My airway is sensitive to most chemicals, especially ozone and smoke. I live in a very humid area so in the summer when the heat, humidity and ozone are all higher my airway becomes enflamed and closes. I have another medical condition which prevents me from using steroids to open the airway. I was required to leave my home and family during the summer to be able to breath. My son found the Airpura UV700 and it has changed my life. With this air purifier I don't notice anything. Last summer it got up to AIQ of over 170 outside and I was just fine. It does mean that I have to stay inside for the worst of the summer but I can breath and function with a clear head. This winter we had several wild fires in our area. I had no problems. The last time we had smoke I was in the hospital for a week. I have a UV700 on each floor of the house along with a dehumidifier. I have tried other expensive air purifiers but non that removed the ozone or smoke