– C –

Cache
A pre-determined complement of tools, equipment and/or supplies stored in a designated location, available for incident use.

Calculation of Probabilities
Evaluation of all factors pertinent to probable future behavior of a going fire and of the potential ability of available forces to perform fire suppression operations on a specified time schedule.

Calibrated Airspeed
Indicated airspeed of an aircraft, corrected for position and instrument error. Equal to true airspeed in standard atmosphere at sea level.

Camp Manager (BCMG)
This ICS position is responsible for ensuring that services, supplies, and non-technical coordination are provided within a camp and reports to the Facilities Unit Leader. There may be one or more camps per incident, each with a Camp Manager.
see also: Base Manager
see also: Facilities Unit

Camp
A geographical site(s), within the general incident area, separate from the incident base, equipped and staffed to provide sleeping, food, water, and sanitary services to incident personnel.
see also: Base

Candling
The burning of the foliage of a single tree or a small group of trees, from the bottom up.
synonym: Torching

Canopy
The stratum containing the crowns of the tallest vegetation present (living or dead), usually above 20 feet.

Carbon Dioxide (CO2)
A colorless, odorless, nonpoisonous gas, which results from fuel combustion and is normally a part of the ambient air.

Carbon Monoxide (CO)
A colorless, odorless, poisonous gas produced by incomplete fuel combustion.

Carcinogen
Any substance that can cause or contribute to the production of cancer.

Cardinal Altitudes
Odd or “even” thousand-foot (305 m) altitudes or flight levels. E.g., 5,000, 6,000, 7,000; FL 250, FL 260, and FL 270.

Cardinal Directions
North, south, east, west; used for giving directions and information from the ground or air in describing the fire (e.g., the west flank or east flank, not right flank or left flank).

Cargo Chute
A parachute designed and rigged for dropping equipment and supplies from an aircraft.

Cargo Compartment
An internal area of an aircraft specifically designed to carry baggage or cargo.

Cargo Drop
Dropping of equipment or supplies, with or without a parachute, from an aircraft in flight.

Cargo Hook
Mechanically and electrically operated hook attached to the bottom of a helicopter to which a sling load is attached.

Cargo Net
Net attached to the cargo hook of a helicopter, used to carry cargo. Also called cargo sling.

Cargo Rack
Externally mounted rack for transporting supplies or cargo aboard a helicopter.

Carousel Hook
A remote hook attached to the end of a longline. It has four or more individual hooks which can be independently released, allowing the pilot to fly cargo loads to different locations without landing.

Carried Wet
Booster hose carried full of water during mild weather to speed discharge of water on fire without filling or priming from tank.

Carrier Fuels
The fuels that support the flaming front of the moving fire.

Casual
A person hired and compensated under the Pay Plan for Emergency Workers.
synonym: Administratively Determined
see also: Emergency Firefighter

Category Day
A numerical index related to the ability of the atmosphere to disperse smoke. Different agencies use different scales [e.g., in South Carolina, the current scale is based on ventilation factor and ranges from 1 (poor) to 5 (excellent)].

Catface
Defect on the surface of a tree resulting from a wound where healing has not re-established the normal cross-section.

Ceiling
(1) Height above the earth’s surface of the lowest layer of clouds or obscuring phenomena aloft that is not classified as a thin layer or partial obscuration, that together with all lower clouds or obscuring phenomena covers more than half the sky as detected from the point of observation.
(2) Maximum height of a temporary flight restriction (TFR).

Celsius
A temperature scale with 0° as the freezing point of water and 100° as the boiling point of water at sea level.

Center Firing
Method of broadcast burning in which fire is ignited in the center of the area to create a strong draft; additional fires are then ignited progressively nearer the outer control lines (sometimes in one step) as indraft increases so as to draw the flames and smoke toward the center.

Centrifugal Pump
Pump which expels water by centrifugal force through the ports of a circular impeller rotating at high speed. With this type of pump, the discharge line may be shut off while the pump is running without damaging the pump or hose.

