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Emissions Inventory

An emissions inventory is a list of sources of air pollution and the amount of each pollutant emitted into the atmosphere. The inventory includes criteria air pollutants (CAPs), Rhode Island air toxics and hazardous air pollutants (HAPs) for sources in several categories (point, nonpoint (area), on-road mobile, and non-road mobile).

The Clean Air Act (CAA) Amendments and the Air Emissions Reporting Rule (40 CFR Part 51 Subpart A), requires that the Office of Air Resources conduct annual inventories of air emissions from point sources and periodic inventories every three years (2011, 2014 etc.…) of emissions from nonpoint (area) sources, non-road mobile sources, and on-road mobile sources. This data is electronically submitted to EPA and is part of the National Emissions Inventory (NEI)

Why Are We Collecting Emissions Inventory Data?

The data is used to: calculate emission fees, determine compliance with emission limitations, identify air toxics sources, identify emission sources that would be regulated by newly promulgated state and federal regulations, respond to citizen inquiries and complaints, model regional ozone levels and to track the success of emission reduction programs.

Do I Need to Submit an Emissions Inventory?

YES, RI Air Pollution control Regulation 14, section 14.2.1 requires:
"The owner or operator of any facility that emits air contaminants shall, at the request of the Director, provide data on operational processes, fuel usage, raw materials, stack dimensions, exhaust gas flow rates and temperatures, emissions of air contaminants, steam or hot water generator capacities, types of equipment producing air contaminants and air pollution control systems or other data that may be necessary to determine if the facility is in compliance with air pollution control regulations."

Annually, permitted and known sources are sent a General Facility Information Sheet and a notice that the air pollution inventory forms are now available online. Sources will need to go online to fill out applicable forms and print them. The forms along with the signed General Information Facility Sheet must be returned to the Office of Air Resources by April 15th each year unless otherwise specified. Alternatively sources that have developed spreadsheets with emissions estimates may email the spreadsheets in lieu of the forms. If the spreadsheets are emailed the source must still mail in the signed General Facility Information Sheet noting that the files have been emailed.

If you did not receive a letter from the Office of Air Resources and you think you should be reporting, please contact Karen Slattery at karen.slattery@dem.ri.gov.

How Are Point Source Emissions Inventories Conducted?

The Office of Air Resources requests information about various processes conducted at industrial and commercial facilities known as point sources. These facilities receive a letter in the early part of the calendar year with instructions and the link to the air emissions inventory forms. Larger emission statement sources are required to submit an emissions statement which contains estimates for all emissions at their facility. Smaller sources are required to submit data on chemical and fuel use by process so that we can make an estimate of air emissions at the facility.

Emissions can be estimated several ways.

  • Mass balance – Facility report inputs and outputs of regulated materials to account for the portion that is emitted to the air. This method works well with uncontrolled use of solvents and volatiles that evaporate during use.
  • AP-42 – contains emissions factors for several types of manufacturing industries and combustion activities. For example AP-42 contains emissions factors for fuel burning activities by type of combustion and pollutant.
  • Stack testing – If available data from the most recent stack test will be used for calculating emissions.
  • Permit data – if the facility has a permit for a particular piece of equipment that emission factors in the permit will be used for estimating emissions.

The Office reviews the submitted inventories for accuracy and thoroughness by comparison to previous year’s submittals.

Point source emissions are stored in our local database and reported through electronic data transfer to the EPA’s National Emissions Inventory by the appropriate due dates.

Nonpoint Sources

Emissions inventories for nonpoint (area) sources, which include small stationary sources that did not receive an air pollution inventory form, are required to be reported to the EPA every three years for the NEI. These data are generated using EPA approved methods and reported as county totals by Office of Air Resources. Reported pollutants include CAPs as well as a number of HAPs. These inventories are used in determining compliance with the NAAQS and for on-going policy development and community planning.

Some examples of nonpoint sources include:

  • Auto body shops
  • Gasoline Service Stations
  • Architectural Coatings
  • Residential Heating
  • Residential Wood Combustion
  • Commercial/Consumer Products
  • Asphalt Paving

Mobile Sources

Emissions inventories for mobile sources are required to be reported to the EPA every three years for the NEI, and are developed for regional air quality planning work. An input file generated using the MOVES software is required to be submitted to the NEI every three years. These inventories are used in determining compliance with the NAAQS for transportation and community planning, and on-going policy development. Both on-road and non-road mobile source emissions are reported.

What Are Emissions Inventories Used for?
Emissions inventories are the basis for numerous efforts including analysis of trends, the impact of regulations on air quality, and human exposure modeling. In addition, inventories are used in local and regional emissions modeling which can help us understand current air quality, and forecast future trends. Quality emissions inventories: me examples of nonpoint sources include:

  • lead to a more thorough consideration of certain industries or emission sources;
  • provide the foundation for the development or evaluation of control strategies;
  • aid in the evaluation of regulation effectiveness;
  • serve as a basis for emissions fee programs, permitting, and air quality assessments; and
  • Support the development of new methodologies and techniques for estimating emissions (including emission factors).

Emissions inventories are an essential component used in assessing, planning for the improvement of, and protecting local air quality. You can check the local air quality where you live at http://www.epa.gov/myenvironment.

For detailed information on uses of emissions inventories please visit EPA’s NEI website at https://www.epa.gov/chief/. National Emissions Inventory Data & Documentation can be found at https://www.epa.gov/air-emissions-inventories.


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