Classification of air cleanliness - ISO 14644-1 covers the classification of air cleanliness in cleanrooms and associated controlled environments. Classification in accordance with this standard is specified and accomplished exclusively in terms of concentration of airborne particulates. The document was submitted as an American National Standard and has been adopted as ANSI/IEST/ISO 14644-1:2015 in the United States, following the cancellation of FED-STD-209E. ASHRAE, the Uptime Institute, the Data Centre Alliance all recommend that Data Centre environments are tested and maintained to an ISO 14644-1:2015 level 8.