GLOSSARY OF FOREST FIRE TERMS -
"Glossary of Forest Fire Terms" are provided only a partial list.

Air Attack – A fire suppression operation involving the use of aircraft to deliver fire fighting forces, suppressants, or retardants to or on a fire.

Anchor Point – An advantage location, usually a barrier to fire spread, from which to start or finish construction of a control line.

Aspect – The direction a slope is facing; its exposure in relation to the sun (e.g. north, east, south, west).

Attack – The actual physical fire fighting operation.

Available Fuel – The quantity of fuel in a particular fuel type that would actually be consumed under specified burning conditions.

Back – That portion of the fire perimeter opposite the head; the slowest spreading part of the fire.

Back Tank – A portable water container equipped with a hand pump and back-pack straps carried on the back of firefighters; used for applying water in suppression and mop-up operations.

Bay – A marked indentation in the fire perimeter, usually located between two fingers.

Being Held – Indicates that with currently committed resources, sufficient suppression action has been taken that the fire is not likely to spread beyond existent or predetermined boundaries under prevailing and forecasted conditions.

Blowup – A somewhat sudden, and sometimes unexpected, major increase in the rate of spread and frontal fire intensity sufficient to upset overall fire suppression action or plans.

Buildup – The cumulative effects of those fire weather elements that cause drying of forest fuels and thereby heighten fire danger.

Burning Period – That part of each 24-hour day when fires are generally the most active. Typically, this is from mid-morning to sundown, although it varies with latitude and the time of year.

Canadian Forest Fire Weather Index (FWI) System – A subsystem of the Canadian Forest Fire Danger Rating System. The components of the FWI System provide numerical ratings of relative fire potential in a standard fuel type (i.e. a mature pine stand) on level terrain, based solely on consecutive observations of four fire weather elements measured daily at noon ( 1200 hours local standard time or 1300 hours daylight saving time) at a suitable fire weather station; the elements are dry-bulb temperature, relative humidity, wind speed and precipitation. The system provides a uniform method of rating fire danger across Canada.

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

Charged Line – A line of fire hose filled with water under pressure.

Cold Trailing – A method of determining whether or not a fire is still burning, involving careful inspection and feeling with the hand, or by use of a hand-held infrared scanner, to detect any heat source.

Combustion – A chemical oxidation-type process in which heat is produced (i.e., a substance is combined with oxygen). In the case of forest fires, living and dead fuels are converted to mainly carbon dioxide and water vapour, and heat energy is released very rapidly. Flaming combustion is characterized by the movement of a visible flame through the fuel bed. On the other hand, smouldering or glowing combustion is generally associated with the residual burning of forest fuels following flaming combustion.

Command Staff – The Command Staff consists of the Information Officer, Safety Officer, and Liaison Officer. They report directly to the Incident Commander. They may have an assistant or assistants, as needed.

Control Line – A comprehensive term for all constructed or natural fire barriers and treated fire perimeter used to control a fire.

Convection Column – The definable plume of hot gases, smoke, firebrands, and other combustion by- products produced by and rising above a fire.

Cover Type – The designation of a vegetation complex according to its dominant species, age, and/or form.

Crown Fuels – The standing and supported forest combustibles not in direct contact with the ground that are generally only consumed in crown fires (e.g. foliage, twigs, branches, cones).

Crowning – A fire ascending into the crowns of trees and spreading from crown to crown.

Direct Attack – A method whereby the fire is attacked immediately adjacent to the burning fuel.

Drop Height – Height of the air tanker at load release, usually given in feet above tree top level.

Drop Zone – Target area for the release of the air tankers load.

Drought – A period of relatively long duration with substantially less than normal precipitation, occurring usually over a wide area.

Duff – The layer of partially and fully decomposed organic materials lying below the litter and immediately above the mineral soil. It corresponds to the fermentation (F) and humus (H) layers of the forest floor.

Escape Route - A planned and cleared path giving fire fighters access to a safety zone

Extreme Fire Behaviour – A level of fire behaviour that often precludes any fire suppression action. It usually involves one or more of the following characteristics: high rate of spread and frontal fire intensity, crowning, prolific spotting, presence of large fire whirls, and a well established convection column. Fires exhibiting such phenomena often behave in an erratic, sometimes dangerous manner.

Financial/Administration Section – The section responsible for all incident costs and financial considerations. Includes the Time Unit, Procurement Unit, Compensation/Claims Unit, and Cost Unit.

Fine Fuels – Fuels that ignite readily and are consumed rapidly by fire (e.g. cured grass, fallen leaves, needles, small twigs).

Finger – An elongated burned area projecting from the main body of the fire resulting in an irregular fire perimeter.

