Wildfire Glossary

Terms commonly used to describe wildfire and fuel management.

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Blow-up - A sudden and unexpected major increase in rate of spread and frontal fire intensity; sufficient to upset overall fire suppression action or plans. Blow-ups can result from small or large fire situations.


Campfire - An open fire that meets both of the following requirements (as defined in the Wildfire Regulation (s.1):

(a) the open fire burns material in one pile no larger than 0.5 m in height and 0.5 m in width;
(b) the open fire is lit, fuelled or used

(i)  by any person for a recreational purpose, or
(ii)  by a first nation for a ceremonial purpose.

Candling - When the foliage on a single tree or a small clump of trees ignites and flares up, usually from bottom to top.

Category 2 open fire - As defined in the Wildfire Regulation (s.1); an open fire, other than a campfire, that burns

(a) material in one pile not exceeding 2 m in height and 3 m in width,
(b) material concurrently in 2 piles each not exceeding 2 m in height and 3 m in width, or
(c) stubble or grass over an area that does not exceed 0.2 ha

Category 3 open fire - As defined in the Wildfire Regulation (s.1); an open fire that burns

(a) material concurrently in 3 or more piles each not exceeding 2 m in height and 3 m in width,
(b) material in one or more piles each exceeding 2 m in height or 3 m in width,
(c) one or more windrows, or
(d) stubble or grass over an area exceeding 0.2 ha

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.

Control line - All constructed or natural fire barriers and treated (e.g. with retardant or water) fire perimeter used to control or contain a fire.


Danger tree - A live or dead tree whose trunk, root system or branches have deteriorated or been damaged to such an extent as to be a potential danger to human safety.

Duff - The layer of partially and fully decomposed organic materials lying on the forest floor below the litter (layer) and immediately above the mineral soil. When moss is present, the top of the duff is just below the green portion of the moss.


Escaped fire/excursion - A wildfire, or a portion of a wildfire, that has breached a control line and remains out of control following initial attack. This term is also used to describe a prescribed fire that has burned beyond its intended area.


Fire danger - A general term used to express an assessment of both fixed and changeable factors of the fire environment that determine the ease of ignition, rate of spread, difficulty of control, and fire impact.

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. The constructed portion of a control line.

Fire hazard -

  1. the risk of fire starting, and
  2. the hazard associated with an industrial activity; and
  3. if a fire were to start,
  • the volatility of the fire’s behaviour,
  • the difficulty of controlling the fire, and
  • the potential threat to values at risk

Fire rank - A numerical value used to communicate a summarized visual assessment of fire behaviour.

Fire risk - Fire risk is a term that combines the probability of fire occurrence with the expected impacts from a fire. It can be defined quantitatively in economic terms or used more generally in a comparative sense; for example, given a similar probability of fire occurrence and spread between different landscapes; the fire risk at X is greater than the fire risk in Y.

Although the impacts of fire can be positive, such as when considering the ecological effects or fuel reduction benefits of a wildfire, this term is generally used to suggest negative consequences of fire.

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

Fuel - Fuel is any organic matter, living or dead, in the ground, on the ground, or in the air that can ignite and burn.

Available fuel - The quantity of fuel (in a particular fuel type) that would actually be consumed under specified burning conditions.

Fine fuels - Fuels that ignite readily and are consumed rapidly by fire (e.g. cured grass, fallen leaves, needles, small twigs). Dead, fine fuels also dry very quickly.

Ground fuels - All combustible materials below the litter layer of the forest floor that normally support smouldering or glowing combustion associated with ground fires (e.g. duff, roots, buried punky wood, peat).

Ladder fuels - Fuels that provide vertical continuity between the surface fuels and crown fuels in a forest stand, thus contributing to the ease of torching and crowning (e.g. tall shrubs, small-sized trees, bark flakes, tree lichens).

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.

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, tree seedlings, stumps, downed-dead roundwood).

Fuel break - a barrier or a change in fuel type or condition (to one that is less flammable than that surrounding it), or a strip of land that has been modified or cleared to prevent fire spread. In the event of fire, may serve as a control line from which to carry out suppression operations.

Fuel management - Fuel management is the modification of forest structure to reduce forest fuel accumulations available to burn in a wildfire. The main goal of fuel management is improving public safety. This may include treatments such as thinning, spacing and pruning trees, and removal of needles and woody debris from the forest floor. 

Fuel type - An identifiable association of fuel elements of distinctive species, form, size, arrangement, and continuity that will exhibit characteristic fire behaviour under defined burning conditions.


