S-190
Fire
A by product of a larger process called combustion
Lesson 4: Weather
Fire weather: Weather conditions that influence fire ignition, behavior and suppression
Fuel Moisture
The amount of moisture present in a fuel, which affects how readily the fuel will ignite and burn.
Black
The burn area
Fireline
- Any cleared strip or portion of a control line where flammable material has been removed by scraping or digging down to mineral soil. - Removing flammable material down to mineral soil.
Anchor Point
- Any good place where you can start constructing a fire line. Using an anchor point minimizes the chance of being outflanked by the fire while the line is being constructed. - Minimizes the chance of being outflanked by the fire.
Lesson 2: Topography
A description of surface features of land.
Removing Oxygen
Smothering the fire with dirt
4 Main Weather Elements
- Temperature and RH - Precipitation - Atmospheric Stability - Wind
Wildland Fire Solids
Dust, Coal, Wood, Paper, Cloth, Leather, Plastic, Sugar, Grain
Smoldering
Fire burning without flame and barely spreading
Slopover
Fire edge that crosses a control line. Also called Breakover.
Spot Fire
Fire ignited outside the perimeter of the main fire by a firebrand.
Torching
Fire ignites the crown of trees, then returns to the surface
Running Fire
Fire spreading rapidly with a well defined head
Backing Fire
Fire that moves away from the head, downhill or against the wind.
Lesson 3: Fuels
Flammable and Combustible substances for a wildland fire to consume.
Wildland Fire Characteristics
Loading, Size and Shape, Continuity, Vertical Arrangement, Moisture, Temperature, Compaction
Safety Zones
Recently burned area or one cleared of vegetation used for escape in the event a line is outflanked or a spot fire outside a control line renders the line unsafe.
Control Line
Refers to all constructed or natural barriers.
Natural Barriers
Rivers, Lakes, Rocks, Burned Areas and Swamps
Man Made Barriers
Roads, Highways, Reservoirs and Firelines constructed by fire resources
Removing Heat
Cooling the fire with Class A foam and water
Islands
Unburned areas inside the fire perimeter. Because they are unburned potential fuels, patrol them frequently and check for spot fires.
Heat
Heat generated by a fire evaporates the moisture in the fuel and heats the fuel to its ignition temperature.
Fuel Size
Help predict how specific weather conditions will affect rate of heat transfer
Fire Whirl
- A spinning mass of hot air and gases rising rapidly (like a tornado), as a dust devil or whirlwind carrying aloft smoke, debris, flames (Extreme Fire Behavior) - Can be caused by thunderstorms, intense heating within a fire and wind shears
Light Fuels
- AKA Fine Fuels, Flashy Fuels or Flash fuels. Take on and give up more moisture faster than heavier fuels. - Examples: Short grasses and light shrubs or brush up to 2ft that burn rapidly with high intensity. - More firefighters have been killed by light fuels than any other type.
Barriers
- An obstruction to the spread of fire. - There are two types of wildland barriers: Natural and Manmade
Green
Area that is not burnt.
Size and Shape
- Affects the rate of heat transfer and the change in moisture content. - Described as light, medium and heavy.
3 Different Types of Canyons
- Box Canyons - Narrow Canyons - Wide Canyons
Local Winds
- By product of the daily heating and cooling of the earths surface referred to as the diurnal cycle. - Darker soils absorb more solar heat - Bare soils absorb more solar heat than grass covered soil - In hilly mountains or terrain heating causes upslope winds and cooling causes downslope winds. - Flat terrain causes whirlwinds or dustdevils
Grasses
- Can be found in all regions of the country and burn the hottest and fastest of all fuel types - Ex: Rye grass, wheat grass, wild oats. Perennial grasses: Saw grass, love grass, bunch grass and various tundra species.
Head
- The part of a wildland fire with the greatest forward rate of spread (ROS). - The head of the fire often burns intensely and may move with alarming speed.
