050 parts per million (or fifty parts for every billion). Equipment that develop a lot more than this cannot be sold or shipped to California. CARB certification is a quick way to find out if an air ionizer makes minimal amounts of ozone. Another identical resource could be the list https://allhealthmarket.com/product/home-care-2/portable-oxygen-and-hydrogen-concentrator/portable-oxygen-concentrator-hydrogen-inhalation-machine-h2-molecule-oxygen-and-hydrogen-generator-home-care-purifier-ionizer/