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)
Pack Test
  • Used to determine the aerobic capacity of fire suppression support personnel and assign physical fitness scores. The test consists of walking a specified distance, with or without a weighted pack, in a predetermined period of time, with altitude corrections. 
Packing Ratio
  • The fraction of a fuel bed occupied by fuels, or the fuel volume divided by bed volume. 
Panoramic Photograph
  • Photographs from a lookout point, bearing azimuth and vertical angle scales, to assist in locating fires with a firefinder. 
  • Anything intentionally dropped, or intended for dropping, from any aircraft by parachute, by other retarding devices, or by free fall. 
Parallel Attack
  • Method of fire suppression in which fireline is constructed approximately parallel to, and just far enough from the fire edge to enable workers and equipment to work effectively, though the fireline may be shortened by cutting across unburned fingers. The intervening strip of unburned fuel is normally burned out as the control line proceeds but may be allowed to burn out unassisted where this occurs without undue delay or threat to the fireline. 
Parallel Lane Technique
Parallel Pumping
  • Procedure by which the flow from two fire pumps is combined into one hose line. 
Parallel Tandem Pumping
  • Procedure by which the flow from two fire pumps is combined into a third pump. 
Partial Risk
  • Part of the National Fire Danger Rating System (NFDRS). Contribution of a specific source to human-caused risk, derived from the daily activity level assigned a risk source and its risk source ratio. 
Partial Risk Factor
  • Part of the National Fire Danger Rating System (NFDRS). Contribution to human-caused risk made by a specific risk source; a function of the daily activity level assigned that risk source and the appropriate risk source ratio. 
Partial-thickness Burn
  • A burn where the outer layer of skin is burned through and the second layer of skin (dermis) is damaged and is typically, a painful injury. Burns of this type cause reddening, blistering, and a mottled appearance. (also called Second Degree Burn).
Particle Size
  • The size of a piece of fuel, often expressed in terms of size classes. 
Particulate Matter
  • Any liquid or solid particles. "Total suspended particulates", as used in air quality, are those particles suspended in or falling through the atmosphere. They generally range in size (diameter) from 0.1 to 100 micrometers.
Parts of a Fire
  • Different areas of the fire usually determined by the predominant direction of fire spread and delineated from the fastest moving area (head) to the slowest moving area (base or tail). The most rapidly moving portion is designated the head of the fire, the adjoining portions of the perimeter at right angles to the head are known as the flanks, and the slowest moving portion is known as the rear or the base of the fire. 
Passenger, Authorized
Passenger, Official
  • The following categories of personnel are official passengers: Officers and employees of the federal government traveling on official business. Members of Congress and employees of congressional committee staffs whose work relates to the agency’s programs. Non-federal passengers when engaged in missions which enhance accomplishment of an agency program such as personnel of cooperating state, county, or local agencies; representatives of foreign governments; and contractors’ representatives to include those employed by such agencies; and private citizens. Source: NWCG Standards for Helicopter Operations, PMS 510.
Passenger, Unauthorized
  • All personnel who are not official or unofficial passengers are considered unauthorized passengers and are not authorized to be transported in any aircraft owned or operated by or on behalf of the government. Source: NWCG Standards for Helicopter Operations, PMS 510.
Passive Crown Fire
  • A fire in the crowns of trees in which trees or groups of trees torch, ignited by the passing front of the fire. The torching trees reinforce the spread rate, but these fires are not basically different from surface fires. 
Patch Burning
  • Burning in patches to prepare sites for group planting or sowing or to form a barrier to subsequent fires. 
  1. To travel over a given route to prevent, detect, and suppress fires. Includes interaction with the public for wildland fire prevention and educational purposes.
  2. To go back and forth vigilantly over a length of control line during and/or after construction to prevent breakovers, suppress spot fires, and extinguish overlooked hotspots.
  3. A person or group of persons who carries out patrol actions. 
Patrol Time
  • Elapsed time from completion of original mopping up until the fire is declared to be extinguished. 
  • 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 fuel within the pattern. 
Pattern Clusters
  • A group of indicators in a close proximity, of the same or different categories, that exhibit consistent directional values. 
  • Weight of passengers and/or cargo being carried by an aircraft. 
