Instrument and equipment qualification follows three sequential stages — Installation Qualification (IQ), Operational Qualification (OQ), and Performance Qualification (PQ) — but the real evidence an auditor traces isn't three separate documents. It's one unbroken chain: from the original User Requirement Specification (URS) and risk assessment, through executed test evidence at each stage, to final approval.
The three stages
- IQ (Installation Qualification) — verifies the equipment is installed correctly, per manufacturer specification and site requirements. Calibration status should be verified and current at IQ execution — a commonly missed step.
- OQ (Operational Qualification) — verifies the equipment operates correctly across its intended operating range. Acceptance criteria here should reflect your actual process requirements, not a wider range that's easier to pass but proves less.
- PQ (Performance Qualification) — verifies the equipment performs consistently under real, routine production conditions, using your actual materials and procedures, not idealized test conditions.
Why the chain-of-evidence framing matters more than the three-stage definition
Most content stops at defining IQ/OQ/PQ. The more sophisticated — and more auditable — framing is the evidence chain: the URS defines what the equipment needs to do; the risk assessment identifies what could go wrong; IQ, OQ, and PQ each produce executed test evidence against defined acceptance criteria; and final approval ties back to all of it. A break anywhere in that chain — OQ criteria that don't trace back to the URS, or PQ conditions that don't match real production — is a real, specific, and common inspection finding.
The re-qualification connection
Instrument qualification doesn't end at initial PQ approval. Every subsequent equipment or process change should trigger an explicit change-control assessment of whether re-qualification is required — the ongoing link between qualification and change control is where many systems lose the thread over time.
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