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)
  • Depression or pass in a ridgeline. 
  • A form and process, used by wildland firefighting agencies, for reporting and resolving incidents relating to firefighter safety. The information collected is used to determine long-term trends and problem areas within the wildland fire industry. 
Safety Advisory
  • A safety alert addressing wildland fire safety information that isn't related to imminent or potential threats of injury. 
Safety Alert
  • A warning or alert concerning critical information relating to firefighter safety, that is distributed via email through an NWCG mail server. There are three types of alerts: Safety Warning, Safety Advisory, and Safety Bulletin. 
Safety Briefing
  • A safety briefing emphasizes key safety concerns on the incident and is presented at each briefing session. The safety briefing should contain information to alert incident personnel of potential risk/hazard considered to be most critical. 
Safety Bulletin
  • A safety alert containing a factual confirmation of a serious wildland fire accident, incident or fatality. 
Safety Circle
  • An obstruction-free circle around the (helicopter) landing pad. 
Safety Warning
  • A safety alert addressing wildland fire safety hazards that pose an imminent threat, or have potential to pose a threat, to life or property. 
Safety Zone
  • An area cleared of flammable materials used for escape in the event the line is outflanked or in case a spot fire causes fuels outside the control line to render the line unsafe. In firing operations, crews progress so as to maintain a safety zone close at hand allowing the fuels inside the control line to be consumed before going ahead. Safety zones may also be constructed as integral parts of fuel breaks; they are greatly enlarged areas which can be used with relative safety by firefighters and their equipment in the event of blowup in the vicinity. 
  • Dropping by an airtanker of its entire load of fire retardant at one time. 
Salvo Drop
  • Total retardant or water load dropped all at once. Usually done to knock down a hotspot. 
  • Part of a population; that portion of the population that is measured. 
Sample Size
  • The number of items or observations in a sample; usually denoted by lower case letter n. 
Sand Table Exercise (STEX)
  • A tactical decision game that employs a three-dimensional terrain model made from sand and various props to provide a visual representation of the situation described in the tactical decision game. 
Scope of Practice
  • The set of responsibilities and ethical considerations that define the extent or limits of the care provider within the current standards of practice. 
Scorch Height
  • Average heights of foliage browning or bole blackening caused by a fire. 
Scratch Line
  • An unfinished preliminary control line hastily established or constructed as an emergency measure to check the spread of fire. 
  • The process of agitating foam solution and air within a confined space (usually a hose) that produces tiny, uniform bubbles - the length and type of hose determine the amount of scrubbing and, therefore, foam quality. 
Sea Breeze
Sea-level Pressure
Season Code
  • One of four designations of seasonal plant development used in the 1988 version of NFDRS. 
Seasonal Monthly Average
  • Historically, the average number of human-caused fires occurring on a protection unit per month during the established fire season. 
Seasonal Risk Class
  • Objective ranking of protection units within an administrative group based on the number of human-caused fires for at least the past five years. 
Second Order Fire Effects (SOFE)
  • The secondary effects of fire such as tree regeneration, plant succession, and changes in site productivity. Although second order fire effects are dependent, in part, on first order fire effects, they also involve interaction with many other non-fire variables. 
  • Pilot who is designated to be second-in-command of an aircraft during flight time. 
Secondary Line
  • Any fireline constructed at a distance from the fire perimeter concurrently with or after a line already constructed on or near to the perimeter of the fire. Generally constructed as an insurance measure in case the fire escapes control by the primary line. 
Secondary Lookout
  • A lookout point intermittently used to supplement the visible area coverage of the primary lookout system when required by fire danger, poor visibility, or other factors.
  • The person who occupies such a station. 
Secondary Weather Station
  • Station at which minimum weather measurements are taken to compute ratings of burning conditions; provides supplementary information on weather experience. 
  • That organizational level with responsibility for a major functional area of the incident, such as operations, planning, logistics, finance/administration. The section is organizationally between branch and incident commander. 
Security Weather Watch
  • Observers are posted at one or more strategic locations in the proximity of a fire to detect and warn fire personnel of pending critical weather changes that might significantly affect the fire. 
  • A geographical area in which a task force/strike team leader or supervisor of a single resource is assigned authority and responsibility for the coordination of resources and implementation of planned tactics. A segment may be a portion of a division or an area inside or outside the perimeter of an incident. Segments are identified with Arabic numbers, i.e., A-1, etc. and are not to be used as radio designators. 
