It works on 3 minutes to 90 minutes iirc and has variable output from 0-200mg (500mg/hr with the dryer - because it reduces the flow!) btw the driers really do work well and I would advise never using one of these types of ozonator without it.
Since i suffer from multiple chemical sensitivity I find I use the ozonator quite often - esp after friends/relatives visit because the amount of chemicals that they use.
At 200mg/hr I have no problem being in a room with it running - if it ever was to get too much Id just open the door! - Ive never had any irritation from this.
I ozonate water fairly often too.
I was lucky enough to get it from ebay for about £50 new.