Grasses-Shrubs
- Can be found in the plains of high deserts - Are a mixture of fine grass and aerial shrub fuels - Aerial Fuels: Standing and supportive live and dead combustibles not in direct contact with the ground and consisting mainly of foliage, twigs, branches, stems, cones bark and vines.
Convective Winds
- Caused by the localized heating of air that expands and rises while cooler denser air comes in to replace it. - Slope and valley winds, land and sea breezes, thunderstorm winds, whirlwinds, firewhirls - Upslope winds become valley winds when they reach 7mph(11 km/h) - Fires in drainages or chutes may spread very quickly - Chimneys can cause updrafts in response to localized heating - East aspects of mountainsides gain and lose solar energy
Removing Fuel
- Clearing a space of all surface fuels down to mineral soil - Throwing dirt containing little or no organic material
Heavy Fuels
- Consists of heavy continuous shrubs or brush more than 6ft in height and timber slash. - High intensity burning but generally a low to moderate ROS.
Slash and Blowdown
- Debris left after natural events or human activities: logging, pruning, thinning, shrub cutting, wind, fire etc. debris may include logs, chunks of wood, branches, fuel for fire spread.
East Facing Slope
- Early heating in the morning. Early cooling in evening. - Have about equal solar heating as the sun moves across the sky from east to west.
Radiation
- Energy that is radiated or transmitted in the form of rays or waves or particles. - Most common spread of wildland fires. - Fire is burning down one side of a steep forested canyon
Narrow Canyons
- Fire can spread easily (in steep narrow canyon) to fuels on the opposite site by radiation and spotting. - Wind eddies and strong upslope air movement may be expected at sharp bends
Box Canyons
- Fires starting near the base can react similar to a fire in a wood burning stove or fireplace. Wind drawn in from the bottom creating upslope drafts. Chimney effect. - The creation of strong upslope drafts results in extreme fire behavior.
Conduction
- Form of heat transfer where heat energy is directly transferred through direct contact. - Has limited effect in wildland fires - A burning log is sitting on a bed of dried leaves
Patchy Fuels
- Fuel that is separated by bare ground that has little or no flammable materials between patches. - Include all fuels distributed unevenly over the area, or areas of fuel with definite breaks or barriers present. - Bare ground, rocky outcropping, green vegetation, plowed grounds, roads, marshy areas.
Continuity
- Fuels distributed uniformly over an area thereby providing a continuous path for fire to spread. - Characteristic used to describe the horizontal and vertical spacing of fuels in a given area. - Influences the spread of the fire. - Fire spreads faster when fuels are close together.
Whirlwind
- Generally happen on hot days over flat dry terrain when skies are clear and winds are light - Also known as dust devils - Size can range from 10ft to over 100ft with windspeeds more than 20mph
Temperature
- Heat energy from the sun warms the earths surface - Heats the surrounding air and wildland fuels, lowers their moisture content and raises their ignition temperature. - Fuels in the sun will ignite more easily than fuels in the shade - Most fuels must reach between 400* and 700* F(204* and 371* C) in order to ignite
Rate of Spread (ROS)
- How fast the fire is moving. Measured in chains or acres per hour. - 1 ft. (0.3M)/minute = 1 chain/hour - 10ft.(3m)/minute = 10 chains/hour
Moisture
- In the earths environment water is present in the form of precipitation, ground moisture and atmospheric moisture which we call humidity. - The amount of water in a fuel expressed as a percentage of the total oven dry weight of that fuel.
South Facing Slope
- In the northern hemisphere, the slopes facing the south receive direct sun rays and become hotter than the slopes facing any other direction. - The higher temperature on the southern hemisphere exposures results in lower humidity, rapid loss of fuel and soil moisture and drier lighter flashy fluids as grass. - Southern slopes are more susceptible to fires than northern slopes.
Direct Wind
- Intensifies the burning by increasing the amount of oxygen to the fire - Bends flames, preheating and drying uninvolved fuels making them more susceptible to ignition - Can carry embers and sparks more than a mile causing the fire to widely spread into unburned areas
West Facing Slope
- Later heating and cooling within the day. Sunrise and sunset.