Self-Contained Breathing Apparatus (SCBA)
  • Portable air (not oxygen) tanks with regulators which allow firefighters to breathe while in toxic smoke conditions. Usually rated for 30 minutes of service. Used primarily on fires involving structures or hazardous materials. 
  1. Spacing of aircraft while landing and taking off at airports to achieve safe and orderly movement in flight.
  2. The horizontal and vertical spacing of aircraft working over or near a wildfire or other incident.
  3. Spacing of personnel while performing line construction activities. 
Serious Accident Investigation Team (SAIT)
  • A formal investigation team that is organized with the purpose of conducting an accident investigation for an occurred serious accident. The team is given full authorization to conduct the investigation from involved agencies through letter of delegation. 
Serious Aircraft Incident
  • An incident or malfunction that could adversely affect the safety of flight. 
Service Branch
  • A branch within the logistics section responsible for service activities at the incident. Includes the communications, medical and food units. 
  1. An individual incendiary fire.
  2. The point or points of origin of an incendiary fire.
  3. Material left to ignite an incendiary fire at a later time.
  4. Individual lightning or railroad fires, especially when several are started within a short time.
  5. Burning material at the points deliberately ignited for backfiring, slash burning, prescribed burning, and other purposes. 
Severity Funding
  • Suppression funds used to increase the level of presuppression capability and fire preparedness when predicted or actual burning conditions exceed those normally expected, due to severe weather conditions. 
Severity Index
  • A number that indicates the relative net effects of daily fire danger on the fire load for an area during a specified period, such as a fire season. 
Shaded Fuel Break
  • Fuel breaks built in timbered areas where the trees on the break are thinned and pruned to reduce the fire potential yet retain enough crown canopy to make a less favorable microclimate for surface fires. 
Shareable Content Object (SCO)
Shareable Content Object Re-usable Model (SCORM)
  • A specification for standardizing the reusability and interoperability of learning content. SCORM has been developed by the Advanced Distributed Learning initiative (ADL). SCORM focuses on two critical pieces of learning content interoperability:
    • It defines an aggregation model for packaging learning content.
    • ​It defines an API for enabling communications between learning content and the system that launches it. 
Shock Wave
  • The leading edge of an expanding air mass. 
Short Takeoff or Landing (STOL) Aircraft
  • An aircraft which has the capability of operating from a STOL runway in accordance with applicable airworthiness and operating regulations. 
Short Takeoff or Landing (STOL) Airstrip
  • Developed or undeveloped area that has been tested and will accommodate STOL aircraft. 
Short-Range Spotting
  • Firebrands, flaming sparks, or embers are carried by surface winds, starting new fires beyond the zone of direct ignition by the main fire. The range of such spotting is usually less than 1/4 mile. 
  • Persons or work for which employment is less than 12 months (excluding firefighters hired for a particular fire). 
Short-Term Fire Retardant
  • Fire retardant that inhibits combustion primarily by the cooling and smothering action of water. Chemicals may be added to the water to alter its viscosity or retard its evaporation, thereby increasing its effectiveness. 
Shoulder Carry
  • Method of carrying hose on the shoulders. 
  • A woody perennial plant differing from a perennial herb by its persistent and woody stem; and from a tree by its low stature and habit of branching from the base. 
Shrub Type
  • The two-category (evergreen, deciduous) classification of shrubs vegetation in the 1988 version of NFDRS. 
Shutoff Nozzle
  • Common type of fire hose nozzle permitting stream flow to be controlled by the firefighter at the nozzle rather than only at the source of supply. 
Shutoff Pressure
  • Maximum pressure a centrifugal pump will attain when water flow is clamped or shut off. 
  • Hose fitting (preferably gated) for combining flow from two or more lines of hose into a single stream; one male coupling to two female couplings. 
Significant Fire Event
  • An event measured by the occurrence of fire(s) that requires mobilization of additional resources from outside the fire event area. 
Significant Fire Potential
  • The likelihood a wildland fire event will require mobilization of additional resources from outside the area in which the fire situation originates. 
Significant Weather Trigger
  • A weather phenomenon resulting in an environment that has a significant impact on fire spread, intensity, or occurrence. Example: strong wind, unstable air mass, etc. 