Peak Fire Season
  • That period of the fire season during which fires are expected to ignite most readily, to burn with greater than average intensity, and to create damages at an unacceptable level. 
Peak Monthly Average
  • Highest monthly average of human-caused fires calculated for a protection unit. 
Peak Wind
  • The greatest 5-second average wind speed during the previous hour that exceeded 25 knots. 
Peak Wind Direction
  • Direction at Peak Wind Speed. 
Peak Wind Speed
  • Maximum wind speed during the previous 60 minutes. 
  • Passage of liquid through a porous body, as movement of water through soil. 
Perennial Plant
  • A plant that lives for more than two growing seasons. For fire danger rating purposes, biennial plants are classed with perennial plants. 
Performance Chart
  • A chart, table, or graph provided by the manufacturer for use in determining an aspect of helicopter and fixed-wing aircraft performance. 
Performance Oriented Objectives
  • On-the-job performance enhancement is a result of online training. Performance oriented objectives or learning objectives for this training is developed, agreed to, and tested to ensure skill transfer. The purpose of learning objectives is to define the type of learning or performance outcomes that will occur at the conclusion of instruction and how learning will be assessed. Both objectives and performance outcomes should be written as precisely as possible in order to best determine whether they have been achieved. 
  • A short term for "permanently frozen ground"; any part of the earth's crust, bedrock, or soil mantle that remains below 32? F (0? C) continuously for a number of years.
Perpendicular Lane Technique
Personal Protective Equipment (PPE)
  • That equipment and clothing required to mitigate the risk of injury from or exposure to hazardous conditions encountered during the performance of duty. PPE includes but is not limited to: fire resistant clothing, hard hat, flight helmets, shroud, goggles, gloves, respirators, hearing protection, chainsaw chaps, and shelter. 
Personnel Accountability
  • The ability to account for the location and welfare of personnel, accomplished when supervisors ensure that the ICS principles and processes are functional and personnel are working within these guidelines. 
Photo Point
Piling and Burning
  • Piling slash resulting from logging or fuel management activities and subsequently burning the individual piles. 
Pilot Balloon Operation (PIBAL)
  • A method of determining winds aloft by periodically reading the elevation and azimuth angles of a theodolite, usually at one-minute intervals, while tracking the ascent of a small free-lift balloon. A PIBAL is commonly used for constructing a wind profile. 
  • Pilot responsible for the operation and safety of an aircraft during flight time. 
  • Navigation of aircraft by visual reference to landmarks. 
Pin Flags
Pin Lug Coupling
  • A hose coupling with one or more cylindrical studs on its outside rim. The studs allow the use of a spanner wrench to tighten the coupling. 
Pincer Action
  • Direct attack around a fire in opposite directions by two or more attack units. Usually conducted from the fire's tail to head. 
Ping-Pong Ball System
  • Mechanized method of dispensing DAIDs (Delayed Aerial Ignition Devices) at a selected rate. The DAIDs are 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). 
Pithy Stalk
Plan of Attack
  • The selected course of action and organization of personnel and equipment in fire suppression, as applied to a particular fire or to all fires of a specific type. 
Planetary Boundary Layer
  • That part of the earth's lower atmosphere that is directly influenced by the presence of the earth's surface and responds to surface forcings such as fronts, friction, evapotranspiration and convective mixing. 
Planned Ignition
Planning Interval
  • Period of time between scheduled planning meetings. 
Planning Meeting
  • A meeting held regularly throughout the duration of an incident, to select specific strategies and tactics for incident control operations and to plan for needed service and support. On larger incidents, the planning meeting is a major element in the development of the Incident Action Plan. 
Planning Section
  • Responsible for the collection, evaluation, and dissemination of tactical information related to the incident, and for the preparation and documentation of incident action plans. The section also maintains information on the current and forecasted situation, and on the status of resources assigned to the incident. Includes the situation, resource, documentation, and demobilization units, as well as technical specialists. 
Plastic Sphere Dispenser (PSD)
  • Device installed, but jettisonable, in a helicopter, which injects glycol into a plastic sphere containing potassium permanganate, which is then expelled from the machine and aircraft. This produces an exothermic reaction resulting in ignition of fuels on the ground for prescribed or wildland fire applications. 
Plow Line
  • A convection column generated by combustion (of wildland fuel). 
