A Cleanroom (or clean room) is a room that has HEPA filtration to remove particles from the
air. Cleanrooms are used for manufacturing where high levels of cleanliness and sterility are
required. Common applications are medical devices, pharmaceutical and semiconductor
manufacturing.

ISO 1 is a super clean cleanroom classification. A cleanroom must have less than 3,520
particles >0.5 micron per cubic meter and 250-300 HEPA filtered air changes per hour.
The equivalent FED standard is class 100 or 100 particles per cubic foot. Common applications
are semiconductor manufacturing and pharmaceutical filling rooms.

ISO 2 is a very clean cleanroom classification. A cleanroom must have less than 35,200
particles >0.5 micron per cubic meter and 180 HEPA filtered air changes per hour.
The equivalent FED standard is class 1000 or 1000 particles per cubic foot

ISO 3 is a common clean cleanroom classification. A cleanroom must have less than 352,000
particles >0.5 micron per cubic meter and 60HEPA filtered air changes per hour.
The equivalent FED standard is class 10.000 or 10,000 particles per cubic foot.
Common applications are pharmacy USP800 compounding rooms, electronics manufacturing
and medical device manufacturing.

ISO 4 A cleanroom must have less than 35, 200,000 particles >0.5 micron
per cubic meter and 20 HEPA filtered air changes per hour.
By comparison a typical office space would be 5-10 times more dirty.
The equivalent FED standard is class 100,000 or 100,000 particles per cubic foot.