Simms Bucket
  • Self-leveling helibucket slung under a helicopter which can be filled by hovering over a water source. 
Simple Hose Lay
  • A hose lay consisting of consecutively coupled lengths of hose without laterals. The lay is extended by inserting additional lengths of hose in the line between pumps and nozzle. Also known as single hose lay. 
  • An activity that imitates something real, but it's not real itself and it can be altered by users for the specific purpose of providing an experiential learning environment. Examples: Sand Table Exercise or CBT/WBT Forest Service Wildland Fire Simulation Scenario Editor. 
Single Arsonist
  • An offender who intentionally sets one fire. 
Single Door Drop
  • Technique whereby fire retardant is released from only one compartment of an airtanker. 
Single Resource
  • An individual, a piece of equipment and its personnel complement, or a crew or team of individuals with an identified work supervisor that can be used on an incident. 
Single Shift
  • Equipment is staffed with 1 operator or crew. A normal shift could be up to 16 hours long and may cross calendar days.
Single Stage Pump
  • Centrifugal pump with a single impeller. 
Site Preparation
  • Removal or killing of unwanted vegetation, residue, etc. by use of fire, herbicides, or mechanical treatment in preparation for reforestation and future management. 
Site Preparation Burning
  • Fire ignited to expose adequate mineral soil and control competing vegetation until seedlings of the desired species become established. 
Situation Analysis
  • Analysis of factors which influence suppression of an escaped fire from which a plan of attack will be developed; includes development of alternative strategies of fire suppression and net effect of each. 
Situation Awareness (SA)
  • An on-going process of gathering information by observation and by communication with others. This information is integrated to create an individual's perception of a given situation. 
Situation Unit
  • Functional unit within the planning section responsible for the collection, organization and analysis of incident status information, and for analysis of the situation as it progresses. Reports to the planning section chief. 
Situational Awareness (SA)
  • An on-going process of gathering information by observation and by communication with others. This information is integrated to create an individual's perception of a given situation.
Six Minutes for Safety (6MFS)
  • A daily safety briefing for wildland fire that focuses on high risk events found within a firefighter's scope of work that are performed on an infrequent basis. Also know as 6 Minutes for Safety.  View the Six Minutes for Safety website at https://www.nwcg.gov/committee/6mfs
Size Class of Fire
  • As to size of wildfire:
    • Class A - one-fourth acre or less;
    • Class B - more than one-fourth acre, but less than 10 acres;
    • Class C - 10 acres or more, but less than 100 acres;
    • Class D - 100 acres or more, but less than 300 acres;
    • Class E - 300 acres or more, but less than 1,000 acres;
    • Class F - 1,000 acres or more, but less than 5,000 acres;
    • Class G - 5,000 acres or more.
  • The evaluation of the fire to determine a course of action for suppression. 
Skid Hose Load
  • Load of hose specially arranged on top of a standard hose load to permit dropping the working line at the fire. 
Skid Trail
  • Any road or trail formed by the process of skidding logs from stump to landing. 
Skidder Unit
  • A self-contained unit consisting of a water tank, fire pump, and hose specially designed to be carried on a logging skidder for use in forest fire suppression. 
  • Any aircraft equipped to pick up water while moving on or over water. 
Sky Cover
  • Debris resulting from such natural events as wind, fire, or snow breakage; or such human activities as road construction, logging, pruning, thinning, or brush cutting. It includes logs, chunks, bark, branches, stumps, and broken understory trees or brush. 
Slash Disposal
  • Treatment of slash to reduce fire hazard or for other purposes. Preferred to "Brush Disposal." 
  • A net attached by a lanyard to a helicopter cargo hook and used to haul supplies. 
Sling Load
  • Any cargo carried beneath a helicopter and attached by a lead line and swivel. 
Sling Psychrometer
Slip-on Tanker
  • A tank, a live hose reel or tray, an auxiliary pump, and an engine combined into a single one-piece assembly which can be slipped onto a truck bed or trailer. 
Slope Class
  • One of five categories used to describe the topography of a fire danger rating area. 
Slope Percent
  • The ratio between the amount of vertical rise of a slope and horizontal distance as expressed in a percent. One hundred feet of rise to 100 feet of horizontal distance equals 100 percent. 
Slope Winds
  • A fire edge that crosses a control line or natural barrier intended to confine the fire. 
