Emissions factors have long been the fundamental tool in developing national, regional, state, and local emissions inventories for air quality management decisions and in developing emissions control strategies. More recently, emissions factors have been applied in determining site-specific applicability and emissions limitations in operating permits by federal, state, local, and tribal agencies, consultants, and industry. AP-42 is a compendium of EPA recommended emissions factors.

The CMAQ Model Outputs data asset includes current and projected future levels of ambient concentrations and deposition to support regulatory impact analyses.

EPA regulations codified in 40 CFR Part 60 and 63 require affected sources to perform emissions source tests, conduct continuous emissions monitoring, and submit compliance and emissions reports . EPA is promulgating "E-Reporting" rules to require affected sources to electronically submit source test results, emissions monitoring data, compliance reports, and emissions reports to EPA. As a result the EPA has developed the Compliance and Emissions Data Reporting Interface (CEDRI) which is located on EPA's Central Data Exchange (CDX). The CDX Web is the application used by EPA programs and various stakeholders to manage environmental data transmitted to EPA in order to meet EPA's reporting requirements.

The EPA Control Measure Dataset is a collection of documents describing air pollution control available to regulated facilities for the control and abatement of air pollution emissions from a range of regulated source types, whether directly through the use of technical measures, or indirectly through economic or other measures.

The EPA Control Strategy Tool (CoST) is a software tool for projecting potential future control scenarios, their effects on emissions and estimated costs. This tool uses the NEI and the Control Measures Dataset as key inputs. CoST outputs are projections of future control scenarios.

The Air Emissions Trends site provides national trends of criteria pollutant and precursor emissions data based on the the National Emissions Inventory (NEI) from 1970 - the latest NEI year.

The Emissions Modeling Clearinghouse (EMCH) supports and promotes emissions modeling activities both internal and external to the EPA. Through this site, the EPA distributes and documents emissions datasets that are formatted for use in emissions models, which are used for emissions preparation for air quality modeling. The inventory data on this site are dervied from previous and current versions of the National Emission Inventory (NEI). This site also distributes the EPA's latest versions of ancillary datasets used to support the temporal, spatial, speciation, and future-year projection of these emissions.

The Monitoring Knowledge Base (MKB) is a compilation of emissions measurement and monitoring techniques associated with air pollution control devices, industrial process descriptions, and permitting techniques, including flexible permit development. Using MKB, one can gain a comprehensive understanding of emissions sources, control devices, and monitoring techniques, enabling one to determine appropriate permit terms and conditions.

OTS is an internal EPA national tribal database to assist the Regions and HQs in tracking tribal performance information.

The Title V Permitting Statistics Inventory contains measured and estimated nationwide statistical data, consisting of counts of permitted sources, types of permits issued, and the timeliness of permit issuance, for the operating permits programs being implemented under CAA authority (40 CFR parts 70 and 71). This data is non-source specific. The statutory authority leading to the collection of this information comes from Title V of the Clean Air Act.Prior to July 2008, data collected on state permit programs (part 70) was not equivalent to that collected when EPA was the permitting agency (part 71). Current system includes semiannual data from 2006-present; prior data is archived.Data is currently not publicly available, certain statistical data has been made available in the past, but not currently. This data is mostly used for ICR and PART reporting purposes.