Certifying Official
The agency official at the home unit who is responsible for authorizing and granting position certification per agency policy. The agency official is responsible for completing the agency certification block located on the inside front cover of a Position Task Book.
see also: Agency Certification
see also: Home Unit
see also: Position Task Book

Chain Lightning
Lightning in a long zigzag or apparently broken line.

Chain of Command
A series of management positions in order of authority.

Chain
Unit of measure in land survey, equal to 66 feet (20 M) (80 chains equal 1 mile). Commonly used to report fire perimeters and other fireline distances, this unit is popular in fire management because of its convenience in calculating acreage (e.g., 10 square chains equal one acre).

Char Height
The vertical distance above ground scorched or blackened on a tree bole.

Char
(1) Carbonaceous material formed by incomplete combustion of an organic material, most commonly wood; remains of burned materials.
(2) In fire simulation, a darkened area within the fire perimeter; usually indicates fire has already passed through; usually created by an opaque material blocking out a selected portion of basic scene illumination.

Charged Line
Hose filled with water under pressure and ready to use.
synonym: Live Line
see also: Live Reel

Chase Truck
Vehicle that carries crew gear, supplies, and operational equipment for initial/extended attack.

Check Line
A temporary fireline constructed at right angles to the control line and used to hold a backfire in check as a means of regulating the heat or intensity of the backfire.

Check Valve
A valve that permits flow of liquid through a hose or pipe in one direction but prevents a return flow. Uses include the prevention of backflow on uphill hose lays, loss of prime with centrifugal pumps and chemical contamination in fire chemical mixing systems.

Check-in
The process whereby resources first report to an incident. Check-in locations include incident command post (ICP), base or camps, staging areas, helibases, or direct to a tactical assignment.
see also: Reporting Locations

Chevron Burn
Burning technique in which lines of fire are started simultaneously from the apex of a ridge point, and progress downhill, maintaining position along the contour; used in hilly areas to ignite ridge points or ridge ends.

Chief of Party
The chief of party is responsible to the sending unit dispatcher until destination is reached. Chief of party is responsible for all traveling personnel assigned on the manifest list.

Chief
The ICS title for individuals responsible for command of functional sections: Operations, Planning, Logistics, and Finance/Administration.

Circumstantial Evidence
Testimony or information not based on actual personal knowledge or observation, but dependent on inference of other facts or experience. For example, testimony that defendant’s cigarette lighter was found in ashes of a fire.

Cirrus
A form of high cloud, composed of ice crystals, which seldom obscures the sun.

Claims Specialist (CLMS)
Person responsible for handling all claims, other than injury, against the incident.

Class A Foam
Foam intended for use on Class A or woody fuels; made from hydrocarbon-based surfactant, therefore lacking the strong filming properties of Class B foam, but possessing excellent wetting properties.

Class B Foam
Foam designed for use on Class B or flammable liquid fires; made from fluorocarbon-based surfactants, therefore capable of strong filming action, but incapable of efficient wetting of Class A fuels.

Class I Areas (Air Quality)
Geographic areas designed by the Clean Air Act subject to the most stringent restrictions on allowable increment of air quality deterioration. Class I areas include Forest Service wildernesses and nation memorial parks over 5,000 acres, National Parks exceeding 6,000 acres, international parks, as well as other designated lands.

Class II Areas (Air Quality)
All areas of the country not designated Class I, including everything from non-Class I areas to urban areas. A greater amount of air pollution can be added to these areas than Class I.

