050 parts for every million (or fifty parts for every billion). Units that generate greater than this can not be offered or shipped to California. CARB certification is really a quick way to ascertain if an air ionizer produces lower amounts of ozone. A different very similar useful resource is 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/