Comparison of char depths should only be made on what basis?

Char depths are indicative of the exposure to heat and the duration of combustion. When assessing char depths, it is crucial to compare similar materials because different types of materials will produce varying depths of char under the same conditions. For instance, wood, plastics, and textiles all react differently to fire, resulting in distinct growth patterns of char formation.

By focusing on like materials, investigators ensure that comparisons are valid and meaningful. If the materials being compared have different thermal properties or burning characteristics, any differences in char depth could lead to misconceptions about the fire’s behavior, origin, or intensity. This practice aids in establishing a reliable basis for drawing conclusions about the fire, enhancing the overall accuracy of the investigation.

The other options touch on relevant factors in fire investigations, but they do not provide the same level of specificity as comparing like materials for char depth assessments.