GLOSSARY OF WILDLAND FIRE TERMINOLOGY

Activity Fuels - Fuels resulting from, or altered by, forestry practices such as timber harvest or thinning, as opposed to naturally created fuels.

Annual Plant - A plant that lives for one growing season, starting from a seed each year.

Aspect - Cardinal direction toward which a slope faces.

Dead Fuels - Fuels with no living tissue in which moisture content is governed almost entirely by absorption or evaporation of atmospheric moisture (relative humidity and precipitation).

Dry Hydrant - Permanent devices with fire engine threads attached to expedite drafting operations in locations where there are water sources suitable for use in fire suppression (e.g., piers, wharves, bridges over streams, highways adjacent to ponds) or Permanently installed supply private fire pumps which depend upon suction sources. Also called suction pipe.

Duff - The layer of decomposing organic materials lying below the litter layer of freshly fallen twigs, needles, and leaves and immediately above the mineral soil.

Extreme Fire Behavior - "Extreme" implies a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning and/or spotting, presence of fire whirls, strong convection column. Predictability is difficult because such fires often exercise some degree of influence on their environment and behave erratically, sometimes dangerously.

Fire - Rapid oxidation, usually with the evolution of heat and light; heat fuel, oxygen and interaction of the three.

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

Fire Danger Rating Area - A geographic area of relatively homogenous climate, fuels and topography, tens of thousands of acres in size, within which the fire danger can be assumed to be uniform. The basic on-theground unit for which unique fire management decisions are made based on fire danger ratings. Weather is represented by one or more NFDRS weather stations.

Fire Dependent - Plants and vegetation communities which have evolved adaptations such as a reliance on fire as a disturbance agent, protection as a species against the effects of wildland fire, or even a strengthening or enhancement by it.

Fire District - A rural or suburban fire organization, usually tax supported, that maintains fire companies and apparatus. It is also called a fire protection district.

Fire Ecology - The study of the effects of fire on living organisms and their environment.

Fire Effects - The physical, biological, and ecological impacts of fire on the environment.

Fire Resistant Tree - A species with compact, resin-free, thick corky bark and less flammable foliage that has a relatively lower probability of being killed or scarred by a fire than a fire sensitive tree.

Fire Retardant - Any substance except plain water that by chemical or physical action reduces flammability of fuels or slows their rate of combustion.

Fire Sensitive Tree A species with thin bark or highly flammable foliage that has a relatively greater probability of being killed or scarred by a fire.

Fire Severity - Degree to which a site has been altered or disrupted by fire; loosely, a product of fire intensity and residence time.

Fire Treatment - The use of fire to accomplish a specified objective.

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 Weather - Weather conditions which influence fire ignition, behavior, and suppression.

Fire Weather Forecast - A weather prediction specially prepared for use in wildland fire operations and prescribed fire.

Fire Weather Index (FWI) - A numerical rating in the Canadian fire danger rating system, based on meteorological measurements of fire intensity in a standard fuel type. (The standard fuel type is representative of jack pine and lodgepole pine.) The FWI is comprised of three fuel moisture codes, covering classes of forest fuel of different drying rates, and two indices that represent rate of spread and the amount of available fuel.

Firebrand - Any source of heat, natural or human made, capable of igniting wildland fuels. Flaming or glowing fuel particles that can be carried naturally by wind, convection currents, or by gravity into unburned fuels.

Firebreak - A natural or constructed barrier used to stop or check fires that may occur, or to provide a control line from which to work.

Fire-proofing - Removal or treatment of fuels to reduce the danger of fires igniting or spreading. (E.g., fireproofing roadsides, campsites, structural timber.) Protection is relative, not absolute.

Firing Technique - Any method or pattern of igniting a wildland area to consume the fuel in a prescribed pattern. E.g., heading or backing fire, spot fire, strip-head fire, and ring fire.

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

Flare-up - Any sudden acceleration in rate of spread or intensification of the fire. Unlike blowup, a flare-up is of relatively short duration and does not radically change existing control plans.

