If you are commissioning a cleanroom, an HVAC system or a compressed air supply in a GMP environment, there is no way around the four qualification stages DQ, IQ, OQ and PQ. The terms are familiar, but in practice the boundaries between them are often blurred. Tests end up in the wrong stage, acceptance criteria are missing or the link to the requirement cannot be traced. This article puts the stages in context and shows what evidence is expected at each one.
The basis: qualification as a traceable chain
Qualification is meant to demonstrate that a system is fit for its intended purpose, from design through to operation. The regulatory framework is the EU GMP Guide (EudraLex Volume 4), in particular Annex 15 on qualification and validation. Cleanrooms used in sterile manufacturing are also subject to Annex 1, and its principles are often applied to other cleanrooms as well. Measurement methods are described in the ISO 14644 series of standards. According to Annex 15, computerised systems are covered by Annex 11, with GAMP 5 as the supplementary industry guide.
Two decisions come before the four stages. The qualification master plan (QMP) determines which items are qualified and to what extent. The risk assessment, following the principles of ICH Q9(R1), shows which characteristics are critical for product and patient. The User Requirement Specification is derived from this. It defines what the system must do and provides the acceptance criteria against which qualification is measured. How the risk assessment determines the scope is explained in the article Risk assessment determines the scope of qualification. What matters in a URS is explained in the article What is a URS in a GMP environment?.
The four stages at a glance
| Stage | Key question | Typical evidence |
|---|---|---|
| DQ – Design qualification | Is the planned design suitable for meeting the requirements? | Review of FS/DS against the URS, drawings, data sheets, risk assessment, DQ report |
| IQ – Installation qualification | Has the system been installed as specified? | Comparison with drawings and parts lists, material certificates, calibration certificates, documentation check |
| OQ – Operational qualification | Does the system work across its specified operating range? | Functional tests, alarm and limit tests, test protocols with target and actual values |
| PQ – Performance qualification | Does the system perform reproducibly under operating conditions? | Measurement series in operation, monitoring data over a defined period, PQ report |
DQ – Design qualification
Objective: The DQ demonstrates and documents that the design complies with GMP and is suitable for its intended purpose. Annex 15 also requires the requirements of the URS to be verified in the DQ. Before implementation, a documented check is therefore made as to whether the supplier specification (German “Pflichtenheft”), meaning the functional and design specification, covers the requirements from the user requirements (German “Lastenheft”) and the URS. “Lastenheft” and “Pflichtenheft” are terms used in practice, not terms from the regulations. In practice, the DQ is a comparison whose outcome the user confirms in writing. For rooms, the room book takes on this role: it contains the quality-relevant room data and is checked point by point. This makes the DQ the cheapest place to find errors. A change on paper costs less than rework after installation. For conversions of existing areas, a DQ with as-built verification has proven useful: document review, a walk-through, simple functional checks and an approval checklist.
Typical test points: Has every GMP-critical URS requirement been implemented in the FS or DS? Are materials, surfaces and cleanability suitable? Do the airflow pattern, filter stages and pressure cascade of a cleanroom fit the room concept? Have measuring points been provided for later tests?
Evidence: A DQ report referring to each requirement checked, open items with owners and due dates, and approval by the personnel defined in the quality management system, usually including Quality Assurance.
IQ – Installation qualification
Objective: To demonstrate that the system has been installed completely and in accordance with the specification.
Typical test points: Components, models and serial numbers match the specification; pipework, ductwork and connections are checked; material certificates for product-contact parts; calibration status of the installed instrumentation; completeness of drawings, manuals and software versions. For a compressed air system, this includes items such as filters, dryers, pipe materials and the location of the points of use.
Evidence: IQ protocols with checklists, drawing revision status, certificates, calibration certificates.
OQ – Operational qualification
Objective: To demonstrate that the system works in all specified operating states, including at the limits of the operating range.
Typical test points: For an HVAC system, for example, air volumes and air changes, temperature and humidity control, filter integrity, alarm functions and behaviour after a power failure. A room can also have its own OQ, for example for airlock door interlocks and airlock and status indicators. The OQ is where the room and the HVAC system come together: differential pressures, airflow direction and airflow visualisation, particle classification at rest and recovery times can only be demonstrated in the finished room with the system running. Which protocol these tests appear in depends on where the qualification plan sets the interface between room and HVAC system. More on this in the article The room book as the basis for room qualification. For compressed air, tests include pressure maintenance and dew point.
