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Emissions Inventory Overview

Background and Overview

An Emissions Inventory is a list of air pollution sources and the amount of air pollution each source releases into the air.  An Emissions Inventory is usually made for one calendar year. The amount of air pollution is calculated using the best available information. Emissions Inventories do not measure air pollution. Measured air pollution is available on the DEQ’s Air Quality Index webpage. Details on where DEQ gets the information to calculate air pollution can be found below in “Where DEQ Gets Information.” 

Making an Emissions Inventory that includes every source of air pollution for the entire state of Oregon is a time consuming and complex task. Dividing air pollution sources into five common groups is done to simplify and standardize the process. An Emissions Inventory typically includes air pollution from these five groups: 

  • Point Sources are commercial, industrial, and institutional facilities that have individual air quality permits with Oregon DEQ.  Examples are factories and power plants.  
  • Non-Point Sources include air pollution from many small sources grouped together. For example: wood stoves, dry cleaners, gas stations, stationary engines and generators, and the use of chemicals (such as paints and cleaners). 
  • Mobile Sources including “On Road” vehicles (cars and trucks) and “non-Road” vehicles (construction equipment, off road recreational vehicles, lawn mowers, airplanes, trains, and ships). 
  • Events are wildfires and prescribed fires. 
  • Biogenic emissions are natural air pollution from vegetation and soils.   
Emissions Inventories are a tool used for many different purposes. Sometimes, Emissions Inventories are made for one industry, a single city, or a specific season and will not include everything. The sources of air pollution included depends on why the information is needed. Find more information by selecting the topics below:

The Environmental Protection Agency (EPA) publishes an Emissions Inventory for the entire country every three years.  This National Emissions Inventory (NEI) is based on national calculations and data provided by State, Local, and Tribal air agencies. 

DEQ must report pollution information every year for the NEI. Every third year, DEQ is required to report the entire state-wide Emissions Inventory. In the two “off" years, DEQ is only required to submit data for the largest Point Sources (about 20 of Oregon's largest industrial facilities). 

Visit the EPA's NEI​ webpage for details.

The EPA also has a webpage with details on how an Emissions Inventory is calculated. Visit EPA EI website to see the methods and calculations. ​


Information from many sources is needed to calculate the amount of air pollution for an Emissions Inventory. Sources of information to calculate air pollution for each group is summarized here: 

  • Point Sources: air pollution is calculated from data each facility is required to report annually about their own pollution. The amount of air pollution is calculated according to the rules in each facility's Air Permit. Annual Reports and Air Permits are posted on DEQ's Permits Online webpage. Point Sources with individual Air Permits must report their Toxic air pollution every three years.  These estimates are collected through the periodic state-wide Air Toxics Emissions Inventory.  
  • Non-Point Sources: Information like population size, fuel use, agriculture activities, and chemical sales are used to estimate air pollution. This category covers a wide range of air pollution sources. Some data is collected by other agencies, some from local surveys, and some is national data that gets parsed to each county.   
  • Mobile Sources: Data comes from national and state sources to estimate emissions from transportation, such as:  
    • ERG Survey​
    • UC Davis Model 
    • ODOT vehicle registration files 
    • EPA models for combustion, evaporation, brake, and tire wear 
    • ATR records (ODOT, FHWA, PORTAL, and PBOT) 
    • Travel Demand Models for speed and VMT distributions. 
  • Events: Wildfire emissions are calculated by computer modeling done by the EPA.  The EPA uses data from the SMARTFIRE2 database. SMARTFIRE2 uses NOAA Satellite images and ground reports to document fires.  The USDA Forest Service developed and maintains the database. Prescribed fire emissions are modeled by DEQ and are based on data from burn permits.  (For more information visit DEQ's Smoke Management web page
  • Biogenic: Air pollution is estimated by computer models run by the EPA. ​

A primary reason to make an Emissions Inventory is to better understand the sources of pollution in order to support DEQ's goal of improving air quality in Oregon. Emissions Inventories are important tools when planning changes to roads, airports or factories.  During the planning process, the State needs to make sure that any changes will not cause an increase in air pollution.  Increases in air pollution could cause bad air quality that would be over the EPA's limits, or negatively affect public health. The EPA has National Ambient Air Quality Standards (NAAQS) that Oregon must meet. Other uses for Emissions Inventories are: 