High risk activity - As defined in the Wildfire Regulation (s.1)

(a) mechanical brushing;
(b) disk trenching;
(c) preparation or use of explosives;
(d) using fire- or spark-producing tools, including cutting tools;
(e) using or preparing fireworks or pyrotechnics;
(f) grinding, including rail grinding;
(g) mechanical land clearing;
(h) clearing and maintaining rights of way, including grass mowing;
(i) any of the following activities carried out in a cutblock excluding a road, landing, roadside work area or log sort area in the cutblock:

(i)  operating a power saw;
(ii)  mechanical tree felling, woody debris piling or tree processing, including de-limbing;
(iii)  welding;
(iv)  portable wood chipping, milling, processing or manufacturing;
(v)  skidding logs or log forwarding unless it is improbable that the skidding or forwarding will result in the equipment contacting rock;
(vi)  yarding logs using cable systems

Holdover fire - A fire that remains dormant and undetected for a considerable time after it starts (particularly lightning-caused fires).


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

Initial attack - The action taken to halt the spread or potential spread of a fire by the first firefighting personnel to arrive at the fire.

Interface fire - Interface fires are fires that have the potential to involve buildings and forest fuel or vegetation simultaneously.


Landscape fire management planning - The intent of landscape fire management planning is to create a more fire resilient landscape to mitigate impacts on priority values in an era of increasing fire hazards and risks. The planning identifies zones with a high hazard, and aims to restore fire in the ecosystem.

Litter - The uppermost part of the forest floor consisting of freshly fallen or slightly decomposed organic materials.


Mineral soil - The layer of the soil profile immediately below the litter and duff. Mineral soil contains very little combustible material.

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


Patrol - To inspect a section of a control line or portion of the fire perimeter to prevent escape of the fire after a wildfire has been contained.

Prescribed fire - The knowledgeable and controlled application of fire to a specific area to accomplish planned resource management objectives. These fires are managed in such a way as to minimize the emission of smoke and maximize the benefits to the site.


Rate of spread (ROS) - The speed at which a fire extends its horizontal dimensions, expressed in terms of distance per unit of time, usually metres per minute (m/min) and kilometres per hour (km/h). Generally thought of in terms of a fire's forward movement or head fire rate of spread, but also applicable to backfire and flank fire ROS.

Resource management open fire - As defined in the Wildfire Regulation (s.1), an open fire that:

(a) burns un-piled slash over an area of any size, or
(b) is not a campfire or a category 2 or 3 open fire and is lit, fuelled or used for silviculture treatment, forest health management, wildlife habitat enhancement, fire hazard abatement, ecological restoration or range improvement.

Risk from wildfire - The exposure to the chance of loss from wildfire. For example, there is a 25% chance that a value at risk will be destroyed by a wildfire sometime in the next 50 years. Risk can also be calculated by multiplying damage (or loss) by uncertainty.


Slash - Debris left as a result of forest and other vegetation being altered by forestry practices and other land use activities (e.g. timber harvesting, thinning and pruning, road construction, seismic line clearing). Slash includes material such as logs, splinters or chips, tree branches and tops, uprooted stumps, and broken or uprooted trees and shrubs.

Smoke management - Scheduling and conducting a prescribed burning program under conditions that will minimize the adverse impacts of the resulting smoke production in smoke sensitive areas.

Spot fire - A spot fire is one that is less than 0.01 hectares (10 metres by 10 metres).

Spotting - A wildfire produces burning embers called firebrands. These firebrands are carried by the surface wind, a fire whirl and/or convection column that fall beyond the main fire perimeter and result in spot fires.


Values-at-risk - The specific or collective set of natural resources and man-made improvements/ developments that have measurable or intrinsic worth and that could of may be destroyed or otherwise altered by fire in any given area.


Wildfire - An unplanned fire - including unauthorized human-caused fires - occurring on forest or range lands, burning forest vegetation, grass, brush, scrub, peat lands, or a prescribed fire set under regulation which spreads beyond the area authorized for burning.

Wildland - An area in which development is essentially non-existent, except for roads, railroads, power lines, and similar transportation facilities. Structures, if any, are widely scattered.

Wildland urban interface - The wildland urban interface (WUI) is any area where combustible forest fuel is found adjacent to homes, farm structures or other outbuildings. This may occur at the interface, where development and forest fuel (vegetation) meet at a well-defined boundary, or in the intermix, where development and forest fuel intermingle with no clearly defined boundary. 

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