Fire Behaviour – The manner in which fuel ignites, flame develops, and fire spreads and exhibits other related phenomena as determined by the interaction of fuels, weather, and topography.

Fire Behaviour Officer – A specialist position under the plans function of a fire overhead team (assigned to a campaign fire) responsible for making predictions of probable fire behaviour based on an analysis of the current and forecasted state of the fire environment.

Fire Bombing – An air attack operation involving the use of aircraft to drop suppressants or retardants to suppress or retard the spread of forest fire.

Fire Detection – A system for or the act of discovering, locating, and reporting wildfires.

Fire Ecology – The study of the relationships between fire, the physical environment, and living organisms.

Fire Edge – Any part of a boundary of a going fire at any given moment.

Fire Environment – The surrounding conditions, influences, and modifying forces of topography, fuel, and fire weather that determines fire behaviour.

Fireguard – A strategically planned barrier, either manually or mechanically constructed, intended to stop or retard the rate of spread of a fire, and from which suppression action is carried out to control a fire.

Fire Incidence – The average number of fires started in a designated area during a specified time.

Fire Interval - The average number of years between the occurrences of fires at a given point.

Fireline – That portion of a fire upon which resources are deployed and are actively engaged in suppression action. Any cleared strip used to control a fire.

Fire Perimeter – The entire outer edge boundary of a fire, usually expressed in metres or kilometres.

Fire Prevention – Activities directed at reducing fire occurrence; includes public education, law enforcement, personal contact, and reduction of fire hazards and risks.

Fire Pump – An engine driven pump, usually gasoline powered, specifically designed for use in fire suppression.

Fire Retardant – A substance that by chemical or physical action reduces flammability of combustibles.

Fire Scouting - Reconnaissance of a fire and its surroundings by any means to obtain fire intelligence information.

Fire Season – The period(s) of the year during which fires are likely to start, spread, and do damage to values-at-risk sufficient to warrant organized fire suppression; a period of the year set out and commonly referred to in fire prevention legislation.

Fire Storm – A large continuous area of intense burning characterized by violent fire-induced convection resulting in gale-force in draft surface winds near and beyond the fire perimeter, a towering convection column, and the occurrence of large fire whirls.

Fire Suppression – All activities concerned with controlling and extinguishing a fire following its detection.

Fire Triangle – An instructional aid in which the sides of an equilateral triangle represent the three factors necessary for combustion and flame production (i.e. oxygen, heat fuel). When any one of these factors is removed, flame production is not possible or ceases.

Flame Angle – The angle formed between the flame at the fire front and the ground surface, expressed in degrees.

Flame Height – The average maximum vertical extension of flames at the fire front; occasional flashes that rise above the ground level of flame are not considered.

Flame Length - The length of flames measured along their axis at the fire front; the distance between the flame height tip and the midpoint of the flame depth at the ground surface. Flame length is an approximate indicator of frontal fire intensity. Recommended SI unit is metres(m).

Flank – Sides of a fire extending from the head to the back.

Forest Fire – Any wildfire or prescribed fire that is burning in forested areas, grass, or alpine/tundra vegetation.

Forest Floor – The organic surface component of the soil supporting forest vegetation; the combined duff (if present) and litter layers.

Forest Protection – That branch of forestry concerned with the prevention and control of damage to forests from fire, insects, disease, and other harmful agents.

Frontal Fire Intensity – The rate of heat energy release per unit time per unit length of fire front. Flame size is its main visual manifestation. Frontal fire intensity is a major determinant of certain fire effects and difficulty of control.

Fuel Arrangement – A general term referring to the horizontal and vertical distribution of all combustible materials within a particular fuel type.

Fuel Moisture Content – The amount of water present in fuel generally expressed as a percentage of the substance’s weight when thoroughly dried at 100 degrees Celsius.

Green Up – The appropriate time during the first half of the fire season in which hardwood trees and/or understory vegetation (e.g. grasses, herbs, shrubs) have more or less completed their flushing of new growth.

Ground Fuels – All combustible materials below the litter layer of the forest floor that normally support smouldering or glowing combustion associated with ground fires.

Head – That portion of the fire perimeter having the greatest rate of spread and frontal fire intensity which is generally on the downwind and/or slope part of the fire.

Heat Transfer – The process by which heat is imparted from one body or object to another. In forest fires, heat energy is transmitted from burning to unburned fuels by:

• Convection – Transfer of heat by the movement of masses of hot air; the natural direction is upwards in the absence of any appreciable wind speed and/or slope.
• Radiation – Transfer of heat in straight lines from warm surfaces to cooler surroundings.
• Conduction – Transfer of heat through solid matter.

Heavy Fuels – Large diameter woody or deep organic materials that are difficult to ignite and burn more slowly than fine or medium fuels.

