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)
Daily Activity Level
  • Part of the National Fire Danger Rating System (NFDRS). In fire danger rating, a subjective estimate of the degree of activity of a potential human-caused fire source relative to that which is normally experienced. Five activity levels are defined: none, low, normal, high, and extreme. 
Daily Rate
  • Paid on a calendar day basis (0001-2400).
Damage Differential
  • The comparative differences of damage to objects resulting from the fire’s passage.  Definition Extension: One of the underlying principles that govern the interpretation of most fire pattern indicators. This principle may be observed on various surfaces of individual objects or by comparing the damage within adjoining areas of the fire. Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.
Damage Differential Indicators
  • The amount of fire related destruction to combustible objects determined by comparing opposing sides of an object. 
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). 
Debris Burning Fire
  1. In fire suppression terminology, a fire spreading from any fire originally ignited to clear land or burn rubbish, garbage, crop stubble, or meadows (excluding incendiary fires).
  2. In prescribed fire terminology, a fire used to dispose of scattered, piled, or windrowed dead woody fuel, generally in the absence of a merchantable overstory. Its purpose is to reduce unsightly fuel concentrations, or consume unwanted natural fuels to facilitate subsequent resource management or land use actions on the area. 
  • The helibase operational area that includes the touchdown pad, safety circle, hover lanes, and external cargo transport area. 
Deep-Seated Fire
  1. A fire burning far below the surface in duff, mulch, peat, or other combustibles as contrasted with a surface fire.
  2. A fire that has gained headway and built up heat in a structure so as to require greater cooling for extinguishment. 
  • As it refers to atmospheric pressure, a decrease in the central pressure of a low. This is usually accompanied by intensification of the cyclonic circulation (counter-clockwise wind flow around the low). 
  1. Chemical decomposition by burning material in which the reaction is less than sonic velocity, for example, low explosives.
  2. A burning with great heat and intense light. 
  • In a discussion of fire retardant slurries, deterioration of viscosity. 
Delayed Aerial Ignition Devices (DAID)
  • Polystyrene balls, 1.25 inches in diameter, containing potassium permanganate. The balls are fed into a dispenser, generally mounted in a helicopter, where they are injected with a water-glycol solution and then drop through a chute leading out of the helicopter. The chemicals react thermally and ignite in 25-30 seconds. The space between ignition points on the ground is primarily a function of helicopter speed, gear ratio of the dispenser, and the number of chutes used (up to four). 
Delegation of Authority
  • A statement provided to the incident commander by the agency executive delegating authority and assigning responsibility. The delegation of authority can include objectives, priorities, expectations, constraints and other considerations or guidelines as needed. Many agencies require written delegation of authority to be given to incident commanders prior to their assuming command on larger incidents. 
  • Release of resources from an incident in strict accordance with a detailed plan approved by the incident commander. 
Demobilization Unit
  • Functional unit within the planning section responsible for assuring orderly, safe and efficient demobilization of incident resources. 
Dense Layer
  • A layer of clouds whose ratio of dense sky cover to total sky cover is more than one-half. 
Dense Sky Cover
  • Sky cover that prevents detection of higher clouds or the sky above it. 
Density (Foam)
  • The ratio of the original volume of the nonaerated foam solution to the resultant volume of foam. The inverse of expansion. 
Departure from Average Greenness (DA)
  • An NDVI-derived image of vegetation greenness compared to its average greenness for the current week of the year. 
Depth of Burn (DOB)
  • The reduction in forest floor thickness due to consumption by fire. 
Depth of Char Indicators
  • Sometimes referred to as "alligatoring", where combustible material appears to have a fissured or scaly appearance similar to an alligator's hide. Most commonly associated with finished lumber products, such as boards and fence posts.
  • A qualified individual who could be delegated the authority to manage a functional operation or perform a specific task. In some cases, a Deputy could act as relief for a superior. Deputies can be assigned to the incident commander, general staff, and branch directors. 
