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  • 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…

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  • 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…

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  • 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.

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  • National Priorities List (NPL)

    The NPL is a list of hazardous waste sites identified by EPA as warranting further investigation into the extent of the risk they pose and whether cleanup of the site under EPA’s Superfund Remedial program is warranted. NPL listing does not promise remedial action, only detailed investigation.

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  • 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/ .

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  • 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 .

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  • 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…

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  • 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…

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