Plume Rise
  • How high above the level of release an emission plume rises. 
Plume-dominated Wildland Fire
  • A wildland fire whose activity is determined by the convection column. 
  • Particulate matter of mass median aerodynamic diameter (MMAD) less than or equal to 10 micrometers. 
  • Particulate matter of mass median aerodynamic diameter (MMAD) less than or equal to 2.5 micrometers. 
Pocket Weather Meter
  • A handheld electronic device that measures temperature, humidity, wind speed, and possibly other atmospheric variables, depending on brand and model.
Pockets of a Fire
  • Unburned indentations in the fire edge formed by fingers or slow burning areas. 
Point of Attack
  • That part of the fire on which work is started when suppression crews arrive. 
Point of Origin
  • The exact physical location within the Ignition Area where a heat source and the local fuel interact, resulting in a fire. Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.
    • Definition Extension: The "exact" location of a point of origin is rarely found due to the rapid destruction and/or dislocation of the first fuels ignited during the combustion process.
Point of Origin on Unprotected Land
  • Point of Origin of an incident for which NO fire agency has been assigned as the protecting unit.
    • Business Rule: A user will be selecting yes/no = true/false.
Point Source
  • A permanent source of air pollution that can be distinctly identified such as a smokestack. 
Point Source Fire Predictions
  • Predictions that apply to an initiating fire burning during a time when conditions have been relatively constant, or where it can be assumed that the fire will maintain a basically elliptical shape. 
Point/Zone Protection
  • A wildfire response strategy which protects specific assets or highly valued resources from the wildfire without directly halting the continued spread of the wildfire. 
    • Definition Extension:  1) Points or zones being protected may be communities, individual structures, areas of high resource value, etc.  2) Continued wildfire spread may be desirable in order to achieve management objectives or may be inevitable due to extreme burning conditions, safety concerns, or other limitations.  
    • See also: Monitoring; ConfineContained; Suppression
  • Unit of fluid viscosity in fire retardant, defined as tangential force per unit area (dynes/square centimeter) required to maintain unit difference in velocity (1 centimeter/second) between two parallel planes separated by 1 cm of fluid (1 poise=1 dyne-second/cubic centimeter). 
Portable Pump
  • Small gasoline-driven pump that can be carried to a water source by one or two firefighters or other conveyance over difficult terrain. 
  • Container, either with rigid frame or self supporting, which can be filled with water or fire chemical mixture from which fire suppression resources can be filled. It can also be a source for charging hose lays from portable pumps or stationary engines. 
Position Currency Requirement
  • The requirement to perform satisfactorily in a specified position within the last five years (three years for aviation and expanded dispatch positions) in order to maintain qualification for the position. 
Position Performance Assignment
  • An assignment in which an individual is being evaluated for tasks found in the position task book. 
Position Task Book (PTB)
  • A document listing the performance requirements (competencies and behaviors) for a position in a format that allows for the evaluation of individual (trainee) performance to determine if an individual is qualified in the position. Successful performance of PTB tasks, as observed and recorded by a qualified evaluator, will result in a recommendation to the trainee's home unit that the individual be certified in the position. 
Positive Displacement Pump
  • A pump which moves a specified quantity of water through the pump chamber with each stroke or cycle; it is capable of pumping air, and therefore is self-priming, but must have pressure relief provisions if plumbing or hoses have shut-off nozzles or valves . Gear pumps and piston pumps are common examples of this type. 
  • A level of certainty that is feasible but does not rise to the level of probable. Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.
    • Definition Extension: If two or more hypotheses are equally likely and no hypothesis rises to the level of probable, then the level of certainty must be "possible" and the cause of the fire would be "undetermined".
Potato Roll
  • Quick method of rolling hose for pick up; hose is rolled as a ball of string. 
Pounds per Square Inch (PSI)
  • Measurement of pressure (e.g., pump pressure, nozzle pressure, friction loss in hose, pressure loss or gain due to elevation). 
  • In the 1978 version of NFDRS, the herbaceous stage approximately 30 days prior to green-up. 
  • A planned, systematic procedure for collecting, recording, and evaluating prefire and fire management intelligence data for a given planning unit or preattack block. The planning phase is usually followed by a construction and development program integrated with other resources and activities. 
