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  • Where can I download hourly emissions data from continuous monitoring?

    Hourly emissions data files are available from the Clean Air Markets Division of EPA, collected as part of 40 CFR Part 75. The download location has changed in February, 2023. The new location is https://campd.epa.gov/data/bulk-data-files . Once on this new site, use the menu (at the left) and the Keyword…

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  • 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.

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  • What is a reactive and non-reactive solid EHS?

    Reactive solid means any extremely hazardous substance denoted with “a” in the “Notes” column in Appendix A or B of 40 CFR 355. Reactive solids are more likely than other solids to be dispersed into the air due to the energy or heat created from their reactivity with water or…

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  • How did states form their SERCs?

    How are States expected to form their State Emergency Response Commission (SERC) as required under Title III? States are required to establish a State Emergency Response Commission (SERC) under Title III. The SERC may consist of existing emergency response organizations or may be an entirely new mechanism to address this…

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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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  • Pesticide applicator quantity applied to threshold or transportation exemption

    A farmer contracts with an applicator to spray pesticides on his fields. The applicator drives a tank truck onto the farmers' field and sprays the pesticide from the truck onto the fields. For purposes of Section 302 emergency planning requirements, are the EHSs in the truck considered present at the…

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  • State refusing to comply with the emergency planning provisions

    What will happen if a State refuses to comply with the emergency planning provisions? A governor who does not designate a State emergency response commission becomes the commission by default. While the governor could choose not to fulfill any of the Title III provisions, the public could still request information…

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  • Section 302 notification requirements and mixtures with unknown components

    Are facilities exempt from Section 302 notification requirements if they produce, use, or store mixtures whose extremely hazardous substance component information is not available on the MSDS provided by the manufacturer? If the facility which produces, uses, or stores mixtures knows or reasonably should know the components of the mixture…

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  • How complete are the data in the National Emissions Inventory?

    While the goal of the National Emissions Inventory (NEI) program is to include all emissions data, there are always challenges meeting this goal. The answer about completeness of coverage of sources depends on the emissions sector and pollutant. In general, the criteria air pollutants and precursors (CAPs) are expected to…

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  • Where is more information available about emissions estimation methods used by the EPA?

    For criteria air pollutants and precursors as well as for hazardous air pollutants, the methods are described in the technical support document (TSD) for the latest National Emissions Inventory (NEI) available from the main NEI page . For greenhouse gas emissions, you can find greenhouse gas inventory methods from the…

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  • TPQ calculations for hazardous substances in molten form

    Facilities are subject to emergency planning and notification requirements under EPCRA (also known as SARA Title III) when an extremely hazardous substance (EHS) is present at a facility in an amount equal to or in excess of its TPQ. For some EHSs that are solids, two TPQs are given (e.g…

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  • Reporting responsibility under EPCRA §302 for a facility with several unrelated companies?

    A public warehouse is used by several unrelated companies to store extremely hazardous substances (EHSs). For purposes of emergency planning notification, who is responsible, under EPCRA Section 302, for notifying the State Emergency Response Commission if a threshold planning quantity (TPQ) of an EHS is present at the warehouse? The…

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  • What sources make up the Tier 1 categories used in the emissions trends?

    Tier 1 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 assignments can be downloaded from the EPA SCC website in Comma Separate Values (CSV) format.

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  • What is the cause of the large decrease in electric utility emissions, particularly sulfur dioxide, starting in 1995?

    SO2 emissions reductions from utilities during this time are primarily attributed to the impacts of the acid rain program. As described on EPA’s Acid Rain Program web page, Phase 1 of this program began in 1995 and affected 263 units at 110 most coal-burning electric utility plants in 21 eastern…

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