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)
  • An area that, in relation to wildland/urban fire, has a set of conditions that provides the opportunity for fire to burn from wildland vegetation to the home/structure ignition zone. 
Identification Run
  • Dry run over the target area by the leadplane to indicate an airtanker's flight path and target, while the airtanker pilot is observing. 
  • A pyrotechnic device specifically designed to initiate burning of a fuel mixture or propellant. 
Ignition Area (IA)
  • The smallest area that a wildland fire investigator can define based on the physical evidence of the fire pattern indicators, within the specific origin area, in which a competent ignition source came into contact with the first fuel ignited and combustion was sustained. Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.
Ignition Component
  • Part of the National Fire Danger Rating System (NFDRS). A rating of the probability that a firebrand will cause an actionable fire. 
Ignition Energy
  • Quantity of heat or electrical energy that must be absorbed by a substance to ignite and burn. 
Ignition Factor
Ignition Method
  • The means by which a fire is ignited, such as hand-held drip torch, helitorch, and backpack propane tanks. 
Ignition Pattern
  • Manner in which a prescribed fire is ignited. The distance between ignition lines or points and the sequence of igniting them is determined by weather, fuel, topography, firing technique, and other factors which influence fire behavior and fire effects. 
Ignition Probability
  • Chance that a firebrand will cause an ignition when it lands on receptive fuels. (Syn. IGNITION INDEX) 
Ignition Sequence
Ignition Source
Ignition Time
  • Time between application of an ignition source and self-sustained combustion of a fuel. 
Ignition Trigger
  • A causative agent for wildland fire. For example, human or lightning. 
IMI Interactivity Levels
IMI Level 1 Interactivity
  • This is the lowest level of courseware development. It is normally a knowledge familiarity lesson, provided in a linear format (one idea after another). Use Level 1 to introduce an idea or concept, or to familiarize. Provide minimal interactivity by using selectable screen icons that are inserted into the linear, or almost linear, flow of the courseware. Allow the student little or no control of the sequence of instructional media presented, including: simple developed graphics, clip art, customer provided video and audio segments (clips). Make use of typical input/output peripherals throughout the lesson. 
IMI Level 2 Interactivity
  • This involves the recall of more information than a level 1 and allows the student more control over the lesson scenario through screen icons and other peripherals, such as light pens or touch screens. Typically level 2 is used for non-complex operations and maintenance lessons. Simple emulations or simulations are presented to the user. As an example, the user is requested to rotate switches, turn dials, make adjustments, or identify and replace a faulted component as part of a procedure. This also may include simple to standard developed graphics, and/or clip art, and video and audio clips. 
IMI Level 3 Interactivity
  • This involves the recall of more complex information (compared to levels 1 and 2) and allows the user an increased level of control over the lesson scenario through peripherals such as light pen, touch screen, track ball, or mouse. Video, graphics, or a combination of both is presented simulating the operation of a system, subsystem, or equipment to the user. The lesson scenario training material typically is complex and involves more frequent use of peripherals to affect a transfer of learning. Operation and maintenance procedures are normally practiced with level 3 scenarios and students may be required to alternate between multiple screens to keep pace with the lesson material. Multiple software branches (two to three levels) and rapid response are provided to support remediation. Emulations and simulations are an integral part of this presentation. This may also include complex developed graphics, and/or clip art, and video and audio clips. 
  • Rotating part of a centrifugal pump which imparts energy to the liquid to be moved. For shearing purposes, the impeller is on a rotating shaft within the body of liquid. 
Implementation Plan
  • The design and definition of all the activities, resources, limitations, and contingencies required for successful wildland fire management. 
  • A term used in weather primarily to describe a weak disturbance that does not necessarily have an associated storm center or surface low. The disturbance usually does not create severe weather and is frequently associated with a marine air push. 
In-stand Wind
  • Wind speed within a stand at about eye level. 
  • A burning compound or metal used to produce intense heat or flame, like a bomb. 
Incendiary Device
  • Contrivance designed and used to start a fire. 
Incendiary Fire
  • A fire that is intentionally ignited in an area or under circumstances where and when there should not be a fire.  Source:  NFPA 921 (2017) 3.3.116
  • An occurrence either human-caused or natural phenomenon, that requires action or support by emergency service personnel to prevent or minimize loss of life or damage to property and/or natural resources. 
