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How do Cleanrooms differ in their cleanliness?
1. What Defines a Cleanroom?
ISO 14644-1 standards define a cleanroom as a controlled space that manages air particle concentrations. It minimizes the introduction, generation, and retention of particles through special design and operation. It also controls parameters like temperature, humidity, and pressure as needed.
A key difference from ordinary spaces lies in the air change rate (ACR). Regular home air conditioners exchange air 0.5-2 times per hour, while cleanrooms, depending on their class and purpose, can achieve 10-600 air changes per hour. This rate serves as a crucial reference for cleanroom classification, influenced by factors such as room size, number of occupants, and equipment.
2. The ISO Cleanroom Classification System
2.1 Origins and Evolution
The ISO 14644-1 standards, introduced in 2001, replaced the earlier Federal Standard 209E.
2.2 Core Differences from Previous Standards
- Measurement Unit: ISO uses cubic meters, while Federal Standard 209E relies on cubic feet.
- Number of Classes: ISO includes 9 classes (ISO 1 to ISO 9), more than the fewer classes in the federal standard.
2.3 Classification Logic
Cleanrooms get categorized based on the maximum allowable number of particles of different sizes per cubic meter of air. ISO 1 represents the cleanest (fewest particles), and ISO 9 the least clean (most particles). Among them, ISO 7 and ISO 8 are the most commonly used classes.
3. Key Parameters of Major ISO Classes
ISO Class | Particle Limits (per m³) | Air Change Rate (per hour) | Other Features |
ISO 1 | ≥0.1μm ≤10; ≥0.2μm ≤2 | 500-750 | The cleanest, requiring ULPA filtration and 100% ceiling coverage |
ISO 7 | ≥0.5μm ≤352,000; ≥1μm ≤83,200; ≥5μm ≤2,930 | 30-60 | Does not count particles <0.5μm (high concentration makes detection difficult); uses HEPA filtration |
ISO 8 | – | 10-25 | Less clean than ISO 7 with a lower air change rate |
ISO 9 | – | – | Controls temperature, humidity, and pressure but not classified by particle count |
4. Key Factors Affecting Cleanliness
4.1 Particle Size
Different classes specify clear requirements for the size of particles to be filtered. For example, ISO 7 focuses on particles ≥0.5μm, ≥1μm, and ≥5μm. The smaller the particles, the stricter the limits for higher cleanliness classes.
4.2 Sources of Contamination
Contaminants mainly come from people (skin flakes, oils, cosmetics, clothing debris, etc.) and internal processes (equipment, materials, water, etc.). ISO 7 and cleaner classes require separate changing rooms to prevent external contamination from entering.
4.3 Air Circulation
Air change rate directly impacts cleanliness. Higher classes demand higher rates (e.g., ISO 7 has about twice the air change rate of ISO 8). Increased air circulation dilutes air to reduce particle concentration, requiring more filters and air conditioning equipment.
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5. Applications and Types of Cleanrooms
5.1 Industries of Application
Cleanrooms serve industries such as pharmaceuticals, medical devices, semiconductors, electronics, aerospace, food, beverages, e-liquids, CBD, and vitamins. The pharmaceutical industry, in particular, needs to control both non-viable (inanimate) and viable (living) contaminants, often using laser particle counters and petri dishes for monitoring.
5.2 Common Types
- Modular Cleanrooms: Feature prefabricated walls, offering quick installation, easy modification, and reasonable costs.
- Hardwall Cleanrooms: Built with traditional steel-framed gypsum boards, costing slightly less.
- Softwall Cleanrooms: Use transparent vinyl curtains, designed as small, movable spaces.
6. Conclusion
Cleanrooms differ significantly in cleanliness, primarily defined by the ISO 14644-1 classification system. Factors like particle limits, air change rates, contamination sources, and air circulation all play key roles. Understanding these differences helps industries choose the right cleanroom class to meet their specific needs, ensuring product quality and process integrity.
