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Title 40Chapter ISubchapter CPart 51Subpart A → §51.50

Title 40: Protection of Environment
Subpart A—Air Emissions Reporting Requirements

§51.50   What definitions apply to this subpart?

Aircraft engine type means a code defining a unique combination of aircraft and engine used as an input parameter for calculating emissions from aircraft.

Annual emissions means actual emissions for a plant, point, or process that are measured or calculated to represent a calendar year.

Control measure means a unique code for the type of control device or operational measure (e.g., wet scrubber, flaring, process change, ban) used to reduce emissions.

Emission calculation method means the code describing how the emissions for a pollutant were calculated, e.g., by stack test, continuous emissions monitor, EPA emission factor, etc.

Emission factor means the ratio relating emissions of a specific pollutant to an activity throughput level.

Emission operating type means the operational status of an emissions unit for the time period for which emissions are being reported, i.e., Routine, Startup, Shutdown, or Upset.

Emission process identifier means a unique code for the process generating the emissions.

Emission type means the type of emissions produced for onroad and nonroad sources or the mode of operation for marine vessels.

Emissions year means the calendar year for which the emissions estimates are reported.

Facility site identifier means the unique code for a plant or facility treated as a point source, containing one or more pollutant-emitting units. The EPA's reporting format allows for state submittals to use either the state's data system identifiers or the EPA's Emission Inventory System identifiers.

Facility site name means the name of the facility.

Lead (Pb) means lead as defined in 40 CFR 50.12. Emissions of Pb which occur either as elemental Pb or as a chemical compound containing Pb should be reported as the mass of the Pb atoms only.

Mobile source means a motor vehicle, nonroad engine or nonroad vehicle, where:

(1) A motor vehicle is any self-propelled vehicle used to carry people or property on a street or highway;

(2) A nonroad engine is an internal combustion engine (including fuel system) that is not used in a motor vehicle or a vehicle used solely for competition, or that is not affected by sections 111 or 202 of the CAA; and

(3) A nonroad vehicle is a vehicle that is run by a nonroad engine and that is not a motor vehicle or a vehicle used solely for competition.

NAICS means North American Industry Classification System code. The NAICS codes are U.S. Department of Commerce's codes for categorizing businesses by products or services and have replaced Standard Industrial Classification codes.

Nitrogen oxides (NOX) means nitrogen oxides (NOX) as defined in 40 CFR 60.2 as all oxides of nitrogen except N2O. Nitrogen oxides should be reported on an equivalent molecular weight basis as nitrogen dioxide (NO2).

Nonpoint sources collectively represent individual sources that have not been inventoried as specific point or mobile sources. These individual sources treated collectively as nonpoint sources are typically too small, numerous, or difficult to inventory using the methods for the other classes of sources.

Particulate matter (PM) is a criteria air pollutant. For the purpose of this subpart, the following definitions apply:

(1) Filterable PM2.5 or Filterable PM10: Particles that are directly emitted by a source as a solid or liquid at stack or release conditions and captured on the filter of a stack test train. Filterable PM2.5 is particulate matter with an aerodynamic diameter equal to or less than 2.5 micrometers. Filterable PM10 is particulate matter with an aerodynamic diameter equal to or less than 10 micrometers.

(2) Condensable PM: Material that is vapor phase at stack conditions, but which condenses and/or reacts upon cooling and dilution in the ambient air to form solid or liquid PM immediately after discharge from the stack. Note that all condensable PM, if present from a source, is typically in the PM2.5 size fraction and, therefore, all of it is a component of both primary PM2.5 and primary PM10.

(3) Primary PM2.5: The sum of filterable PM2.5 and condensable PM.

(4) Primary PM10: The sum of filterable PM10 and condensable PM.

(5) Secondary PM: Particles that form or grow in mass through chemical reactions in the ambient air well after dilution and condensation have occurred. Secondary PM is usually formed at some distance downwind from the source. Secondary PM should not be reported in the emission inventory and is not covered by this subpart.

Percent control approach capture efficiency means the percentage of an exhaust gas stream actually collected for routing to a set of control devices.

Percent control approach effectiveness means the percentage of time or activity throughput that a control approach is operating as designed, including the capture and reduction devices. This percentage accounts for the fact that controls typically are not 100 percent effective because of equipment downtime, upsets and decreases in control efficiencies.

Percent control approach penetration means the percentage of a nonpoint source category activity that is covered by the reported control measures.

Percent control measures reduction efficiency means the net emission reduction efficiency across all emissions control devices. It does not account for capture device efficiencies.

Physical address means the location address (street address or other physical location description), locality name, state, and postal zip code of a facility. This is the physical location where the emissions occur; not the corporate headquarters or a mailing address.

Point source means large, stationary (non-mobile), identifiable sources of emissions that release pollutants into the atmosphere. A point source is a facility that is a major source under 40 CFR part 70 for one or more of the pollutants for which reporting is required by §51.15 (a)(1). This does not include the emissions of hazardous air pollutants, which are not considered in determining whether a source is a point source under this subpart. The minimum point source reporting thresholds are shown in Table 1 of Appendix A.

Pollutant code means a unique code for each reported pollutant assigned by the reporting format specified by the EPA for each inventory year.

Release point apportionment percent means the average percentage(s) of an emissions exhaust stream directed to a given release point.

Release point exit gas flow rate means the numeric value of the flow rate of a stack gas.

Release point exit gas temperature means the numeric value of the temperature of an exit gas stream in degrees Fahrenheit.

Release point exit gas velocity means the numeric value of the velocity of an exit gas stream.

Release point identifier means a unique code for the point where emissions from one or more processes release into the atmosphere.

Release point stack diameter means the inner physical diameter of a stack.

Release point stack height means physical height of a stack above the surrounding terrain.

Release point type code means the code for physical configuration of the release point.

Reporting period type means the code describing the time period covered by the emissions reported, i.e., Annual, 5-month ozone season, summer day, or winter.

Source classification code (SCC) means a process-level code that describes the equipment and/or operation which is emitting pollutants.

State and county FIPS code means the system of unique identifiers in the Federal Information Placement System (FIPS) used to identify states, counties and parishes for the entire United States, Puerto Rico, and Guam.

Throughput means a measurable factor or parameter that relates directly or indirectly to the emissions of an air pollution source during the period for which emissions are reported. Depending on the type of source category, activity information may refer to the amount of fuel combusted, raw material processed, product manufactured, or material handled or processed. It may also refer to population, employment, or number of units. Activity throughput is typically the value that is multiplied against an emission factor to generate an emissions estimate.

Type A source means large point sources with a potential to emit greater than or equal to any of the thresholds listed in Table 1 of Appendix A of this subpart. If a source is a Type A source for any pollutant listed in Table 1, then the emissions for all pollutants required by §51.15 must be reported for that source.

Unit design capacity means a measure of the size of a point source, based on the reported maximum continuous throughput or output capacity of the unit.

Unit identifier means a unique code for the unit that generates emissions, typically a physical piece of equipment or a closely related set of equipment.

VOC means volatile organic compounds. The EPA's regulatory definition of VOC is in 40 CFR 51.100.

[80 FR 8796, Feb. 19, 2015]

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