The Federal Standard 209E "Airborne Particulate Cleanliness Classes in Cleanrooms and Cleanzones" graded cleanrooms as "Class 1/10/100/1000/10000/100000".

FED-STD-209E was discontinued in 2001 and superseded by the ISO standard. However, this standard is retained on many standard comparison tables to maintain consistency between older and newer facilities.

Air Changes by Cleanroom Classification

This table details the recommended air changes per hour for ISO 14644-1:2015 cleanrooms and their associated GMP Grade and Federal Standard.
Cleanroom StandardCleanroom Classification Guidelines
ISO 14644-1 Class 3 Class 4 Class 5 Class 6 Class 7 Class 8
Federal Standard 209E 1 10 100 1,000 10,000 100,000
EU GMP - - A/B - C D
Air changes / hour 360-540 300-540 240-480 150-240 60-90 5-48

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