Slug Flow
  • The discharge of distinct pockets of water and air due to the insufficient mixing of foam concentrate, water, and air in a compressed air foam system. 
Small Aircraft
  • An aircraft of 12,500 pounds (5,669 kg) or less, maximum certificated takeoff weight. 
  • Small particles of carbon, tarry and water vapor resulting from the incomplete combustion of carbonaceous materials such as wood, coal or oil. 
Smoke Concentration
  • The amount of combustion products found in a specified volume of air, commonly expressed as micrograms of emission per cubic meter of air. 
Smoke Intrusion
  • Smoke from prescribed fire entering a designated area at unacceptable levels. 
Smoke Management
  • The policies and practices implemented by air and natural resource managers directed at minimizing the amount of smoke entering populated areas or impacting sensitive sites, avoiding significant deterioration of air quality and violations of National Ambient Air Quality Standards, and mitigating human-caused visibility impacts in Class I areas. 
Smoke Pall
  • Extensive, thick blanket of smoke spreading more or less horizontally from a fire. 
Smoke Plume
Smoke Sensitive Area (SSA)
  • Area in which smoke from outside sources is intolerable, for reasons such as heavy population, existing air pollution, or intensive recreation or tourist use. 
Smoke Target
  • An area that may be adversely affected by smoke from a prescribed burn. Also known as a smoke sensitive area. 
Smoke Vent Height
  • Level, in the vicinity of the fire, at which the smoke ceases to rise and moves horizontally with the wind at that level. 
Smokey Bear
  • The symbol of the Cooperative Forest Fire Prevention Program since 1945. Smokey's image is protected by US Federal Law and is administered by the USDA Forest Service, the National Association of State Foresters and the Ad Council. 
Smoking (As a Fire Cause)
  • Wildfires caused by smokers from matches, lighters, tobacco, or other smoking material. 
Smoldering Combustion
  • Combined processes of dehydration, pyrolysis, solid oxidation, and scattered flaming combustion and glowing combustion, which occur after the flaming combustion phase of a fire; often characterized by large amounts of smoke consisting mainly of tars. 
Smoldering Combustion Phase
  • Phase of combustion immediately following flaming combustion. Emissions are at twice that of the flaming combustion phase. 
  • A standing dead tree or part of a dead tree from which at least the leaves and smaller branches have fallen. Often known as a stub, if less than 20 feet tall. 
Snorkel Tank
  • A fixed tank attached to the belly of the helicopter that has a pump-driven snorkel attached. The helicopter hovers over the water source with the end of the snorkel immersed, the pump then fills the tank. 
Soft Suction
  • Commonly accepted term for short length of large diameter soft hose used to connect a structural or wildland engine with a hydrant. No vacuum is involved because the hose is useful only when the engine receives water at a rate of flow in excess of the demand of the pump. 
Solar Radiation
  • The amount of sunlight exposed to the fuels. 
  • Carbon dust formed by incomplete combustion. 
  • Single round trip made by an airtanker from a tanker base to a fire and return. 
Sound Warbler
  • A signaling device mounted on retardant aircraft which generates a tremulous siren sound to warn firefighters on the ground that a plane is approaching to drop retardant. 
Sounding (Upper Air Sounding)
  • A sampling of upper air conditions made by means of instruments and a small radio transmitter on a free balloon. Automatic radio signals originated by action of weather instruments are sent to a ground receiver. These signals are interpreted for use in analyzing and predicting upper air conditions over a wide area of the earth. Weather elements determined at a number of altitude points as the balloon rises are temperature, atmospheric moisture, pressure, wind direction and speed. Similar soundings may be made using fixed balloons or tethersondes.  Source:  http://glossary.ametsoc.org/wiki/Upper-air_sounding
  • A point, line, or area, at which mass or energy is added to a system, either instantaneously or continuously. Examples of sources in the context of air pollution are as follows: a smoke stack is a point source; a freeway is a line source; field or slash burning are area sources. 
  • Chipping or pitting of concrete, masonry, or stone surfaces. 
  • Distance equal to the wingspread of the airtanker being used; used for corrections right or left of the flight path. 
Span of Control
  • The supervisory ratio of from three-to-seven individuals, with five-to-one being established as optimum. 
  • Metal wrench used to tighten and free hose connections. 
Spark Arrester
  • A device installed in a chimney, flue, or exhaust pipe to stop the emission of sparks and burning fragments. 
