Which air permit do I need? Where to start

Start with jurisdiction

Air permits are issued by the agency with jurisdiction over the site. In most places that is the state air agency, but some counties and cities run their own air programs, and EPA or a tribe may issue permits on tribal lands. Confirm the agency before reading any rule, because the same equipment can follow different paths in different jurisdictions.

Every AirPermitHub state hub lists the state agency and, where they exist, local agencies with their own permitting authority.

Inventory every emission unit

Permitting decisions are made unit by unit and then added up for the site. List every piece of equipment that emits or could emit an air pollutant, with its make, model, capacity, fuel or material, and construction or modification date. Dates matter because many federal standards apply only to units built or changed after a specific date.

• Combustion: engines, turbines, heaters, boilers, flares
• Storage and loading: tanks, truck and railcar loading
• Process vents, dehydrators, and controls
• Equipment leaks (fugitive components)

Estimate potential to emit

Most applicability questions are answered by comparing the facility's potential to emit (PTE) with the criteria in a rule. PTE is based on maximum capacity under the facility's physical and operational design, not on typical operations. Limits on hours, throughput, or control devices count only when they are enforceable.

Calculate PTE per unit and per pollutant, cite each emission factor, and keep the calculations. The Emission Calculators show every step so a reviewer can reproduce the result.

Look for an existing authorization

An existing permit, registration, or permit-by-rule claim at the site can change the answer. A change may be handled as an amendment, a new registration, or a new permit, depending on the agency's rules. Search the agency's permit records for the site before choosing a path.

Screen the state authorization options

States offer a ladder of options, from exemptions and de minimis levels, through permits by rule, registrations, standard or general permits, to case-by-case construction permits. Each option has eligibility conditions in rule. If the facility is a major source, or a change is a major modification, federal major New Source Review (PSD or Nonattainment NSR) applies through the state's program.

Screen federal standards separately

New Source Performance Standards (40 CFR Part 60) and National Emission Standards for Hazardous Air Pollutants (40 CFR Parts 61 and 63) apply on their own terms, whatever permit path the facility takes. A unit can be exempt from a state permit and still be subject to an NSPS or NESHAP. Check each candidate subpart's applicability section against the unit's type, size, and dates.

Check operating permit requirements

Construction authorization and operating permits are separate questions. Major sources, and some other sources, need a Title V operating permit. Many states also issue state operating permits, including synthetic minor permits that take enforceable limits to stay below major source status.

Confirm with the agency

Many agencies offer pre-application meetings or technical assistance. Bring the inventory, PTE calculations, and the path you think applies. The agency's interpretation governs; AirPermitHub screening results are a starting point, not a determination.