Cleanrooms are controlled environments that play a critical role in manufacturing and research settings where airborne particles can negatively impact product quality or safety. These environments are used in a variety of industries, including pharmaceuticals, biotechnology, microelectronics, aerospace, food processing, and healthcare.
Understanding cleanroom classifications is essential for designing, certifying, and operating facilities that meet industry-specific regulatory requirements. This article explains the ISO cleanroom classification system, outlines key differences between ISO classes, compares ISO with older standards like FED STD 209E, and offers guidance on selecting the right cleanroom class for your application.
What Is a Cleanroom Classification?
Cleanroom classifications define the maximum allowable number of airborne particles per cubic meter of air, based on particle size. The classification level determines how “clean” the air in the room must be. Lower ISO numbers indicate stricter cleanliness standards.
The ISO 14644-1 standard is the international benchmark for cleanroom classification. It specifies the limits for particles ≥0.1 μm, ≥0.2 μm, ≥0.3 μm, ≥0.5 μm, ≥1.0 μm, and ≥5.0 μm.
| ISO Class | ≥0.5 µm Particles/m³ | ≥1.0 µm Particles/m³ | ≥5.0 µm Particles/m³ |
|---|---|---|---|
| ISO 5 | 3,520 | 832 | 29 |
| ISO 6 | 35,200 | 8,320 | 293 |
| ISO 7 | 352,000 | 83,200 | 2,930 |
| ISO 8 | 3,520,000 | 832,000 | 29,300 |
Applications of ISO Cleanroom Classes
Each ISO class has specific applications depending on the sensitivity of processes and the level of contamination control required:
ISO 5 Cleanroom
Used in: aseptic pharmaceutical manufacturing, semiconductor wafer fabrication, and optical assembly
Key features: ULPA/HEPA filtration, laminar flow, gowning protocols
Example: Sterile fill-finish suites for injectable drug products
ISO 6 Cleanroom
Used in: biotechnology, medical device manufacturing, precision assembly
Key features: HEPA filtration, controlled humidity and temperature, moderate gowning
Example: Production of implantable devices or reagents
ISO 7 Cleanroom
- Used in: pharmaceutical packaging, microelectronics, automotive components
- Key features: HEPA-filtered air, modular panels, standard airlocks
- Example: Blister packaging for tablets
ISO 8 Cleanroom
Used in: food production, storage areas, incoming inspection
Key features: positive pressure, filtered ventilation, standard cleaning protocol
Example: Food-grade processing zones
ISO vs. FED STD 209E Cleanroom Standards
Before ISO 14644-1, the U.S. Federal Standard 209E was commonly used. Though it has been officially retired, it is still referenced in some industries.
| FED STD 209E Class | ISO Equivalent |
|---|---|
| Class 100 | ISO 5 |
| Class 1,000 | ISO 6 |
| Class 10,000 | ISO 7 |
| Class 100,000 | ISO 8 |
Air Changes Per Hour by ISO Class
The number of air changes per hour (ACH) indicates how frequently filtered air replaces the volume inside the cleanroom. Higher ISO classes require fewer air changes, while stricter classes (like ISO 5) demand rapid circulation:
| ISO Class | Recommended ACH Range | Typical Ceiling Coverage |
|---|---|---|
| ISO 5 | 240–480 | 100% ULPA/HEPA ceiling |
| ISO 6 | 90–180 | 60–100% |
| ISO 7 | 30–60 | 15–60% |
| ISO 8 | 10–25 | 5–15% |
How to Certify a Cleanroom
Cleanroom certification confirms that your environment meets the required ISO class. Certification involves:
Measuring particle counts using a calibrated airborne particle counter
Conducting tests for airflow velocity, uniformity, and air changes per hour
Checking differential pressure between cleanroom zones
Performing smoke studies for airflow visualization (particularly in ISO 5–6)
Documenting results in compliance with ISO 14644-2 monitoring protocols
Refer to FDA Aseptic Processing Guidelines for industry-specific cleanroom expectations.
How to Choose the Right ISO Class
Selecting the correct cleanroom class depends on:
Industry requirements (e.g. GMP, FDA, ISO 13485)
Product sensitivity (e.g. sterile injectables vs. circuit boards)
Manufacturing process (e.g. open filling vs. enclosed systems)
Audit readiness and regulatory inspections
Conclusion
Understanding cleanroom classifications is fundamental for maintaining product quality, ensuring regulatory compliance, and designing environments that meet industry standards. Whether you’re operating a pharmaceutical facility, an electronics manufacturing line, or a biotech lab, choosing the correct ISO class can directly impact the success and efficiency of your operation. For facilities aiming for ISO certification or needing to evaluate their current cleanroom setup, regular testing, proper filtration design, and adherence to global standards like ISO 14644-1 and GMP Annex 1 are critical steps.
Still unsure which classification your cleanroom should follow? Consult with a cleanroom engineering expert or request a particle count analysis to evaluate your current setup.
Cleanroom ISO Class Estimator (Interactive Tool)
Use the simple calculator below to estimate the ISO class of your cleanroom based on your measured particle count at ≥0.5 µm.
ISO Class Estimator
Frequently Asked Questions (FAQ)
Q1: What’s the difference between ISO and FED STD 209E classifications?
FED STD 209E was a U.S. standard that classified cleanrooms by particles per cubic foot. ISO 14644-1 replaced it and uses particles per cubic meter. While ISO is now globally accepted, some industries still reference the older standard.
Q2: Is ISO 5 always better than ISO 7 or 8?
Not necessarily. ISO 5 is stricter but also more costly to build and maintain. Your choice should be based on application need—not simply on achieving the “cleanest” classification.
Q3: How often should I re-certify my cleanroom?
Re-certification frequency depends on the industry. In pharmaceutical manufacturing, for example, cleanrooms are typically tested semi-annually or annually. Follow ISO 14644-2 and GMP requirements.
Q4: Can I upgrade an ISO 8 cleanroom to ISO 6?
Yes, but it requires significant infrastructure changes such as improved filtration, increased air changes, and potentially new layout designs to control contamination sources.
Q5: What certifications do cleanroom contractors need?
Contractors should be familiar with ISO 14644-1, GMP standards, and use calibrated equipment for testing. Look for providers with IEST or CETA credentials.
References
ISO. ISO 14644-1: Cleanrooms and associated controlled environments. Link
FDA. Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing. Link
CDC. Environmental Infection Control Guidelines. Link
NCBI. Particle Size Distribution and Cleanroom Monitoring. Link
IEST. ISO 14644 Cleanroom Standards Overview. Link
