Living material in the fine fuel complex reduces the efficiency of ignition. Therefore, an adjustment to the ignition component is made based on the percentage of live fuel (herbaceous vegetation) in the fine fuel complex.
The moisture content of the dead component of the fine fuel (1-hr. timelag fuel moisture) is determined by the state of the weather (sunny or cloudy), air temperature, and relative humidity at the time of the 2 p.m. fire weather observation.
The condition of the herbaceous (live) vegetation and the 1-hr. timelag fuel moisture are then integrated in the calculation the fine fuel moisture (FFM) which expresses the effective moisture content of the fine fuels.
The closer the initial temperature of the fuel is to the ignition temperature, the more likely a fire will result when a firebrand in introduced into the fine fuel complex, since not a much energy is required to raise the fuel particle to its ignition temperature.