050 parts per million (or fifty parts for each billion). Units that make much more than this can not be bought or shipped to California. CARB certification is often a quick way to determine if an air ionizer produces low amounts of ozone. A different similar resource will be the https://allhealthmarket.com/product/home-care-2/hydrogen-generator/hydrogen-inhalation-machine-300ml-450ml-hydrogen-water-generator-h2-inhaler-therapy-hydrogen-gas-generator-water-purifier-ionizer-2/