Special Interest Group (SIG)
  • In WIMS, a group of weather stations. 
Special Visual Flight Rules (VFR)
  • Aircraft operating in accordance with clearances within control zones in weather conditions less than the basic Visual Flight Rules weather minima. 
Specific Heat
  • The heat required to raise a unit mass of a substance one degree kelvin. It is the heat capacity of a system per unit mass; i.e., the ratio of the heat absorbed (or released) to the corresponding temperature rise (or fall). 
Specific Origin Area (SOA)
  • The smaller area within the general origin area where the fire's direction of spread was first influenced by fuel, weather, and/or topography. Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.
    • Definition Extension: The SOA will contain the Ignition Area. Generally this area is characterized by subtle and microscale fire pattern indicators as a result of less intense burning associated with the initial stages of the fire.
Speed of Attack
  • Elapsed time from origin of fire to arrival of the first suppression force. 
  • Standby crew in an area of expected high fire occurrence, generally on a day of critical fire weather. 
Split Drop
  • Retardant drop made from one compartment at a time from an airtanker with a multi-compartment tank. 
Split Flow
  • A divergent wind field. Storms moving into a split field tend to lose strength. Winds are generally light in such a flow field. 
Spontaneous Combustion
  • Combustion of a thermally isolated material initiated by an internal chemical or biological reaction producing enough heat to cause ignition. 
Spot Burning
  • A modified form of broadcast slash burning in which the greater accumulations of slash are fired and the fire is confined to these spots. Sometimes known as "Jackpot Burning" or "Jackpotting."
Spot Change
  • The second continuous day of an incident, a regular government employee's normal daily tour of duty is "spot changed" to where the first 8, 9, or 10 hours worked are base hours.
Spot Fire
  • Fire ignited outside the perimeter of the main fire by a firebrand. 
Spot Fire Technique
  • A method of lighting prescribed fires where ignition points are set individually at a predetermined spacing and with predetermined timing throughout the area to be burned. 
Spot Weather Forecast
  • A special forecast issued to fit the time, topography, and weather of a specific incident. These forecasts are issued upon request of the user agency and are more detailed, timely, and specific than zone forecasts. Usually, on-site weather observations or a close, representative observation is required for a forecast to be issued. 
  • In smokejumping, rappelling, and paracargo operations, the individual responsible for selecting drop target and supervising all aspects of dropping smokejumpers, rappellers, or cargo. 
  • Behavior of a fire producing sparks or embers that are carried by the wind and which start new fires beyond the zone of direct ignition by the main fire. 
  • Water applied through an orifice in finely divided particles to absorb heat and smother fire, to protect exposures from radiated heat, and to carry water toward otherwise inaccessible fire. 
Spread Component
  • Part of the National Fire Danger Rating System (NFDRS). A rating of the forward rate of spread of the head of a fire. 
Spread Index
  • A number used to indicate relative (not actual) rate of spread. 
Spread Index Meter
  • Device for combining measured ratings of various fire danger factors into numerical classes or rates of spread. 
Spur Ridge
  • A small ridge which extends finger-like from a main ridge. 
Squall Line
  • Any nonfrontal line or narrow band of active thunderstorms extending across the horizon. It is of importance to fire behavior due to accompanying strong gusty winds and the possibility of such a line passing between regular weather observation stations without being reported. Also known as line squall.  Source:  http://glossary.ametsoc.org/wiki/Squall_line
Stable Atmosphere
  • Condition of the atmosphere in which the temperature decrease with increasing altitude is less than the dry adiabatic lapse rate. In this condition, the atmosphere tends to suppress large-scale vertical motion. Also known as stable air. 
Stable Layer of Air
  • A layer of air having a temperature change (lapse rate) of less than dry adiabatic (approximately -5.4 degrees F per 1,000 feet) thereby retarding either upward or downward mixing of smoke. 
  • Aircraft orbiting the rendezvous area; usually refers to vertical deployment at 500-foot (150 m) altitudinal separation between aircraft. 
Staff Ride
  • A case study of a previous incident that is conducted on the actual physical site where the incident occurred. A staff ride is an experiential learning method that involves three distinct parts: a preliminary study, a site visit, and a post-visit integration session. 
Staffing Index
  • A NFDRS component, index or related indicator (ignition component, spread component, energy release component, burning index, Keetch-Byram drought index) whose outputs are correlated to the local fire problem, used to determine staffing levels. 
