IQ, OQ, PQ Explained: Equipment Qualification Made Simple

IQ, OQ and PQ are the three core stages of equipment qualification. Installation qualification (IQ) shows equipment is installed correctly, operational qualification (OQ) shows it works as specified across its operating ranges, and performance qualification (PQ) shows it performs consistently under real conditions of use.

They sit inside a wider sequence that starts with user requirements and design and ends with periodic review. Getting the sequence right matters because a process, method or batch is only as reliable as the equipment behind it, and qualification records are among the first documents an inspector requests.

The full qualification sequence

EU GMP Annex 15 describes qualification as a series of stages, which most companies follow whatever their market:

• User requirements specification (URS): what the equipment must do, written by the user before purchase, including GMP, safety and data requirements.
• Design qualification (DQ): documented review that the proposed design and supplier meet the URS.
• Factory acceptance test (FAT): testing at the supplier's site before shipment, useful for complex equipment.
• Site acceptance test (SAT): testing after delivery and installation at your site.
• IQ, OQ and PQ: formal qualification at your site under approved protocols.

Annex 15 allows FAT and SAT results to support IQ and OQ where they are documented and shown to remain valid after transport and installation. It also recognises that PQ may sometimes be performed together with OQ or process validation.

IQ, OQ and PQ defined

Installation qualification

IQ verifies that equipment, components and utilities are delivered and installed as specified. Typical checks include model and serial numbers against the purchase order, materials of construction, utility connections, drawings, software and firmware versions, calibration certificates for critical instruments, and manuals and spare parts lists.

Operational qualification

OQ tests that the equipment operates as intended across its specified operating ranges, including upper and lower limits. It covers functions, controls, alarms, interlocks, power failure recovery and, for computerised equipment, access control and audit trails.

Performance qualification

PQ shows that the equipment performs consistently with real or representative materials under routine conditions. For manufacturing equipment, PQ may overlap with process validation; for laboratory instruments, USP general chapter <1058> on analytical instrument qualification is widely used (check the current version, as it has been under revision).

What each stage looks like in practice

For autoclave PQ in more depth, see our guide to autoclave validation with biological indicators.

The V-model and a risk-based approach

The V-model links each specification on the left side to a verification stage on the right: the URS is verified by PQ, the functional specification by OQ, and the design specification by IQ. It makes traceability visible, so every requirement has a test and every test has a reason.

Not every requirement needs the same depth of testing. ICH Q9(R1) on quality risk management and ASTM E2500, a standard guide to a science- and risk-based approach to specification, design and verification, both support focusing effort on what affects product quality and patient safety. For computerised systems, GAMP 5 categories help scale the effort, as described in our guide to GAMP 5 software categories.

Documentation that stands up to inspection

Each stage needs an approved protocol before execution and a report afterwards. Good qualification documents share some features:

• Pre-defined, measurable acceptance criteria traceable to the URS.
• Raw data, printouts and calibration certificates for every test instrument used.
• Deviations recorded and resolved before the next stage, or justified if carried forward.
• Clear sign-off by the user, engineering and QA, with release for use only after approval.

Vendor-executed protocols are acceptable, but your site must review and approve them.

Requalification and change control

Qualification is not permanent. Annex 15 expects equipment to be evaluated at appropriate intervals to confirm it remains in a state of control. Many sites use a periodic review of calibration, maintenance, deviations and changes to decide whether requalification is needed, rather than repeating full protocols on a fixed calendar.

Any change that could affect the qualified state, such as relocation, major repair, software upgrade or a new load pattern, goes through change control. The impact assessment decides which tests to repeat. Our guide to calibration vs verification explains how routine checks support the qualified state between reviews.

Worked example: qualifying a new HPLC in a Dubai QC lab

A pharmaceutical QC laboratory in Dubai buys a new HPLC with a UV detector for assay and related substances testing. The instrument will run on the lab's networked chromatography data system (CDS).

1. URS: the lab defines flow range, gradient capability, detector wavelength range, injection volume range, column oven range and CDS requirements, including unique logins, audit trails and electronic signatures in line with 21 CFR Part 11 and EU GMP Annex 11.
2. DQ: two supplier proposals are compared against the URS, and the selected model's compatibility with the existing CDS is confirmed.
3. IQ: on delivery, modules, serial numbers and firmware are recorded, the bench, power supply and room temperature are checked, and the instrument is connected to the CDS with user roles configured.
4. OQ: the supplier's engineer runs OQ with calibrated tools under the lab's approved protocol. The column oven fails accuracy at its upper setpoint. A deviation is raised, the heating module is replaced, and the oven tests are repeated and pass.
5. CDS checks: QA verifies that audit trails capture changes, users cannot delete data, and backups restore correctly.
6. PQ: the lab runs its validated assay method over several days, meeting system suitability criteria for resolution, tailing, plate count and repeatability each time.
7. Release: the report is approved, the instrument is added to the calibration schedule and the equipment list, and any future firmware or CDS upgrade will go through change control.

Common mistakes

• Writing the URS after the equipment has been bought, so it simply describes what arrived.
• Accepting vendor protocols without site review or traceability to the URS.
• Testing only nominal settings in OQ instead of the ranges actually used.
• Starting routine use before the PQ report is approved.
• Forgetting the data system, audit trails and backups when qualifying instruments.
• Making changes without assessing their impact on the qualified state.

Key takeaway: IQ asks whether equipment is installed correctly, OQ whether it works as specified, and PQ whether it performs consistently in real use. Start from a clear URS, scale testing to risk, and protect the qualified state through change control.

Frequently Asked Questions

What is the difference between IQ, OQ and PQ?

IQ verifies that equipment is delivered and installed as specified, including utilities, documents and software versions. OQ tests that it operates correctly across its specified ranges, including alarms and controls. PQ shows that it performs consistently with real or representative materials under routine conditions. Each stage builds on the previous one.

What is a URS in qualification?

A user requirements specification describes what the equipment or system must do, written by the users before purchase. It covers functional, GMP, safety and data integrity needs. The URS is the foundation of qualification, because DQ checks the design against it and PQ ultimately confirms the requirements are met.

Can IQ and OQ be combined?

Often, yes, where justified. Combined IQ/OQ protocols are common for simpler equipment, and EU GMP Annex 15 recognises that PQ may sometimes be performed with OQ. Testing, acceptance criteria and approvals must stay clear, and the decision should be risk-based and documented. Check your site procedures and your regulator's expectations.

How often should equipment be requalified?

There is no single fixed interval. Annex 15 expects equipment to be evaluated at appropriate intervals to confirm it remains in a state of control. Many sites use periodic reviews of calibration, maintenance, deviations and changes to decide whether requalification is needed, with change control triggering targeted retesting after relocation, repair or upgrades.

Next steps

Our Data Integrity & Computerised System Validation course covers qualifying instruments and data systems together, and Good Documentation Practices & Data Integrity Essentials builds strong protocol and record habits. For related reading, see GAMP 5 software categories explained, calibration vs verification in laboratories and process validation stages explained. If you would like guidance, speak to a counsellor.