Cleanrooms are classified according to airborne particle concentration, based on the ISO 14644-1 standard, ranging from ISO Class 1 (maximum cleanliness) to ISO Class 9, depending on process and product requirements.
Cleanroom Classification
How is ISO classification determined?
ISO classification is based on the number of airborne particles present in the cleanroom environment, measured using specialized particle counters during cleanroom certification.
Different particle sizes are analyzed, including: 0,1 µm; 0,3 µm; 0,5 µm; 1 µm; 5 µm
The results are compared against the maximum limits established by ISO 14644-1.
ISO 14644 cleanroom classification table
| ISO Class | ≥0.1 µm | ≥0.2 µm | ≥0.3 µm | ≥0.5 µm | ≥1 µm | ≥5 µm |
|---|---|---|---|---|---|---|
| ISO 1 | 10 | 2 | – | – | – | – |
| ISO 2 | 100 | 24 | 10 | 4 | – | – |
| ISO 3 | 1000 | 237 | 102 | 35 | 8 | – |
| ISO 4 | 10000 | 2370 | 1020 | 352 | 83 | – |
| ISO 5 | 100000 | 23700 | 10200 | 3520 | 832 | 29 |
| ISO 6 | – | – | – | 35200 | 8320 | 293 |
| ISO 7 | – | – | – | 352000 | 83200 | 2930 |
| ISO 8 | – | – | – | 3520000 | 832000 | 29300 |
| ISO 9 | – | – | – | 35200000 | 8320000 | 293000 |
Most commonly usedISO classes
Although ISO 14644 defines nine cleanroom classes, the most commonly used in industrial applications are:
- ISO 5 → critical processes (pharmaceutical manufacturing, aseptic filling)
- ISO 7 → controlled production areas
- ISO 8 → support and preparation areas
Applications by cleanliness level
- ISO 1–3 → microelectronics, nanotechnology
- ISO 4–5 → sterile processes, pharmaceutical industry
- ISO 6–7 → medical devices, biotechnology
- ISO 8–9 → controlled industrial production
Importance of ISO classification in cleanroom design
ISO classification directly defines:
- HVAC system requirements
- Air filtration systems
- Air changes per hour (ACH)
- Pressure control strategy
- Airflow type
For this reason, ISO classification is one of the first parameters established during the cleanroom design process.
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