Man made fuel sources
- Log decks at saw mills - Authorized and Unauthorized dump sites - Above ground oil and natural gas pipelines - Can represent the main source of fuel that burns and spreads fire. - One type of fuel you might find no matter where you are fighting fires.
Shrubs
- Mature shrubs such as high pocosin, Alaska black spruce, buckeye, chamise, chaparral, coyote bush, manzanita, mesquite sagebrush and sugar brush. - Found in moist geographical regions and have very high flammable content - Have chemical content adding to fire intensity
Timber litter
- Most dominant in mountainous topography, especially in the northwest and provides fuel for ground fire. - The bottom part of the trees consists of small matter such as needles, leaves, twigs, and other natural debris found on the forest floor.
Slope
- Natural or artificial topographic incline - In the absence of winds, fires usually move faster uphill than downhill so the steeper the slope the faster a fire moves. - Upslope fires can cause burning debris to roll downhill - Upslope fires can increase the rate of fire spread
Escape Routes
- Pathway to safety. It can lead to an already burned area, a previously constructed safety area, a meadow that will not burn, or a natural rocky area that is large enough to take refuge without being burned. - When escape routes deviate from a defined physical path they must be clearly marked (flagged).
Relative humidity
- Percentage of moisture the air holds compared to the maximum amount of moisture that air will hold at that temperature. - Higher RH makes it feel hotter outside in the summer - More moisture makes it easier to control the wildland fire, reducing the ignition point of fuels - Less moisture makes it more difficult, increase in fire activity - RH below 30% means the air absorbs moisture from fuels and dehydrates them. - Low Humidity: Increase fire intesity, more spot fires and increase fire activity
Wide Canyons
- Prevailing wind direction can be altered by the direction of the canyon. Strong differences in behavior between north and south aspects - Cross canyon spotting of fires is not common except in high winds
Medium Fuels
- Shrubs or Brush. Bushes, dead fuels under 3 inches in diameter, and live fuels less than 6 feet tall. - Can produce moderate to very high intensity burning but with slower ROS than light fuels
Indirect Wind
- Strong dry winds absorb moisture from the fuels. Coll winds can help retain moisture
Vertical Arrangement
- Subsurface fuels: Below the surface litter such as tree shrub, shrub, roots, peat and sawdust - Surface fuels: Surface of the ground such as grasses, duff, needles, dead branches and anything on the ground that can be ground fuel. Don not burn rapidly but can continue to burn below the ground causing hidden voids to fall into. - Ladder fuels: Provide vertical fire continuity allowing fire to carry to the surface ensuring the continuation of crowning. Shrubs. - Aerial fuels: Sometimes referred to as crown fuels. Tree tops, leaves on branches, Hanging moss, tall shrubs.
Fuel Loading
- The amount of live or dead fuel in a given area - The total quantity of combustible contents of a building, space, or fire area, including interior finish and trim, expressed in heat units of the equivalent weight in wood. - With all other factors affecting fire behavior being equal, areas of HIGHER fuel loading will generate more heat than those with LESSER fuel loads.
Timber-Understory
- The area under the forest canopy such as surface fuels. - Found throughout most areas Provides ladder to aerial crown fuels. - Timber consists of large trees - Deciduous trees: Alder, Ash, Aspen, Birch, Cottonwood, Dogwood, Hickory, Maple and some oaks - Evergreens: Cedar, Cypress, Eucalyptus, Fir Hemlock, Live Oak and different kind of pine and spruce
Elevation
- The height of terrain above mean sea level. - Fuels at lower elevations dry out earlier and burn faster in the year than those at higher elevations
Compaction
- The spacing between fuel particles. EX: Hay standing in a field before harvesting is less compact than hay that has been cut and baled. - Disturbing unburned fuel beneath the surface of compact fuels may cause it to reignite - Fire generally burns at a low intensity and spreads slowly in highly compact fuels
Convection
- The transfer of thermal energy by the circulation or movement of a liquid or gas. - Can help start spot fires. - Wind is blowing from a grass fire into tree branches
General Winds
- Two types are "Frontal" and "Foehn" - Frontal: Leading edge of air masses are warm and cold fronts. Be aware of cold fronts. Cold fronts have much more impact on wildland fire. - Foehn: AKA Santa Ana, North WInd and Chinook. Result from air being forced over mountian ridges by convection or high barmetric pressure described as strong, hot, dry, persistent and unfavorable for wildland control. Can turn a fire into a fire storm.
