The worst case scenario of a full surface crude oil tank fire occurs when burning material is violently ejected from the tank due to the vaporization water that has settled from the contents to the bottom of the tank. During the fire, heat accumulates with convection causing an increase in the temperature beneath the surface. The result is a hot, heavy oil fraction moving downwards to form a hot zone. When the heat reaches the bottom, the water rapidly vaporizes. Steam ejects from the tank over a wide distance, dragging burning liquids with it.