Class of Fire
As to kind of fire for purpose of using a proper extinguisher: Class A — Fires involving ordinary combustible materials (such as wood, cloth, paper, rubber, and many plastics) requiring the heat absorbing (cooling) effects of water, water solutions, or the coating effects of certain dry chemicals, which retard combustion. Class B — Fires involving flammable or combustible liquids, flammable gases, greases, and similar materials where extinguishment is most readily secured by excluding air (oxygen), inhibiting the release of combustible vapors, or interrupting the combustion chain reaction. Class C — Fires involving live electrical equipment where safety to the operator requires the use of electrically nonconductive extinguishing agents. Class D — Fires involving certain combustible metals (such as magnesium, titanium, zirconium, sodium, potassium, etc.) requiring a heat absorbing extinguishing medium not reactive with burning metals.
see also: Size Class of Fire

Clean Air Act
A federal law enacted to ensure that air quality standards are attained and maintained. Initially passed by Congress in 1963, it has been amended several times.

Clear Text
The use of plain English in radio communications transmissions. No Ten Codes or agency specific codes are used when using Clear Text.

Climate Class
In NFDRS, one of four classifications of general climate of an area.

Climate
The prevalent or characteristic meteorological conditions of any place or region, and their extremes.

Climatological Breakpoint
Points on the cumulative distribution of one fire weather/fire danger index without regard to associated fire occurrence/business.

Clock Method
Means of establishing a flight path to a target on a fire by referring to clock directions from the aircraft’s present location, with the nose of the aircraft pointing at 12:00.

Closed Area
An area in which specified activities or entry are temporarily restricted to reduce risk of human-caused fires or to mitigate the risk to human health or safety by potential or on-going wildland fires.

Closure
An administrative action limiting or prohibiting access to a specific geographic or jurisdictional area for the purposes of reducing wildfire or the risk it poses to life, property, and/or resources. Example of use: “Pursuant to 36 C.F.R. 261.50 (a) and (b), it is hereby ordered that the prohibitions hereinafter set forth apply to the general forest area of the Ozark-St. Francis National Forests until further notice.”
see also: Restrictions

Cloud
A visible cluster of minute water/ice particles in the atmosphere.

Cloudy
Adjective class representing the degree to which the sky is obscured by clouds. In weather forecast terminology, expected cloud cover of about 0.7 or more warrants use of this term. In the National Fire Danger Rating System, 0.6 or more cloud cover is termed “cloudy.”

Cold Front
The leading edge of a relatively cold air mass which displaces warmer air, causing it to rise. If the lifted air contains enough moisture, cloudiness, precipitation and even thunderstorms may result. As fronts move through a region, in the Northern Hemisphere, the winds at a given location will experience a marked shift in direction. Ahead of an approaching cold front, winds will usually shift gradually from southeast to south, and on to southwest. As a cold front passes, winds shift rapidly to west, then northwest. Typical cold front windspeeds range between 15 and 30 mph but can be much higher.

Cold Line
Fireline that has been controlled. The fire has been mopped up for a safe distance inside the line and can be considered safe to leave unattended.

Cold Trailing
A method of controlling a partly dead fire edge by carefully inspecting and feeling with the hand for heat to detect any fire, digging out every live spot, and trenching any live edge.

Collective Control
Controls the pitch angle of the main (helicopter) rotor blades. Used as primary altitude control.

Colonizer
Species of vegetation that establish on a burned (or otherwise denuded) site from seed.

Combination Nozzle Tip
Two attached straight stream nozzle tips of different orifice size used to increase or restrict water flow.

Combination Nozzle
A nozzle is designed to provide either a solid stream or a fixed spray pattern suitable for applying water, wet water or foam solution. Also called: Adjustable Fog Nozzle.

Combustion Efficiency
The relative amount of time a fire burns in the flaming phase of combustion, as compared to smoldering combustion. A ratio of the amount of fuel that is consumed in flaming combustion compared to the amount of fuel consumed during the smoldering phase, in which more of the fuel material is emitted as smoke particles because it is not turned into carbon dioxide and water.

Combustion Period
Total time required for a specified fuel component to be completely consumed.

Combustion Rate
Rate of heat release per unit of burning area per unit of time.
see also: Reaction Intensity

Combustion
The rapid oxidation of fuel in which heat and usually flame are produced. Combustion can be divided into four phases: preignition, flaming, smoldering, and glowing.

