Thermal fogging is used after fire and smoke cleanup when odor compounds have followed smoke into small openings, pores, and cavities. The fog is heated so its particle behavior mimics some smoke movement, helping deodorizing chemistry reach places ordinary spray applications cannot.
It is not a magic cover-up. Source removal still comes first: soot cleaning, debris removal, contents decisions, and sealing where needed. Fogging a dirty structure mostly masks odor temporarily. Used in sequence, it helps finish an odor job after the source is removed.
The decision to use thermal fogging depends on residue type, occupancy, ventilation, and whether other methods such as hydroxyl processing are safer or more appropriate for the setting.
Practically, fogging is a vacate-and-ventilate procedure: people, pets, and sensitive items leave the space, the fog is applied to follow the same paths the smoke took, and the structure is aired out before re-occupancy. That's also the tell for judging an odor plan — a company proposing to fog an occupied home the same afternoon, without any source cleaning first, is selling a masking treatment.
Expect fogging to appear near the end of a fire-restoration sequence, after soot removal, contents decisions, and any sealing of surfaces that can't be fully cleaned. When odor returns weeks after a fogging-only treatment, the source was never removed — which is the most common reason smoke-odor jobs get redone.