Flash Fuels - Highly combustible fine fuels such as grass, leaves, draped pine needles, fern, tree moss and some kinds of slash, which ignite readily and are consumed rapidly when dry.

Fuel - Any combustible material, especially petroleum-based products and wildland fuels.

Fuel Arrangement - A general term referring to the spatial distribution and orientation of fuel particles or pieces.

Fuel Bed - An array of fuels usually constructed with specific loading, depth, and particle size to meet experimental requirements; also, commonly used to describe the fuel composition.

Fuel Characteristics - Factors that make up fuels such as compactness, loading, horizontal continuity, vertical arrangement, chemical content, size and shape, and moisture content.

Fuel Class - Part of the National Fire Danger Rating System (NFDRS). Group of fuels possessing common characteristics. Dead fuels are grouped according to 1-, 10-, 100-, and 1000-hour timelag, and living fuels are grouped as herbaceous (annual or perennial) or woody.

Fuel Condition - Relative flammability of fuel as determined by fuel type and environmental conditions.

Fuel Continuity - The degree or extent of continuous or uninterrupted distribution of fuel particles in a fuel bed thus affecting a fire's ability to sustain combustion and spread. This applies to aerial fuels as well as surface fuels.

Fuel Depth - The average distance from the bottom of the litter layer to the top of the layer of fuel, usually the surface fuel.

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

Fuelbreak - A natural or manmade change in fuel characteristics which affects fire behavior so that fires burning into them can be more readily controlled.

Fuelbreak System - A series of modified strips or blocks tied together to form continuous strategically located fuel breaks around land units.

Ground Fire - Fire that consumes the organic material beneath the surface litter ground, such as a peat fire.

Growing Season Burning - Prescribed burning or wildland fire use during the photosynthetically-active growing season, where live fuel moistures are relatively high and the dominant vegetation, grasses, forbs, and herbaceous vegetation are fully greened.

Home Assessment - Evaluation of a dwelling and its immediate surrounding to determine its potential to escape damage by an approaching wildland fire. Includes the fuels and vegetation in the yard and adjacent to the structure, roof environment, decking and siding materials, prevailing winds, topography, fire history, etc., with the intent of mitigating fire hazards and risks.

Incident Command System (ICS) - A standardized on-scene emergency management concept specifically designed to allow its user(s) to adopt an integrated organizational structure equal to the complexity and demands of single or multiple incidents, without being hindered by jurisdictional boundaries.

Incident Commander (ICT1, ICT2, ICT3, ICT4, or ICT5) - This ICS position is responsible for overall management of the incident and reports to the Agency Administrator for the agency having incident jurisdiction. This position may have one or more deputies assigned from the same agency or from an assisting agency(s).

Ladder Fuels - Fuels which provide vertical continuity between strata, thereby allowing fire to carry from surface fuels into the crowns of trees or shrubs with relative ease. They help initiate and assure the continuation of crowning.

Live Fuels - Living plants, such as trees, grasses, and shrubs, in which the seasonal moisture content cycle is controlled largely by internal physiological mechanisms, rather than by external weather influences.

Mutual Aid - Assistance in firefighting or investigation by fire agencies, without regard for jurisdictional boundaries.

Mutual Aid Agreement - Written agreement between agencies and/or jurisdictions in which they agree to assist one another upon request, by furnishing personnel and equipment.

Mutual Threat Zone - A geographical area between two or more jurisdictions into which those agencies would respond on initial attack. Also called mutual response zone or initial action zone.

National Association of State Foresters (NASF) - An organization consisting of the State Forester from each state and territory which promotes cooperation in forestry matters between the states and territories, the federal government and private forestry groups. It promotes legislation, programs and activities which will advance the practice of forestry and use of forest products.

National Fire Danger Rating System (NFDRS) - A uniform fire danger rating system that focuses on the environmental factors that control the moisture content of fuels.

National Fire Protection Association (NFPA) - A private, non-profit organization dedicated to reducing fire hazards and improving fire service.

Natural Fuels - Fuels resulting from natural processes and not directly generated or altered by land management practices.

Plow Line - Fireline constructed by a fire plow, usually drawn by a tractor or other motorized equipment.

