1. Mild:
- slow spread
- low intensity
- small area burnt [but depends on duration]
- low level spread [not applicable to grass fires]
- usually only one ignition point
Often associated with:
- low temperatures
- high humidity [direction of wind may be important]
- low wind speed
- recent high rainfall
- level or undulating terrain
- vegetation type not fire prone
- moist fuel
- low fuel build-up
2. Moderate: like mild but with some mention in the references of a factor likely to make the fire greater than mild [e.g. dry fuel, or rapid spread, or high temperatures, or wind-assisted spread & etc.
3. Moderately severe: like mild but with some mention in references of several factors likely to make the fire greater than mild or moderate [e.g. high temperatures, and strong winds and build up of dry fuel]
4. Severe: like an extremely severe fire but with no mention in references of crown spreading or fire balls
5. Extremely Severe:
- rapid spread
- high intensity [fireballs]
- often extensive areas burnt
- high level spread [crowning] [not applicable to grass fires]
- often many ignition points
Often associated with:
- high temperatures
- low humidity [direction of the wind may be important]
- high wind speed
- drought
- steep slopes or mountainous terrain
- fire prone vegetation types
- dry fuel
- high fuel build up
The rate of fire spread is influenced by the temperature, humidity, windspeed, and terrain.
The intensity
of a fire [kW/m/sec] is influenced by the amount, kind and moisture in fuel.
