What is a common indicator that a fire has smoldered in a structure?

A common indicator that a fire has smoldered in a structure is the presence of charred debris. When a fire smolders, it often produces limited visible flames and significant amounts of smoke, which can lead to the charring of materials. This charring can be found on surfaces or in the environment where the fire was located, indicating that the materials have been subjected to heat over a period of time, even if the fire has not been actively burning with flames.

The presence of charred debris signifies that combustion has taken place, albeit at a lower intensity than with an actively burning fire. This kind of evidence is crucial for firefighters and investigators to determine the nature and extent of the fire's impact on the structure, allowing them to assess potential hazards and plan for further action or investigation.

In contrast, other indicators such as a distinct smoke odor typically accompany a smoldering fire but are less definitive than charred debris, as odors can linger long after a fire has been extinguished. Increased structural integrity would not be aligned with smoldering fires; rather, they could compromise structural safety. Finally, visible flames usually indicate an active fire rather than a smoldering one.