When ozone is formed in a generator and dispersed indoors, some of it reverts back into oxygen (O2). This step occurs by several processes including the following:
Oxidation reacts with an organic material such as odors or smoke. Reactions with bacteria etc., which again consume ozone by oxidation reactions.
Additionally, ozone breaks down thermally. Higher temperatures destroy ozone quicker than lower temperatures. The ozone that remains is referred to as Residual ozone. "Residual" ozone created will return to oxygen usually within 30 minutes, in amounts equal to half its level.
Therefore, ozone, while very powerful oxidation, doesn't last too long. It does its job and then disappears back into safe oxygen (O2).