Preparedness - Activities that lead to a safe, efficient, and cost-effective fire management program in support of land and resource management objectives through appropriate planning and coordination. Mental readiness to recognize changes in fire danger and act promptly when action is appropriate. The range of deliberate, critical tasks, and activities necessary to build, sustain, and improve the capability to protect against, respond to, and recover from domestic incidents.

Preparedness Level - Increments of planning and organization readiness commensurate with increasing fire danger.

Preparedness Plan - A written plan providing for timely recognition of approaching critical fire situations, priority setting, the deployment of forces, and other actions to respond to those situations.

Prescribed Burning - Application of prescribed fire.

Prescribed Fire - Any fire ignited by management actions to meet specific objectives. A written, approved prescribed fire plan must exist, and NEPA requirements (where applicable) must be met, prior to ignition.

Prescribed Fire Burn Plan - A plan required for each fire application ignited by management. Plans are documents prepared by qualified personnel, approved by the agency administrator, and include criteria for the conditions under which the fire will be conducted (a prescription). Plan content varies among the agencies.

Rate of Spread - The relative activity of a fire in extending its horizontal dimensions. It is expressed as rate of increase of the total perimeter of the fire, as rate of forward spread of the fire front, or as rate of increase in area, depending on the intended use of the information. Usually it is expressed in chains or acres per hour for a specific period in the fire's history.

Red Flag Warning - Term used by fire weather forecasters to alert forecast users to an ongoing or imminent critical fire weather pattern.

Relative Humidity (RH) - The ratio of the amount of moisture in the air, to the maximum amount of moisture that air would contain if it were saturated. The ratio of the actual vapor pressure to the saturated vapor pressure.

Resource Ordering and Status System (ROSS) - A national system that provides automated support to interagency and agency dispatch and coordination offices. The system will provide current status of resources available to support all-risk activities; enable dispatch offices to exchange and track resource ordering information electronically; enable dispatch offices to rapidly and reliably exchange mission-critical emergency electronic messages.

Safety Zone - An area cleared of flammable materials used for escape in the event the line is outflanked or in case a spot fire causes fuels outside the control line to render the line unsafe. In firing operations, crews progress so as to maintain a safety zone close at hand allowing the fuels inside the control line to be consumed before going ahead. Safety zones may also be constructed as integral parts of fuelbreaks; they are greatly enlarged areas which can be used with relative safety by firefighters and their equipment in the event of blowup in the vicinity.

Size Class of Fire - As to size of wildfire:
Class A - one-fourth acre or less;
Class B - more than one-fourth acre, but less than 10 acres;
Class C - 10 acres or more, but less than 100 acres;
Class D - 100 acres or more, but less than 300 acres;
Class E - 300 acres or more, but less than 1,000 acres;
Class F - 1,000 acres or more, but less than 5,000 acres;
Class G - 5,000 acres or more.

Sizeup - The evaluation of the fire to determine a course of action for suppression.

Spontaneous Combustion - Combustion of a thermally isolated material initiated by an internal chemical or biological reaction producing enough heat to cause ignition.

Spot Weather Forecast - A special forecast issued to fit the time, topography, and weather of a specific incident. These forecasts are issued upon request of the user agency and are more detailed, timely, and specific than zone forecasts. Usually, on-site weather observations or a close, representative observation is required for a forecast to be issued.

Structural Fire Protection - The protection of homes or other structures from wildland fire.

Suppression - All the work of extinguishing or confining a fire beginning with its discovery.

Tractor Plow - Any tractor with a plow for constructing fireline by exposing mineral soil. Also as a resource for typing purposes, a tractor plow includes the transportation and personnel for its operation.

Underburn A fire that consume surface fuels but not the overstory canopy.

Volunteer Fire Company - A fire department company or a response unit, the members of which are not paid.

Volunteer Fire Department (VFD) - A fire department of which some or all members are unpaid.

Wildland Urban Interface (WUI) - The line, area, or zone where structures and other human development meet or intermingle with undeveloped wildland or vegetative fuels.