Minor source facilities located in the eastern third of Iowa (counties listed below) must submit their Minor Source Emission Inventory (MSEI) for calendar year 2024 emissions by May 15, 2025. If your facility is required to complete this year’s report, you will receive a letter from DNR.
A complete air pollutant inventory is required by 567 Iowa Administrative Code (IAC) sub rule 21.1(3). DNR uses the data collected from an emissions inventory to identify emission levels and trends throughout the state, track Iowa's progress towards meeting national air quality standards, and develop control and maintenance strategies required by the federal Clean Air Act.
The MSEI is required to be submitted using the State and Local Emissions Inventory System (SLEIS). The only exceptions are for group 2 grain elevators, concrete batch plants, crushing plants, and hot mix asphalt plants that use specialized forms or standardized online spreadsheets for emissions reporting. These forms and spreadsheets may continue to be used. The DNR offers several resources to assist facilities with emission inventories:
- SLEIS - Online emissions reporting tool: https://programs.iowadnr.gov/sleis
- SLEIS training dates and links to register: eAirServices
- Instructions, forms, and example calculations: gov/minorsourceforms
- Emissions estimate tools (including spreadsheets for many processes): gov/eetools
- Exemptions, FAQs, and tips to complete the inventory: gov/minorsources
- Facilities with less than 100 employees may also contact the Iowa Air Emissions Assistance Program (IAEAP) at the University of Northern Iowa for free training and assistance. For more information, please visit https://msei.iwrc.org.
Please note that EPA recently required DNR to change several data elements in SLEIS from optional to mandatory. These changes may result in additional data validation errors that must be fixed prior to submitting the inventory. The new required fields are:
- Maximum Hourly Design Rate and Maximum Hourly Design Rate Unit of Measure Code for several types of combustion units or for facilities under a specific NAICS code, such as landfills
- If actual emissions are calculated using a stack test, the date of the stack test is now required
These changes will be discussed in the 2025 SLEIS training sessions.
For questions related to the emissions inventory, please contact:
Below is a list of Eastern Iowa counties included in the 2024 Minor Source Emissions Inventory:
In north-eastern Iowa, DNR Field Office 1 region: Allamakee, Benton, Black Hawk, Bremer, Buchanan, Chickasaw, Clayton, Delaware, Dubuque, Fayette, Howard, Jackson, Jones, Linn, and Winneshiek.
In south-eastern Iowa, DNR Field Office 6 region: Cedar, Clinton, Davis, Des Moines, Henry, Iowa, Jefferson, Johnson, Keokuk, Lee, Louisa, Muscatine, Scott, Van Buren, Wapello, and Washington.