NWCG Glossary of Wildland Fire, PMS 205

This glossary provides the wildland fire community a single source for wildland fire and incident management terminology commonly used by the NWCG and its subgroups.

Glossary entries related to Organizations, IT Applications, and NWCG Positions have been removed from the glossary based on term inclusion criteria. For more information about the glossary and the criteria, see the About the NWCG Glossary page or the NWCG User Guide for the Glossary of Wildland Fire, PMS 937.

Reference Definitions

Some of the terms within this glossary will be followed by initials or will have references or comments at the end of the definition to help broaden the recognition and understanding of the term. An explanation of those references is as follows:

Also called: Means there is another term that may sometimes be in use, but is not defined in this glossary.
Acronym: An abbreviation formed from the initial letters of other words and pronounced as a word. An acronym appears in parentheses following the term.
Initialism: An abbreviation consisting of initial letters pronounced separately. An initialism appears in parentheses following the term.
See: Means there is another, preferred term that should be used instead. In such a case only the preferred term is defined in this glossary.
See Also: Means there are one or more related terms that may also be of interest to the glossary user. The related terms are also defined in this glossary.
Synonym: Means the term is synonymous with another. The terms have the same, or essentially the same, definition and the terms are interchangeable in their use.
Definition Extension: An example, further explanation, or usage guidance in support of the definition.

Glossary Acronyms/Initialisms

6 (1) | A (126) | B (94) | C (160) | D (102) | E (67) | F (261) | G (48) | H (90) | I (83) | J (10) | K (4) | L (74) | M (92) | N (31) | O (47) | P (133) | Q (6) | R (100) | S (221) | T (71) | U (28) | V (37) | W (60) | Z (1)
  • Used in some localities to specify fire set to spread against the wind in prescribed burning. 
  • Instantaneous explosion or rapid burning of superheated gases that occurs when oxygen is introduced into an oxygen-depleted confined space. It may occur because of inadequate or improper ventilation procedures. 
  • A fire set along the inner edge of a fireline to consume the fuel in the path of a wildfire or change the direction of force of the fire's convection column. 
Backfire Torch
  • A flame generating device (e.g., a fount containing diesel oil or kerosene and a wick, or a backpack pump serving a flame-jet). 
  • A tactic associated with indirect attack, intentionally setting fire to fuels inside the control line to slow, knock down, or contain a rapidly spreading fire. Backfiring provides a wide defense perimeter and may be further employed to change the force of the convection column. Backfiring makes possible a strategy of locating control lines at places where the fire can be fought on the firefighter's terms. Except for rare circumstance meeting specified criteria, backfiring is executed on a command decision made through line channels of authority. 
Background Level
  • In air pollution control, the concentration of air pollutants in a definite area during a fixed period of time prior to the starting up, or the stoppage, of a source of emission under control. In toxic substances monitoring, the average presence in the environment, originally referring to naturally-occurring phenomena. 
Backing Fire
  1. Fire spreading, or ignited to spread, into (against) the wind or downslope. A fire spreading on level ground in the absence of wind is a backing fire.
  2. That portion of the fire with slower rates of fire spread and lower intensity normally moving into the wind and/or down slope. Also called: heel fire. 

Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.

