Under the federal Clean Air Act (CAA), the following definitions of key Title V terms apply:

Major source

Any stationary source, or group of stationary sources that are located on one or more contiguous or adjacent properties and that are under the control of the same person(s), belonging to a single major industrial grouping (all pollutant-emitting activities belong to the same major group and have the same two-digit Standard Industrial Classification (SIC) code as described in the 1987 edition of the SIC Manual) and that is:

Defined as a major source under Section 112 of the CAA.

A major stationary source of air pollutants, as defined in Section 302 of the CAA, that directly emits or has the potential to emit (PTE) 100 tons per year (tpy) or more of any air pollutant subject to regulation, including any major source of fugitive emissions of any pollutant subject to regulation. Fugitive emissions should not be considered in determining whether a source is a major stationary source under the CAA unless that source belongs to one of the following categories:

• Coal cleaning plants (with thermal dryers);
• Kraft pulp mills;
• Portland cement plants;
• Primary zinc smelters;
• Iron and steel mills;
• Primary aluminum ore reduction plants;
• Primary copper smelters;
• Municipal incinerators capable of charging more than 250 tons of refuse per day;
• Hydrofluoric, sulfuric, or nitric acid plants;
• Petroleum refineries;
• Lime plants;
• Phosphate rock processing plants;
• Coke oven batteries;
• Sulfur recovery plants;
• Carbon black plants (furnace process);
• Primary lead smelters;
• Fuel conversion plants;
• Sintering plants;
• Secondary metal production plants;
• Chemical process plants (except for ethanol production facilities that produce ethanol by natural fermentation and that are included in North American Industry Classification System (NAICS) code 325193 or 312140);
• Fossil fuel boilers totaling more than 250 million British thermal units (Btu) per hour heat input;
• Petroleum storage and transfer units with a total storage capacity exceeding 300,000 barrels;
• Taconite ore processing plants;
• Glass fiber processing plants;
• Charcoal production plants;
• Fossil fuel-fired steam electric plants of more than 250 million Btu per hour heat input; or
• Any other stationary source category regulated under Section 111 or 112 of the CAA.

A major stationary source as defined in Part D of Title I of the CAA, including:

• For ozone nonattainment areas (NAAs), sources with the PTE 100 tpy or more of volatile organic compounds (VOCs) or nitrogen oxides (NOx) in areas classified or treated as marginal or moderate, 50 tpy or more in areas classified or treated as serious, 25 tpy or more in areas classified or treated as severe, and 10 tpy or more in areas classified or treated as extreme. This condition does not apply to sources noted under CAA Section 182(f);
• For ozone transport regions established under Section 184 of the CAA, sources with the PTE 50 tpy or more of VOCs;
• For carbon monoxide (CO) NAAs, those that are classified or treated as serious and those in which stationary sources contribute significantly to CO levels with the PTE 50 tpy or more of CO; and
• For PM10 NAAs classified or treated as serious, sources with the PTE 70 tpy or more of PM10.

Regulated air pollutant

• NOx or any VOCs;
• Any pollutant for which National Ambient Air Quality Standards (NAAQS) have been established;
• Any pollutant subject to New Source Performance Standards (NSPS) under Section 111 of the CAA;
• Any Class I or Class II substance subject to a standard under or established by Title VI of the CAA; and
• Any hazardous air pollutant (HAP) subject to a standard or requirement under Section 112 of the CAA.

Note: Greenhouse gases (GHGs) are “subject to regulation” if a stationary source emits or has the PTE at least 100,000 tpy carbon dioxide equivalent (CO2e) emissions. GHGs are defined as the aggregate group of these six gases:

• Carbon dioxide (CO2),
• Nitrous oxide (N2O),
• Methane (CH4),
• Hydrofluorocarbons (HFCs),
• Perfluorocarbons (PFCs), and
• Sulfur hexafluoride (SF6).

Stationary source

Any building, structure, facility, or installation that emits or may emit any regulated air pollutant or any HAP listed under Section 112(b) of the CAA.

Governing laws and regulations:
40 Code of Federal Regulations (CFR) 70.2