Frequently Asked Questions

Stack Testing

What is a Compliance Stack Test?

A compliance stack test is a stack emissions measurement performed following the procedures specified and developed by the US EPA. Such testing is required by DES to be conducted by various stationary sources in the state to determine compliance with the applicable air emission limits. Approximately 50 stack tests are performed each year, all which are coordinated and witnessed by a DES representative. A typical compliance stack test will consist of three one- to two- hour measurement runs (at maximum representative plant operating conditions) where concentration measurements are taken of the compound of interest, as well as stack flow, oxygen/carbon dioxide, and water concentrations. Generally speaking, each stack test requires: (1) the submission of a pretest protocol report presenting the stack test program description; and (2) a pretest meeting to be held approximately 2 weeks prior to the test date in order to comprehensively plan for the test. DES is involved in all aspects of the testing and technically reviews and approves the final test report that shows the emission results. For more information on stack testing requirements please refer to PART Env-A 802, COMPLIANCE STACK TESTING FOR STATIONARY SOURCES.

When is a compliance stack test needed?

A compliance stack test is required if any one of the following applies:

• A stationary source is subject to the Federal New Source Performance Standards and the standard requires stack testing.
• A stationary source is subject to a state rule which requires stack testing.
• It is determined that the emission rate estimated using available technical data is close to the threshold above which a violation of the ambient air limit or emission standard might occur.
• A stationary source is opting out of a Federal permitting program and DES needs verification of the emissions in order to ensure the source is below those limits.
• There is a technical concern that an emission limit may be exceeded.

Depending on the situation or applicable regulation requirements, the stack test can be a one time only requirement or can be required at regular intervals (i.e. once every three years, etc.).

Does the Division charge for its time spent in observing/ coordinating a Compliance Stack Test?

For those sources required to perform stack testing as part of the conditions of a temporary permit, a charge is imposed which covers expenses incurred for the engineer's time and travel in witnessing the stack test and reviewing the final stack test report.
For stack testing performed for all other situations (e.g., Title V permit or operating permit requirement), no charge is imposed on the facility.