  • For public information requests, public education and the public's right-to-know what is in the air.  
  • Data is used by DEQ for air quality permitting of new and existing industrial facilities.
  • Emissions Inventories are important for developing plans to assure we have clean air in the future.  This planning is done through State Implementation Plans (SIPs), air quality modeling, rulemaking, and for Regional Haze planning. 
  • DEQ must report Emissions Inventory data every year for the National Emissions Inventory. Every third year DEQ is required to report the entire, state-wide Emissions Inventory. In the two “off" years, DEQ is only required to submit data for the largest Point Sources (about 20 of Oregon's largest industrial facilities). ​

​For the National Emissions Inventory, the six Criteria Air Pollutants (CAPs) and 187 Hazardous Air Pollutants (HAPs) are reported. Other Emissions Inventories could be developed for specific pollutants, depending on the purpose. For example, an Emissions Inventory of just sources of particulate matter small enough to inhale could be estimated for a State Implementation Plan (SIP).  

Many Oregon companies must report air pollution of over 600 toxic air contaminants every three years as part of the Periodic State-wide Air Toxics Emissions Inventory. These toxic pollutants are listed in in the Cleaner Air Oregon Cleaner Air Oregon state rules. 

Greenhouse Gasses are inventoried every year by DEQ's Greenhouse Gasses group. Their website lists pollutants​ that are estimated.​

​Every year the amount of forest burned in Oregon wildfires varies greatly. During years with a lot of wildfires, they can be the largest contributor to Oregon's total air pollution. Wildfire air pollution is estimated by the EPA every three years as part of the National Emissions Inventory. Wildfire size and intensity is modeled using the SMARTFIRE2 database. SMARTFIRE2 uses satellite images and ground reports to document each fire. The database was developed for the USDA Forest Service. The EPA uses the output from the database to estimate each fire's air pollution using the BlueSky computer model.​​

​​DEQ collects toxic air pollution estimates from large facilities every three years. These are Point Sources with individual air quality permits. The reporting years will be the same as EPA's National Emissions Inventory. Reports will be available every three years starting for 2020. Facilities must submit an Emissions Inventory of their air pollution of over 600 toxic chemicals. The Emissions Inventories must include details for each piece of equipment at the facility. The total amount of toxic air pollution for each facility is available on the DEQ's Permits Online webpage. Detailed information and a state summary are available on the Air Toxics Emissions Reporting​ webpage. ​

​Cleaner Air Oregon (CAO) is a DEQ program designed to reduce toxic air pollution from Point Sources. Point Sources are commercial, industrial, and institutional facilities that have individual air quality permits. When a site has a CAO review, they must provide a detailed Emissions Inventory of toxic air pollution. These CAO Emissions Inventories are carefully reviewed by DEQ. All new facilities must go through this review before they can receive an individual Air Permit. DEQ is also requiring all existing sites to go through this review process.  The order of when they must go through is based on how much toxic air pollution the facility produces.  The highest risk plants are being reviewed first. These CAO Emission Inventories include more detail than a normal air toxic Emissions Inventory. These estimates must include air pollution from the facility's normal operations, from operating at maximum capacity, and for the maximum daily operations. These Emissions Inventories are used with computer modeling to analyze health risks to the public. A guide for sites going through the CAO review can be found on the CAO website​ on the For Facilities page. Emissions Inventories for facilities that have finished the CAO review are available on the For Communities​ page.​

​The EPA requires some facilities to report emissions under the Toxics Release Inventory (TRI)​. These rules were written to help track toxic chemicals that can pose a threat to human health and to provide community-right-to-know information. TRI reports include more than just air pollution. There is information on production of toxic chemicals and how all the chemicals leave the site. This includes air pollution, water pollution, disposal, spills, and those chemicals that are in the products the site manufactures. Some Oregon sites report directly to EPA under these rules. The purpose of the TRI reporting rules is not the same as DEQ's periodic Air Toxics Emissions Inventory or CAO review. The resulting data should be similar, but the differences in reporting rules explain why the two sets of data may not match. DEQ does not have the opportunity to review the pollution information before they are provided to the public. 

​​Greenhouse Gases are inventoried by the DEQ's Climate Protection Program (CPP). Their webpage​ contains a summary of Oregon's Greenhouse Gas emissions as well as links to reporting and general Climate Protection Program information.    ​


For more information contact David Broderick.