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 (128) | B (97) | C (165) | D (102) | E (69) | F (270) | G (49) | H (90) | I (88) | J (10) | K (4) | L (78) | M (93) | N (32) | O (47) | P (138) | Q (6) | R (102) | S (230) | T (74) | U (27) | V (38) | W (58) | Z (1)
Walk Test
  • The walk test is designed to determine the ability to carry out light duties. It consists of a one-mile test with no load that approximates an aerobic fitness score of 35. A time of 16 minutes, the passing score for this test, ensures the ability to meet emergency and evacuate to a safety zone. 
Warm Front
  • The leading edge of a relatively warm air mass which moves in such a way that warm air replaces colder air that moves away from a region. Winds associated with warm frontal activity are usually light and mixing is limited. The atmosphere is relatively stable when compared to cold front activity.  Source:  http://glossary.ametsoc.org/wiki/Warm_front
  • The official delegation of authority to contracting officers and procurement officers establishing the dollar amount and type limits for acquisitions.
Water Bar
  • A shallow channel or raised barrier, e.g., a ridge of packed earth or a thin pole laid diagonally across the surface of a road or trail so as to lead off water, particularly storm water. (Frequently installed in firelines on steep slopes to prevent erosion.) 
Water Expansion Pumping System (WEPS)
  • Apparatus utilizing an air compressor and positive displacement pump coupled to the same engine, plumbed to a non-pressurized tank, for producing foam. The operation involves injecting compressed air into a liquid stream containing a suitable foaming agent. 
Water Expansion System (WES)
  • Apparatus utilizing a pressurized tank, hose, and nozzle for producing foam by injection of compressed air or gas into a liquid stream downstream from the pumping source. The liquid stream must contain a suitable foaming agent. 
Water Hammer
  • A force created by the rapid acceleration or deceleration of water, commonly created by opening or closing a valve too quickly. Pressures developed in a water hammer, proportional to the mass multiplied by the square of the velocity, can damage a pipe or hose. 
Water Source
  • Any strategically located supply of water that is readily available for pumps, tanks, trucks, helicopters, or fire camp use. 
Water Supply Map
  • A map showing location of supplies of water readily available for pumps, tanks, trucks, camp use, etc. 
Water Tender
  • Any ground vehicle capable of transporting specified quantities of water. 
Water Thief
  • A type of bleeder valve designed for installation at convenient points in hose lines to permit drawing off water for filling backpack pumps or other use without interfering with pump or nozzle operation. 
  • A disturbance that transfers energy from one point to another point and may take the form of a deformation of pressure or temperature. In the atmosphere such disturbances may result in major storms or merely result in changes in cloud, wind and temperature conditions. Development of a wave on a front usually slows the advance of the front due to transfer of energy to the wave development and movement. 
Weather Advisory
  • In aviation forecasting, an expression of hazardous weather conditions not predicted in the zone weather forecast, as they affect the operation of air traffic. 
Weather Information Management System (WIMS)
  • A centralized weather data processing system at which daily fire danger ratings are produced. 
Weighted Monthly Occurrence
  • Part of the National Fire Danger Rating System (NFDRS). Number used to determine seasonal risk class for a protection unit, calculated by multiplying peak monthly average by two and adding seasonal monthly average. 
  • The contractor furnishes all equipment operating supplies.
Wet Foam
  • A low expansion foam type with few and varied bubbles and rapid drain time which is used for rapid penetration and fire extinguishment. 
Wet Line
  • A line of water, or water and chemical retardant, sprayed along the ground, and which serves as a temporary control line from which to ignite or stop a low-intensity fire. 
Wet Storage
  • Fire retardants mixed with water and stored in tanks at air attack bases for immediate use by airtankers. 
Wet Water
  • Water with added chemicals, called wetting agents, that increase water's spreading and penetrating properties due to a reduction in surface tension. 
Wet-bulb Depression
Wet-bulb Temperature
  • The lowest temperature to which air can be cooled by evaporating water into it at a constant pressure when the heat required for evaporation is supplied by the cooling of the air. It is measured by the wet bulb thermometer, which usually employs wetted wicking on the bulb as a cooling (through evaporation) device.  Source:  http://glossary.ametsoc.org/wiki/Wet-bulb_temperature
Wet-bulb Thermometer
Wetting Agent
  • A chemical that when added to water reduces the surface tension of the solution and causes it to spread and penetrate exposed objects more effectively than the untreated water. 
