However, the radiation from a burning fuel package can just as easily produce distinct burn patterns, even if flashover has not occurred. A major cause of distinct burn patterns is the protection provided by irregularly shaped objects, such as broken pieces of sheetrock wall or ceiling that fall on the floor during a fire. Clothing on the floor will also cause irregular burn patterns with sharp, continuous, irregular lines of demarcation between burned and unburned areas. Downward burning . Everybody knows heat rises.
Fire investigators know that heat travels by conduction, convection, and radiation.
Downward burning occurs in every fire in which flashover occurs. It occurs in every black hole. It even occurs in some accidental fires that are not accelerated. The investigator should keep in mind that during the progress of a fire, burning debris often falls to lower levels and then burns upwards from there. In a fire that goes to flashover, radiation is the primary means by which fire spreads.