050 parts per million (or fifty parts for every billion). Equipment that produce in excess of this can not be bought or shipped to California. CARB certification is usually a quick way to ascertain if an air ionizer creates minimal amounts of ozone. Yet another similar source is the listing 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/