Staffing Level
  • The basis for decision support for daily staffing of initial attack resources and other activities. A level of readiness and an indicator or daily preparedness. 
Staging Area
  • Locations set up at an incident where resources can be placed while awaiting a tactical assignment on a three (3) minute available basis. Staging Areas are managed by the Operations Section. 
Stagnant Conditions
  • Atmospheric conditions under which pollutants build up faster than the atmosphere can disperse them. 
Stand Replacing Fire
  • Fire which kills all or most of the living overstory trees in a forest and initiates forest succession or regrowth. Also explicitly describes the nature of fire in grasslands and some shrublands. 
Stand-By Crew
  • A group of trained firefighters stationed at a dispatch point for quick, rapid deployment. 
Standard Coupling
  • Fire hose coupling with American National Standard (NH) threads. 
Standard Drying Day
  • Part of the National Fire Danger Rating System (NFDRS). Day which produces the same net drying as experienced during a 24-hour period under laboratory conditions in which dry-bulb temperature is maintained at 80º F and relative humidity is maintained at and relative humidity is maintained at 20%. 
Standard Hydrologic Exchange Format code (SHEF)
  • A two-character code to describe each measurement taken at a weather station. 
Standard Operating Procedure (SOP)
  • Specific instructions clearly spelling out what is expected of an individual every time they perform a given task. A standard operating procedure can be used as a performance standard for tasks that are routinely done in the operational environment. 
Standard Operational Procedure (SOP)
  • Specific instructions clearly spelling out what is expected of an individual every time they perform a given task. A standard operational procedure can be used as a performance standard for tasks that are routinely done in the operational environment. 
Standards, Incident Position
  • Incident Position standards are a component of NWCG standards. They enable consistent and uniform performance by personnel mobilized by position under NIMS-ICS principles. Incident position standards include incident position descriptions (duties and responsibilities) and position qualification requirements for training, experience, physical fitness, and position currency.
Standards, NWCG
  • NWCG standards establish common practices and requirements that enable efficient and coordinated national interagency wildland fire operations. These standards may include guidelines, procedures, processes, best practices, specifications, techniques, and methods. NWCG standards are interagency by design; however, the decision to adopt and utilize them is made independently by the individual member agencies and communicated through their respective directives systems.
State Forest
  • Forests owned and administered by a state, and not by a federal government. 
State of Weather
  • A code which expresses the amount of cloud cover, kind of precipitation, and/or restrictions to visibility being observed at the fire danger station at basic observation time. 
State Park
  • An area established by the government of a state primarily for public recreation or for the preservation of unique natural or historic resources, administrative details varying widely. NOTE: Such parks may also be established by lesser administrative units, e.g. counties, municipalities, and also by large private owners. 
Static Pressure
  • Water pressure head available at a specific location when no water is being used so that no friction loss is being encountered. Static pressure is that pressure observed on the engine inlet gauge before any water is taken from the hydrant. 
Static Water Supply
  • Supply of water at rest which does not provide a pressure head for fire suppression but which may be employed as a suction source for fire pumps (e.g., water in a reservoir, pond, or cistern). 
Station Catalog
  • A WIMS file that contains all the information defined for a weather station. 
Station ID
  • A six-digit number assigned to a specific weather station by the servicing National Weather Service Fire Weather Office. 
Station Pressure
  • The number that results from manipulating raw data according to a specified procedure; associated with samples. 
Statistical Fire
  • In general, an actionable fire, on which any fire agency reports and maintains specified information (e.g., cause, date and point of origin, size, fire damage). 
  • A branch of mathematics dealing with the collection, analysis, and interpretation of numerical data. 
Step Test
  • Five-minute test used to predict a person's ability to take in, transport, and use oxygen (aerobic capacity), the most important factor limiting the ability to perform arduous work. 
Storm Center
  • The central point or area of a weather system associated with increased winds, clouds or precipitation (or any combination thereof). 
Straight Stream
  • Water or fire retardant projected directly from the nozzle (as contrasted with a fog or spray cone), provided by a solid stream orifice or by adjusting a fog jet into a straight stream pattern. 
Straight Stream Nozzle
  • A hose tip spout designed to provide the maximum reach of water without feathering. 
