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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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  • 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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  • Hot Work Definition and Requirements

    Facilities subject to the Program 3 Prevention Program requirements in 40 CFR Part 68 must include in their Risk Management Plan the date of the most recent review or revision of hot work permit procedures in Section 7.13. What is considered hot work and what are the requirements related to…

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  • Do I have to conduct incident investigations of releases resulting from theft?

    The incident investigation provisions of 40 CFR Part 68 (§§68.60 and 68.81) require facilities to investigate incidents that resulted in or could reasonably have resulted in a catastrophic release. Are covered facilities required to perform incident investigations of releases resulting from theft of covered substances, such as anhydrous ammonia? If…

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  • Do Program 1 processes have to complete a process hazard analysis?

    Do owners or operators of Program 1 processes have to complete a process hazard analysis? No. The Program 1 requirements do not include a process hazard analysis (40 CFR §68.12(b)). Program 3 processes require completion of a process hazard analysis (40 CFR §68.12(d)(3)) while Program 2 processes must complete a…

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  • Is a hazard review synonymous with a process hazard analysis (PHA)?

    The prevention program requirements under 40 CFR Part 68, Subparts C and D, include hazard reviews and process hazard analyses. Is a hazard review synonymous with a process hazard analysis (PHA)? No. A hazard review is different from a PHA. A hazard review is part of the Program 2 prevention…

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  • How often must compliance audits be performed?

    How often must owners or operators of stationary sources subject to the risk management program regulations perform compliance audits? The regulations at 40 CFR §§68.58(a) and 68.79(a) state that owners or operators must certify that they have evaluated compliance with the applicable prevention program provisions at least once every three…

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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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  • 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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  • Does compliance under OSHA's PSM demonstrate compliance with the risk management program?

    The Clean Air Act Amendments of 1990 (CAAA) mandated the Occupational Safety and Health Administration (OSHA) to develop a regulatory program to protect workers from the risk of accidents that involve hazardous chemicals. OSHA promulgated its Process Safety Management Standard (PSM) on February 24, 1992 (57 FR 6356), codified at…

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  • Applicability of compliance audit provisions to non-prevention program elements

    I have a Program 2 covered process and a Program 3 covered process at my stationary source. I am required (by 40 CFR Section 68.58 and 40 CFR Section 68.79) to certify compliance with prevention program requirements every three years. These compliance audits specifically address the prevention program portions of…

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