  • Chemical that, when applied to a living plant, causes or accelerates drying of its aerial parts; used to facilitate burning of living vegetation by substantially lowering fuel moisture content within a few hours. 
Designated Area
  • Those areas identified as principal population centers or other areas requiring protection under state or federal air quality laws or regulations. 
Designated Dispatch Point (DDP)
  • The address where the unit must be physically located, and dispatched from, during the mandatory availability period. 
  • An extreme rapid decomposition of a material in which the reaction is more than a sonic velocity, for example, high explosives. 
Dew Point
  • Temperature to which a specified parcel of air must cool, at constant pressure and water-vapor content, in order for saturation to occur. The dew point is always lower than the wet-bulb temperature, which is always lower than the dry-bulb temperature, except when the air is saturated and all three values are equal. Fog may form when temperature drops to equal the dew point. 
  • A scale drawing showing information about a fire scene. 
Die-Out Pattern Indicators
  • Fingers or islands of less intensely burned areas or areas where the fire has self extinguished. 
Digital Elevation Model
  • A set of points which defines the terrain as numbers for computer applications. This data may be used to draw contours, make ortho photos, slope maps, and drive fire models. 
  • A control strategy used in managing smoke from prescribed fires in which smoke concentration is reduced by diluting it through a greater volume of air, either by scheduling during good dispersion conditions or burning at a slower rate. 
Direct Attack
  • Any treatment applied directly to burning fuel such as wetting, smothering, or chemically quenching the fire or by physically separating the burning from unburned fuel. 
Direct Line
  • Any treatment applied directly to burning fuel such as wetting, smothering, or chemically quenching the fire or by physically separating the burning from unburned fuel. 
Direct Protection Area
  • That area for which a particular fire protection organization has the primary responsibility for attacking an uncontrolled fire and for directing the suppression action. Such responsibility may develop through law, contract, or personal interest of the firefighting agent (e.g., a lumber operator). Several agencies or entities may have some basic responsibilities (e.g., private owner) without being known as the fire organization having direct protection responsibility. 
Directional Vectors
  • The physical characteristics of the indicators that show the direction of fire spread, i.e., advancing, backing, or lateral. 
  • The ICS title for an individual responsible for supervision of a branch. 
  • Determination that a fire exists. Location and reporting of a fire is not required as is with detection. 
Discovery Time
  • Elapsed time from start of fire (known or estimated) until the time of the first discovery that results directly in fire suppression action. 
Discrete Frequency
  • A separate radio frequency most commonly used in air traffic control which reduces frequency congestion by controlling the number of aircraft or other resources operating on a particular frequency. 
  • The implementation of a command decision to move a resource or resources from one place to another. 
Dispatch Center
  • An organization from which resources are ordered, mobilized or assigned to an incident and/or demobilized. The center may process requests, coordinate response, or track resources and information under the delegation of its benefiting agency(s).
Dispatch Center, Current
  • The dispatch center actively supporting an incident and the resources assigned or a resource who is temporarily transferred for official action i.e. details, temporary duty station, etc.
    • Definition extension: The current dispatch center for an incident may change to support other centers, units or agencies. The current dispatch center may be the same as the incident dispatch center or home dispatch center or may be different. Current dispatch center for tactical aviation resources is directly associated with the resource independent of an incident.
Dispatch Center, Home
  • The dispatch center associated with a resource’s home unit. The Home Dispatch Center is responsible for initial mobilization and is the Center associated with the resource when an assignment is completed.
    • Definition extension: Every resource has a home dispatch center.
Dispatch Center, Ordering
  • The current dispatch center for an incident.
Dispatch Center, Sending
  • Either the home or current dispatch center for a resource.
  • The decrease in concentration of airborne pollutants as they spread throughout an increasing volume of atmosphere. 
Display Class
  • In WIMS, a one-digit number representing the number of decision points used to evaluate the magnitude of the Staffing Index. 
