Fire Terms
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Prescribed Fire: (also called prescribed or controlled burn) A fire ignited under known conditions of fuel, weather, and topography to achieve specific objectives.

Prescribed Natural Fire:

Prescription A statement or plan specifying management objectives to be obtained, and air temperature, humidity, season, wind direction and speed, fuel and soil moisture conditions under which a fire will be started or allowed to burn.

Relative Humidity: The ratio of water vapor in the air to the maximum amount of vapor the air can hold at a given temperature and pressure. Fire behavior is dependent on, and can be predicted from, relative humidity.

Rate of Spread: The speed a fire travels, generally expressed as chains/hour.

Safety Zone: A area of low fuel density created around structures in the wildland/urban interface for protection against fire.

Self-Sustaining Reaction: A chemical reaction that perpetuates (sustains) itself by providing the conditions that were required to initially start the reaction. A fire, for instance, provides enough heat to create still more fire.

Serotinous: A pine cone or other seed case that requires heat from a fire to open and release the seed.

Snags: Standing dead trees.

Spot Fire: A smaller fire that has started from sparks and brands thrown in the air by the main fire.

Spotting: Mass transfer of firebrands ahead of a fire front.

Surface Fire: A fire burning along the surface without significant movement into the understory or overstory, with flame length usually below 1 m.

Timelag Class: A method of categorizing fuels by the rate at which they are capable of moisture gain or loss, indexed by size class (see fuel definition).

Torching Fire: Fire burning principally as a surface fire that intermittently ignites the crowns of trees or shrubs as it advances.

Understory Fire: A fire burning in the understory, more intense than a surface fire with flame lengths of 1-3 m.

Urban-Rural Interface: (See Wildland-Urban Interface)

Vegetation Type: A standardized description of the vegetation in which a fire is burning. The type is based on the dominant plant species and the age of the forest and indicates how moist a site may be and how much fuel is likely to be present.

Water Repellency: The resistance to soil wettability, which can be increased by intense fires.

WFRB: Wild Fire for Resource Benefit.

Wildfire: A fire, naturally caused or caused by humans, that is not meeting land management objectives.

Wildland Fire: All fires that burn in wildlands, including wildfires and all prescribed fires.

Wildland-Urban Interface: Zone where structures and other human developments meet, or intermingle with, undeveloped wildlands

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