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Definitions

Point Sources
The major point source emissions categories are power plants, industrial boilers, petroleum refineries, industrial surface coatings and chemical manufacturing industries. Point sources' emissions are generated from stack emissions. Since most of the records are kept in AIRS/AFS, the point sources information is readily available for developing a control strategies, tracking and implementation of the State Implementation Plans (SIP). For SIP inventory purposes, the point source emission cutoff is 10 tons per year for VOC and 100 tons per year for NOx and CO sources. For VOC sources emitting 10 tons per year or more, base year inventory emissions must be determined from each facility.
Area Sources
Area sources are those emissions that are too small to be treated as point sources. Area sources' emissions can be generated from solvents used for surface coating operation, degreasing, graphic arts, dry cleaning and gasoline station (tank truck unloading and refueling). Area sources are the activities where aggregated source emissions information is maintained for the entire source categories instead of each point source, and are reported at the county level.
Mobile Sources
Mobile sources are categorized for highway and off-highway sources. The highway sources include the automobile, buses truck and other vehicle traveling on local and highway roads. The emission from highway vehicles represents one third of the overall national volatile organic compounds (VOC) and 40 percent of the overall nitric oxide (NOx) emissions. Highway emissions are calculated using MOBILE models. States must present highway mobile source emissions by pollutant (VOC, NOx and CO) and by individual nonattainment county. Off-highway sources are any mobile combustion sources such as railroads, marine vessel, off-road motorcycle, snowmobiles, farm, construction, industrial and lawn/garden equipment. Emissions are determined based on a source activity variable. Activity levels for each off-highway category must be developed using EPA guidance documents.
Actual Emissions
The annual "actual" emissions which have been estimated or calculated for a plant in the State Emission Inventory, added to those annual emissions that have been removed by the application of a control factor.
Allowable Emissions
Maximum emissions for a pollutant that a plant or a source is allowed to discharge into the atmosphere legally.
Potential Controlled Emissions
Pollutant emissions while operating at the maximum design capacity, a schedule of 8760 hours per year and considering the efficiency of the pollution control equipment.
Potential Uncontrolled Emissions
Pollutant emissions while operating at the maximum design capacity and a schedule of 8760 hours per year.

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