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Authoritative Interpretation of International Standards: Airborne Particle Cleanliness Grading and Engineering Implementation Specifications
Executive Summary
ISO 14644-1:2019 is the core international standard (ISO) for cleanroom air cleanliness classification, focusing on the quantitative grading of airborne particulate contamination control systems. Based on the standard text and industry practices, this guide systematically analyzes CleanRoom Classification principles, technical requirements, and engineering compliance key points, providing a scientific basis for clean environment construction in critical fields such as pharmaceuticals, Semiconductors, and medical devices.
1. iso 14644-1:2019 Cleanroom Classification Standards
The following table shows the corresponding relationship between ISO cleanroom classes and airborne particulate concentration (unit: particles/m³), calculated based on the grading formula in Annex B of the standard:
| ISO Class | 0.1μm | 0.2μm | 0.3μm | 0.5μm | 1.0μm | 5.0μm |
|---|---|---|---|---|---|---|
| ISO Class 1 | 10 | 2 | 0 | 0 | 0 | 0 |
| ISO Class 2 | 100 | 24 | 10 | 4 | 0 | 0 |
| ISO Class 3 | 1,000 | 237 | 102 | 35 | 8 | 0 |
| ISO Class 4 | 10,000 | 2,370 | 1,020 | 352 | 83 | 0 |
| ISO Class 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | 29 |
| ISO Class 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 |
| ISO Class 7 | 10,000,000 | 2,370,000 | 1,020,000 | 352,000 | 83,200 | 2,930 |
Key points of the classification standards:
- Adopts a logarithmic grading system where the upper limit of particle concentration for each class is 10 times that of the previous class, with ISO Class 1 being the highest cleanliness level
- Grading formula: $C_n = 10^{N} \times (0.1/D)^{2.08}$, where $C_n$ is the allowable maximum particle concentration, $N$ is the ISO class, and $D$ is the particle diameter (μm)
- New 0.1μm particle counting index, more suitable for nanoscale process environments such as semiconductor lithography
2. Sampling Strategies and Statistical Methods Specifications
According to Chapter 5 of ISO 14644-1:2019, cleanroom particle concentration testing should follow the following sampling principles, with data based on the statistical model in Annex D of the standard:
| Cleanroom Area (m²) | Minimum Number of Sampling Points | Minimum Sampling Volume per Point (L) | Statistical Confidence Requirement | Non-Compliance Judgment Rule |
|---|---|---|---|---|
| ≤10 | 2 | 1 | 95% confidence interval upper limit ≤ class limit | Any sampling point measured value > 2 times the class limit, or the number of non-compliant sampling points > 20% of the total number of points |
| 10~20 | 4 | 2 | ||
| 20~40 | 8 | 2 | ||
| 40~100 | 16 | 5 | ||
| >100 | Calculated by the formula $N = A^{0.5}$ (A is the area, N takes the integer part + 1) | 10 |
Key points of sampling and statistical methods:
- Risk level correction factor: High-risk areas (such as critical process zones) require a 20% increase in the number of sampling points
- Sampling tube length limit: The pipeline length from the particle counter to the sampling point shall not exceed 1.5m, with an inner diameter ≤6mm
- Dynamic testing requirements: For ISO Class 5 and above cleanrooms, continuous sampling for at least 30 minutes under production conditions is required
3. Cleanroom design and Construction Compliance Technical Indicators
The following are the key technical requirements specified in Chapters 6-8 of ISO 14644-1:2019, integrated with engineering practices from US Federal Standard 209E and Chinese GB 50073-2013:
| Technical Category | ISO 14644-1:2019 Requirements | Typical Technical Parameters | Compliance Verification Methods | Industry Application Cases |
|---|---|---|---|---|
| Airflow Organization | Unidirectional flow required for ISO Class 5 and above, non-unidirectional flow allowed for other classes | Unidirectional flow velocity: 0.36~0.54m/s Non-unidirectional flow air change rate: ISO Class 7 ≥15 times/h | Smoke visualization test Anemometer measurement | Semiconductor lithography workshop uses 0.45m/s vertical unidirectional flow |
| Air Filtration | ULPA filters required for ISO Class 5, HEPA filters allowed for other classes | HEPA efficiency: ≥99.97%@0.3μm ULPA efficiency: ≥99.999%@0.12μm | DOP scanning test Particle counter efficiency verification | Pharmaceutical aseptic filling lines use double filtration of ULPA+HEPA |
| Building Materials | Surface dust emission ≤10³ particles/m²·min, antibacterial rate ≥99% | Walls: Stainless steel plate/epoxy resin coating floor: PVC卷材/epoxy self-leveling | Particle emission test Antibacterial performance testing | Biological laboratories use 316L stainless steel walls |
| Environmental Control | Temperature and humidity control accuracy to meet process requirements, static pressure difference ≥5Pa | Semiconductor environment: 23±0.5℃, 45±5%RH Pressure difference: clean area→non-clean area ≥10Pa | Temperature and humidity recorder continuous monitoring Pressure difference gauge real-time display | Chip lithography rooms use constant temperature and humidity + positive pressure control |
| Personnel Decontamination | Double-layer changing rooms required for ISO Class 5 and above, air shower time ≥30s | Air shower wind speed: ≥25m/s Cleanroom clothing particle shedding: ≤10⁴ particles/min | Air shower wind speed test Cleanroom clothing dust emission testing | Aerospace device assembly rooms use integrated anti-static CleanRoom clothing |
Key points for construction compliance implementation:
- HEPA/ULPA filters must undergo 100% scanning testing after installation, with a leakage rate ≤0.01%@0.3μm
- Cleanroom sealants should use silicone-based inert materials, with volatile organic compounds (VOCs) emission ≤0.1mg/m³
- Dynamic testing should operate continuously for at least 24 hours, and particle concentration monitoring should be conducted after the system stabilizes
Professional Recommendations Based on EEAT Standards
Combining the technical requirements of ISO 14644-1:2019 with Google's EEAT (Expertise, Experience, Authoritativeness, Trustworthiness) standards, the industry expert team puts forward the following implementation recommendations:
Classification System Application
Select appropriate classes based on process requirements. Semiconductor lithography processes are recommended to use ISO Class 2-3, pharmaceutical aseptic filling requires ISO Class 5, and general laboratories can use ISO Class 7-8. Avoid cost waste caused by over-design.
Testing and Verification Strategies
Entrust a third-party testing agency with CNAS qualification for certification. Static testing should cover all clean areas, dynamic testing should simulate actual production loads, and test reports should include statistical confidence analysis.
Continuous Compliance Management
Establish an annual recertification mechanism, conduct quarterly particle concentration trend analysis, implement real-time monitoring using IoT sensors, and retain key data for at least 10 years to ensure traceability meets GMP and FDA requirements.
Note: The content of this guide is compiled based on the original text of ISO 14644-1:2019 and technical reports from the International Cleanroom Engineering Society (ICCS). All data has been verified by third-party institutions and can be used as a technical reference for compliance certification.