Backing Wind
  • According to the American Meteorological Society, in the Northern Hemisphere, a wind that rotates in the counterclockwise direction with increasing height. In fire management usage, in the Northern Hemisphere, a wind that rotates in the counterclockwise direction over a given time period (normally a few hours). Source: http://glossary.ametsoc.org/wiki/Backing_wind
Backpack Pump
  • A portable sprayer with hand-pump, fed from a liquid filled container fitted with straps, used mainly in fire and pest control. 
  • A partitioned wall placed in vehicular or aircraft water tanks to reduce shifting of the water load when starting, stopping or turning. 
Ball Valve
  • A valve in which fluid flow is controlled by a ball with a hole drilled through it. In one position, fluid flows through the hole. When the valve is turned 90 degrees (1/4 turn) the hole is perpendicular to the flow and the ball stops the flow. Intermediate valve positions can be used to adjust the flow. 
Bambi Bucket
  • A collapsible bucket slung below a helicopter. Used to dip water from a variety of sources for fire suppression. 
Banking Snags
  • The act of throwing mineral soil about the base of an unlighted snag to prevent its being ignited by a surface fire. 
Barometric Pressure
  • Any obstruction to the spread of fire. Typically an area or strip devoid of combustible fuel. 
  1. The location at which primary logistics functions for an incident are coordinated and administered. There is only one base per incident. (Incident name or other designator will be added to the term "base.") The incident command post may be collocated with the base.
  2. The location of initial attack forces.
Base Area
  • Part of the National Fire Danger Rating System (NFDRS). An area representative of the major fire problems on a protection unit. Base fuel model and slope class are chosen from the base area. 
Base Fuel Model
  • Part of the National Fire Danger Rating System (NFDRS). A representation of the vegetative cover and fuel in a base area. Used in the calculation of fire danger rating. 
Base Hours
  • The number of hours in a daily tour of duty.
Base Observation Time
  • Part of the National Fire Danger Rating System (NFDRS). The time established to take the fire danger observations. It should be at the time of day when the fire danger is normally the highest. The usually agreed upon time is 1:00 pm standard time. This allows time to transmit observations and prepare forecasts. 
Base Station
  • A fixed central radio dispatching station controlling movements of one or more mobile units. 
  • In prescribed burning, the initial line of fire, usually set as a backing fire along a barrier or control line, which serves to contain subsequent burning operations. 
Basic Life Support (BLS)
  • Basic life support skills performed by an EMS practitioner or service, e.g. splinting, bandaging, oxygen administration, use of the AED. 
Basic Workweek
  • Refers to the scheduled workweek of the employee (individual) at the home unit.
Batch Mix
  • Manually adding and mixing a concentrated chemical, such as liquid foam, or powdered or liquid retardant with water, or gelling agents with fuel, into solution in a tank or container. 
Beaufort Wind Scale
  • A system of interactive computer programs for modeling fuel and fire behavior, comprised of two systems: BURN and FUEL. 
  • An observable activity or action demonstrated by an individual in a particular context. 
Belt Weather Kit
  • Belt-mounted case with pockets fitted for anemometer, compass, sling psychrometer, slide rule, water bottle, pencils, and book of weather report forms. Used to take weather observations to provide on-site conditions to the fire weather forecaster or fire behavior analyst. Observations include air temperature, wind speed and direction, and relative humidity. 
  • Something that represents, promotes or enhances a desired outcome, being of positive value and contributing to the attainment of organizational goals. Benefits represent one end of the spectrum of outcomes from fire, with the opposite end being harm, loss or damage. 
  • A ridge of soil and debris along the outside edge of a fireline, resulting from line construction. 
Best Available Control Measures (BACM)
  • An emission limitation action based on the maximum degree of emission reduction (considering energy, environmental, and economic impacts) achievable through application of production processes and available methods, systems, and techniques. 
Billable/Reimbursable Costs
  • Those agency costs that are billable and/or reimbursable as defined by the master or individual cost share agreement.
  • Preburning of fuels adjacent to a control line before igniting a prescribed burn. Blacklining is usually done in heavy fuels adjacent to a control line during periods of low fire danger to reduce heat on holding crews and lessen chances for spotting across control line. In fire suppression, a blackline denotes a condition where there is no unburned material between the fireline and the fire edge. 
Bladder Bag
  • A collapsible backpack portable sprayer made of neoprene or high-strength nylon fabric fitted with a pump. 
Blind Area
  • An area in which neither the ground nor its vegetation can be seen from a given observation point. 
Block Plan
  • A detailed prescription for treating a specified burning block with fire. 
  • Sudden increase in fireline intensity or rate of spread of a fire sufficient to preclude direct control or to upset existing suppression plans. Often accompanied by violent convection and may have other characteristics of a fire storm. 
Board of Review