Command Climate
The working environment within the influence of a particular leader or chain of command. The command climate is based on the subordinates’ understanding of how they are expected to perform, how they are treated, and how they must conform to the leader’s style.

Command Presence
How leaders present themselves to others. The personal attributes and traits that determine whether leaders are worthy of trust and respect from their subordinates.

Command Staff
The command staff consists of the information officer, safety officer and liaison officer. They report directly to the incident commander and may have an assistant or assistants, as needed.

Command
The act of directing, and/or controlling resources by virtue of explicit legal, agency, or delegated authority.

Commercial Forest Land
Land that is producing, or is capable of producing, crops of industrial wood and is not withdrawn from timber use by statute or administrative regulation.

Commissary Manager (CMSY)
Person responsible to the time unit leader for operating the commissary at an incident base or camp.

Commissary
Supply of items such as candy, tobacco products, toilet items, and work clothes that are made available for sale to all incident personnel.

Communications Unit Leader (COML)
The ICS position responsible for supervising the Communications Unit. Reports to the Service Branch Director or Logistics Section Chief.
see also: Communications Unit

Communications Unit
An organizational unit in the Logistics Section responsible for providing and maintaining communication services at an incident. May also be a facility (e.g., a trailer or mobile van) used to provide the major part of an incident communications center.

Community Wildfire Protection Plan (CWPP)
A plan developed in the collaborative framework established by the Wildland Fire Leadership Council and agreed to by state, tribal, and local government, local fire department, other stakeholders and federal land management agencies managing land in the vicinity of the planning area. A Community Wildfire Protection Plan (CWPP) identifies and prioritizes areas for hazardous fuel reduction treatments and recommends the types and methods of treatment on Federal and non-Federal land that will protect one or more at-risk communities and essential infrastructure and recommends measures to reduce structural ignitability throughout the at-risk community. A CWPP may address issues such as wildfire response, hazard mitigation, community preparedness, or structure protection — or all of the above.

Compact
A formal working agreement among agencies to obtain mutual aid.

Compactness
Spacing between fuel particles.
see also: Bulk Density

Company
Any piece of (fire) equipment having a full complement of personnel.

Compare and Contrast
An investigative technique that involves comparing same sized indicators within a category at separate locations; looking for either differences or similarities in appearance.

Compass Rose
A circle, graduated in degrees, printed on some charts or marked on the ground at an airport or heliport. It is used as a reference to either true or magnetic direction.

Compensation/Claims Unit Leader (COMP)
The ICS position responsible for supervising the Compensation/Claims Unit. Reports to the Finance/Administration Section Chief.
see also: Compensation/Claims Unit

Compensation/Claims Unit
Functional unit within the Finance/Administration Section responsible for the overall management and direction of all Compensation-for-Injury and Claims Specialists assigned to the incident.

Compensation-for-Injury Manager
Person responsible to the Compensation/Claims Unit Leader for administrative matters arising from serious injuries and fatalities occurring on the incident.

Competency
A broad description that groups core behaviors necessary to perform a specific function.
see also: Behavior

Competent Ignition Source
A source of heat that is capable of kindling a wildfire. It may be in the form of a mechanical or electrical spark, glowing ember, open flame, chemical reaction or friction.

Complex
Two or more individual incidents located in the same general area which are assigned to a single incident commander or unified command.

Compressed Air Foam Systems (CAFS)
A generic term used to describe foam systems consisting of an air compressor (or air source), a water pump, and foam solution.

Computed Gross Weight
Term used in calculating from performance charts the permissible helicopter payload at which a helicopter is capable of hovering in ground effect or hovering out of ground effect, based on pressure altitude and air temperature.

Concentrate
A substance that has been concentrated; specifically, a liquid that has been made denser, as by the removal of some of its water.

Conceptual Model
A model that is a diagram or description of a set of relationships between factors that describe how a system works, such as an ecological model.
see also: Model

Condensation
The process by which a gas becomes a liquid.