Helibase – The main location for parking, fuelling, maintenance, and loading of helicopters operating in support of a fire, usually located near the incident.

Helibucket – A specially designed rigid or collapsible container slung by a helicopter and used for picking and dropping suppressants or retardants on a fire.

Helitack – Initial attack on wildfires involving the use of helicopters and trained crews, deployed as a complete unit.

Hose-Lay – The arrangement of connected lengths of fire hose and accessories on the ground beginning at the first pump unit and ending at the point of water delivery.

Hot-Spot – A small area of smouldering or glowing combustion which may be exhibiting smoke, located within the fire perimeter.

Ignition – The beginning of flame production or smouldering combustion; the starting of a fire.

Incident Commander – The individual responsible for the management of all operations at the Incident site.

Incident Command System – A standardized on-scene emergency management concept specifically designed to allow its user(s) to adopt an integrated organizational structure equal to the complexity and demands of single or multiple incidents.

Initial Attack – The action taken to halt the spread or potential spread of a fire by the first fire fighting force to arrive at the fire.

Initial Attack Crew – Personnel trained, equipped and deployed to conduct suppression action to halt the spread or potential spread of a wildfire within the first burning period.

Island – An area of unburned fuel located within the perimeter.

Ladder Fuels – Fuels that provide vertical continuity between the surface and crown fuels in a forest stand, thus contributing to the ease of torching and crowning.

Liaison Officer – A member of the command staff responsible for coordinating with representatives from cooperating and assisting agencies.

Litter – The uppermost part of the forest floor consisting of freshly cast or slightly decomposed organic material.

Medium Fuels – Fuels too large to be ignited until after the leading edge of the fire front passes, but small enough to be completely consumed.

Mineral Soil – That portion of the soil stratum immediately below the litter and duff layer. Mineral soil contains very little combustible material except on highly productive sites where an upper soil horizon may be enriched with organic matter.

Mop-up – The act of extinguishing a fire after it has been brought under control.

Mutual Aid Agreement – Written agreement between participating agencies and/or jurisdictions in which they agree to assist one another upon request, by furnishing resources.

Natural Fire – Any fire of natural origin.

Personal Protective Equipment (PPE) – Any piece of equipment or clothing designed to be used to protect the health and/or safety of an individual.

Point of Origin – The location within the fire perimeter where ignition first occurred.

Precipitation – Any or all the forms of water, whether liquid (i.e. rain or drizzle) or solid (e.g. snow or hail) that fall from the atmosphere and reach the ground.

Rate of Spread (ROS) – The speed at which a fire extends its horizontal dimensions, expressed in terms of distance per unit of time. Recommended units are metres per minute or kilometres per hour.

Relative Humidity (RH) – The ratio, expressed as a percentage, of the amount of water vapour or moisture in the air to the maximum amount of moisture that the air would hold at the same dry-bulb temperature and atmospheric pressure. (For example, 60% RH means the air contains 60% of the moisture it is capable of holding).

Safety Officer – A member of the Command Staff responsible for monitoring and assessing safety hazards or unsafe situations, and for developing measures for ensuring personnel safety.

Safety Zone – A safety zone is a location where fire fighters can shelter from threatening fireline hazards.

Slash – Debris left as a result of forest and other vegetation being altered by forestry practices and other land use activities. Slash includes materials such as logs, branches, tree tops, stumps and shrubs.

Slope – The upward or downward inclination of the earth’s surface. Most commonly expressed as a percentage.

Span of Control – the supervisory ratio of from three to seven individuals, with five to one being established as optimum.

Spot Fire – A fire ignited by embers that are carried outside the main fire perimeter by air currents, gravity and/or fire whirls.

Suppression Crew – A unit of fire fighters assembled and organized for conducting fire suppression, either for initial attack and/or continuing work on fires.

Surface Fuels – All combustible materials lying above the duff layer between the ground and ladder fuels that are responsible for propagating surface fires (e.g. litter, herbaceous vegetation, low and medium shrubs, seedlings, downed dead wood and stumps).

Torching – A single tree or a small clump of trees is said to “torch” when its foliage ignites and flares up, usually from bottom to top.

Unity of Command – The concept by which each person within an organization reports to one and only one designated person.

Water Bombing – The act of dropping suppressants (water or short-term retardant) on a wildfire from an aircraft in flight.

Wildfire – An unplanned or unwanted natural or human caused fire.

Wildland Urban Interface – A popular term used to describe an area where various structures (most notably private homes) and other human developments are meet or are intermingled with forest and other vegetation fuel types.

Wind Speed – The rate of horizontal motion of the air past a given point expressed in terms of distance per unit of time.