What does the term 'mop-up' refer to in firefighting?

Mop-up refers to the actions taken to extinguish residual heat and fire debris near the control lines and within the burned area after a wildfire has been suppressed. This process includes checking for hot spots, extinguishing any lingering embers, and ensuring that there is no potential for flare-ups that could escape the control lines. Felling snags (hazardous trees that could fall) may also be part of this effort to improve safety for firefighters and prevent new fire starts.

The term is distinct from constructing firelines or digging control lines, which are related to the initial containment efforts during an active fire. Additionally, while declaring a wildfire contained signifies that it is no longer spreading, mop-up actions are critical to ensure that the fire is fully out to prevent re-ignition and ensure safety in the area.