Difference and Connection between Cleanliness ISO 14644-1 and FED 209E

The international cleanroom standard ISO 14644-1:2015 (https://www.iso.org/standard/53394.html)  replaced the earlier U.S. FED 209E standard. Both documents define air cleanliness classes based on particle concentration, but ISO 14644-1 uses SI units (particles per cubic meter), while FED 209E used imperial units (particles per cubic foot). Although FED 209E was officially canceled in 2001, many engineers and factories still refer to it, especially in historical projects. The connection is that ISO 14644-1 was developed as the global successor, harmonizing the classification system worldwide.

For cleanroom design, construction, and cleanroom technology, understanding both standards helps engineers compare specifications across old and new , ensuring accurate cleanliness classification and compliance with modern requirements