050 parts per million (or 50 parts per billion). Equipment that generate in excess of this can't be marketed or shipped to California. CARB certification is often a quick way to ascertain if an air ionizer makes small amounts of ozone. An additional equivalent resource would be the listing of https://allhealthmarket.com/product/home-care-2/oxygen-and-hydrogen-generator/hydrogen-water-generator-300ml-450ml-hydrogen-inhalation-machine-99-99-oxygen-and-hydrogen-generator-ionizer-home-care/