Incident Action Plan (IAP)
  • Contains objectives reflecting the overall incident strategy and specific tactical actions and supporting information for the next operational period. The plan may be oral or written. When written, the plan may have a number of attachments, including: incident objectives, organization assignment list, division assignment, incident radio communication plan, medical plan, traffic plan, safety plan, and incident map. Formerly called shift plan. 
Incident Agency
  • The organizational unit responsible for the incident activities.
Incident Assignment
  • An assignment to an incident that requires a length of commitment.
Incident Base
  • Location at the incident where the primary logistics functions are coordinated and administered. (Incident name or other designator will be added to the term Base.) The incident command post may be collocated with the base. There is only one Base per incident. 
Incident Blanket Purchase Agreement (IBPA)
  • A pre-season agreement for equipment, supplies, or services to be used on fire and all-hazards incidents, issued on a Solicitation/Contract/Order for Commercial Items, SF-1449 form. I-BPAs are awarded on a competitive basis using commercial item procedures.
Incident Command Post (ICP)
  • Location at which primary command functions are executed. The ICP may be collocated with the incident base or other incident facilities. 
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 Communications Center
  • The location of the communications unit and the message center. 
Incident Complex
  • Business Rules
    • An Incident complex is not a wildfire incident and is not interchangeable with a wildfire record.
    • An Incident Commander or Incident Management Team may manage multiple wildfires without creating an incident complex.
  • Source: Event Kind Category Revision Rational Document
Incident Management Team
  • The incident commander and appropriate general and command staff personnel assigned to an incident. 
Incident Medical Specialist Program
  • An incident-based program to care for emergent and minor medical as well as common occupational health care problems of incident personnel. This program may be deployed to Type I and Type II incidents. Currently, this program is only available in three regions: Northwest (R6), Northern Rockies (R1) and Alaska (R10). In Alaska, the program is known as the Firemedic. 
Incident Objectives
  • Incident-specific statements of direction necessary for the selection of strategy(s) and tactical activities of resources on an incident.
    • Definition Extension:  1)  Incident objectives are derived from the management goals of the Authority Having Jurisdiction (AHJ).  2)  Incident Objectives should be attainable and measurable, yet flexible enough to allow for strategic and tactical alternatives.
Incident Order Number
  • The number assigned to an incident. This number follows a standard format where the first two letters indicate the state, the next letters are the incident agency, and the last six digits are agency assigned.
Incident Organization
  • Resources, together with a complement of overhead personnel, calculated to be sufficient to provide fire efficient incident management. 
Incident Overhead
  • All supervisory positions described in the Incident Command System. 
Incident Qualifications Card
  • A card issued to persons showing their incident management and trainee qualifications to fill specified fire management positions in an incident management organization. 
Incident Support Cache
  • Refers to type 1 (national interagency support cache), type 2 (national interagency support cache satellite), and type 3 (local interagency support cache). Caches may consist of a pre-determined complement of tools, equipment and/or supplies stored in a designated location, available for incident use.
Incident Support Organization
  • Includes any off-incident support provided to an incident. Examples would be agency dispatch centers, airports, mobilization centers, etc. 
Incident Weather Forecast
Incident with Potential
  • Wildland fire-related mishap that results in serious or non-serious injuries involving multiple personnel, near accident (which would have resulted in a serious injury or fatality), or substantial loss of property (less than $250,000). The mishap may be so complex and fraught with operational discrepancies that it has the potential to produce an accident, serious injury, or fatality given a similar environment or set of circumstances that existed at the time of the incident. 
  • Increasing coupling used on hose, pump, or nozzles to permit connection of a larger size of hose. 
Incremental Drop
  • Airtanker drop in which tank doors are opened in sequence so that fire retardant cascades somewhat continuously. 
Independent Action
  • Fire suppression activities by other than regular fire suppression organizations or a fire cooperator. 
Independent Crown Fire
  • A fire that advances in the tree crowns alone, not requiring any energy from the surface fire to sustain combustion or movement. Also called running crown fire. 
Indicated Airspeed (IAS)
  • The speed of an aircraft as shown on its pitot static airspeed indicator. Calibrated to reflect standard atmosphere adiabatic compressible flow at sea level, uncorrected for airspeed system errors. 
  • Visual remains at a fire scene revealing the fire?s progress and action. 
Indicator Categories
  • Classification of indicators into a variety of categories based on how they are formed and the types of material they are found on. 