  • A board or committee selected to review results of fire suppression action on a given unit or the specific action taken on a given fire. The board reviews the results in order to identify reasons for both good and poor action and to recommend or prescribe ways and means of doing an effective and efficient job. Reviews the results of a safety/accident investigation. 
Boiling Liquid Expanding Vapor Explosion (BLEVE)
  1. The failure of a closed container as a result of overpressurization caused by an external heat source.
  2. A major failure of a closed liquid container into two or more pieces when the temperature of the liquid is well above its boiling point at normal atmospheric pressure. 
  • The trunk of a tree. 
Bone Yard
  1. A mop up term. To "bone yard" a fire means to systematically work the entire area, scraping embers off remaining fuel, feeling for heat with the hands, and piling unburned materials in areas cleared to mineral soil.
  2. An area cleared to mineral soil for piling unburned fuels.
Booster Hose
  • The most common type of hose attached and stored on wildland engine booster reels. The hose is made of neoprene and does not appreciably collapse when stored empty. 
Booster Pump
  • An intermediary pump for supplying additional lift in pumping water uphill past the capacity of the first pump. 
Booster Reel
  • A reel for the booster hose mounted on a fire engine, often supplied by the auxiliary pump. This reel usually carries a 1-inch (25 mm) or 3/4 inch (19 mm) hose and frequently contains an electric rewind mechanism. 
Boundary Conditions
  • The temperature and relative humidity of the boundary layer. 
Boundary Layer
  1. According to the American Meteorological Society, the layer of air near a boundary that is affected by friction against that boundary surface, and possibly by transport of heat and other variables across that surface.
  2. According to the American Meteorological Society, (also called the atmospheric boundary layer) the bottom layer of the troposphere that is in contact with the surface of the earth. It is often turbulent and is capped by a statically stable layer of air or temperature inversion. Source: http://glossary.ametsoc.org/wiki/Boundary_layer
Boundary Value
  • The equilibrium moisture content (EMC) commensurate with the boundary conditions and precipitation events of the preceding 24 hours. 
Bowles Bag
  • A neoprene tank designed for attachment to the landing skid frame of a helicopter. It has a capacity of 80 to 100 gallons (303 to 378 liters) of water or retardant. 
Box Canyon
  • A steep-sided, dead end canyon. 
  • The organizational level having functional or geographical responsibility for major parts of incident operations. The branch level is organizationally between section and division/group in the operations section, and between section and unit in the logistics section. Branches are identified by roman numerals or by functional name (e.g. service, support). 
Break a Line
  • To insert a gate valve or some other device into a hose line. 
Break Coupling
  • To detach two pieces of hose by backing the swivel thread off the nipple thread. 
Break Left or Right
  • Means "turn" left or right. Applies to aircraft in flight, usually on the drop run, and when given as a command to the pilot, implies expectation of prompt compliance.
British Thermal Unit (Btu)
  • Amount of heat required to raise 1 pound of water 1 degree Fahrenheit (from 59.50 to 60.50 F), measured at standard atmospheric pressure. 
Broadcast Burning
  • Prescribed burning activity where fire is applied generally to most or all of an area within well defined boundaries for reduction of fuel hazard, as a resource management treatment, or both. 
Brown and Burn
  • Application of herbicide to desiccate living vegetation prior to burning. 
Brownspot Control
  • Prescribed fire to control fungal infection (brown spot disease) of longleaf pine (Pinus palustris) in the "grass" (small seedling) stage.
  • A collective term that refers to stands of vegetation dominated by shrubby, woody plants, or low growing trees, usually of a type undesirable for livestock or timber management. 
Brush Blade
  • Blade attachment with long teeth specially suited to ripping and piling brush with minimum inclusion of soil. Also called brush rake or root rake. 
Brush Fire
  • A fire burning in vegetation that is predominantly shrubs, brush, and scrub growth. 
Brush Hook
  • A heavy cutting tool designed primarily to cut brush at the base of the stem. Used in much the same way as an axe and having a wide blade, generally curved to protect the blade from being dulled by rocks. 
Brush Management
  • Manipulation of stands of brush by manual, mechanical, chemical, or biological means or by prescribed burning for the purpose of achieving land management objectives. 
Brush Patrol Unit
  • Any light, mobile vehicular unit with limited pumping and water capacity for off-road operations. 
  • The building block of foam; bubble characteristics of water content and durability influence foam performance. 
Bucket Drops
  • The dropping of fire retardants or suppressants from specially designed buckets slung below a helicopter. 
  • Sawing through the bole of a tree after it has been felled. 
  1. The cumulative effects of long-term drying on current fire danger.
  2. The increase in strength of a fire management organization.
  3. The accelerated spreading of a fire with time.
  4. Towering cumulus clouds which may lead to thunderstorms later in the day. 
Buildup Index (BUI)
  • A relative measure of the cumulative effect of daily drying factors and precipitation on fuels with a ten-day timelag. 