  • A wire or metal guard used to keep debris from clogging pipe or other openings made for removing water; used in pumps and on suction hose to keep foreign material from clogging or damaging pumps. 
Strategic Objective
  • A broad statement, specified in a land/resource management or fire management plan that identifies change in water, soil, air, or vegetation from the present to proposed conditions, or describes an existing resource condition that should be maintained. Strategic objectives deal with large areas over long time periods and project intended outcomes of management activities that contribute to the maintenance or achievement of desired conditions. 
  • The general plan or direction selected to accomplish incident objectives. 
Strength of Attack
  • Number of resources used to attack a fire. 
Strength of Force
  • Total firefighting resources available, during a specified period, to conduct and support firefighting operations. 
Strike Team
  • Specified combinations of the same kind and type of resources, with common communications, and a leader. 
  • A narrow finger or band of fuel that connects two or more patches or areas of wildland fuel. 
Strip Burning
  1. Burning by means of strip firing.
  2. In hazard reduction, burning narrow strips of fuel and leaving the rest of the area untreated by fire. 
Strip Firing
  • Setting fire to more than one strip of fuel and providing for the strips to burn together. Frequently done in burning out against a wind where inner strips are fired first to create drafts which pull flames and sparks away from the control line. 
Strip-Head Fire
  • A series of lines of fire ignited near and up wind (or downslope) of a firebreak or backing fire so they burn with the wind (or upslope) toward the firebreak or backing fire. 
Structural Fire Protection
  • The protection of homes or other structures from an active wildland fire.
  • A constructed object, usually a free-standing building above ground. 
Structure (Vegetative)
  • The arrangement of vegetation in terms of density, basal area, cover, and vertical arrangement. 
Structure Fire
  • Fire originating in and burning any part or all of any building, shelter, or other structure. 
Structure Protection Plan
  • A plan developed by the Structure Protection Specialist that provides operational guidelines to suppression resources responsible for providing wildland fire structure protection. 
  • Downward or sinking motion of air in the atmosphere. Subsiding air warms due to compression. Increasing temperature and decreasing humidities are present in subsiding air. Subsidence results in a stable atmosphere inhibiting dispersion. Subsidence is generally associated with high atmospheric pressure. 
Subsidence Inversion
  • An inversion caused by subsiding air, often resulting in decreased atmospheric mixing conditions. 
  • The process of vegetational development whereby an area becomes successively occupied by different plant communities of higher ecological order. 
Suction Lift
  • In fire service, the number of feet (meters) of vertical lift from the surface of the water to the center of the pump impeller. In testing, e.g., fire department pumpers are required to discharge their rated capacity at 150 pounds (1034 kPa) net pump pressure at a 10-foot (3 meter) lift. The suction gauge would indicate the vertical suction lift in inches of mercury when the pump was primed with no appreciable water flowing. 
  • The adjective classification of the sky when 5/10 or less of the sky is obscured by clouds. Part of the National Fire Danger Rating System (NFDRS). 
Sunset and Sunrise
  • The mean solar times of sunset and sunrise as published in the Nautical Almanac, converted to local standard time for the locality concerned. 
Superficial Burn
  • A minor thermal burn involving the outer layer of skin, i.e. "a sunburn". It is characterized by reddening of the skin and perhaps some swelling without blisters. Also known as First Degree Burn.
  • The ICS title for individuals responsible for command of a division or group. 
Supplemental Fire Department Resources
  • Overhead tied to a local fire department, generally by agreement, who are mobilized primarily for response to incidents or wildland fires outside their district or mutual aid zone. Supplemental fire department resources are not a permanent part of the local fire organization and are not required to attend scheduled training, meetings, etc. of the department staff. 
  • Minor items of equipment and all expendable items assigned to an incident. 
Supply Unit
  • Functional unit within the support branch of the logistics section responsible for ordering equipment and supplies required for incident operations. 
Support Branch
  • A branch within the logistics section responsible for providing personnel, equipment and supplies to support incident operations. Includes the supply, facilities and ground support units. 
Support Costs
  • On-incident costs and off-incident costs. On-incident costs include caterer, shower units, mobile commissary, cache supplies, and materials, etc. Off-incident costs include expanded dispatch, buying teams, administrative payment teams, cache personnel, area command, transportation to/from incident, etc. 
Support Resources
  • Non-tactical resources under the supervision of the logistics, planning, finance/administration sections or the command staff. 
