How are lines of demarcation created?

Lines of demarcation are created when flame, heat, and smoke impact an object, resulting in visible changes that indicate the extent of exposure to fire conditions. These lines typically show where materials have been affected by varying intensities of heat or combustion. A clear line will often differentiate between areas that have been burned or damaged by smoke and those that remain untouched, providing valuable information for fire investigators.

This understanding is crucial for assessing the fire's origin and cause, as well as for determining the path of the fire's spread. The observable effects on the structure or materials—such as charring, discoloration, or smoke staining—occur in direct relation to the intensity and duration of heat exposure, which ultimately forms these lines of demarcation.