Cleanroom classes compared: ISO 14644, Fed Std 209E and EU GMP

Rough equivalence only. GMP grades also set microbial limits. Your quality team maps grades and classes for your site.

ISO 14644-1

The current international standard. It sets the class by the number of particles allowed in one cubic metre of air, from ISO 1 (cleanest) to ISO 9. Most new rooms are specified this way.

Federal Standard 209E

The older US standard. Classes were named by particles of 0.5 micron and larger per cubic foot, so Class 100 means about 100 per cubic foot. It was withdrawn in 2001 and replaced by ISO 14644-1, but the names are still common in drawings, specifications and conversation.

EU GMP Annex 1

Used for sterile pharmaceutical manufacture. It uses grades A to D, set for two states: at rest and in operation. It also sets limits for micro-organisms, which the other two do not.

How they line up

ISO 14644-1	Fed Std 209E	EU GMP	Typical use
ISO 5	Class 100	Grade A (and B at rest)	Aseptic filling, critical wafer steps
ISO 6	Class 1,000	No direct grade	Clean assembly, medical devices
ISO 7	Class 10,000	Grade B in operation, C at rest	Pharma support areas, electronics assembly
ISO 8	Class 100,000	Grade C in operation, D at rest	Gowning areas, general controlled spaces

What to remember

Lower numbers are cleaner in ISO. In Fed Std, a lower class number is also cleaner.
The match is approximate. The methods and test conditions differ, so treat the table as a guide.
Grades are not just particles. GMP also looks at microbes, gowning and process controls.
Supplies follow the class. Tighter rooms need low-shedding wipers, sealed-border garments and cleanroom gloves.

Limits, test methods and grades come from the standards and your regulator. Check the current edition and confirm with your quality team. This is not a compliance statement.