Indirect Attack
  • A method of suppression in which the control line is located some considerable distance away from the fire's active edge. Generally done in the case of a fast-spreading or high-intensity fire and to utilize natural or constructed firebreaks or fuel breaks and favorable breaks in the topography. The intervening fuel is usually backfired; but occasionally the main fire is allowed to burn to the line, depending on conditions. 
  • A control mechanism that allows a regulated quantity of foam concentrate to be introduced into the main hose line. 
Industrial Fire Precaution Level (IFPL)
  • An application of fire danger rating to support regulation of contractors involved in land management activities for fire prevention purposes in the Pacific Northwest. 
Infrared (IR)
  • A heat detection system used for fire detection, mapping, and hotspot identification.
Infrared Groundlink (IR)
  • A capability through the use of a special mobile ground station to receive air-to-ground IR imagery at an incident. 
  • Process of extinguishing fire by the use of an agent that interrupts the chemical reactions in the combustion process. 
  • Any agent which retards a chemical reaction. 
Initial Action
Initial Attack (IA)
Initial Attack Crew
  • Specially trained and equipped fire crew for initial attack on a fire. 
Initial Attack Fire (IAF)
  • Fire that is generally contained by the attack units first dispatched, without a significant augmentation of reinforcements, within two hours after initial attack, and full control is expected within the first burning period. 
Initial Investigative Area
Initial Response
Inmate Crew
  • Any fire crew composed of prison inmates or wards. 
Inside Diameter (ID)
  • The internal diameter of a tube, conductor, or coupling, as distinguished from its OD (Outside Diameter). Fire hose sizes are classified by a nominal internal diameter. 
Instrument Flight Rules Conditions (IFR)
  • Weather conditions below the minimum for flight under Visual Flight Rules and therefore requiring the observance of instruments inside the aircraft for controlling flight; generally considered to be less than 1000' AGL and 3 miles distant. 
Instrument Landing System (ILS)
  • System for airplane landing in which the pilot is guided by radio beams. 
Instrument Shelter
  • Naturally or artificially ventilated structure, constructed to specifications and used to shield weather measuring instruments from direct sunshine and precipitation. 
Interactive Multimedia Instruction (IMI)
  • A group of predominantly interactive, electronically delivered training. IMI products include instructional software and software management tools used in support of instructional programs. IMI products are teaching and management tools and may be used in combination or individually. Used individually, not all IMI products can be considered interactive, multimedia, or instructional. However, IMI products, when used in combination with one another, are interactive, multimedia, and instructional. IMI technology is one of the primary technologies to be used in distance learning. 
Interagency Authoritative Data Source (IADS)
  • A product, tool, or IT application that has been designated as the trusted source for wildland fire data. This source may also create and update transactional data for use in other applications. There may be more than one IADS and it can change depending on business process complexity and life cycle. An IADS may be a compilation or subset of data from other authoritative sources. The DLM process ensures sources, limitations, currency, and attributes for the IADS are documented.
Interagency System of Record (ISOR)
  • Agencies and bureaus may have their own SOR for their data. An ISORs are identified by an interagency business area as the official application source of interagency data. An ISOR is the source that resolves duplicate records that may arise from various IADSs and ensures the data meets defined quality standards before it is included in official historical data sets. An ISOR can be an external source of data used by wildland fire.
Intermittent Smoke
  • Smoke which becomes visible only at intervals. 
Internal Load
  • Load carried inside the fuselage structure of an aircraft. 
Internal Payload
  • Allowable aircraft cabin load, in pounds, with full fuel and pilot in calm air at standard atmosphere. 
  • Atmospheric inversion. The departure from the usual increase or decrease with altitude of the value of an atmospheric property. In fire management usage, nearly always refers to an increase in temperature with increasing height. Also, the layer through which this departure occurs (also called inversion layer.) The lowest altitude at which the departure is found is called the base of the inversion. 
Iron Pipe Thread (IPT)
  • A tapered thread standard that is used for connecting various sizes of rigid pipe. This standard may be referred to as tapered iron pipe thread (TIPT), National pipe thread (NPT), iron pipe thread (IPT), or iron pipe standard thread (IPS). With tapered thread, the threads and pipe sealant perform the seal at the connection. This is opposed to straight thread connectors which use a gasket to form the seal. 
  • An unburned area within a fire perimeter. 
  • A line connecting points of equal atmospheric pressure on a weather map. 
  • A line connecting points of equal temperature on a weather map. 
Isothermal Layer
  • Layer through which temperature remains constant with elevation.