Condition Class
Depiction of the degree of departure from historical fire regimes, possibly resulting in alternations of key ecosystem components. These classes categorize and describe vegetation composition and structure conditions that currently exist inside the Fire Regime Groups. Based on the coarse-scale national data, they serve as generalized wildfire rankings. The risk of loss of key ecosystem components from wildfires increases from Condition Class 1 (lowest risk) to Condition Class 3 (highest risk).
synonym: Fire Regime Current Condition Class

Condition of Vegetation
Stage of growth or degree of flammability of vegetation that forms part of a fuel complex. Herbaceous stage is at times used when referring to herbaceous vegetation alone. In grass areas minimum qualitative distinctions for stages of annual growth are usually green, curing, and dry or cured.

Conduction
Heat transfer through a material from a region of higher temperature to a region of lower temperature.

Confinement
The strategy employed in appropriate management responses where a fire perimeter is managed by a combination of direct and indirect actions and use of natural topographic features, fuel, and weather factors.

Conflagration Threat
Likelihood that a wildfire capable of causing considerable damage will occur.

Conflagration
A raging, destructive fire. Often used to connote such a fire with a moving front as distinguished from a fire storm.

Consistency (Foam)
Uniformity and size of bubbles.

Constant Danger
Resultant of all fire danger factors that are relatively unchanging in a specific area (e.g., resource values at risk, topography, fuel type, exposure to prevailing wind).

Consumption
The amount of a specified fuel type or strata that is removed through the fire process, often expressed as a percentage of the preburn weight.

Contained
The status of a wildfire suppression action signifying that a control line has been completed around the fire, and any associated spot fires, which can reasonably be expected to stop the fire’s spread.
see also: Containment

Containment
(1) The status of a wildfire suppression action signifying that a control line has been completed around the fire, and any associated spot fires, which can reasonably be expected to stop the fire’s spread.
(2) The act of controlling hazardous spilled or leaking materials.
see also: Contained

Continental Climate
Climate that is characteristic of the interior of a land mass of continental size, marked by large annual diurnal and day-to-day ranges of temperature, low relative humidity and irregular precipitation.

Contingency Actions
A back-up plan of action when actions described in the primary plan are no longer appropriate. Contingency actions are required to be taken when the result exceeds its intent. Actions are taken to return the project to its intended design.

Contingency Plan
The portion of a prescribed fire plan, incident action plan, or wildland fire use implementation plan that identifies possible but unlikely events and the contingency resources needed to mitigate those events.

Contingency Resources
Planned and identified fire suppression personnel and equipment that mitigate possible but unlikely events that exceed or are expected to exceed holding resource capabilities.

Contour Map
A map having lines of equal elevation that represent the land surface (Topographic).

Control Force
Personnel and equipment used to control a fire.

Control Line
An inclusive term for all constructed or natural barriers and treated fire edges used to control a fire.

Control Time
The time a fire is declared controlled.

Controlled Airspace
Airspace of defined dimensions within which air traffic control service is provided to IFR and VFR flights in accordance with the airspace classification.

Controlled
The completion of control line around a fire, any spot fires therefrom, and any interior islands to be saved; burned out any unburned area adjacent to the fire side of the control lines; and cool down all hot spots that are immediate threats to the control line, until the lines can reasonably be expected to hold under the foreseeable conditions.

Controlling Nozzle
Shut-off nozzle that permits the nozzle operator to open or close the nozzle or adjust the pattern of the stream.

Convection Column
The rising column of gases, smoke, fly ash, particulates, and other debris produced by a fire. The column has a strong vertical component indicating that buoyant forces override the ambient surface wind.
see also: Smoke Plume

Convection
(1) The transfer of heat by the movement of a gas or liquid; convection, conduction, and radiation are the principal means of energy transfer.
(2) As specialized in meteorology, atmospheric motions that are predominantly vertical in the absence of wind (which distinguishes this process from advection), resulting in vertical transport and mixing of atmospheric properties.

