Buyer guide
Class 100, 1,000, 10,000 and 100,000 Cleanrooms Explained
Class 100, 1,000, 10,000 and 100,000 are cleanroom classes from the old US Federal Standard 209E. The number is the maximum count of particles 0.5 µm or larger in one cubic foot of air. The standard was cancelled in 2001 and replaced by ISO 14644-1, which counts per cubic metre: Class 100 is ISO 5, Class 1,000 is ISO 6, Class 10,000 is ISO 7 and Class 100,000 is ISO 8.
By ZY Cleanroom · Updated · Sources at the end of the page
The four names and their ISO equivalents
| Old FED-STD-209E name | ISO 14644-1 class | Max particles ≥0.5 µm per ft³ | Max particles ≥0.5 µm per m³ |
|---|---|---|---|
| Class 100 | ISO 5 | 100 | 3,520 |
| Class 1,000 | ISO 6 | 1,000 | 35,200 |
| Class 10,000 | ISO 7 | 10,000 | 352,000 |
| Class 100,000 | ISO 8 | 100,000 | 3,520,000 |
The conversion is simple: one cubic metre is about 35.3 cubic feet, so 100 particles per ft³ is about 3,530 per m³. ISO rounded it to 3,520. Each step is ten times the one before.
Chinese suppliers often still quote by the old class names. If a quotation says "class 10,000", read it as ISO 7, and ask for the occupancy state.
Full particle limits (ISO 14644-1:2015, Table 1)
The limits are cumulative: a count at 0.5 µm includes every particle 0.5 µm or larger.
| ISO class (old name) | ≥0.1 µm | ≥0.2 µm | ≥0.3 µm | ≥0.5 µm | ≥1 µm | ≥5 µm |
|---|---|---|---|---|---|---|
| ISO 5 (Class 100) | 100,000 | 23,700 | 10,200 | 3,520 | 832 | — |
| ISO 6 (Class 1,000) | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 |
| ISO 7 (Class 10,000) | — | — | — | 352,000 | 83,200 | 2,930 |
| ISO 8 (Class 100,000) | — | — | — | 3,520,000 | 832,000 | 29,300 |
Values are particles per cubic metre. A dash means the 2015 table sets no limit at that size for that class.
What each class is commonly used for
These are starting points from our industry pages, not requirements. Your process, customer and regulator set the class.
| Class | Common use |
|---|---|
| Class 100 / ISO 5 | Aseptic filling and other critical zones, often as a unidirectional-flow zone inside a cleaner background room |
| Class 1,000 / ISO 6 | Precision assembly, some electronics work |
| Class 10,000 / ISO 7 | Pharmaceutical support areas, medical device assembly, electronics assembly |
| Class 100,000 / ISO 8 | Packaging, gowning, food and cosmetics production |
For pharmaceutical work, start from the EU GMP grade, not the class. Grade C is ISO 7 at rest and ISO 8 in operation, so one GMP grade is not one old class. See GMP grades vs ISO classes.
Three things the class name does not tell you
- The occupancy state. ISO 14644-1 lets you set a class as-built, at rest or operational. "Class 10,000" at rest and in operation are different targets, and the second is harder to hold. Write the state next to each room.
- The air change rate. Neither 209E nor ISO 14644-1 sets one. Air volume comes from room size, people, process and the pressure plan. See air changes per hour by class.
- Microbial limits. ISO classes count particles only. GMP grades add microbial limits.
How to write the class in a specification
- Use the ISO name, and put the old name in brackets if your team still uses it: "ISO 7 (Class 10,000), at rest".
- Give the class for each room in the room list, with the occupancy state.
- State the test: particle count to ISO 14644-1 at handover, and who performs it.
Our room list builder has a class column for each room.
Questions
Common questions
What is a Class 10,000 cleanroom?
It is a room with no more than 10,000 particles of 0.5 µm or larger per cubic foot of air, under the old US Federal Standard 209E. The ISO 14644-1 equivalent is ISO 7: 352,000 particles of 0.5 µm or larger per cubic metre.
Is Class 100 the same as ISO 5?
Yes, for particles of 0.5 µm and larger: 100 per cubic foot is about 3,520 per cubic metre, the ISO 5 limit. ISO 5 also sets limits at other particle sizes.
Is FED-STD-209E still valid?
No. The US General Services Administration cancelled it in November 2001 and pointed users to ISO 14644-1 and 14644-2. The old names are still common in quotations and in China.
Is Class 100,000 the same as ISO 8?
Yes. Class 100,000 allows 100,000 particles of 0.5 µm or larger per cubic foot. ISO 8 allows 3,520,000 per cubic metre, the same limit in metric units.
Related guides
- Cleanroom pressure alarm: how to find the cause
- Medical device cleanrooms: writing ISO 13485 design inputs
- HEPA and ULPA filters: EN 1822, ISO 29463 and integrity testing
- Cleanroom temperature and humidity requirements
- Turnkey cleanroom contractor
- Room list builder
Sources
- ISO 14644-1:2015, Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration (ISO)
- FED-STD-209E Notice 1, cancellation notice, November 2001: superseded by ISO 14644-1 and 14644-2 (EverySpec index)
- EudraLex Volume 4, Annex 1: Manufacture of Sterile Medicinal Products (European Commission, 25 August 2022)
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