FED-STD-209 E Airborne Particulate Cleanliness Classes in Cleanrooms and Cleanzones was a federal standard concerning classification of air cleanliness, intended for use in environments like clean rooms. The standard based its classifications on the measurement of airborne particles.
Cancellation
The standard was canceled on November 29, 2001 by the United States General Services Administration (GSA). The document was superseded by standards written for the International Organization for Standardization (ISO).
References
FED-STD-209E Wikipedia(Text) CC BY-SA