Convective Activity
General term for manifestations of convection in the atmosphere, alluding particularly to the development of convective clouds and resulting weather phenomena, such as showers, thunderstorms, squalls, hail, tornadoes, etc.

Convective-lift Fire Phase
The phase of a fire when most of the emissions are entrained into a definite convection column.

Convergence Zone
(1) The area of increased flame height and fire intensity produced when two or more fire fronts burn together.
(2) In fire weather, that area where two winds come together from opposite directions and are forced upwards often creating clouds and precipitation.

Convergence
The term for horizontal air currents merging together or approaching a single point, such as at the center of a low pressure area producing a net inflow of air. When this occurs in the lower atmosphere, the excess air is removed by rising air currents. Expansion of the rising air above a convergence zone results in cooling, which in turn often gives condensation (clouds) and sometimes precipitation.

Conversion Burning
Burning an area where brush has excluded forest reproduction to prepare the area for tree planting.

Co-op Fire
Refers to federal, state, and local cooperative fire programs.

Cooperating Agency
An agency supplying assistance including but not limited to direct tactical or support functions or resources to the incident control effort (e.g. Red Cross, law enforcement agency, telephone company, etc.).
see also: Agency
see also: Agency Representative
see also: Assisting Agency
see also: Supporting Agency

Cooperative Fire Protection (CFP)
A staff unit within the branch of State and Private Forestry or Aviation and Fire Management in the National Forest System, USDA Forest Service, that coordinates cooperative fire activities.

Cooperator
Local agency or person who has agreed in advance to perform specified fire control services and has been properly instructed to give such service.

Coordinated Resource Management
A process that directly involves everyone concerned with resource management in a given planning area.

Coordinates
The intersection of lines of reference, usually expressed in degrees/minutes/seconds of latitude and longitude, used to determine or report position or location.

Coordination Center
Term used to describe any facility that is used for the coordination of agency or jurisdictional resources in support of one or more incidents.

Coordination
The process of systematically analyzing a situation, developing relevant information, and informing appropriate command authority of viable alternatives for selection of the most effective combination of available resources to meet specific objectives. The coordination process (which can be either intra- or interagency) does not involve dispatch actions. However, personnel responsible for coordination may perform command or dispatch functions within limits established by specific agency delegations, procedures, legal authority, etc.

Coriolis Force
An apparent force due to the rotation of the earth that causes a deflection of air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This force maximizes at the poles and is essentially zero at the equator.

Corrosion
Result of chemical reaction between a metal and its environment (i.e., air, water, and impurities in same).

Cost Sharing Agreements
Agreements that document the financial responsibility for incident resource costs, possibly identifying requirements of other party payments.

Cost Unit Leader (COST)
The ICS position responsible for supervising the Cost Unit. Reports to the Finance/Administration Section Chief.
see also: Cost Unit

Cost Unit
Functional unit within the Finance/Administration Section responsible for collecting all cost data, performing cost effectiveness analyses, and providing cost estimates and cost saving advice.

Council Tool
Long-handled combination rake and cutting tool, the blade of which is constructed of a single row of three or four sharpened teeth. Also called fire rake, council rake.
see also: Rich Tool

Counter Fire
(1) Fire set between main fire and backfire to hasten spread of backfire. Also called draft fire.
(2) Emergency firing to stop, delay, or split a fire front, or to steer a fire. Also called draft fire.

Coupling
Device that connects the ends of adjacent hoses or other components of hose.
see also: Adapter

Course
In aviation, the intended direction of horizontal flight.

Cover Type
The designation of a vegetation complex described by dominant species, age, and form.

Cover
The area on the ground covered by the combined aerial parts of plants expressed as a percent of the total area.

Coverage Level
Recommended amount of aerially applied retardant keyed to the NFDRS fuel models and/or fire behavior models. Coverage level 2 represents 2 gallons of retardant per hundred square feet. Levels range from 1 to 6 for most fuel models. A coverage level of greater than 6 is for heavy fuels. The levels can be adjusted for fire behavior.

