The line that is the border between two different fire effects on a material. One example is a line of demaraction on a wall with smoke staining above and none below. This line shows the height of the smoke layer in the room. Another example is the edge of a "V" pattern with soot deposits inside and undamaged wallboard outside. This "V" radiated upward and the line of demarcation can be traced back to the base of that fire plume. A third example is the line of demarcation between a clean burn area and the surrounding sooty wall. This line may show the limit of where flame was in contact with the non-combustible wall surface.