EPA Air · stack tests by county and year
Air-emissions stack tests in Yellowstone County, Montana, 2025
- 52Stack tests
A stack test measures what a source actually emits, at the stack, against the limit in its permit. Each row below is one stack test recorded against a source in Yellowstone County, Montana during 2025. A facility can appear several times: this is the year’s record of what happened, not a list of places. The sources themselves are on the Yellowstone County facility page.
Yellowstone County, Montana, 2025
Air-emissions stack tests in Yellowstone County, other years
Air-emissions stack tests recorded in Yellowstone County, Montana, 2025
| Date | Facility | Kind | Agency |
|---|---|---|---|
| 2025-12-12 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | Pass | State |
| 2025-12-12 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-12-04 | BILLINGS REFINERY | Pass | State |
| 2025-11-18 | YELLOWSTONE COUNTY GENERATING STATION | Pass | State |
| 2025-11-13 | BILLINGS REFINERY | Pass | State |
| 2025-10-28 | BILLINGS REFINERY | Pass | State |
| 2025-10-28 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-28 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-28 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-10 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-10-09 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-09-02 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-09-02 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-22 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-13 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-13 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-08 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-08 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-08 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-06 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-06 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2025-08-04 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-07-22 | PAR MONTANA BULK TERMINAL | Pass | State |
| 2025-07-02 | YELLOWSTONE POWER PLANT — high-priority violation on file | Pass | State |
| 2025-05-30 | YELLOWSTONE POWER PLANT — high-priority violation on file | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-05-01 | CHS INC REFINERY LAUREL | Pass | State |
| 2025-04-25 | YELLOWSTONE POWER PLANT — high-priority violation on file | Pass | State |
| 2025-04-25 | YELLOWSTONE POWER PLANT — high-priority violation on file | Pass | State |
| 2025-01-20 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | Pass | State |
| 2025-01-20 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | Pass | State |
| 2025-01-14 | WESTERN SUGAR COOPERATIVE — high-priority violation on file | Pass | State |
Dates as filed by the agency that recorded the stack test. Figures from EPA’s ICIS-AIR download.
What this page shows
This page covers stack tests at Clean Air Act facilities in the EPA air register in Yellowstone county, MT, for 2025. It lists 52 stack tests recorded in 2025.