HEPA or OZONE? An Ozone Air Filter is really not a filter at all. And Ozone is just 1 of the 10 air purifier technologies available. Besides explaining the differences between them we'll also cover the limitations of each, and the dangers of Ozone, as well as why some people like ozone.
For a complete explanation of the 10 technologies, what they do, and which to choose for your particular need, I suggest watching the video below. It also covers the use of ozone...
It's the instability of that third "wheel" that makes it very effective against mold, mildew, smoke, and odors. Unfortunately the instability can also damage or irritate tissue in high amounts (see the video). Brand names heap ozone air filter machines include multi-level brands like Alpine, Ecoquest, and Vollara (all the same company and design) as well as a few Chinese air purifiers. These Ozone molecules go out into a room and kill odor, mold spores, smoke molecules, and other gases. They don't work inside the machine itself. The fan in an ozone machine works to send the highly ozonated air out into the far corners of the room.
The dangers of ozone hasn't removed it from the market, as ozone continues to have practical use in industries other than air purification. The US government has a lot to say about the dangers and safe levels of ozone as you can read here.
For myself, I have an old ozone generator in the closed which I use on occasion to "treat" a room (while I am not in it) from musty, or mildew smells or from extreme odor problems.