Chapter 1 Flashcards
Fire triangle
Heat- lightning,humans
Fuel-everything
O2- only thing that can’t be removed
Fire behaviour triangle
Fuel- fine or heavy, arrangement and continuity, fuel moisture
Topography- aspect(facing sun or not, direction, flat or slopes
Weather- wind, temperature, rh, rain
Temperature
As temp rises, more moisture evaporates and fuels get dryer
RH
Amount of moisture in the air. When high, forest fuels absorb moisture from air, when low fuels release moisture into air.
Highest during morning and late night. Lowest during late afternoon-
Flammable
Crossover
RH is less or equal to the ambient air temp. Can increase fire and alter strategies
Inversions
Cold air on valley floor and warm air on top of it. Fire burns lower intensity on cool floor but if it reaches warm air intensity grows rapidly
Wind
Drys fuels
Direction and speed affect spread rates, direction, and shape of fire
Affects amount and distance of spotting
Increase o2 to fire
Cumulonimbus cloud
Passing over fire causes extreme wind shifts
Rain
Affects moisture
Downdrafts
Bring more o2 to fire and winds. Causes flare ups and changes direction of fire spread
Fuel moisture content
Determines burn potential cause it affects ignitability. Lower moisture = more ignitable
Curing
Drying of grasslands or crops when they die. Fire has minimal spread when material is less than 50%
States of fuel
Live/green and dead
Live/green fuels
Always have some moisture,
Dead fuels
Primary drive of all wildfires. Fine dead fuels soak up rain, moisture from air and dry out quicker. Medium and large fuels take more rain to increase moisture
Fine fuels
Cured grass, leaves, things smaller than 0.6cm Ignite easily, respond quick to wind and humidity
Medium fuels
1-7 cm, dry slower than fine, more energy to ignite but burn longer, needed to hear heavy fuels
Heavy fuels
Large woody materials greater than 7cm, hard to ignite and burn slow, longer to change moisture
Fuel load
Dry weight of combustible materials per unit area