Coyote Tactics
A progressive line construction duty involving self-sufficient crews which build fire line until the end of the operational period, remain at or near the point while off duty, and begin building fireline the next operational period where they left off.

Crazing
Fine cracking of glass, usually from heat of fire.

Creeping Fire
Fire burning with a low flame and spreading slowly.

Crew Boss (CRWB)
A person in supervisory charge of usually 16 to 21 firefighters and responsible for their performance, safety, and welfare.

Crew Shuttle
Transportation of fireline personnel to and/or from assigned fireline locations.

Crew Transport
Any vehicle capable of transporting a specified number of personnel in a specified manner.

Crew
An organized group of firefighters under the leadership of a crew boss or other designated official.

Criteria Pollutants
Pollutants deemed most harmful to public health and welfare and that can be monitored effectively. They include carbon monoxide (CO), lead (Pb), nitrogen oxides (Nox), sulfur dioxide (SO2), ozone (O3), particulate matter (PM) of aerodynamic diameter less than or equal to 10 micrometers (PM10) and particulate matter of aerodynamic diameter less than or equal to 2.5 micrometers (PM2.5).

Critical Burnout Time
Total time a fuel can burn and continue to feed energy to the base of a forward-traveling convection column.

Critical Incident Stress Debriefing (CISD)
The process in which teams of professional and peer counselors provide emotional and psychological support to incident personnel who are or have been involved in a critical (highly stressful) incident.

Cross Shot
Intersecting lines of sight from two points to the same object, frequently used to determine location of a fire from lookouts. Also called cross bearing.

Crown Consumption
Combustion of the twigs, and needles or leaves of a tree during a fire.

Crown Cover
The ground area covered by the crown of a tree as delimited by the vertical projection of its outermost perimeter.

Crown Fire
A fire that advances from top to top of trees or shrubs more or less independent of a surface fire. Crown fires are sometimes classed as running or dependent to distinguish the degree of independence from the surface fire.

Crown Out
A fire that rises from ground into the tree crowns and advances from tree top to tree top. To intermittently ignite tree crowns as a surface fire advances.

Crown Ratio
The ratio of live crown to tree height.

Crown Scorch Height
The height above the surface of the ground to which a tree canopy is scorched.

Crown Scorch
Browning of needles or leaves in the crown of a tree or shrub caused by heating to lethal temperature during a fire. Crown scorch may not be apparent for several weeks after the fire.

Crowning Potential
A probability that a crown fire may start, calculated from inputs of foliage moisture content and height of the lowest part of the tree crowns above the surface.

Cumulonimbus
The ultimate growth of a cumulus cloud into an anvil-shaped cloud with considerable vertical development, usually with fibrous ice crystal tops, and usually accompanied by lightning, thunder, hail, and strong winds.

Cumulus
A principal low cloud type in the form of individual cauliflower-like cells of sharp non-fibrous outline and less vertical development than cumulonimbus.

Cup Trench
A fireline trench on the downhill side of fire burning on steep slopes that is supposed to be built deep enough to catch rolling firebrands that could otherwise start fire below the fireline. A high berm on the outermost downhill side of the trench helps the cup trench catch material. Also called gutter trench.

Cupping Indicators
A concave or cup-shaped depression on grass stem ends, small stumps, and terminal ends of brush and tree limbs.

Curb Weight
Weight of a truck empty (without payload and driver) but ready to drive, including a full fuel tank, cooling system, crankcase, tools, spare wheel, and all other equipment specified as standard.

Cured
In the 1978 version of NFDRS, the herbaceous stage when herbaceous fuel moisture falls to 30% or less.

Curing
Drying and browning of herbaceous vegetation due to mortality or senescence, and also loss of live fuel moisture content of woody fuel following mechanically-caused mortality (e.g., woody debris slash.)

Curling Indicators
Green leaves on succulent, uncured vegetation which bends and curls inwards towards the heat source.

Source: National Wildfire Coordinating Group