What method is effective for cooling hot spots in a structure after fire extinguishment?

Hydraulic ventilation is an effective method for cooling hot spots in a structure after fire extinguishment due to its ability to remove hot air, smoke, and gases from the building. This technique involves using a controlled process where thermal layers within the structure are effectively displaced by creating airflow. The principle relies on the fact that hot air rises, and by opening windows or doors opposite the direction of the wind while using fans, fire fighters can create a flow of cooler air that pushes the hot air and smoke out of the upper openings.

In contrast, the other methods, while they may have their uses, do not effectively address the need for cooling hot spots after extinguishment. Displacing air with CO2 gases doesn't provide the necessary cooling effect, as it primarily displaces oxygen rather than mitigating heat. Thermal imaging cameras are excellent for locating hot spots but don’t actively cool them; they only identify areas that require further attention. Lastly, applying smooth bore nozzles focuses on delivering a specific stream of water but is less applicable in the context of cooling ambient temperatures in a structure post-extinguishment.