Wetting Rain
  • A widespread rain that over an extended period of time significantly reduces fire danger. One-tenth of an inch may be sufficient to reduce fire danger in grass fuel models. One half inch may be necessary for timber fuels under closed canopies. 
  • The distance from the centerline of the front axle to the centerline of the rear axle. For a tandem rear axle vehicle the center line is midpoint between the centers of the two rear axles. 
  • A loose limb, top, or piece of bark lodged in a tree, which may fall on anyone working beneath it. 
Wildfire Response Strategies
  • The range of options available for response to a wildfire. 
    • Definition Extensions: 1)  Common strategies include Monitor, Confine, Contain, Point/Zone Protection, and Suppression, but hybrids and novel strategies may also be developed as the situation demands.  2)  One or more strategies may be employed on any given wildfire.  The strategy or strategies being employed may vary temporally or spatially.
Wildfire Suppression
  • An appropriate management response to wildfire or prescribed fire that results in curtailment of fire spread and eliminates all identified threats from the particular fire. 
  • An area in which development is essentially non-existent, except for roads, railroads, powerlines, and similar transportation facilities. Structures, if any, are widely scattered. 
Wildland Fire
Wildland Fire Assessment System (WFAS)
  • An internet-based information system, providing national views of weather and fire potential, including national fire danger and weather maps and satellite-derived greenness maps. 
Wildland Fire Leadership Principles
  • Eleven principles describing tangible behaviors that reflect and demonstrate the wildland fire leadership values. The eleven principles are:
    • Be proficient in your job.
    • Make sound and timely decisions.
    • Ensure tasks are understood, supervised, and accomplished.
    • Develop your subordinates for the future.
    • Know your subordinates and look out for their well-being.
    • Keep your subordinates informed.
    • Build the team.
    • Employ your subordinates in accordance with their capabilities.
    • Know yourself and seek improvement.
    • Seek responsibility and accept responsibility for your actions.
    • Set the example. 
Wildland Fire Leadership Values
  • Three guiding values that should be the basis for the decisions that leaders make. The three values are:
    • Duty ─ How a leader values their job. Duty begins with everything required by law and policy, but is much more than that. A leader commits to excellence in all aspects of their professional responsibility so that when the job is done they can look back and say, "I couldn't have given any more."
    • Respect ─ How a leader values their co-workers. Respect for the individual forms the very basis for the rule of law in America. This value reminds leaders that those who follow are their greatest resource. Not all followers will succeed equally, but they all deserve respect.
    • Integrity ─ How a leader values himself or herself. An individual cannot be in charge of others unless they are in charge of their own actions. People of integrity separate what is right from what is wrong and act according to what they know is right, even at personal cost.
Wildland Fire Management Information (WFMI)
  • A web site providing current weather and lightning data, as well as historic fire occurrence data. NWCG Unit Identifiers are also maintained on the site. 
Wildland Fire Module
  • A group of 7-10 highly skilled personnel specifically associated with the planning and implementation of planned and unplanned wildland fire and hazardous fuels treatments. Maybe classified as a Type 1 or Type 2 dependent on qualifications and experience. 
Wildland Fire Serious Accident
  • Any accident where one or more fatalities occur and/or three or more personnel are inpatient hospitalized as a direct result, or in support of wildland fire suppression or prescribed fire operations. Accident may result in substantial property or equipment damage of $250,000 or more. 
Wildland Urban Interface (WUI)
Wind Direction
Wind Profile
Wind Shear
  • A variation in wind speed and/or direction in a layer of the atmosphere or between layers. The variation may be in the horizontal or vertical dimensions and may result in significant turbulence depending upon the magnitude of the wind speed/direction differences. A strong wind shear may act like an inversion and inhibit plume rise. It may also fracture the smoke plume, not allowing smoke to rise much above terrain levels. A strong horizontal anticyclonic shear results in downward motion and may bring smoke aloft to the surface.  Source:  http://glossary.ametsoc.org/wiki/Wind_shear
Wind Shift
  1. For aviation purposes, a change in the average wind direction of 45 degrees or more which takes place in less than 15 minutes if the wind speed during this period is 6 knots (3 m/s) or greater.
