Test frequency plans

Please note MPCA compliance staff may not change a testing schedule already established in a permit which typically requires a major permit amendment. The following is only guidance which the MPCA reserves the right to deviate from based on the consideration of additional factors such as compliance history, previous test results, stringency of limit, use of emission factor, etc.

While some permits require initial performance testing only, others require performance testing on a set schedule determined by the initial performance test. If you are required to test on a set schedule after your initial test, you should have a permit requirement to submit a test frequency plan after conducting your initial performance tests. After a test frequency plan is submitted to the MPCA, Performance Testing staff review the proposed test frequency and issue a review letter. If it is evident that problems exist with the equipment a more stringent testing frequency may be required. The testing frequency defined in the MPCA review letter becomes effective when it is received by the facility and will be incorporated into the facility’s permit in the next permit amendment.

A facility may request to relax a testing frequency if there is adequate historical information suggesting that the testing frequency could be reduced. Typically, adequate historical information consists of data from three or more performance tests. Below is MPCA guidance for establishing a testing frequency for emission limit testing.

Test result minus permit limit expressed as percentage of limit:

Then:

Test Result ≥ 90% of limit

Performance Test due every 12 months

60% ≤ Test Result < 90% of limit

Performance Test due every 36 months

Test Result < 60% of limit

Performance Test due every 60 months

A permit may have an emission limit to avoid a specific permitting or applicability threshold (usually a 12-month rolling sum limit). Demonstration of compliance with the limit may be done by calculating emissions using an emission factor.

The permit may also require testing to verify and/or update the emission factor, as well as submittal of a test frequency plan for future testing to update the emission factor. Unlike emission limit and control efficiency testing where a large margin of compliance is desirable, the desirable outcome of emission factor testing is a test result that is close as possible to the current emission factor. Based on this concept, the following is proposed guidance for emission factor testing frequency:

Absolute value of test result minus permit emission factor expressed as percentage of emission factor (see equation below):

Then:

X ≥ 40% of permit emission factor

Performance Test due every 12 months

10% ≤ X ≤ 40% of permit emission factor

Performance Test due every 36 months

X < 10% of permit emission factor

Performance Test due every 60 months

Note: Guidance not intended for use in revising emission factors assumed when doing ambient air analyses, risk analyses, or other pre-permit issuance analyses only for emission factor testing frequency for emission factors used to calculate emissions to avoid a permitting threshold.


X = | T-A |/ A x 100%
A = permit emission factor
T = emission factor measured during test