ISO 14644 Cleanroom Classes Explained

What is ISO 14644?

ISO 14644-1 is the international standard that classifies the cleanliness of air in cleanrooms and controlled environments by the maximum allowed concentration of airborne particles. It replaced the older US Federal Standard 209E (Class 100, 1000, etc.).

The ISO classes

ISO 14644-1 defines classes from ISO 1 (cleanest) to ISO 9. In practice, most pharmaceutical, biotech and electronics work uses ISO Class 5 to ISO Class 8. ISO Class 5 allows a maximum of 3,520 particles ≥0.5µm per cubic metre — the level provided by a laminar flow hood or a Grade A zone.

How to choose your class

The required class depends on your process. Sterile compounding and aseptic filling typically need ISO 5 at the point of work; surrounding areas may be ISO 7 or 8. Our team helps you specify the right class for each zone. See our modular cleanrooms and laminar flow hoods.

Particle limits by class

ISO 14644-1 ranks cleanliness from ISO 1 (cleanest) to ISO 9. The higher the number, the more airborne particles are allowed. As a reference point, ISO Class 5 permits no more than 3,520 particles ≥0.5 µm per cubic metre; ISO 7 and ISO 8 allow progressively more and are typical for surrounding cleanroom space.

ISO class vs GMP grade

For pharmaceutical work, ISO classes map to EU/PIC’s GMP grades: Grade A ≈ ISO 5 (the critical zone, in operation), Grade B is ISO 5 at rest / ISO 7 in operation, Grade C ≈ ISO 7–8, and Grade D ≈ ISO 8. The critical compounding or filling point is always Grade A / ISO 5.

How cleanliness is achieved and verified

Target cleanliness is reached with HEPA or ULPA filtration, a controlled number of air changes per hour, and pressure cascades between rooms. Classification is verified by particle counting per ISO 14644-1. Our modular cleanrooms are built and qualified to these classes.

Frequently Asked Questions

Questions about your project?

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