The federal government tracks gases that the U.S. releases into the atmosphere in emission inventories. An emission inventory is an accounting of the amount of air pollutants discharged into the atmosphere. It is generally characterized by the following factors:
the chemical or physical identity of the pollutants included,
the geographic area covered,
the institutional entities covered,
the time period over which emissions are estimated, and
the types of activities that cause emissions.
Emission inventories are developed for a variety of purposes. Inventories of natural and anthropogenic emissions are used by scientists as inputs to air quality models, by policy makers to develop strategies and policies or track progress of standards, and by facilities and regulatory agencies to establish compliance records with allowable emission rates. A well constructed inventory should include enough documentation and other data to allow readers to understand the underlying assumptions and to reconstruct the calculations for each of the estimates included.