  2. For ground observation purposes, a change of at least 45 degrees in the direction of a significant wind, which occurs in a relatively short time frame. 
Wind Speed
  1. Wind, in miles per hour, measured at 20 feet above open, level ground or as adjusted to meet this standard to compensate for height of ground cover, uneven ground, and nearby obstructions.
  2. (NFDRS) Wind, in mph, measured at 20 feet above ground, or above the average height of vegetation, and averaged over at least a 10-minute period. Also known as wind velocity. 
Wind Vectors
Wind-driven Wildland Fire
  • A wildland fire that is controlled by a strong consistent wind. 
  • Tree that has been uprooted or broken off by wind. 
Windrow Burning
  • Burning slash that has been piled into long continuous rows. Also includes wildfire in vegetation planted to protect improvements or agriculture. 
Winds Aloft
Windspeed Meter
  • A handheld device which indicates wind speed, usually in miles per hour. 
Woody Fuel Moisture
  • In NFDRS, a calculated value representing the approximate moisture content of the live woody vegetation in the rating area expressed as a percentage of the oven dry weight of the sample. 
Woody Vegetation Condition
  • Part of the National Fire Danger Rating System (NFDRS). A code reflecting the moisture content of the foliage and small twigs [less than 1/4 inch (0.6 cm)] of living woody plants. 
Work Capacity Test (WCT)
  • The Work Capacity Test (WCT) is a test to ensure a person is physically capable of meeting the minimum fitness requirement associated with assigned wildfire or prescribed fire duties as described in the NWCG Standards for Wildland Fire Position Qualifications, PMS 310-1.  Below are the three defined duty levels with examples of associated essential functions:  
    • Arduous
      • Arduous duty field work requires above-average endurance and superior conditioning.  Duties may include an occasional demand for extraordinarily strenuous activity in emergency situations under adverse environmental conditions over extended periods. The pace of work typically is set by the emergency condition.  Essential functions include, but are not limited to: running, walking or hiking, climbing, jumping, twisting, bending, lifting more than 50 pounds, and carrying 45 pounds or more for extended periods over difficult terrain. 
    • Moderate
      • Moderate duty field work requires the average endurance and conditioning of an individual who possesses complete control of all their physical faculties. Occasional demands may be required for moderately strenuous activities in emergencies over long periods. The pace of work is usually set by the current environmental conditions.  Essential functions include, but are not limited to: considerable walking over irregular ground, standing for long periods, lifting 25 to 50 pounds, climbing, bending, stooping, squatting, twisting, and reaching.
    • Light
      • Light duty mainly involves office-type work with occasional field activity characterized by light physical exertion requiring basic good health.  Individuals almost always can govern the extent and pace of their physical activity.  Essential functions include, but are not limited to: climbing stairs, standing, operating a vehicle, and long hours of work, as well as some bending, stooping, or light lifting.
  • The WCT consists of three separate levels of tests which correspond with the three duty types.  The tests are defined as follows:

    • Pack Test - This is a job-related test to determine an individual’s ability to perform the minimum standards of arduous duty.  It consists of completing a 3-mile walk over level terrain in 45 minutes or less while carrying a 45-pound pack.  
    • Field Test – This is a job-related test to determine an individual’s ability to perform the minimum standards of moderate duty. It consists of completing a 2-mile walk over level terrain in 30 minutes or less while carrying a 25-pound pack.
    • Walk Test – This is a job-related test to determine an individual’s ability to perform the minimum standards of light duty.  The test consists of completing a 1-mile walk over level terrain in 16 minutes or less with no load.
  • For more information about the Work Capacity Test consult the Work Capacity Test Administrator’s Guide, PMS 307.
Work Rate
  • A daily, hourly, or mileage rate shall apply when equipment is under hire as ordered by the government and on shift, including relocation of equipment under its own power.
Work/Rest Ratio
  • An expression of the amount of rest that is required for each hour an individual is in work status. Current NWCG guidelines require one hour of rest for every two hours in work status. 
Woven Jacket Fire Hose
  • Fire hose of conventional construction, woven on looms from fibers of cotton or synthetic fibers. Most fire department hose is double jacketed (i.e., it has an outer jacket protecting the inner one against wear and abrasion). 
  • A hose connection with two outlets permitting two connections of the same coupling diameter to be taken from a single supply line.