Display Class Breakpoints
  • In WIMS, the climatological breakpoints separating the highest staffing levels. Commonly these are the index values corresponding to the 90th and 97th or 80th and 95th percentiles for the staffing index. 
Distance Learning (DL)
  • A concept of providing access to quality wildland fire education and training using appropriate instructional technology, delivered anywhere, anytime to prepare a fire management work force to safely achieve fire management objectives. 
Distance Measuring Equipment (DME)
  • Aircraft navigational equipment that provides the slant range distance in miles (kilometers) from the aircraft to the VOR station to which the DME is tuned, usually at or near an airport. 
Distributed Incident Simulation Exercise (DISE)
  • An on-line mission rehearsal event providing an individual or team with an experiential learning environment utilizing the National Interagency Incident Management System to "game" a computer generated incident from multiple training locations.
  • A weather system usually associated with clouds, rain and/or wind. 
  • Daily, especially pertaining to cyclic actions which are completed within 24 hours, and which recur every 24 hours, such as temperature, relative humidity and wind. 
  • The expansion or spreading out of a horizontal wind field. Generally associated with high pressure and light winds. 
  • The ICS organization level between the branch and the task force/strike team. Divisions are used to divide an incident into geographical areas of operation. Divisions are established when the number of resources exceeds the span-of-control of the operations chief. 
Documentation Unit
  • Functional unit within the planning section responsible for collecting, recording and safeguarding all documents relevant to the incident. 
Dormant Season Burning
  • Prescribed burning early in the dry season before the leaves and undergrowth are completely dry or before the leaves are shed, as an insurance against more severe fire damage later on. 
Double Arsonist
  • An offender who sets two fires at one site, at the same time, in a single event. 
Double Doughnut
  • Two lengths of hose rolled side by side or a single length rolled into two small coils for convenient handling. 
Double Female Coupling
  • A hose-coupling device having two female swivel couplings to permit joining two male hose nipples of the same size and thread type when lines are laid with couplings in opposite or reverse directions. 
Double Jacket Hose
  • Fire hose having two cotton or other fiber jackets outside the rubber lining or tubing. 
Double Male Coupling
  • A hose-coupling device having two male thread nipples for connecting hose and for connecting two female couplings of the same diameter. 
Double Shift
  • Equipment is staffed with 2 operators or crews (1 per shift) and must be ordered and documented on a resource order. (Reference OF-294 general clauses for payment information.) Regardless of hiring method, on-shift time for operated equipment will be recorded with clock hours on the appropriate document, e.g., equipment hired under a daily rate will be posted with start and stop time for daily work.
Doughnut Roll
  • A 50 or 100-foot length of hose or a 50-foot length of hose rolled up for easy handling. There are various ways of forming the doughnut. A convenient one has both couplings close together with the male thread protected by the female coupling. 
  • A calculated reduction in actual payload to provide a margin of safety. 
  • Any steel tracked vehicle equipped with a front mounted blade used for exposing mineral soil.
Dozer Company
  • A resource that includes a dozer, its transportation unit and a standard complement of personnel for its operation. 
Dozer Line
  • Fireline constructed by the front blade of a dozer. 
Dozer Tender
  • Any ground vehicle with personnel capable of maintenance, minor repairs, and limited fueling of dozers. 
  • Drawing water from static sources such as a lake, pond, cistern, river, etc. into a pump which is above the level of the water supply. This is done by removing the air from the pump and allowing atmospheric pressure [14.7 psi (101 kPa) at sea level] to push water through a noncollapsible suction hose into the pump. 
Drain Time
  • The time (minutes) it takes for foam solution to drop out from the foam mass; for a specified percent of the total solution contained in the foam to revert to liquid and drain out of the bubble structure. 
Draped Fuels
  • Needles, leaves, and twigs that have fallen from above and have lodged on lower branches or brush. Draped fuels are part of aerial fuels. 
