Where is a doughnut-shaped pattern typically found during a fire investigation?

A doughnut-shaped pattern in a fire investigation is typically found within irregularly shaped areas of burning, where damage surrounds less damaged material. This pattern often indicates the progression of the fire and the presence of fuel that was consumed in a circular manner.

When a fire burns, it may not spread evenly due to the availability of combustible materials, barriers, or changes in airflow. This can lead to a scenario where the most severely burned areas form a ring around less damaged or unburned materials, creating the characteristic doughnut shape. Not only does this help in understanding how the fire spread, but it also provides critical insights into the sequence of events and potential ignition sources during the investigation.

In contrast, the other options do not accurately describe the doughnut pattern. Areas where the fire has spread uniformly would not create a distinctive caloric gradient, thus failing to produce the doughnut shape. Furthermore, stating that such a pattern appears only at the center of the fire scene overlooks its potential occurrences across various locations, and patterns at the base of walls generally correspond to different fire dynamics, such as the effects of heat and smoke movement rather than a doughnut configuration.