Emission Inventories

Inventories are important tools, enabling us to better comprehend the types and quantities of pollutants that are emitted to the air we breathe over a specific time period.  In order for the Air Division to create these inventories, it is necessary to have:

• Established the identities of important emission sources

• Knowledge of what pollutants are emitted from these sources

• Access to high quality source-specific emission factors (EFs), as often can be found in EPA's AP-42 document series or Emission Inventory Improvement Program (EIIP). (for example:  lbs of benzene emitted per mile traveled by a vehicle, or lbs of carbon monoxide emitted per ton of wood burned).

• An estimate of "activity" (for example:  how many miles were traveled by the vehicle in a given year, or how many tons of wood were burned in a given year)

In general, "sources" fall into one of the following categories:

• Point:       Refers to emissions that can be traced to a specific concentrated point (such as a factory, power plant, hospital, etc.)  This category is extensively inventoried through the Air Division's annual Point Source Registration Program.  According to U.S. EPA definition, however, most of Vermont's "Point Sources" would be considered "Area Sources" for annual emissions of certain pollutants.  For example, if potential emissions from a particular factory are less than the defined threshold, it will be classified as an Area Source.  For more information, please reference Table 1 of EPA's Consolidated Emissions Reporting Rule (CERR) published in the Federal Register.

• Area:        Stationary sources of air pollution for which it is difficult to attribute emissions to a concentrated point (such as emissions from livestock, open burning of trash, residential woodstoves, etc.).  In some cases, this category may include "Point Sources" having emissions below a certain defined threshold. (see Point above)

• Mobile:     Includes both Onroad (automobiles, trucks, buses, motorcycles, etc) and Nonroad (construction equipment, lawnmowers, snowmobiles, motorboats, aircraft, etc.)

• Biogenic:  Natural sources of air pollution (ex:  Isoprene emitted from plants, Ammonia emitted from the soil, etc.)

Click here to view information regarding Historical Air Emissions inventories compiled by the Air Division.

Questions or comments? - contact Jeff Merrell

Last Updated:7/16/12