EPA Air · stack tests by county and year
Air-emissions stack tests in Yellowstone County, Montana, 2026
- 22Stack 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 2026. 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, 2026
Air-emissions stack tests in Yellowstone County, other years
Air-emissions stack tests recorded in Yellowstone County, Montana, 2026
| Date | Facility | Kind | Agency |
|---|---|---|---|
| 2026-08-17 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-13 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-13 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2026-08-13 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2026-08-13 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2026-08-11 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-05 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-05 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-05 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-04 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-08-04 | CHS INC REFINERY LAUREL | Fail | State |
| 2026-06-24 | PAR MONTANA BULK TERMINAL | Pass | State |
| 2026-05-18 | YELLOWSTONE POWER PLANT — high-priority violation on file | Pass | State |
| 2026-05-07 | YELLOWSTONE POWER PLANT — high-priority violation on file | Pass | State |
| 2026-05-07 | BILLINGS TRANSPORTATION OPERATIONS | Pass | State |
| 2026-04-27 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-04-27 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-04-27 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-04-27 | CHS INC REFINERY LAUREL | Pass | State |
| 2026-02-17 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2026-01-29 | PAR MONTANA BILLINGS REFINERY | Pass | State |
| 2026-01-07 | BILLINGS REFINERY | Pass | State |
Dates as filed by the agency that recorded the stack test. Figures from EPA’s ICIS-AIR download.