I'll throw my 2 cents in as well. Especially if you are wanting it for ozone sauna, I think the Synergy would be fine, since ozone sauna doesn't require as much precision. Basically, because of the fact that heat breaks down ozone, you want as much ozone as you can get into the cabinet. Therefore, the lack of calibration on the Synergy shouldn't matter. Just crank the sucker up all the way for ozone sauna.