Ozone treatment effectively eliminates organic and inorganic odors, including the smell of tobacco smoke. Ozone does not mask odors, but removes them by reacting with volatile molecules that carry odors causing them to decay.
Properly made ozone treatment permanently destroys (oxidizes) also the source of odors so removed once odor will not return.
If, however, has not been removed cause of formation of odor source it may come back after some time. For example, if moisture constantly accumulates in the room, then after some time fungi and molds, that cause smell of mustiness, will appear again (all the time they have an ideal environment to grow).