13.1 Sector Descriptions

Wildfires and prescribed burns (Wildland Fires in sum, WLFs) that occur during the inventory year are included as “non-point” sources beginning with the 2020 NEI. Previous NEIs had wildland fires labeled as “events” sources. Emissions from these fires, as well as agricultural fires, make up the National Fire Emissions Inventory (NFEI). Agricultural field burning has been treated as non-point sources in previous NEIs and has had a separate section in the NEI Technical Support Document. All these fire types will be combined into one section of this TSD beginning with the 2020NEI.

Estimated emissions from all these fire types in the 2023 NEI are calculated from burned area data. Input data sets are collected from State/Local/Tribal (S/L/T) agencies and from national agencies and organizations. S/L/T agencies that provide input data were also asked to complete the NEI Wildland Fire Inventory Database Questionnaire, which consists of a self-assessment of data completeness. Raw burned area data compiled from S/L/T agencies and national data sources are cleaned and combined to produce a comprehensive burned area data set. Emissions are then calculated using fire emission tools/models that rely on burned area as well as fuel and climatological weather information. These emissions tools/models will be described later in this section. The resulting emissions are compiled by date and location as day-specific emission estimates.

For purposes of emission inventory preparation, wildland fire (WLF) is defined as “any non-structure fire that occurs in the wildland (an area in which human activity and development are essentially non-existent, except for roads, railroads, power lines, and similar transportation facilities). Wildland fire activity is categorized by the conditions under which the fire occurs. These conditions influence important aspects of fire behavior, including smoke emissions. In the 2023 NEI, data processing is conducted differently depending on the fire type, as defined below:

Wildfire (WF): Any fire started by an unplanned ignition caused by lightning; volcanoes; other acts of nature; unauthorized activity; or accidental, human-caused actions, or a prescribed fire that has developed into a wildfire.

Prescribed (Rx) fire: Any fire intentionally ignited by management actions in accordance with applicable laws, policies, and regulations to meet specific land or resource management objectives. Prescribed fire is one type of fuels treatment. Fuels treatments are vegetation management activities intended to modify or reduce hazardous fuels. Fuels treatments include prescribed fires, wildland fire use, pile burns, and mechanical treatment.

Agricultural burning: A type of prescribed fire, specifically used on land used or intended to be used for raising crops or grazing.