies, and support scientific research.

The EPA Office of Research and Development (ORD) has developed Federal Reference Methods (FRMs) and Federal Equivalent Methods (FEMs) for sampling and analysis of pollutants in the ambient air and from emissions sources. As technology changes, EPA updates and revises these methods. FRMs and FEMs can be either manual or automated. Manual methods are specific techniques that must be followed when collecting and analyzing an air pollutant sample. An automated method usually refers to an instrument that has been approved by EPA as meeting the technical requirements for accurate collection and analysis of a pollutant. In the monitoring stations used throughout the country, automated methods are primarily used to collect and analyze ambient air on a continuous basis.

The EPA has established ambient air monitoring methods for the criteria pollutants, as well as for toxic organic (TO) compounds and inorganic (IO) compounds. The designated ambient methods for the criteria pollutants are listed on the EPA Ambient Monitoring Technology Center's (AMTIC) Ambient Air Monitoring Methods for Criteria Pollutants Web page. In addition, the TO Compendium contains standardized methods for monitoring VOC's and selected toxic organics, and the IO Compendium contains methods for monitoring inorganic compounds.

The methods specify precise procedures that must be followed for any monitoring activity related to the compliance provisions of the Clean Air Act. These procedures regulate sampling, analysis, calibration of instruments, and calculation of emissions. The specific method chosen for an analysis depends on a number of factors, the most important being the chemical characteristics and state of the pollutant. All the reference methods are designed to determine the actual concentration of a pollutant in a sample. The concentration is expressed in terms of mass per unit volume, usually micrograms per cubic meter (µg/m3).

More information for sampling and analysis of pollutants in the ambient air can be found at http://www.epa.gov/ttn/emc/