I've been using ozone for at least 10 years. I have a medical ozone machine and an ozone air purifier. I love the ozone and feel it's been so good for me. However, I do feel that there is a need to be cautious when using ozone. In the past I used it without enough ventilation and I started to have some very serious effects on my lungs and heart. I had to stop the ozone completely for quite some time. Now when I use the medical ozone machine, I do it with a fan blowing in my face and a lot of ventilation. I also do not generally use the ozone air purifier when I'm home. Occasionally I do use it directly into my air uptakes so that it's circulated in my air conditioning (I live in a warm climate) when I'm home. If I start smelling it I turn it off. I personally don't believe that breathing ozone is great for the lungs. Now please don't attack me out there - as I said, I love the stuff. It's helped me tremendously and I use it almost every day. I just think we need to use it wisely.