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Glossary of Terms

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- F -

A person who cuts down or fells trees. Also called a sawyer or cutter.

Field Observer:
Person responsible to the Situation Unit Leader for collecting and reporting information about an incident obtained from personal observations and interviews.

Fine Fuels:
Fast-drying fuels, generally with a comparatively high surface area-to-volume ratio, which are less than 1/4-inch in diameter and have a timelag of one hour or less. These fuels ignite readily and are rapidly consumed by fire when dry.

Fingers of a Fire:
The long narrow extensions of a fire projecting from the main body.

Fire Behavior:
The manner in which a fire reacts to the influences of fuels, weather, and topography.

Fire Behavior Forecast:
A prediction of probable fire behavior, usually prepared by a Fire Behavior Analyst, in support of fire suppression or prescribed burning operations.

Fire Behavior Specialist:
A person responsible to the Planning Section Chief for establishing a weather data collection system and for developing fire behavior predictions based on fire history, fuels, weather, and topography. Also called Fire Behavior Analyst.

Fire Break:
A natural or constructed barrier used to stop or check fires, or to provide a control line from which to work.

Fire Cache:
A supply of fire tools and equipment assembled in planned quantities or standard units at a strategic point for exclusive use in fire suppression.

Fire Crew:
An organized group of firefighters under the leadership of a crew leader or other designated official.

Fire Front:
The part of a wildland fire in which continuous flaming combustion is taking place. Unless otherwise specified the fire front is assumed to be the leading edge of the fire perimeter. In ground fires, the fire front may be mainly smoldering combustion.

Fire Intensity:
A general term relating to the heat energy released by a fire.

A linear fire barrier that is scraped or dug to mineral soil after being cleared of all vegetation.

Fire Load:
The number and size of fires historically experienced on a specified unit over a specified period (usually one day) at a specified index of fire danger.

Fire Management Plan (FMP):
A strategic plan that defines a program to manage wildland and prescribed fires and documents the Fire Management Program in the approved land use plan. The plan is supplemented by operational plans such as preparedness plans, preplanned dispatch plans, prescribed fire plans, and prevention plans.

Fire Perimeter:
The entire outer edge or boundary of a fire, which may contain within it substantial areas of unburned fuels.

Fire Season:
1) Period(s) of the year during which wildland fires are likely to occur, spread, and affect resource values sufficient to warrant organized fire management activities. 2) A legally enacted time during which burning activities are regulated by state or local authority.

Fire Shelter:
An aluminized tent offering protection by means of reflecting radiant heat and providing a volume of breathable air in a fire entrapment situation.

Fire Shelter Deployment:
Removing a fire shelter from its case and using it as protection against fire.

Fire Storm:
Violent convection caused by a large continuous area of intense fire. Often characterized by destructively violent surface indrafts, near and beyond the perimeter, and sometimes by tornado-like whirls.

Fire Triangle:
Instructional aid in which the sides of a triangle are used to represent the three factors (oxygen, heat, fuel) necessary for combustion and flame production; removal of any of the three factors causes flame production to cease.

Fire Use Module:
A team of skilled and mobile personnel dedicated primarily to prescribed fire management. These are national and interagency resources, available throughout the prescribed fire season, trained to ignite, hold, and monitor prescribed fires.

Fire Weather:
Weather conditions that influence fire ignition, fire behavior, and suppression.

Fire Weather Watch:
A term used by fire weather forecasters to notify firefighters and agencies, usually 24 to 72 hours ahead of the event, that current and developing meteorological conditions may evolve into a dangerous fire weather situation.

Fire Whirl:
A spinning vortex column of ascending hot air and gases rising from a fire and carrying aloft smoke, debris, and flame. Fire whirls range in size from less than one foot to more than 500 feet in diameter. Large fire whirls can equal the intensity of a small tornado.

Firefighting Resources:
All people and major items of equipment that are or could be assigned to fires, ranging from crews and other personnel to engines to aircraft to dozers to water tenders and including a large variety of support personnel and services.

Flame Height:
The average maximum vertical extension of flames at the leading edge of the fire front . Occasional flashes that rise above the general level of flames are not considered. The flame height is less than the flame length if flames are tilted by winds or slope.

Flame Length:
The distance between the flame tip and the midpoint of the flame depth at the base of the flame (generally the ground surface); flame length is an indicator of fire intensity .

Flaming Front:
The zone of a moving fire where the combustion is primarily flaming. Behind this flaming zone, combustion is primarily glowing. Light fuels typically have a shallow flaming front, and heavy fuels have a deeper front. Also called fire front.

Flanks of a Fire:
The parts of a fire's perimeter that are roughly parallel to the main direction of spread.

Any sudden acceleration of fire spread or intensification of a fire. Unlike a blow-up, a flare-up lasts a relatively short time and does not radically change control plans.

Flash Fuels:
Fuels such as grass, leaves, pine needles, ferns, tree moss, and some types of slash, flash fuels or flashy fuels ignite readily and are consumed rapidly when dry. Also called fine fuels.

A plant with a soft rather than permanent woody stem, that is not a grass or grass-like plant.

Combustible material. Includes vegetation such as grass, leaves, ground litter, plants, shrubs, and trees that feed a fire. (Also see Surface Fuels.)

Fuel Bed:
In a research setting, an array of fuels usually constructed with specific loading, depth, and particle size to meet experimental requirements; also commonly used to describe the fuels composition in natural settings.

Fuel Loading:
The amount of fuels present expressed quantitatively in terms of weight per unit area.

Fuels Management:
Management of wildland fuel complexes to achieve hazardous fuel reduction, to achieve and maintain ecosystem restoration, and to maintain ecosystem health and other resource benefits. Management includes strategic planning and site-specific and landscape-scale treatments designed to improve abilities to protect life and property, and to maintain or restore the sustainability of healthy ecosystems. Fuel management is accomplished by the application and integration of a variety of treatments that will minimize the probability and effects of large-scale, high-intensity fires. These treatments, a variety of fire and non-fire techniques, include, but are not limited to, mechanical, chemical, biological, and manual methods, and prescribed fire and wildland fire use. Both naturally occurring fuels and hazardous fuel accumulations resulting from resource management and land use activities must be addressed.

Fuel Model:
Simulated fuel complex (or combination of vegetation types) for which all fuel descriptors required for the solution of a mathematical rate of spread model have been specified.

Fuel Moisture:
The quantity of moisture in fuels expressed as a percentage of the weight when thoroughly dried at 212 degrees Fahrenheit. Also referred to as fuel moisture content.

Fuels Reduction:
Manipulation, including combustion or removal of fuels to reduce the likelihood of ignition and/or to lessen potential damage and resistance to control. Often includes thinning and/or prescribed burning.

Fuel Treatment:
Any vegetation manipulation and/or removal/modification of wildland fuels to reduce the likelihood of ignition, to reduce potential fire intensity and spread rates, to lessen potential damage and resistance to control, or to limit the spread and proliferation of invasive species and diseases. Fuels treatments achieve site-specific fire and resource management objectives under approved land use plans and with full compliance to NEPA and other regulatory statutes.

Fuel Type:
An identifiable association of fuel elements of a distinctive plant species, form, size, arrangement, or other characteristics that will cause a predictable rate of fire spread or difficulty of control under specified weather conditions.

A colored flare originally designed as a railway warning device and widely used to ignite suppression and prescription fires.