Flame Length

Flame length is another estimator of fire intensity. Flame length estimates have been made for many experimental fires, wildfires and prescribed burns. In the South, flame lengths may vary from less than 1 ft in slow moving backfires in leaves and short grass to over 100 ft in extreme wildfire conditions in dense shrubs and pines. Flame length is measured from ground level from the mid-point of the base of the flame to the tip of the flame, whether the flame is vertical or slanted.

Flame characteristics

In theory, flame length has been defined as the distance from the fuel surface to the point on the flame axis where the CO concentration is 5000 ppm. In wildland fires, it is difficult to determine these theoretical parameters and measurements are generally based on video or time-lapse photography. Flame length also provides an estimate of the difficulty in fighting fires. For instance, flame lengths less than four feet can be attacked at the head of the fire, while fires with flame lengths over eleven feet should not be controlled from the head and often lead to crowning and long range spotting.