I am a Home Inspector and I do repairs as well. One of my services is Ozone treatment. It works. No doubt about it, but you need to have enough of it, for long enough for it to work. It requires the home owners to vacate usually at least 6 hours.

If the smell persists afterwards, it is being re-generated by something and there is active mold growth or something going on.

I bought a Condo that was smoked in for a couple of years. After closing, I went to the Condo, turned on my Ozone machine and left it running for a few days. Smell gone, never to return!

Ozone will degrade plastics, so there's a balance :).

No doubt it works. That said, it is a health hazard, so it needs to be used tactically. I'd be concerned that a condo with a shared wall would experience some spill over into an occupied spaced.

I guess it also would depend on your machine. I have some machines that produce fairly high levels of Ozone. After they run, it's not uncommon to smell it when walking up to a home.