Fire whirls are a typically rare but potentially catastrophic form of fire. They are observed during urban and forest fires, where fire 'tornadoes' are characterized by large-scale whirling flames which rise in 2 to 360 m diameter vortices from 10 to 1200 m high. These fire whirls accelerate combustion, produce significant suction pressures and lifting forces, and can carry burning debris, logs and even buildings thousands of meters from the main fire. Unfortunately, as building atria get larger, attempts to control ventilation during fires in atria may introduce vorticity, which can also generate "internal" fire whirls. This paper will examine historical observations of urban and forest fire whirls, fire whirl dynamics, the physical simulation of fire whirls in the laboratory, and consider numerical simulations of laboratory and building scale fire whirls.

[This publication is referenced in the "Synthesis of knowledge of extreme fire behavior: volume I for fire managers" (Werth et al 2011).]