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Emissions Inventory


The Maricopa County Air Quality Department's (MCAQD) Emissions Inventory (EI) Unit collects, reviews, stores and manages stationary source air pollution emissions data for sources in Maricopa County. The EI Unit also collects emission fees from Title V sources and provides data to county, state and federal agencies.

A point source emissions inventory shows annual air pollutant emissions for one specific business location. An emissions inventory may be requested by MCAQD of any facility with an air quality permit in Maricopa County. At the beginning of each year, the EI unit distributes reporting forms and instructions to those businesses that have been requested to submit an emissions report for the prior calendar year.

Annual emissions inventories serve a number of purposes:

  • They help determine a source's compliance with its air quality permit conditions as well as Maricopa County rules and regulations.
  • They help identify pollutant sources that may need new or additional controls, and thus provide a basis for improved air pollution control strategies.
  • They also provide a means of assessing progress in achieving reductions from existing controls.
  • They provide the basis for determining annual emission fees from Title V sources.
  • Inventory data are used as input for air quality modeling to demonstrate attainment of national ambient air quality standards (NAAQS).

Annual Series of Reporting Workshops Concludes

May 2016 – The series of workshops providing assistance in completing annual emissions surveys for calendar year 2015 activity have concluded for this year. A new series of workshops will be announced early next year, when emissions survey forms for 2016 activity are distributed. If you have questions regarding the annual emissions reporting processes, please contact the MCAQD Emissions Inventory Unit at (602) 506-6790 or email

Addendum to 2011 Ozone Precursor Report Released August 2015

August 2015 – An addendum to the 2011 Periodic Emissions Inventory for Ozone Precursors for the Maricopa County, Arizona, Eight-Hour Ozone Nonattainment Area, originally published in February 2014, has been prepared. This document has been developed by the Maricopa County Air Quality Department (MCAQD) for three purposes:

  • It adds a facility to the list of available Emission Reduction Credits (ERCs) in the Arizona Emissions Bank.
  • In response to inquiries from EPA staff, it provides a "recasting" of the emissions calculations to develop an ozone season-day inventory reflecting the June-August 2011 period (vs. July-September addressed in the original Periodic Emissions Inventory [PEI] report).
  • It provides further details on facility-specific emissions levels from County-permitted sources that are reflected in the original PEI report as area-source (nonpoint) emissions in Chapter 3.

The Addendum to the 2011 PEI for Ozone Precursors, as well as the complete original document, can be found on the 2011 Periodic EI Reports Page.

2011 Emissions Inventory Reports for PM10 and Ozone Precursors Published

February 2014 – MCAQD has prepared 2011 Periodic Emissions Inventory (PEI) reports for PM10 and ozone precursors. The PM10 emissions inventory includes emissions estimates for PM10, PM2.5, NOx, SOx, and NH3, while the ozone precursor emissions inventory includes emission estimates for VOC, NOx and CO. Each report includes detailed descriptions of the calculation methods, activity levels, data sources, and other background information used to develop annual and daily estimates of emissions from a broad range of source categories. Emission estimates for each source category are provided for both Maricopa County as a whole, as well as the respective nonattainment areas. Click here to view or download the reports.

Other Emissions Inventory Resources

Emission factor reference materials
U.S. EPA's publication "Compilation of Air Pollutant Emission Factors "AP-42"):
Fifth Edition, Volume 1: Stationary Point and Area Sources"
U.S. EPA - WebFIRE - an Internet based search application
U.S. EPA's TANKS 4.09d software
Landfill Gas Emissions Model (version 3.02)
Materials related to coding industries and processes
NAICS and SIC industry codes
Process Tier CodesThis link opens a new page containing an Adobe Acrobat PDF document.
Control Device CodesThis link opens a new page containing an Adobe Acrobat PDF document.