Initial Spread Index (ISI)

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The ISI is an indicator of the head fire indicator, rate of fire spread, and for difficulty of control in grasslands. It is a combination of the effects of the wind speed and FFMC.

For the interpretation of the map, please refer to the table below :-

Class-Difficulty of ControlInterpretation
LowFires will be self-extinguishing.
MediumFire can be easily suppressed with hand tools.
HighMost fire can be successfully controlled using power pumps and hose.
ExtremeSome fires will be difficult to control.

Low = 0 – 1 Moderate = 2 – 3 High = 4 – 5 Extreme >5


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