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Monitoring of Source Emission Testing

Taking a sample of pollutants from a stack or vent is usually the most direct, and often the only, way of determining if a source's emissions comply with regulations or with the limits set in a permit. Emission, or "stack", testing may be required when a new piece of equipment is installed, or when a new or revised permit is issued. Or, a facility may be required to routinely perform emission testing every two or three years. Stack tests are complex: test equipment and procedures vary widely depending on the pollutants being measured. Due to the difficulty of the procedures and expense of the equipment, stack tests are normally performed by a professional consultant who specializes in this type of work and is hired by the facility doing the test. Occasionally, the AQCD conducts research projects to determine the contribution of emissions from a particular type of source to the overall levels of pollution in Vermont. In this case the AQCD hires the testing consultant and the facilities involved in the test are volunteer participants. 

An example of some of the equipment that is used to conduct stack testing. This meter console is used in particulate tests.
This console holds instruments to measure gaseous emissions. Calibration gas cylinders are also present. This equipment is typically installed in a trailer which is hauled to the job site.
Sample extraction equipment. Scaffolding to provide access to the exhaust stack and support the sampling equipment is frequently required.

(The photographs above are by David Manning. They are for illustration purposes and do not constitute an endorsement of the manufacturers).

In a typical stack test program, the AQCD first reviews a "pretest report" that lists the equipment and procedures the consultant intends to use to perform the test. The AQCD recommends any changes needed to ensure that the results of the test will be acceptable for comparison to the emission limits. An AQCD staff member will then visit the site during the testing to observe the operation of the equipment being tested and the testing procedures actually used by the consultant. Finally, a report of the test results is filed with the AQCD, typically within about 30 days after completion of the test.

Written guidelines regarding the use of stack test procedures and data handling conventions required by the AQCD for compliance testing are available. 



last updated 8/23/13


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