S-290 Unit 3, Fuels
Why is knowledge about fuel characteristics and topographic and weather factors useful
when working on a fire? - answer It allows us to effectively assess current and expected
fire behavior.
What are ground fuels? - answer All combustible materials lying beneath the surface:
• Deep duff
• Tree roots
• Rotten buried logs
• Other organic material
Because of their compactness, fire spread will be slowest-typically smoldering or
creeping.
Ground fuels have been known to hold fire through
winter snows.
What are surface fuels? - answerAll combustible materials lying on or immediately
above the
ground:
• Needles or leaves
• Duff
• Grass
• Small dead wood
• Downed logs
• Stumps
• Large limbs
• Shrubs to about six feet in height
• Litter
Surface fuels are less compact than ground fuels, favoring faster spread, but there are
other reasons, e.g., wind. In areas without a tree canopy, winds are free to fan surface
flames. Exposed areas also experience more heating and drying by the sun. As a result,
surface fires on grasslands or chaparral often spread faster than surface fires in forests.
Most wildfires start in and are carried by surface fuels, so understanding them is most
important to understanding how a given fire spreads.
What are aerial fuels? - answerAll green and dead materials located in the upper
canopy:
• Tree branches and crowns
• Snags
• Hanging moss
• Tall shrubs
Why is knowledge about fuel characteristics and topographic and weather factors useful
when working on a fire? - answer It allows us to effectively assess current and expected
fire behavior.
What are ground fuels? - answer All combustible materials lying beneath the surface:
• Deep duff
• Tree roots
• Rotten buried logs
• Other organic material
Because of their compactness, fire spread will be slowest-typically smoldering or
creeping.
Ground fuels have been known to hold fire through
winter snows.
What are surface fuels? - answerAll combustible materials lying on or immediately
above the
ground:
• Needles or leaves
• Duff
• Grass
• Small dead wood
• Downed logs
• Stumps
• Large limbs
• Shrubs to about six feet in height
• Litter
Surface fuels are less compact than ground fuels, favoring faster spread, but there are
other reasons, e.g., wind. In areas without a tree canopy, winds are free to fan surface
flames. Exposed areas also experience more heating and drying by the sun. As a result,
surface fires on grasslands or chaparral often spread faster than surface fires in forests.
Most wildfires start in and are carried by surface fuels, so understanding them is most
important to understanding how a given fire spreads.
What are aerial fuels? - answerAll green and dead materials located in the upper
canopy:
• Tree branches and crowns
• Snags
• Hanging moss
• Tall shrubs
