Fuels do not ignite readily from small firebrands although a more
intense heat source, such as lightning, may start fires in woods.
Fires in open cured grasslands may burn freely a few hours after
rain, but woods fires spread slowly by creeping or smoldering, and burn
in irregular fingers. There is little danger of spotting.

 

 

Fires can start from most accidental causes but, with the exception of
lightning fires in some areas, the number of starts is generally low.
Fires in open cured grasslands will burn briskly and spread rapidly on
windy days. Timber fires spread slowly to moderately fast. The
average fire is of moderate intensity, although heavy concentrations
of fuel, especially draped fuel, may burn hot. Short-distance spotting may
occur, but is not persistent. Fires are not likely to become serious and
control is relatively easy.

 

 

All fine dead fuels ignite readily and fires start easily from most causes.
Unattended brush and campfires are likely to escape. Fires spread
rapidly and short-distance spotting is common. High-intensity burning
may develop on slopes or in concentrations of fine fuels. Fires may
become serious and their control difficult unless they are attacked
successfully while small.

 

 

Fires start easily from all causes and, immediately after ignition, spread
rapidly and increase quickly in intensity. Spot fires are a constant
danger. Fires burning in light fuels may quickly develop high intensity
characteristics such as long-distance spotting and fire whirlwinds when
they burn into heavier fuels.

 

 

Fires start quickly, spread furiously, and burn intensely. All fires are
potentially serious. Development into high intensity burning will
usually be faster and occur from smaller fires than in the very high fire
danger class. Direct attack is rarely possible and may be dangerous
except immediately after ignition. Fires that develop headway in heavy
slash or in conifer stands may be unmanageable while the extreme
burning condition lasts. Under these conditions the only effective and
safe control action is on the flanks until the weather changes or the fuel
supply lessens.