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 APCD 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 APCD 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 APCD first reviews a "pretest report" that lists the equipment and procedures the consultant intends to use to perform the test. The APCD recommends any changes needed to ensure that the results of the test will be acceptable for comparison to the emission limits. An APCD 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 APCD, 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 APCD for compliance testing are available.  Additional information regarding application of visible emissions data to Vermont's opacity time-exception regulation is available in USEPA's proposed Method F-1. Please note that this is a large (5.7 megabyte) file.

Information:

• Source Emission Testing Guidelines (.doc)
• Source Emission Testing Guidelines (.pdf)
• USEPA Proposed Method F-1 (note: 5.7 megabyte file).

last updated 4/5/06