I was not aware when I purchased one of these that it produced ozone which is harmful. I have to assume when used in a small area like a car for hours that it may produce undesirable health effects. Some of the effects I read about online and maybe someone could weigh in on whether this is misinformation: Certainly wasn't good for my dog whose radiographs revealed an alveolar pattern. Ozone can cause shortness of breath, lung inflammation, reduced lung function and difficulty breathing. I don't think the cautions of use are stated like they should be such as time limits to breathing the air or cautions about use in smaller spaces such as a car without ventilation. I assumed there were no downsides to using such gadgets and that we all needed to get one of these for our pets. I think the cautions should be given equal time. I DO believe this was harmful to my dog who indeed developed changes in his lung function, body temperature and ultimately died when he had normal parameters 12 hours before using this gadget, my word for a non medical device. Personally I would not purchase anything in the future that was not classified as a medical device. I did use a coupon from this site but feel these things should be fully researched before broadly recommending them without equal time to the cautions for use. I had no idea it had a harmful side.