Blowup
- When there is a sudden increase in ROS sufficient to prevent or rule out direct control of the fire. - Fire intensity increases suddenly posing a setback to suppression plans.
Wind
-The horizontal movement of air relative to the surface of the earth - It is measured by Direction, Speed and Turbulence
Chute
A steep "V-shaped" drainage
Flaming Front
Also known as "Fire Front" is the part of the fire within which continuous flaming combustion is taking place. The leading edge of the fire perimeter.
Rear
Also known as the heel of the wildland fire is the end opposite of the head. The back of the fire. Relatively closer to the origin of the fire.
Barriers
Any obstruction of the spread of fire
Flare-up
Any sudden acceleration in the ROS or intensification of the fire. A flare-up is of relativity short duration and does not radically change existing control plans.
Creeping Fire
Burns with a low flame and spreads slowly
Saddle
Common name for the depression between two adjacent hilltops.
Aspect
Compass direction toward which a slope faces
Wet Fuels
Fuels that have a high moisture content because of exposure to precipitation or high relative humidity
Ladder
Fuels that provide vertical continuity between strata thereby allowing fire to carry from the surface fuels into the crowns of trees or shrubs with relative ease
Wildland Fire Liquids
Gasoline, Kerosene, Turpentine, Alcohol, Cod liver oil, Paint, Varnish
Fuel Position
Helps firefighters predict how the fire will behave
Atmospheric Moisture
Humidity; Percentage of moisture in the air compared to the maximum amount of moisture that air will hold at that temperature.
Dry fuels
Ignite and burn more easily than the same fuels when they are wet. Low moisture because of prolonged sunshine exposure.
Smoldering FIre
Is one that burns without flame and is barely spreading
Fingers
Long, narrow strips of fire that extend from the main body of a fire. They form: -When a fire burns into mixed fuels; slowing in heavy fuel, but spreading quickly in light fuels -Due to variations in terrain or wind direction -When the head is split by natural features such as fields, water, or rock outcroppings
North Facing Slopes
More shade. Heavier fuels, low temperature, high humidity, high fuel moisture. Less fire activity than south facing slope.
Wildland Fire Gases
Natural Gas, Propane, Butane, Hydrogen, Oxygen, Acetylene, Carbon Monoxide
Firewhirl
Spinning vortex column of ascending hot air and gases rising from a fire and carrying aloft smoke, debris, and flame. Fire whirls range in size from less than one foot to over 500 feet in diameter. large fire whirls have the intensity of a small tornado
Chimneys
Steep, narrow draws or canyons in which heated air rises rapidly as it would in a flue pipe
Origin
The area where the fire started. It is also the point from which the fire spreads, depending on the fuels present and the effects of the wind slope.
Perimeter
The outer boundary- or the distance around the outside edge. Also commonly called the fire edge.
Control
The point in time when the perimeter spread of a wildland fire has been halted and can reasonably be expected to hold under foreseeable conditions.
Flanks
The sides of a wildland fire, roughly parallel to the main direction of fire spread. Flanks are identified as either left or right as you are looking from the heel of a fire toward the head.
Containment
The status of a wildfire suppression action that can reasonably be expected to stop the fire spread under prevailing and predicted conditions.
The unburned area between the main fire and any fingers.
Mop-Up
This phase marks the final extinguishing of a fire after it has been completely surrounded by control lines.
Crowning
When the fire advances across the tops of trees or shrubs more or less independent of the surface fire
