Buyer guide
Writing a cleanroom URS: contents and testable wording
A user requirement specification (URS) states what the room must do in testable terms before anyone designs it. EU GMP Annex 15 (2015) calls the URS a point of reference throughout the validation life cycle, and the design is checked against it at design qualification.
By ZY Cleanroom · Updated · Sources at the end of the page
What the URS is
Annex 15 defines the URS as the owner, user and engineering requirements needed for a feasible design that meets the intended purpose. It allows a URS, a functional specification, or both (para 3.2). The URS says what the room must do. The design says how.
Keep requirements apart from solutions. The line "use FFUs" is a solution. The line "ISO 7 in operation" is a requirement. Give the designer room to choose, and give yourself a test to judge the result.
Contents table
Use one section per row. Number every requirement so it can be traced.
| Section | State | Check at handover |
|---|---|---|
| Purpose and process | Product, process steps, what the room protects | Process walk-through |
| Room list | Names, areas, heights, adjacencies, people and material flows | Drawing review |
| Cleanliness | ISO class per room and occupancy state: as-built, at rest or operational | ISO 14644-1 classification, ISO 14644-3 tests |
| Air and pressure | Pressure differences between named rooms, air speed or recovery targets, filter grade | Pressure and airflow tests |
| Temperature and humidity | Setpoints, tolerances, sensor positions, dew point if low humidity | Mapping |
| Envelope | Panel fire report, finishes, cleaning agents, doors, windows, floor, ceiling loads | Report review, leak test |
| Services | Power, gases, drains, and who supplies each | Site inspection |
| Monitoring and alarms | Parameters, limits, logging, alarm delays | Alarm test |
| Documents | Drawings, manuals, test reports, training | Document check |
| Qualification | Tests, who performs them, acceptance criteria, independent validation | FAT and SAT records |
Write lines you can test
Weak wording hides risk. Rewrite each line with a value, a position, a state and a test. Square brackets mark values the owner fills in.
State tolerances. HTM 03-01 uses design airflow +10% and −0% as its usual commissioning tolerance (para 11.29).
State outcomes, not air changes alone. ISO 14644-1 sets no air change rate. FDA's 2004 guidance gives 20 per hour only as a typical floor for ISO 8 rooms.
| Weak | Testable |
|---|---|
| The room shall be clean. | Room 2.04 shall meet ISO 7 in operation, classified to ISO 14644-1. |
| Positive pressure. | At least [value] Pa above the corridor, doors closed, read at the monitoring point. |
| Good temperature control. | [value] ± [value] °C at [position], at [occupancy state]. |
| Fire-safe walls. | Fire classification report for the finished panel at the installed thickness. |
| A tight room. | Leakage test method, test pressure and limit stated. |
| Alarms fitted. | Alarm below [value] Pa after a [value] s delay, logged. |
Trace every line
Number each requirement. Link it to a design item and to a test. Re-issue the URS with a revision number and date when anything changes. Annex 15 says the essential elements of quality need to be built in at the URS stage (para 3.2).
Check the design against it
Annex 15 expects the URS requirements to be verified at design qualification (para 3.3). Equipment can be checked at the vendor before delivery, as factory acceptance testing (paras 3.4 and 3.5). HTM 03-01 expects independent validation on the client's behalf (para 11.16). Name these steps and the sign-off roles in the URS.
Review the URS with the designer before tender. Ask them to mark every line they cannot test, and rewrite those lines.
Who approves the room
The regulator approves the owner's facility, not the contractor. The URS is the owner's document. The contractor comments on it, then builds to it. To have a room list reviewed, send it to ZY Cleanroom, a cleanroom design-and-build contractor with its own panel factory in Tianjin, China.
Questions
Common questions
Who writes the URS?
The owner, with process, quality and engineering input. Annex 15 describes it as owner, user and engineering requirements.
What is the difference between a URS and a functional specification?
Annex 15 allows either or both (para 3.2). Usually the URS states needs and the functional specification states how the system meets them.
Should a URS state air changes?
State the outcome first: class, recovery, pressure. ISO 14644-1 sets no air change rate, so add one only if your process needs it.
Does every cleanroom need a URS?
Annex 15 applies to EU GMP manufacturers. Other owners gain the same discipline: a written, testable basis for design and handover.
Related guides
- How to audit a cleanroom panel factory, on site or by video
- Building a cleanroom inside an existing building
- Cleanroom cost per m²: published ranges by ISO class
- How long does it take to build a cleanroom?
- Turnkey cleanroom contractor
- Room list builder
Sources
- EudraLex Volume 4, Annex 15: Qualification and Validation (Brussels, 30 March 2015, in operation from 1 October 2015; checked 31 October 2026)
- NHS England, Health Technical Memorandum 03-01, Specialised ventilation for healthcare premises, Part A (published 22 June 2021; checked 31 October 2026)
- ISO 14644-1:2015, Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration (published 9 December 2015; checked 31 October 2026)
- ISO 14644-3:2019, Cleanrooms and associated controlled environments, Part 3: Test methods (published August 2019; 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]
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