The construction seems good. The outer case is made of some kind of steel. I've opened it up to look inside. Of course I don't really know what I'm looking at. I know that the ozone flow from inside is using a silicon tube, which is consistent with a medical grade unit that has ozone resistent parts on the ozone path.
Yes, there is a fan at one end to cool it. What Pressman said is probably true. When I do insufflation, the air is just a tad warm, implying that some heat somewhere has to be involved.
As for making ozonated oil 24 hours a day, as long as you have a closet or room where you can close the door I wouldn't think it would be a problem. It's annoying when you're right next to it, but behind a door it's not very loud. We're not talking hurricane siren here. But it would definitley get on your nerves if you had to leave it on in the same room for long periods of time.