What is ISO 14644?
If you’re involved in any Cleanroom project in the UK, Europe or America, the term “ISO 14644” will most likely appear constantly — on drawings, validation reports, supplier quotes, and regulatory submissions. But what exactly is it, and why does it matter?
In simple terms, ISO 14644 is the world’s most widely adopted family of Cleanroom standards. Published by the International Organisation for Standardization (ISO), it replaced the older US Federal Standard 209E in the early 2000s and is now the global benchmark for designing, testing, and operating Cleanrooms.
The ISO 14644 series comprise of 21 numbered parts. Together, the standards provide a comprehensive framework for the specification, design, construction, operation, testing, monitoring and ongoing management of cleanrooms and other controlled environments.
The standard is split into multiple parts, but the two you will refer to most often are:
- ISO 14644-1 – Classification of air cleanliness by particle concentration
- ISO 14644-2 – Monitoring to provide evidence of Cleanroom performance
ISO 14644-1: The Classification Standard (2015 version)
This is the part everyone means when they say, “we need an ISO 7 Cleanroom” (or insert relevant classification).
It defines nine classes of air cleanliness (ISO 1 through ISO 9) based on the maximum allowed number of airborne particles of various sizes per cubic metre. ISO 1 is the cleanest (typically used in extreme semiconductor and nanotechnology processes, though it is a rare classification to see), while ISO 9 is the ‘dirtiest’ of the classes.
| ISO Class | Typical real-world example* |
| ISO 1–5 | Leading-edge Semiconductor, EUV lithography |
| ISO 5-6 | Pharmaceutical aseptic filling, chip packaging |
| ISO 6–8 | Medical device, Optical Coating, Aerospace & Defence applications |
| ISO 8-9 | Secondary packaging and support rooms |
* It should be noted the above table is only typical and indicative. In many cases particular facilities fall outside of the above industry classifications depending on their particular product, process and user requirements.
ISO 14644-2: Ongoing Monitoring (2015)
This part shifted the focus from one-off certification to continuous performance evidence. Instead of re-testing the entire Cleanroom every year, you now create a risk-based monitoring plan that proves the Cleanroom stays in control between formal re-qualifications (typically every 6–24 months depending on the grade).
Other Relevant Parts of ISO 14644
- Part 3 – Test methods (how to measure airflow, recovery rate, etc.)
- Part 4 – Design, construction, and start-up
- Part 8 – Classification of air cleanliness by chemical concentration (AMC/VOCs)
- Part 14 – Assessment of suitability for use of equipment by airborne particle concentration
How ISO 14644 Relates to Pharmaceutical GMP Grades
Pharmaceutical Cleanrooms in the UK (MHRA) and EU (EMA) still use the older Grade A/B/C/D terminology from EU GMP Annex 1, but the particle limits for each grade are now directly linked to ISO 14644-1 (see our blog titled ATL Blog #6 – What is the difference between GMP and ISO 14644 for more information):
| GMP Grade | Equivalent ISO 14644-1 class (at rest) |
| Grade A | ISO 5 |
| Grade B | ISO 5 |
| Grade C | ISO 7 |
| Grade D | ISO 8 |
Why Understanding ISO 14644 Matters to You
- It is the language buyers and regulators speak – specifying “ISO 14644-1:2015 Class 7 at rest and in operation” removes ambiguity.
- It protects you from over- or under-specifying – choosing the correct class prevents both unnecessary expense and costly compliance failures.
- It is regularly updated – the 2015 version is still current in 2025, but a new revision cycle is underway, so working with an up-to-date Cleanroom partner is essential.
In short, ISO 14644 is not just another document; it is the global rulebook that keeps Cleanrooms consistent, comparable, and compliant across industries and borders.
Need help translating your process requirements into the correct ISO classification? Angstrom Technology can guide you – get in touch today.
Click this link for more information on ISO 14644 and other ISO standards: www.iso.org
