Search Frequent Questions

Displaying 1 - 15 of 15 results

• Where can I find older NEI data (prior to 2008)?

  The raw data and summaries that are still available (dating back to 1990) can be obtained from the web page https://www.epa.gov/air-emissions-inventories/pollutant-emissions-summary-files-earlier-neis . Starting with 2001 data, a more limited selection of summary files are available.

  • Last published: March 18, 2024

• How do the different parts of particulate matter (PM) fit together?

  The various parts of PM in the NEI are related as follows. PM10-FIL > PM25-FIL because PM10-FIL includes PM25-FIL PM25-PRI = PM25-FIL + PM-CON This equation only applies at the process level. Because some sources only can report PM2.5 (due to test method differences), this equation does not apply to…

  • Last published: April 17, 2024

• How does PM2.5 relate to PM species such as EC, OC, SO4, NO3, PMFINE, and DIESEL-PM25?

  Primary PM2.5 estimates are speciated into the five PM species in the NEI: elemental (black) carbon (EC), organic carbon (OC), nitrate (NO3), sulfate (SO4), and the remainder of PM25-PRI (PMFINE). Diesel engine PM25-PRI and PM10 emissions are also labeled as DIESEL-PM25 and DIESEL-PM10 for mobile source diesel engines. For all…

  • Last published: April 17, 2024

• Are biogenic emissions included in the emissions trends Tier 1 data?

  No, the biogenic emissions are not included in the emissions trends Tier 1 data. If needed, users can add the biogenic data either as a separate Tier, or specify its inclusion in the “Miscellaneous” Tier 1 group.

  • Last published: August 15, 2024

• What is included in the emissions “Tiers”?

  The Tiers are assigned by a Source Classification Code (SCC), which has the most detail about the emissions processes that generate the emissions. The full list of SCCs, their associated Tiers, and the SCC descriptions is available online at https://ofmpub.epa.gov/sccwebservices/sccsearch/ .

  • Last published: March 18, 2024

• If I certify a nonroad flexible-fuel engine under 40 CFR Part 1054, are owners and operators prohibited from using gasoline-ethanol blended fuels containing greater than 10 volume percent ethanol under 40 CFR 80.1504(a)(1) in my nonroad flexible-fuel engi

  See More Frequent Questions about Fuels Registration, Reporting, and Compliance Help . No, owners and operators of nonroad engines, vehicles, and equipment where the nonroad engine is certified under 40 CFR Part 1054 as a flexible-fuel engine are not prohibited from using gasoline-ethanol blended fuels containing greater than 10 volume…

  • Last published: July 15, 2024

• What does an annual emissions value in the NEI represent (one year or multiple years)?

  The NEI provides total annual emissions for a single year.

  • Last published: January 7, 2025

• What sources make up the Sectors or Tiers used in the emissions data summaries?

  Tier 1 and Sector categories are assigned by source classification codes (SCCs) that are the most specific processes available in the NEI. The latest SCC list with the Tier 1 and Sector assignments can be downloaded from the EPA SCC website in Comma Separate Values (CSV) format.

  • Last published: May 1, 2024

• Where can I obtain the hourly data from Continuous Emissions Monitors (CEMs)?

  The CEM emissions data are available from the EPA Clean Air Markets Program Data website.

  • Last published: August 15, 2024

• What are the units of NEI emissions data?

  NEI emissions values represent total annual emissions for the inventory reporting year. Criteria air pollutants and precursors (CAPs) are reported in short tons per year , and hazardous air pollutants (HAPs) are reported in lbs per year .

  • Last published: January 7, 2025

• What is the definition of VOC?

  There is a regulatory definition of VOC. It is found in 40 CFR 51.100. CFR - code of federal regulations. The definition relates to the intent and requirements of the Clean Air Act. Excerpt from “Volatile Organic Compounds” Definition per 40 CFR Part 51.100(s): " Volatile organic compounds (VOC) means…

  • Last published: March 18, 2024

• How can I get more detailed information? What measurements/sensors are used to measure emissions?

  Access the latest NEI data set . Under 'Sector Summaries - Criteria and Hazardous Air Pollutants by 60 EIS emission sectors', > choose National > for Pollutant, choose PM10 Primary and/ or PM2.5-PRI > Sector, choose all sectors >Submit Query to see results at bottom of page. Open the results…

  • Last published: March 18, 2024

• What does "NEC" stand for in the emissions sectors?

  NEC means “not elsewhere classified” and includes SCCs that are not assigned to any of the other specific industrial process sectors. If you look at the SCC code table available at the SCC web site and filter on the Sector name that includes “NEC”, you can see the type of…

  • Last published: March 18, 2024

• Can product codes satisfy the product transfer documentation requirements set forth at 40 C.F.R. 80.1503(a)?

  See More Frequent Questions about Fuels Registration, Reporting, and Compliance Help . EPA believes that parties normally are able to meet the product transfer requirements by including the required information in the documents that the parties currently use to memorialize the transfer of title or custody of the gasoline. Product…

  • Last published: July 15, 2024

• Where can I get maps and/or emissions of facility emissions data?

  The EPA provides emissions maps in two ways. First, each of the last three NEI years have a “Facility Mapping” tab available on the main NEI page for that inventory year (for example, see the 2020 NEI page). With this tool, maps can be created for one state at a…

  • Last published: January 7, 2025