050 parts for each million (or 50 parts per billion). Products that deliver greater than this can not be bought or shipped to California. CARB certification is usually a quick way to determine if an air ionizer provides very low amounts of ozone. A different comparable resource could be the 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/