Preattack Block
  • Unit of wildland delineated by logical and strategic topographic features for preattack planning. 
Preattack Planning
  • Within designated blocks of land, planning the locations of firelines, fire camps, water sources, and helispots; planning transportation systems, probable rates of travel, and constraints of travel on various types of attack units; and determining what types of attack units likely would be needed to construct particular firelines, their probable rate of fireline construction, and topographic constraints on fireline construction. 
Precautionary Landing
  • A landing necessitated by apparent impending failure of engines, systems, or components which makes continued flight unadvisable. 
  • Any or all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground. 
Precipitation Amount
  • The total amount of precipitation that occurred within the preceding 24-hour period. 
Precipitation Duration
  • Time, in hours and fraction of hours, that a precipitation event lasts. More precisely, for fire danger rating purposes, the length of time that fuels are subjected to liquid water. 
Precipitation Gauge
  • Device commonly used to collect and permit measurement of any form of rain and snow sufficiently heavy to have fallen to the earth's surface. Also known as a rain gauge. 
Precision Approach Procedure
  • A standard instrument approach procedure for fixed-wing aircraft in which an electronic glide slope is provided, such as ILS and PAR. 
Precision Approach Radar (PAR)
  • Blind landing in which the aircraft is observed from the ground by means of radar and directed along a suitable glide path by instructions radioed to the pilot. 
  • Hard suction hose or discharge hose carried connected to pump, eliminating delay occasioned when hose and nozzles must be connected and attached at fire. 
Predictive Services
  • Those Geographic Area and National-level fire weather or fire danger services and products produced by wildland fire agency meteorologists and intelligence staffs in support of resource allocation and prioritization. 
Preignition Combustion Phase
  • Thermal or chemical decomposition of fuel at an elevated temperature. This is the pre-combustion stage of burning during which distillation and pyrolysis predominate. Heat energy is absorbed by the fuel which, in turn, gives off water vapor and flammable tars, pitches, and gases. These ignite when mixed with oxygen to initiate the flaming combustion phase. 
Preignition Phase
  • Preliminary phase of combustion in which fuel elements ahead of the fire are heated, causing fuels to dry. Heat induces decomposition of some components of the wood, causing release of combustible organic gases and vapors. 
  1. 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.
  2. Mental readiness to recognize changes in fire danger and act promptly when action is appropriate.
  3. 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 organizational readiness dictated by burning conditions, fire activity, and resource availability.
    • Definition Extension:  Response and support to non-fire incidents requiring a significant commitment of resources may also affect Preparedness Levels.
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
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.
Prescribed Fire Module
  • A team of skilled and mobile personnel dedicated primarily to prescribed fire management that can ignite, hold and monitor prescribed fires.
Prescribed Fire Plan
  • A plan for each prescribed fire, prepared by qualified personnel, approved by the agency administrator, which includes criteria for the conditions under which the fire will be conducted (a prescription).
  • In the context of wildland fire, a prescription is measurable criteria that define conditions under which a prescribed fire may be ignited. Prescriptions may also be used to guide selection of management responses to wildfire to define conditions under which management actions are most likely to achieve incident management objectives. Prescription criteria typically describe environmental conditions such as temperature, humidity and fuel moisture, but may also include safety, economic, public health, geographic, administrative, social, or legal considerations. 
Pressure Gradient
  • The difference in atmospheric pressure between two points on a weather map. That is, the magnitude of pressure difference between two points at sea level, or at constant elevation above sea level. Wind speed is directly related to pressure gradient. If distance between constant pressure lines is reduced by one-half, wind speed will be doubled. Conversely, if distance between lines is doubled, wind speed will be reduced by one-half. 
Pressure Loss
  • Reduction in water pressure between a pump or hydrant and a nozzle due to expenditure of pressure energy required to move water through a hose; includes losses due to back pressure, friction loss, elevation loss, and/or losses in fittings. 
Pressure Pattern
  • The distribution of surface atmospheric pressure features over an area of the earth as shown on a weather map. Surface pressure features include lines of constant pressure (isobars), highs, lows, and pressure gradient. The pressure pattern is directly related to wind speeds and directions at specific locations. 
