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Potential To Emit and Source Category

The type of permit any particular source needs will be determined by its potential to emit (PTE) and source category, its types of equipment and operations, and the area’s air quality where it is located.


Determining the PTE is often the most challenging part of the air permitting process. It is a calculation of the regulated pollutants a source could potentially release to the air if it were to operate 24 hours a day, 365 days a year, at full capacity, without air pollution controls. PTE is compared with emissions thresholds to determine what type of air permit a source must have, unless the source is subject to requirements based on its source category.

Source Category

U.S. EPA identifies applicable regulations for industry sectors. For example, there are New Source Performance Standards (NSPS) that set certain requirements for new or modified sources and Halogenated Solvent Cleaning - National Emissions Standards for Hazardous Air Pollutants (NESHAPs) that set requirements for specific industries in limiting the release of hazardous air pollutants (HAP).

The North American Industry Classification System (NAICS) and Standard Industrial Classification (SIC) codes are used to identify establishments by type of activity(ies). SIC codes are used for IDEM permits. The U.S. Occupational Health and Safety Administration (OSHA) provides an SIC search. IDEM does not assign SIC codes but can assist applicants in determining their SIC code(s).

The type of air permit a source must have can also be dependent on its industry source category as follows:

  • A Registration is required for a source that is subject to 326 IAC 20-8 (Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks) and consists of only decorative chromium electroplating tanks that use a trivalent chromium process that incorporates a wetting agent.
  • A Minor Source Operating Permit (MSOP) (or higher level permit based on PTE) is required for a source consisting of a chromium electroplating tank, chromium anodizing tank, or an operation subject to 326 IAC 20-8.
  • A Minor Source Operating Permit (MSOP) (or higher level permit based on PTE) is required for a source that includes medical waste incinerators subject to 40 CFR 60, Subpart Ec.
  • A Minor Source Operating Permit (MSOP) (or higher level permit based on PTE) is required for a source that has a PTE (before controls) equal to or greater than one ton per year of lead or lead compounds measured as elemental lead and operates one of the following types of facilities:
    • A primary lead smelter;
    • A secondary lead smelter;
    • A primary copper smelter;
    • A lead gasoline additive plant; and
    • A lead-acid storage battery manufacturing plant that produces 2,000 or more batteries per day.
  • A Part 70 operating permit is required for a certain sources that are subject to a New Source Performance Standards (NSPS) under 40 CFR Part 60 or a National Emissions Standards for Hazardous Air Pollutants (NESHAP) in 40 CFR Part 61 or 40 CFR Part 63 that requires the source to apply for a Part 70 operating permit.

For sources (or nested sources) belonging to one of the source categories listed in 326 IAC 2-7-1(22)(B), the fugitive emissions of all regulated pollutants must be included in the PTE. These source categories include:

  • The following source categories (normally referred to as the list of 28 source categories):
    1. Coal cleaning plants (with thermal dryers);
    2. Kraft pulp mills;
    3. Portland cement plants;
    4. Primary zinc smelters;
    5. Iron and steel mills;
    6. Primary aluminum ore reduction plants;
    7. Primary copper smelters;
    8. Municipal incinerators, or combinations of municipal incinerators, capable of charging more than fifty (50) tons of refuse per day;
    9. Hydrofluoric acid plants;
    10. Sulfuric acid plants;
    11. Nitric acid plants;
    12. Petroleum refineries;
    13. Lime plants;
    14. Phosphate rock processing plants;
    15. Coke oven batteries;
    16. Sulfur recovery plants;
    17. Carbon black plants (furnace process);
    18. Primary lead smelters;
    19. Fuel conversion plants;
    20. Sintering plants;
    21. Secondary metal production plants;
    22. Chemical process plants;
    23. Fossil fuel boilers (or combination thereof) totaling more than two hundred fifty million (250,000,000) British thermal units per hour heat input;
    24. Petroleum storage and transfer units with a total storage capacity exceeding three hundred thousand (300,000) barrels;
    25. Taconite ore processing plants;
    26. Glass fiber processing plants;
    27. Charcoal production plants;
    28. Fossil fuel fired steam electric plants of more than two hundred fifty million (250,000,000) British thermal units per hour heat input;
  • Any other stationary source category regulated under Section 111 or 112 of the Clean Air Act (CAA) and for which the U.S. EPA has made an affirmative determination under Section 302(j) of the CAA. These sources categories include all source categories that are regulated under the New Source Performance Standards (NSPS) or National Emissions Standards for Hazardous Air Pollutants (NESHAP) as of August 7, 1980.

These source categories include asphalt plants, glass manufacturing plants, grain elevators, and automobile or light-duty truck coating at assembly plants. For a list of source categories regulated by an NSPS or NESHAP prior to August 7, 1980, see Table A-2 of U.S. EPA’s Draft New Source Review Workshop Manual [PDF].

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