Evidence: Test protocols with predefined acceptance criteria, documented target and actual values, the measuring equipment used with its calibration status, and the signatures of those performing the tests.
PQ – Performance qualification
Objective: To demonstrate that the system performs reproducibly under operating conditions.
Typical test points: For cleanrooms used in sterile manufacturing, Annex 1 provides for classification at rest and in (simulated) operation, and for microbiological qualification in both states. The measurements in operation are therefore still part of qualification and must be clearly separated from later routine monitoring. Further test points include the stability of differential pressures, temperature and humidity over a representative period; quality of the compressed air at the points of use in terms of particles, water and oil, and microbiology where applicable. Duration and scope are defined on a risk basis and justified in the plan.
For cleanrooms, qualification is structured by defined states: ISO 14644-1 distinguishes “as-built”, “at-rest” and “operational”, and Annex 1 requires classification “at rest” and “in operation”. The IQ and OQ tests are assigned to these states. In practice, the PQ of a room is often the demonstration of operational readiness: sampling plan, provisional alert and action limits, approved SOPs and trained staff.
Evidence: Evaluations of the measurement series, trend analyses, a PQ report with an assessment and a recommendation for routine monitoring.
Link with URS, risk assessment and traceability
The stages only form a coherent picture if they can be traced back to the requirements. The risk assessment evaluates which requirements and functions are GMP-critical and so determines what is tested and to what depth. Not every function needs a formal OQ test. Supplier tests such as FAT and SAT can be included where this is justified and it can be shown that transport and installation do not affect the functionality. Documents from suppliers or service providers are checked for suitability by the operating company before they are used. It has proven useful to define this in the qualification plan from the outset, with acceptance criteria at least as strict as for an in-house test and with approval by Quality Assurance. We always test site-specific functions, such as the connection to the building management system and other interfaces, on site.
The traceability matrix links every URS requirement to the specification and to the test step that verifies it. It shows auditors at a glance that no critical requirement has gone untested. More on this in the article Traceability matrix in a GMP environment.
Qualification plan, VMP and final report
The validation master plan (VMP) describes at a high level how a site or project organises qualification and validation: responsibilities, approach, scope and document structure.
The qualification plan puts this into concrete terms for one system. It defines which stages are carried out, which tests are planned, which acceptance criteria apply and who approves. It is important that the plan and test protocols are approved before execution. Criteria set after the fact are very hard to defend in an audit.
The final report summarises the results, assesses deviations and documents the release of the system for its intended use. Depending on the project, there are reports for each stage or a single summary report.
In larger projects, we work in practice with an overarching quality plan, sub-quality plans for each system and a RACI matrix for responsibilities. Construction or supplier acceptance does not replace GMP approval.
Handling deviations
Deviations are normal in qualification. What matters is how they are documented and dealt with:
- Record: Each deviation is documented with a unique number, a description and a reference to the test step.
- Assess: What impact does the deviation have on product quality and on the requirement concerned?
- Define actions: Correction, retest or justified acceptance.
- Close: The deviation is closed before the system is released, or carried as open in the final report with a justification.
For the move to the next stage, Annex 15 provides for a formal release by the responsible personnel. If certain acceptance criteria or deviations have not been fully addressed, conditional approval is possible where a documented assessment shows that there is no significant impact on the next activity. The rules for this belong in the qualification plan. Non-critical items then do not hold up project progress unnecessarily. In practice, we only carry open deviations into the next stage with an assessment, an action, a due date and the agreement of Quality Assurance.
A note on medical devices
For medical devices, other regulations apply: ISO 13485 for the quality management system, which the MDR refers to, and for the US market 21 CFR Part 820 (QMSR), which has incorporated ISO 13485 by reference since 2 February 2026. Risk management follows ISO 14971, cleanrooms are classified according to ISO 14644 classes such as ISO 7 or ISO 8, and the manufacturer’s SOPs govern the details. The terms IQ, OQ and PQ are used there too and applied as appropriate to the system. The EU GMP annexes are often applied by analogy.
Conclusion
DQ, IQ, OQ and PQ form a chain in which each stage builds on the previous one, and the chain is only as robust as its foundation: a testable URS, a traceable risk assessment and acceptance criteria defined in advance. If you set these elements up properly at an early stage, you get a testable qualification structure and documentation that holds up in an audit without rework.
For support with planning, execution and documentation, see Qualification.