Overhaul, in firefighting, is the opening of walls, ceilings, and anywhere else the fire may have extended to that isn’t easily seen. When this fire extension isn’t extinguished, it will cause the fire to reignite and need to be put out again.
Overhaul is a dirty, dangerous, and time-consuming job. It’s done when the adrenaline from battling the blaze has worn off, and is one of the least desirable tasks during a fire. It’s also very necessary. Of course, this has to be balanced against leaving an undisturbed area for the fire to be investigated, among other concerns.
Some of the dangers of overhaul include: structural members, floor joists, ceilings, and walls that may be compromised; chimneys that may have lost support; and compromised stairways all mean a firefighter must remain vigilant. And as the main fire has been extinguished, they may become complacent. A few other problems can be debris(such as puddles of water and broken glass), a toxic atmosphere, and decreased visibility. Added to this is the fact the area is crowded with firefighters, who are likely already fatigued after fighting the fire, using hand and power tools which can lead to more problems.
The senses need to be relied on when performing overhaul, as well as understanding fire behavior. Observing the structure and how it’s built, knowing the way heat travels, and ductwork that could channel fire into other areas of a building all can help find areas where fire may be hidden.
Smoke coming from enclosed spaces is one good indicator of a hidden fire. As well as discoloration on studs, joists, and rafters. These spaces would need to be opened up and investigated for signs of fire. Thermal imaging can also help reveal some of these hidden fires. Listening for crackling or hissing sounds can also lead to more of these. However, with power tools running, hearing these sounds will be more difficult. Excess heat can also be detected by touching the back of your hand to walls, floors, or ceilings.
Some objects in a fire may require even more extensive overhaul, such as overstuffed chairs, sofas, and even mattresses. These should be removed from the structure and dismantled rather than allow a fire to be rekindled in them.