Montana Air Permits

Air permits & authorizations

• Montana Air Quality Permit (MAQP)

  Minor NSR

  Preconstruction permit required before constructing, installing, or altering a facility above the MAQP threshold. DEQ states MAQPs do not expire. DEQ lists typical processing of roughly 75 to 90 days for a complete application.

  Thresholds (summarized from source, not a quotation)

  Facilities with the potential to emit more than 5 tons per year of lead or more than 25 tons per year of any other airborne pollutant, and any incinerator, need an MAQP unless exempt (restated from DEQ's air permitting assistance page).

  ARM 17.8 Subchapter 7 (ARM 17.8.743)Official page

• De minimis changes

  Exemption

  Certain small changes at permitted facilities may proceed without a permit modification if they meet the de minimis criteria; DEQ requires advance notice of the change.

  Thresholds (summarized from source, not a quotation)

  DEQ's page states the owner/operator must notify DEQ at least 10 days before beginning a de minimis change (restated).

  ARM 17.8.745Official page

• Registration: Oil and gas well facilities

  Registration / Notice

  Oil and gas well facilities that would otherwise need an MAQP may register instead of permitting. Title V sources are not eligible. See the Oil and Gas section.

  Thresholds (summarized from source, not a quotation)

  Oil and gas well registration: for well facilities with potential emissions above 25 tons per year, constructed after November 23, 1968; Title V sources are not eligible; due within 60 days of initial well completion (restated from DEQ).

  ARM 17.8 Subchapter 17 (ARM 17.8.1701-17.8.1713)Official page

• Registration: Nonmetallic mineral processing (crushers and screeners)

  Registration / Notice

  Portable and stationary crushing and screening operations may register under the registration rules instead of obtaining an MAQP, subject to eligibility and production limits in the rule.

  ARM 17.8 Subchapter 18 (ARM 17.8.1802)Official page

• Registration: Concrete batch plants and asphalt plants

  Registration / Notice

  DEQ lists registration options for concrete batch plants and asphalt plants, with associated fees and production limits.

  ARM 17.8 Subchapter 18Official page

Major NSR (PSD & nonattainment)

• Prevention of Significant Deterioration (PSD)

  PSD

  Major source preconstruction review in attainment areas. DEQ's PSD web section was marked 'under construction' on the review date; consult the rule text.

  ARM 17.8 Subchapter 8Official page

Title V operating permits

• Title V Operating Permit

  Title V

  Operating permit for major sources. Permits have a 5-year term; renewal applications are due at least 6 months before expiration.

  Thresholds (summarized from source, not a quotation)

  Potential to emit more than 100 tons per year of any criteria pollutant, more than 10 tons per year of any single hazardous air pollutant, or more than 25 tons per year of combined hazardous air pollutants (restated from DEQ's page).

  ARM 17.8 Subchapter 12Official page

Oil & Gas

Montana lets oil and gas well facilities register with DEQ in place of an MAQP. Eligibility, timing, and exclusions are in the registration program entry. Federal NSPS OOOO/OOOOa/OOOOb and NESHAP HH may also apply.

• Oil and Gas Well Facility Registration

  Registration / Notice

  Registration in lieu of an MAQP for qualifying oil and gas well facilities. DEQ lists a registration fee and an annual fee; see the fee schedule.

  Thresholds (summarized from source, not a quotation)

  Register within 60 days of initial well completion; DEQ lists a $500 registration fee and $850 annual fee (restated; confirm in the current fee schedule). Oil and gas well registration: for well facilities with potential emissions above 25 tons per year, constructed after November 23, 1968; Title V sources are not eligible; due within 60 days of initial well completion (restated from DEQ).

  ARM 17.8.1701, 17.8.1703, 17.8.1704Official page

State air regulations

• ARM Title 17, Chapter 8Air Quality (Administrative Rules of Montana)
• ARM 17.8 Subchapter 7Permit, Construction, and Operation of Air Contaminant Sources (MAQP)
• ARM 17.8 Subchapter 8Prevention of Significant Deterioration of Air Quality
• ARM 17.8 Subchapter 12Operating Permit Program (Title V)
• ARM 17.8 Subchapter 17Registration of Air Contaminant Sources: Oil and Gas Well Facilities
• ARM 17.8 Subchapter 18Registration of Air Contaminant Sources: Nonmetallic Mineral Processing and other portable sources
• Title 75, Chapter 2, MCAClean Air Act of Montana

Forms

• Stationary Source MAQP Application (2025)
• Oil and Gas Registration Form
• Oil and Gas Registration Instructions

Guidance

• DEQ Air Permitting Assistance

Compliance

State compliance obligations (reporting, emissions inventory, testing) are being indexed. Use the Compliance dashboard preview to see how they will be tracked.

Sources

• Montana DEQ Air Permitting Assistance
• EPA CAA Permitting in Montana