ISO 14644
ISO 14644 is the international standard family for cleanrooms and controlled environments. Its core part, ISO 14644-1, classifies air cleanliness by counting airborne particles per cubic metre, assigning an ISO Class from 1 (cleanest) to 9 for pharmaceutical, semiconductor and healthcare facilities.
ISO 14644
ISO 14644 is the international standard family for cleanrooms and controlled environments. Its core part, ISO 14644-1, classifies air cleanliness by counting airborne particles per cubic metre, assigning an ISO Class from 1 (cleanest) to 9 for pharmaceutical, semiconductor and healthcare facilities.
ISO 14644 is the international family of standards for cleanrooms and associated controlled environments, published by the International Organization for Standardization (ISO). It defines how the cleanliness of air is classified, measured and maintained wherever airborne particle contamination must be controlled.
The standard matters because contamination directly affects product quality, patient safety and process yield. A shared classification lets a cleanroom in one country be specified, validated and audited to the same criteria anywhere else, which is essential for regulated supply chains.
This article covers:
- how ISO 14644-1 classifies air cleanliness and the formula behind it
- the ISO Classes 1 to 9 and their particle limits
- the parts that make up the ISO 14644 family
- how a cleanroom is classified step by step
- where the standard is applied and how it relates to GMP
How ISO 14644-1 classifies air cleanliness
ISO 14644-1 assigns an ISO Class based on the maximum concentration of airborne particles allowed per cubic metre. The limit for each class comes from the formula Cₙ = 10ⁿ × (0.1 / D)²·⁰⁸, where Cₙ is the concentration of particles equal to or larger than size D (in µm) and N is the ISO Class number.
| ISO Class | Max particles ≥0.5 µm per m³ | Former FS 209E |
|---|---|---|
| ISO 5 | 3.520 | 100 |
| ISO 6 | 35.200 | 1.000 |
| ISO 7 | 352.000 | 10.000 |
| ISO 8 | 3.520.000 | 100.000 |
The table shows common classes used in industry; ISO Class 5 is typical for aseptic filling, while ISO Class 7 and 8 suit support and packaging areas.
The parts of the ISO 14644 standard
ISO 14644 is a multi-part family. Each part governs a different aspect of cleanroom life, from classification to design and operation.
- Part 1 – Classification of air cleanliness by particle concentration.
- Part 2 – Monitoring to provide evidence of cleanroom performance.
- Part 3 – Test methods.
- Part 4 – Design, construction and start-up.
- Part 5 – Operations.
- Part 7 – Separative devices (isolators, gloveboxes, mini-environments).
- Parts 8 & 9 – Air chemical contamination and surface particle cleanliness.
How a cleanroom is classified step by step
Classifying a cleanroom under ISO 14644-1 follows a defined sequence.
- Define the target ISO Class for the process and its occupancy state (as-built, at-rest or operational).
- Calculate the minimum number of sampling points from the room area.
- Count airborne particles at each point with a calibrated particle counter.
- Compare the results against the class limits and document conformity.
The occupancy state must always be stated, because particle counts rise sharply once people and equipment are active.
Where ISO 14644 is applied
ISO 14644 underpins contamination control in pharmaceutical manufacturing, sterile compounding, microelectronics and semiconductors, medical devices, aerospace, optics and analytical laboratories. It gives regulators, auditors and suppliers a common language for specifying, qualifying and auditing controlled environments worldwide.
ISO Class 5 allows no more than 3,520 particles ≥0.5 µm per cubic metre — the benchmark for aseptic pharmaceutical processing.
Frequently asked questions
What is ISO 14644?
ISO 14644 is the international standard for cleanrooms and associated controlled environments. It defines how airborne particle cleanliness is classified, tested and monitored, using ISO Classes 1 to 9. It is the global reference for pharmaceutical, semiconductor, medical device and biotechnology contamination control.
What are the ISO 14644 cleanroom classes?
ISO 14644-1 defines nine classes, from ISO Class 1 (the cleanest) to ISO Class 9. Each class sets the maximum number of airborne particles allowed per cubic metre at given particle sizes. Lower class numbers mean fewer particles and stricter contamination control for critical processes.
What is the difference between ISO 14644 and GMP grades?
ISO 14644-1 classifies air by particle count alone, while EU GMP grades A to D add microbiological limits and operational context for sterile manufacturing. They overlap: GMP Grade A and B at rest correspond roughly to ISO Class 5, but GMP adds requirements ISO 14644 does not cover.
How often should a cleanroom be reclassified?
ISO 14644-2 requires a risk-based monitoring plan rather than fixed intervals. In practice, GMP environments reclassify Grade A and B (about ISO Class 5) at least every six months, and lower grades every twelve months, plus after any significant change to the facility or equipment.
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