Frequently Asked Questions: Stack Tests

What is a stack test?

Most air pollution emissions from an industry exit the facility through a stack (also known as a smokestack). Scientific tests can sample a portion of the exhaust gas and determine concentrations of the pollutants emitted. When the DNR is unsure of the concentration of pollutants in the exhaust gas or when a facility needs to demonstrate it is complying with specific emission limitations, the Department can require a facility to sample its exhaust gas by using a stack test. The facility must hire a private firm which will propose a test plan to the Department and schedule the test. During the test, a Department representative may witness the procedure. A formal report documenting all testing data and results must be submitted to the Department within 60 days after completion of the test. The results of this stack test plus operation schedules allow the facility and the Department to calculate air pollutant emissions on an annual and hourly basis.

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