  • Effect of wind on smoke, retardant drops, paracargo, smokejumper streamers, etc. 
Drift Smoke
  • Smoke that has drifted from its point of origin and is no longer dominated by convective motion. May give false impression of a fire in the general area where the smoke has drifted. 
Drip Torch
  • Hand-held device for igniting fires by dripping flaming liquid fuel on the materials to be burned; consists of a fuel fount, burner arm, and igniter. Fuel used is generally a mixture of diesel and gasoline. 
Drive Axle
  • An axle that supports a portion of the vehicle weight and transmits a driving force to the wheels. 
Drive Wheels
  • Wheels powered by all of the vehicle's drive axles. Dual tires are considered as single wheels. The number of wheels is commonly referenced by the terms "4x2", "4x4", etc. where the first figure indicates the total number of wheels on the ground and the second figure, the number of drive wheels.
  • Precipitation composed exclusively of water drops smaller than 0.02 inches (0.5 mm) in diameter. 
Drop Configuration
  • The type of retardant drop selected to cover a ground target. Terms that can specify the type of drop configuration include Salvo Drop and Trail Drop. 
Drop Pass
  • Indicates that the airtanker has the target in sight and will make a retardant drop on this run over the target. 
Drop Pattern
  • The distribution of an aerially delivered retardant drop on the target area in terms of its length, width, and momentum (velocity x mass) as it approaches the ground. The latter determines the relative coverage level of the fire retardant on fuels within the pattern. 
Drop Zone (DZ)
  • Target area for airtankers, helitankers, cargo dropping. 
  • A period of relatively long duration with substantially below-normal precipitation, usually occurring over a large area. 
Drought Index
  • A number representing the net effect of evaporation, transpiration and precipitation in producing cumulative moisture depletion in deep duff or upper soil layers. 
Drum Lifter
  • Device used to transport a 55-gallon drum (208 L) via sling on a helicopter. 
  • The government furnishes all operating supplies after the equipment arrives at the incident.
Dry Adiabatic Lapse Rate
  • The rate of decrease of temperature with height of a parcel of dry air lifted adiabatically through an atmosphere in hydrostatic equilibrium. Numerically equal to 9.7670 C degrees per km or about 5.40 F degrees per thousand feet. 
Dry Air Mass
  • A portion of the atmosphere that has a relatively low dew point temperature and where the formation of clouds, fog, or precipitation is unlikely. 
Dry Bulb
  • A name given to an ordinary thermometer used to determine the temperature of the air (to distinguish it from the wet bulb). 
Dry Bulb Temperature
  • The temperature of the air measured in the shade 4-8 feet above the ground. 
Dry Episode (DE)
  • A contiguous series of days having a pre-established number of fire ignitions with a fuel dryness level that historically resulted in a significant fire event for a particular area. 
Dry Foam
  • A low expansion foam type with stable bubble structure and slow drain time which is used primarily for resource and property protection. 
Dry Hydrant
  1. 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).
  2. Permanently installed supply private fire pumps which depend upon suction sources. Also called suction pipe. 
Dry Lightning Storm
  • Thunderstorm in which negligible precipitation reaches the ground. Also called dry storm. 
Dry Run
  • A trial pass over the target area by a leadplane and/or an airtanker to pinpoint target areas and warn ground personnel of the impending retardant or extinguishing agent drop. 
Dry Storage
  • Refers to dry chemical retardants stored at air attack bases and available for mixing with water. 
Dry-bulb Temperature
  • Temperature of the air. 
Dry-bulb Thermometer
  • In a psychrometer, the thermometer not covered with muslin which is used to determine air temperature.
  • The layer of decomposing organic materials lying below the litter layer of freshly fallen twigs, needles, and leaves and immediately above the mineral soil. 
Durability (Foam)
  • The effective life span of foam bubbles. 
Duty Week
  • Regular number of hours worked per week by a full-time firefighter, excluding overtime.