I just purchased and used this model for the first time today too!
I had it on the lowest setting (40%) and within 2-3 minutes, big-time ozone smell that made head light and chest tight THIS CAN'T BE GOOD! I didn't see any leaks in the hose and since I'm not the only one with this problem, I think you get what you pay for.
Just how bad is this for the lungs? How much does one have to breathe before it gets bad?