The problem with using your 'water ozonator' Vs. a Medical ozone machine is NOT the length of time that you are exposed to the ozone. Rather it is the potential risk of creating poisonous 'nitrous oxide compounds(monoxide/dioxide). Remember, a medical ozone generator uses PURE OXYGEN Vs "Air" that is passed though the plates that generate ozone. "AIR" contains a number of other elements (ozygen, nitrogen, hydrogen, etc etc)which when passed through the machine could become poisonous.
I too have an 'water' ozonator.. and despite the fact the the manufacturer states that it does NOT produce any 'noticable' nitrous compounds.. you still don't know. Whereas using a 'medical ozonator' (which uses a tank of Oxygen) will only produce ozone (ozonated Oxygen. Its just a 'risk' to use your machine for 'air ozonation'.