Fire intensity is the energy released during various phases of combustion (flaming, glowing, smoldering) and it is useful to describe the propagation of a fire and predict fire effects. However,  sometimes fire intensity is used incorrectly to describe fire effects (Keeley, 2009): The same fire intensity can produce different fire severity, depending on the residence time and the ecosystem type. Direct measurements of fire intensity in the field are difficult and different metrics can be used depending on the purpose (Keeley 2009).