  • Activities in advance of fire occurrence to ensure effective suppression action. Includes planning the organization, recruiting and training, procuring equipment and supplies, maintaining fire equipment and fire control improvements, and negotiating cooperative and/or mutual aid agreements. 
  • The use of water, foam or retardant along a control line in advance of the fire. Often used where ground cover or terrain is considered best for control action. 
  • Activities directed at reducing the incidence of fires, including public education, law enforcement, personal contact, and reduction of fuel hazards (fuels management). Actions to avoid an incident, to intervene for the purpose of stopping an incident from occurring, or to mitigate an incident's effect to protect life and property. Includes measures designed to mitigate damage by reducing or eliminating risks to persons or property, lessening the potential effects or consequences of an incident. 
Prevention of Significant Deterioration (PSD)
  • A program identified by the Clean Air Act to prevent air quality and visibility degradation and to remedy existing visibility problems. Areas of the country are grouped into 3 classes which are allowed certain degrees of pollution depending on their uses. National Parks and Wilderness Areas meeting certain criteria are "Class I" or "clean area" in that they have the smallest allowable increment of degradation. 
Prevention Team
  • Provides support to fire prevention and wildland fire educational needs preceding and during periods of high wildland fire danger or prescribed fire activity. The teams provide assistance to wildland fire managers with coordination of fire loss mitigation efforts with public, state or local agencies.
  • Filling pump with water when pump is taking water not under a pressure head. Necessary for centrifugal pumps. 
  • A number representing the chance that a given event will occur. The range is from 0% for an impossible event, to 100% for an inevitable event. 
Probability Forecast
  • A forecast of the probability of occurrence of one or more of a mutually exclusive set of weather contingencies as distinguished from a series of categorical statements. 
Probability of Ignition
  • The chance that a firebrand will cause an ignition when it lands on receptive fuels. 
Procurement Office
  • Agency personnel with specific delegation of procurement authority, acting within the limits of agency policy of said authority.
Procurement Unit
  • Functional unit within the Finance/Administration Section responsible for managing all financial matters pertaining to vendor contracts. 
Progressive Hose Lay
  • A hose lay in which double shutoff wye (Y) valves are inserted in the main line at intervals and lateral lines are run from the wyes to the fire edge, thus permitting continuous application of water during extension of the lay. 
Progressive Method of Line Construction
  • A system of organizing workers to build fireline in which they advance without changing relative positions in line. 
Project Activity Level (PAL)
  • An application of fire danger rating to support regulation of contractors involved in land management activities for fire prevention purposes in California. 
  • A device that adds a predetermined amount of foam concentrate to water to form foam solution. 
Protected Lands
  • Areas for which a fire protection organization has the primary responsibility for managing a wildfire and directing fire management actions. Such responsibility may be authorized by law, contract, or personal interest of the firefighting agent (e.g., a lumber operator). Note: Several agencies or entities may have some basic responsibilities (e.g., private owner) without being known as the fire organization having primary responsibility. 
Protected Side
Protecting Agency
Protection Area
  1. 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. 
  2. A geographical area which is administratively defined and for which organized fire suppression activities are formally planned.
Protection Boundary
  • The exterior perimeter of an area within which a specified fire agency has assumed a degree of responsibility for wildland fire control. It may include land in addition to that for which the agency has jurisdiction or contractual responsibility. 
  • General name for instruments designed to determine the moisture content of air. A psychrometer consists of dry- and wet-bulb thermometers that give the dry- and wet-bulb temperatures, which in turn are used to determine relative humidity and dew point. 
Public Aircraft
  • Aircraft used only in the service of a government or a political subdivision. It does not include any government-owned aircraft engaged in carrying persons for commercial purposes. 
  • A combination chopping and trenching tool widely used in fireline construction, which combines a single-bitted axe blade with a narrow adze-like trenching blade fitted to a straight handle. 
Punky Material
  • Partly decayed material, such as old wood, in which fire can smolder unless it is carefully mopped up and extinguished. A good receptor for firebrands when dry. 
  • The thermal or chemical decomposition of fuel at an elevated temperature. This is the preignition combustion phase of burning during which heat energy is absorbed by the fuel which, in turn, gives off flammable tars, pitches, and gases. 
  • A mixture of chemicals designed to produce heat, light, gas, smoke or noise.