Major vs. Minor Sources

Regarding construction permits

If the source is located in an area that has attained minimum federal air quality standards (an attainment area), the source is considered major when it has the potential to emit:

1. more than 250 tons per year of a regulated air pollutant, or
2. more than 100 tons per year of a regulated air pollutant IF the source is classified as a:

• fossil-fuel-fired steam electric plant or boiler exceeding 250 million BTUs/hour heat input, coal cleaning plant (with thermal dryer), kraft pulp mill, portland cement plant, primary zinc smelter, iron or steel mill plant, primary aluminum ore reduction plant, primary copper smelter, municipal incinerator capable of charging more than 250 tons of refuse per day, hydrofluoric, sulfuric, or nitric acid plant, petroleum refinery, lime plant, phosphate rock processing plant, coke oven battery, sulfur recovery plant, carbon black plant (furnace process), primary lead smelter, fuel conversion plant, sintering plant, secondary metal production plant, chemical process plant, petroleum storage or transfer unit with a storage capacity exceeding 300,000 barrels, taconite ore processing plant, glass fiber processing plant, or charcoal production plant.

Regarding construction permits

If the source is located in an area that has NOT attained minimum federal air quality standards (a non-attainment area), the source is considered major if it emits 100 tons per year or more of any regulated air contaminant except ozone. Ozone non-attainment areas may have lower thresholds for volatile organic compounds and nitrogen oxides, depending on the severity of the pollution.

Regarding operation permits

Any source that has the potential to emit 100 tons per year or more of any criteria air pollutant is a major source and must obtain a Title V operating permit.

Major/minor distinctions are different for hazardous air pollutants. Facilities are considered major sources if they have the potential to emit 10 tons per year of any one federally listed hazardous air pollutant or 25 tons per year of any combination of hazardous air pollutants.