Supporting Agency
Supporting Technologies
  • Any technology which may be used to support NIIMS. Examples of these technologies include GIS mapping, infrared technology, NFDRS, communications, dispatch coordination, and national cache system. 
Suppress a Fire
  • An agent that extinguishes the flaming and glowing phases of combustion by direct application to the burning fuel. 
Suppression Crew
  • Two or more firefighters stationed at a strategic location for initial action on fires. Duties are essentially the same as those of individual firefighters. 
Suppression Firing
  • Intentional application of fire to speed up or strengthen fire suppression action on wildfires. Types of suppression firing include burning out, counter firing, and strip burning. 
Surface Area-to-Volume Ratio
  • The ratio between the surface area of an object, such as a fuel particle, to its volume. The smaller the particle, the more quickly it can become wet, dry out, or become heated to combustion temperature during a fire. 
Surface Fire
  • Fire that burns loose debris on the surface, which includes dead branches, leaves, and low vegetation. 
Surface Fuel
  • Fuels lying on or near the surface of the ground, consisting of leaf and needle litter, dead branch material, downed logs, bark, tree cones, and low stature living plants. 
Surface High
  • An area on the earth's surface where atmospheric pressure is at a relative maximum. Winds blow clockwise around highs in the Northern Hemisphere but, due to friction with the earth's face, tend to cross constant pressure lines away from the high center. Air is usually subsiding above a surface high. This causes warming due to air compression. This results in stable atmospheric conditions and light surface winds. 
Surface Low
  • An area on the earth's surface where atmospheric pressure is at a relative minimum. Winds blow counter-clockwise around lows in the Northern Hemisphere but, due to friction with the earth's surface, tend to cross constant pressure lines toward the low center. Upon converging into the low's center, air currents are forced to rise. As air rises it cools due to expansion. Cooling reduces its capacity to hold moisture; so cloudiness and precipitation are common in lows. If a low center intensifies sufficiently it will take on the characteristics of a storm center with precipitation and strong winds.
Surface Tension
  • The elastic-like force at the surface of a liquid, tending to minimize the surface area and causing drops to form. Expressed as Newtons per meter or dynes per centimeter (1 Newton/m=1,000 dynes/cm). 
Surface Wind
  • Wind measured at a surface observing station, customarily at some distance (usually 20 feet) above the average vegetative surface to minimize the distorting effects of local obstacles and terrain. 
  • A surface active agent; any wetting agent. A formulation which, when added to water in proper amounts, will materially reduce the surface tension of the water and increase penetration and spreading abilities of the water. 
  • Rapid increase in water flow which may result in a corresponding pressure rise. 
Surplus Property
  • Any excess personal property not required for the needs and the discharge of the responsibilities of all federal agencies as determined by the General Services Administration (GSA). 
Survival Zone
  • A natural or cleared area of sufficient size and location to protect fire personnel from known hazards while inside a fire shelter. Examples include rock slides, road beds, clearings, knobs, wide ridges, benches, dozer lines, wet areas, cleared areas in light fuels, and previously burned areas. These are all areas where you expect no flame contact or prolonged heat and smoke. 
Suspended Fuel
  • A wildland fuel that is suspended off the ground in such a way that fire may burn both over and under it. Source: Guide to Wildland Fire Origin and Cause Determination, PMS 412.
    • Definition Extension: Heated air and fire moving under the suspended fuel wraps around the backside due to wind vortex flame wrap creating a fire pattern indicator the opposite of a typical protection fire pattern indicator.
Sustained Attack
  • Continuing fire suppression action until fire is under control. 
  1. A worker who assists fallers and/or sawyers by clearing away brush, limbs and small trees. Carries fuel, oil and tools and watches for dangerous situations.
  2. A worker on a dozer crew who pulls winch line, helps maintain equipment, etc., to speed suppression work on a fire. 
  • Act of clearing brush and other material from around the base of trees and where trees are to be bucked, prior to falling or bucking, as protection against saw kickback and to provide safe footing. 
  • An accessory used between the helicopter cargo hook and sling load to allow free turning of the load. 
  • Literally, at one time. Thus, in meteorological usage, the weather conditions over a large area at a given point in time. 
Synoptic Chart
  • In meteorology, any chart or map on which data and analyses are presented that describe the state of the atmosphere over a large area at a given moment in time. 
Systematic Methodology