Febreze works to remove smoke odors by trapping the odor molecules that the human nose recognizes inside molecules of a chemical called cyclodextrin, blocking the olfactory receptors in the nose from coming into contact with the odor. This deactivates smoke odors or replaces them with a different scent.
Febreze comes in scented and unscented varieties, and the unscented options simply trap odor molecules without applying any additional fragrance. Scented Febreze also traps unwanted smells, while allowing the scent included with the cyclodextrin to reach odor receptors in a person's olfactory system. Febreze continues to bind the molecules that cause odors as it dries. Once dried, the cyclodextrin washes away along with the trapped offensive odors as users add water or rinse objects.
Beta-cyclodextrin, the active ingredient in Febreze, is naturally donut-shaped. This contributes to its ability to trap offensive odors and help keep olfactory receptors from sensing them. Febreze may also include unlisted ingredients that may further enhance odor elimination, according to About.com. Zinc chloride, which may be present but unlisted in some varieties of Febreze, is especially helpful at neutralizing sulfur-containing odors. The chemical can also help dull nasal receptors, but its inclusion in the Febreze formula remains speculative.