Air Resources and Publications

Opportunity for public comments.

Guidance Documents

• Licensing Acronyms (.docx) - A list of acronyms/abbreviations that may be used in processing Air Emissions Licenses.
• NESCAUM BACT Guidance (pdf, offsite) - Guidance for determining BACT from the Northeast States for Coordinated Air Use Management (NESCAUM)
• State of Maine BACT Guidance (.docx) - Summary of general requirements when preparing a BACT analysis for the Maine DEP
• Construction Guidance (.docx) – Information on what construction activities may take place prior to issuance of an air emission license.
• Reminder to Obtain an Air Emission License Prior to Beginning Construction of a New or Modified Source (.pdf) – Memo dated July 29, 2024
• NMMPP FAQ (pdf) - Frequently Asked Questions about Nonmetallic Mineral Processing Plants (Rock Crushers)
• Temporary Insignificant Activities (.docx) - Guidance on what equipment is eligible to be considered a temporary insignificant activity and the process for requesting approval
• Clean Air Act Section 176A Petition (.docx) – Frequently Asked Questions about implementation of Maine’s approved Clean Air Act Section 176A Petition
• Chapter 138, NOx RACT – Frequently Asked Questions about implementation of revisions to this rule effective May 7, 2025

Guidance Specific to Engines

• Inclusion in Applications (.pdf) - When to include portable engines in Air Emission License applications.
• Modeling Guidance (.pdf) - When to exempt stationary internal combustion engines from a modeling analysis if used for maintenance, stand-by, or emergency use.
• QAISA Guidance (.docx) - When and how to submit a Qualitative Ambient Impact Screening Analysis (QAISA) pursuant to Chapter 169.
• Very Small Engine (.docx) - Guidance on requirements for stationary engines smaller than licensing thresholds
• Mineral Processing Industry Engines (.pdf) – Article on the difference between stationary and portable engines.

Additional Compliance Resources are available on our Air Compliance webpage.

Reports

• Air Emissions Inventory Data - Maine DEP provides summaries of criteria air pollutant and greenhouse gas emissions inventories, as well as other inventory products, through its FTP site. Please view the readme.txt file for a full description of available information.
• Annual Air Monitoring Plan
• Five Year Assessment of Ambient Air Monitoring Network (pdf)
• Department Reports