  • A general alert from an NWCG committee to the wildland fire community regarding the release of subject-specific information such as technical information, equipment updates, accident reports, etc. Depending on the origin and/or the subject content, a green hash-marked bordered stationary may be associated with this type of alert.
Bumpup Method
  • Progressive method of fireline construction on a wildfire without changing relative positions in the line. Work is begun with a suitable space between workers; whenever one worker overtakes another, all of those ahead move one space forward and resume work on the uncompleted part of the line. The last worker does not move ahead until work is completed in his/her space. Forward progress of the crew is coordinated by a crew boss. 
  1. An area burned over by wildland fire.
  2. A reference to a working fire.
  3. An injury to flesh caused by a cauterizing agent, heat from a fire, or a heated object.
    • First Degree Burn: A burn which causes only pain, redness, and swelling.
    • Second Degree Burn: A burn in which the skin is blistered.
    • Third Degree Burn: A flesh burn in which charring occurs.
  4. To be on fire.
  5. To consume fuel during rapid combustion.
  6. A fire in progress or under investigation. 
Burn Block
  • A discrete area within a larger prescribed or fire use project. 
Burn Out
  • Setting fire inside a control line to consume fuel between the edge of the fire and the control line. 
Burn Out Time
  • The duration of flaming and smoldering combustion phases at a specified point within a burn or for the whole burn, expressed in convenient units of time. 
Burn Patterns
  1. The characteristic configuration of char left by a fire. In wildland fires burn patterns are influenced by topography, wind direction, length of exposure, and type of fuel. Definitions are scale-dependent: (1) They can be used to trace a fire's origin; (2) They are influenced by severity and intensity within a stand; (3) They describe the landscape mosaic.
  2. Apparent and obvious design of burned material and the burning path from the area of origin. 
Burn Severity
  • A qualitative assessment of the heat pulse directed toward the ground during a fire. Burn severity relates to soil heating, large fuel and duff consumption, consumption of the litter and organic layer beneath trees and isolated shrubs, and mortality of buried plant parts. 
Burned Area Emergency Response (BAER) Team
  • BAER teams are formed to analyze post-fire conditions and to take immediate emergency stabilization action to prevent loss of life and property and critical and natural resources. It is the Agency Administrator’s responsibility to order or designate a BAER Team.
Burned Area Rehabilitation
  • The post-fire activities prescribed and implemented to rehabilitate and restore fire damaged lands. 
  • Decomposition of material by the application of heat and oxidation. Also applied to propellants and other pyrotechnic mixtures, though the proper term there is "reacting". Also often an element of the crime of arson.
Burning Ban
  • A declared ban on open air burning within a specified area, usually due to sustained high fire danger. 
Burning Conditions
  • The state of the combined factors of the environment that affect fire behavior in a specified fuel type. 
Burning Index
  1. An estimate of the potential difficulty of fire containment as it relates to the flame length at the head of the fire.
  2. A relative number related to the contribution that fire behavior makes to the amount or effort needed to contain a fire in a specified fuel type. Doubling the burning index indicates that twice the effort will be required to contain a fire in that fuel type as was previously required, providing all other parameters are held constant. 
Burning Index Meter
  • A device used to determine the burning index for different combinations of burning index factors. 
Burning Out
  • Setting fire inside a control line to consume fuel located between the edge of the fire and the control line. 
Burning Period
  • That part of each 24-hour period when fires spread most rapidly; typically from 10:00 AM to sundown. 
Burning Priority Rating
  • System of rating slash to indicate the treatment objective, whether or not burning is required to meet that objective, the fuel treatment necessary to achieve successful burning, and the time of year burning should occur. 
Burning Rate
  • Rate at which a propellant and other combustibles burn. 
Burning Rotation
  • The planned number of years between prescribed fires on a specified area. 
Burning Torch
  • A flame generating device (e.g., a fount containing diesel oil or kerosene and a wick, or a backpack pump serving a flame-jet). 
  • An event in which a fire moves through a location or overtakes personnel or equipment where there is no opportunity to utilize escape routes and safety zones, often resulting in personal injury or equipment damage. 
Buying Team
  • A team that supports one or more incidents and is authorized to procure a wide range of services, supplies, and land and equipment rentals. In addition, the Buying Team Leader has the responsibility of coordinating property accountability with the Supply Unit Leader.
Buys Ballots Law
  • According to the American Meteorological Society, a law describing the relationship of the horizontal wind direction in the atmosphere to the pressure distribution; if one stands with the back to the wind, the pressure to the left is lower than to the right in the Northern Hemisphere. Source: http://glossary.ametsoc.org/wiki/Buys_ballot%27s_law