Buyer guide
What is a cleanroom? How it works and what to do next
A cleanroom is a room where airborne particles are counted against a class and held within it. It works through filtered air, pressure differences, smooth sealed surfaces and controlled entry for people and materials.
By ZY Cleanroom · Updated · Sources at the end of the page
The definition
ISO 14644-1:2015 defines a cleanroom as a room within which the number concentration of airborne particles is controlled and classified. It is designed, constructed and operated to control the introduction, generation and retention of particles. Notes to the definition add that temperature, humidity, pressure and other parameters might also be controlled as required.
What you buy
A project has four parts. The envelope is the walls, ceiling, floor and doors. The air system is the air-handling units, filters and fan-filter units. The entry route is the change rooms, air showers and pass boxes. Controls and monitoring complete it.
How it works
Annex 1 is a pharmaceutical rule. It is used here as a clear published example of each control.
| Control | What it does | Source |
|---|---|---|
| Filtered air | Supply air passes through filters. An intact HEPA filter retains at least 99.97% of particles larger than 0.3 µm | Annex 1, para 4.1; FDA, 2004 |
| Pressure | Cleaner rooms sit at higher pressure, so air flows out to lower grades. 10 Pa minimum is guidance | Annex 1, para 4.14 |
| Surfaces | Smooth, impervious and unbroken, so they shed and trap fewer particles | Annex 1, para 4.5 |
| Entry | People and materials enter through change rooms and airlocks | Annex 1, para 4.1 |
ISO classes
ISO 14644-1 has nine classes. It sets a maximum number of particles per m³ for each size, from 0.1 µm to 5 µm, counted with light-scattering particle counters. Lower class numbers are cleaner. FDA (2004) says at least 20 air changes per hour is typically acceptable for ISO 8 supporting rooms. It says significantly higher rates are normally needed for ISO 7 and ISO 5 areas.
| ISO class | Particles at 0.5 µm and larger, per m³ | Older US name |
|---|---|---|
| ISO 5 | 3,520 | Class 100 |
| ISO 6 | 35,200 | Class 1,000 |
| ISO 7 | 352,000 | Class 10,000 |
| ISO 8 | 3,520,000 | Class 100,000 |
Classification is a test
Annex 1 (para 4.26) treats classification as part of qualification. It means measuring total particle concentration against the specification. A room with filters is not a classified cleanroom until it has been tested. The class also depends on the state. In operation means the installation is complete and HVAC is fully operational. Equipment runs and the maximum number of people are present, working or simulating work (para 4.29).
Example: ISO 8 allows 3,520,000 particles per m³ at 0.5 µm. That is 3,520 per litre.
Who needs one
ISO 14644-1 names aerospace, microelectronics, pharmaceuticals, medical devices, food and healthcare. FDA explains the risk for sterile drugs: particles can enter a product and can carry microorganisms. The class you need follows product risk, set by your process, customer or regulator.
Your next steps
| Decision | Guide on this site |
|---|---|
| Set the class and state for each room | EU GMP grades A to D compared with ISO classes |
| Write requirements you can test | Writing a cleanroom URS |
| Choose the air system | Cleanroom HVAC design |
| Choose walls, floor and doors | Cleanroom panel selection |
| Plan tests and handover | Cleanroom validation and handover |
| Compare budgets and contractors | Cleanroom cost per m²; How to choose a cleanroom contractor |
Who approves the room
Your regulator or customer auditor judges the facility, not the contractor. The contractor builds to your room data sheet and supplies test data. To have a room list reviewed, send it to ZY Cleanroom, a cleanroom design-and-build contractor.
Questions
Common questions
What does ISO class mean?
ISO 14644-1 sets a maximum number of airborne particles per m³ for each size. ISO 5 allows 3,520 at 0.5 µm and larger. ISO 8 allows 3,520,000.
How is a cleanroom different from an ordinary room?
Its particle count is controlled and measured against a class, using filtered air, pressure control, smooth sealed surfaces and controlled entry.
Is an ISO class the same as an EU GMP grade?
Not exactly. FDA (2004) says ISO 5 approximately equals grade A. Annex 1 grades also set limits for the at-rest and in-operation states.
Who signs off a cleanroom?
Classification is part of qualification, which the owner arranges (Annex 1, paras 4.24 to 4.26). A regulator inspects the owner's facility, not the contractor.
Related guides
- How long does it take to build a cleanroom?
- What a cleanroom costs to run: energy, filters and testing
- Cleanroom cost per m²: published ranges by ISO class
- The Cleanroom Project Lifecycle
- Turnkey cleanroom contractor
- Room list builder
Sources
- ISO 14644-1:2015, Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration (redline comparison preview on iTeh Standards, introduction, scope and Table 1; published December 2015, the 2015 edition; checked 31 October 2026)
- ISO 14644-16:2019, Cleanrooms and associated controlled environments, Part 16: Energy efficiency in cleanrooms and separative devices (preview copy on iTeh Standards; clause 3.1.4 repeats the ISO 14644-1:2015 definition and notes; checked 31 October 2026)
- EudraLex Volume 4, Annex 1: Manufacture of Sterile Medicinal Products (published 25 August 2022, applied from 25 August 2023; checked 31 October 2026)
- FDA, Guidance for Industry: Sterile Drug Products Produced by Aseptic Processing, Current Good Manufacturing Practice (September 2004, nonbinding; checked 31 October 2026)
Project enquiry
Send what you have
A room list, a floor plan or only the floor area is enough to start. After you submit, send drawings by email or WhatsApp.
We reply by email within one working day. We can sign an NDA before you send drawings.
WhatsApp +44 7962 561184 is our UK number for export enquiries. The factory is in Tianjin, China.
Email: [email protected]
WhatsApp: +44 7962 561184