When you step into a Munich semiconductor chip factory, a biopharmaceutical sterile workshop, or a high-end medical device production line, you are not just entering a room, but a “man-made environment” where every microparticle in the air is precisely controlled. The cleanliness level of this environment is not a vague concept, but is strictly defined and graded by the international standard ISO 14644-1. From ISO 1 to ISO 9, each number corresponds to a stringent “air cleanliness test” standard.
How are ISO cleanliness levels classified?
The core logic of the ISO standard is very clear: what is the allowable number of particles of a specific size in a unit volume of air (usually 1 cubic meter)? The smaller the class number, the more stringent the cleanliness requirements.
This standard primarily focuses on two particle sizes:
1. Particles ≥ 0.1 micrometers (µm): This is a key indicator for measuring ultra-clean environments (such as ISO 1-3).
2. Particles ≥ 0.5 micrometers: This is a common benchmark for evaluating most industrial cleanrooms (ISO 4-9).
| ISO Class | Maximum Permissible Number of Particles ≥ 0.5µm per cubic meter of air | Maximum Permissible Number of Particles ≥ 0.1µm per cubic meter of air (if applicable) | Typical Application Scenarios |
| ISO 1 | Not Allowed to be Counted (Extremely Low) | 10 | Extreme Cleanliness: The world’s most advanced laboratories, such as lithography machine development and certain nanotechnology research. |
| ISO 2 | 4 | 100 | Advanced Manufacturing: Internal environment of extreme ultraviolet (EUV) lithography machines, etc. |
| ISO 3 | 35 | 1,000 | Ultra-High Standard: High-end semiconductor (nanoscale) chip manufacturing, aerospace gyroscope assembly. |
| ISO 4 | 352 | 10,000 | High-cleanliness production: General silicon wafer production, precision hydraulic/pneumatic system assembly. |
| ISO 5 | 3,520 | 100,000 | Aseptic drug filling, implantable medical device production, large-volume parenteral solution production, integrated circuit assembly. |
| ISO 6 | 35,200 | 1,000,000 | Strict cleanliness: Medical device assembly, aseptic filling of food and beverages, optical product manufacturing. |
| ISO 7 | 352,000 | Not a primary consideration. | Routine cleanliness: Operating rooms, isolation wards, automotive paint booths, pre-treatment areas of high-level laboratories. |
| ISO 8 | 3,520,000 | Not a primary consideration. | Basic cleanliness: Electronic product assembly areas, food packaging areas, non-core pharmaceutical production areas. |
| ISO 9 | 35,200,000 | Not a primary consideration. | General air-conditioned environments: Offices, warehouses, etc. |
How to achieve cleanroom standards and maintain “cleanliness”?
A room achieving and maintaining its ISO rating requires more than just frequent cleaning. It relies on a highly integrated cleanroom system, primarily including:
1. High-efficiency particulate air (HEPA) filtration system: This is the “heart” of the cleanroom. Driven by fans, air undergoes multi-stage filtration (pre-filter, medium-efficiency filter), and finally, terminal purification is performed by HEPA or ULPA filters installed in the ceiling or side walls, continuously removing constantly generated particulate matter. The higher the ISO rating, the higher the requirements for the efficiency (e.g., filtration efficiency for 0.12μm particles) and coverage area of the terminal filters.
2. Airflow organization design:
Unidirectional flow (laminar flow) : Air flows parallel in a single direction at a uniform cross-sectional velocity (e.g., 0.45±0.1 m/s), acting like an “air piston” to quickly push away contaminants. This is standard for high-level cleanrooms such as ISO 3-5.
Non-unidirectional flow (turbulent flow): Air is introduced from the top and returns from the side walls or floor, reducing the concentration of contaminants through dilution. Applicable to ISO Class 6-8 cleanrooms.
3.Differential Pressure Control: The cleanroom must maintain positive pressure relative to adjacent lower-cleanliness areas (e.g., a sterile room to a corridor) to ensure clean air escapes when the door is open, preventing contaminated air from flowing back in.
4. Strict Material and Personnel Control: Walls, floors, and ceilings must use smooth, dust-free materials. Personnel must undergo rigorous procedures such as changing clothes and air showers, wearing specialized cleanroom garments to completely cover the human body, the largest source of contamination.
The ISO 14644-1 standard provides a globally unified basis for dialogue. The choice of class depends entirely on the “vulnerability” of your product, process, or research—how small a speck of dust can cause product failure? Could a single microorganism cause an entire batch of pharmaceuticals to be scrapped? Trenntech believes that understanding ISO levels is the first step towards cutting-edge fields such as precision manufacturing and biomedicine. Trenntech is committed to providing high-standard HEPA/ULPA products for cleanrooms, building a top-tier cleanroom barrier together.