How ISO Cleanroom Classification Works
The ISO 14644-1 standard defines nine distinct cleanliness classes, numbered ISO Class 1 (the cleanest) to ISO Class 9 (the least clean). Classification is determined by measuring the concentration of airborne particles equal to or larger than specific threshold sizes (ranging from 0.1 µm to 5.0 µm) within a cubic meter of air.
- Measurement: Particle concentrations are measured using Light Scattering Airborne Particle Counters (LSAPCs) at designated sampling locations within the cleanroom or clean zone.
- Occupancy States: Classification can be specified for different operational states:
As Built: Room complete, services running, but no equipment, materials, or personnel.
At Rest: Cleanroom equipment installed and operating per agreement, but no personnel present.
Operational: Room functioning as specified, with equipment operating and the required personnel present.
- Compliance: A cleanroom meets a specific ISO Class if the average particle concentration at each sampling location, for each specified particle size, is less than or equal to the maximum concentration defined for that class in the standard.
Understanding the ISO Cleanroom Classes
| ISO Class | Maximum Particles per Cubic Meter | |||||
| ≥0.1 µm | ≥0.2 µm | ≥0.3 µm | ≥0.5 µm | ≥1.0 µm | ≥5.0 µm | |
| ISO 1 | 10 | - | - | - | - | - |
| ISO 2 | 100 | 24 | 10 | - | - | - |
| ISO 3 | 1,000 | 237 | 102 | 35 | - | - |
| ISO 4 | 10,000 | 2,370 | 1,020 | 352 | 83 | - |
| ISO 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | - |
| ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 |
| ISO 7 | - | - | - | 352,000 | 83,200 | 2,930 |
| ISO 8 | - | - | - | 3,520,000 | 832,000 | 29,300 |
| ISO 9 | - | - | - | 35,200,000 | 8,320,000 | 293,000 |
ISO Cleanroom Class 1-3 (Ultra-Clean Environments)
These represent the most stringent levels of air cleanliness. Achieving and maintaining these classes requires extreme measures like extensive HEPA/ULPA filtration, unidirectional (laminar) airflow covering the entire work area, stringent gowning, and rigorous protocols. Applications include cutting-edge semiconductor manufacturing, advanced nanotechnology research, and certain critical biological procedures.
ISO Cleanroom Class 4-5 (Critical Clean Environments)
These are highly controlled environments forming the backbone of many critical industries. ISO Class 5 is arguably the most commonly referenced class. It's the standard for:
- Critical zones within pharmaceutical aseptic filling operations (the point where the product or container is exposed).
- Hospital operating rooms for major surgeries like joint replacements or organ transplants.
- Core areas in microelectronics and optics manufacturing.
- Biotechnology cleanrooms for cell culture and sterile product handling. Unidirectional airflow is often used within critical zones (like an RABS or isolator in pharma) to achieve Class 5.
ISO Cleanroom Class 6-7 (Controlled Environments)
These classes offer significant particle control suitable for less critical stages of sensitive processes or supporting areas adjacent to cleaner zones. Applications include:
- Non-critical filling areas in pharmaceuticals.
- Background environments around ISO 5 critical zones in cleanrooms.
- Preparation areas for sterile products.
- Medical device assembly.
- Some food processing cleanrooms. These often utilize non-unidirectional airflow with good filtration and air change rates.
ISO Cleanroom Class 8-9 (Basic Clean Environments)
These represent the least stringent ISO classes, providing basic particle control. They act as transition zones or buffer areas leading into cleaner rooms. Applications include:
- Gowning rooms and airlocks adjacent to cleaner cleanrooms.
- Component preparation areas.
- Warehousing for clean materials.
- Some packaging areas. These environments rely primarily on good ventilation and filtration to reduce general particulate levels.
Why ISO Cleanroom Classification Matters
The ISO 14644-1 standard provides a globally recognized and consistent benchmark for cleanroom air quality. This enables:
- Clear Communication: Cleanroom Manufacturers, suppliers, and regulators worldwide share a common understanding of cleanliness requirements.
- Reliable Design & Validation: Engineers can design facilities targeting specific ISO classes, and validation protocols based on the standard ensure the room performs as intended.
- Quality & Safety Assurance: Meeting the required ISO class for a process helps ensure product quality by preventing contamination in products such as semiconductor chips or pharmaceutical drugs, and also supports patient safety in environments like sterile surgical settings.
- Regulatory Compliance: Many industries, including pharmaceuticals, medical device manufacturing, and aerospace, reference ISO 14644-1 as part of their regulatory frameworks, such as those outlined in the European Union Good Manufacturing Practice (EU GMP) and guidelines issued by the U.S. Food and Drug Administration.