How-to guide · Equipment Qualification

IQ vs OQ vs PQ, explained with examples

Team ValidLeaf · September 2026 · 7 min read

IQ, OQ, PQ — three of the most cited and most confused terms in equipment qualification. Teams argue about where one ends and the next begins, test the same attribute three times, and still get asked by an auditor: "but did you prove it works?" This guide draws clean lines between the three, with examples from real manufacturing floors.

The 30-second version

• IQ (Installation Qualification) — was the equipment built and installed correctly, per specification?
• OQ (Operational Qualification) — does it operate correctly across its full operating range, including worst cases?
• PQ (Performance Qualification) — does it consistently produce acceptable product under real production conditions?

IQ — was it installed right?

IQ verifies the equipment as delivered and installed matches what was specified and purchased. Typical checks: model and serial numbers against the purchase order, materials of construction (mill certs for product-contact 316L stainless, for example), utility connections per drawings, and calibration of critical instruments before use.

Example: a new V-blender for supplement powder blending. IQ confirms the delivered blender matches the approved specification, the contact surfaces are the specified grade of stainless with certs on file, it's wired to the correct voltage per the electrical drawing, and the load cells were calibrated before first use. Nothing has run yet — that's the point.

OQ — does it work across its range?

OQ challenges the equipment at the edges of its operating parameters — the worst cases it will ever see. Speeds, temperatures, pressures, times: tested at minimum, nominal, and maximum, with acceptance criteria written before testing starts.

Example: a filling line for cannabis-infused beverages. OQ tests fill-volume accuracy at the slowest and fastest line speeds, at the coldest and warmest product temperatures in the specified range. If it holds accuracy at the edges, the middle takes care of itself. A common OQ for food plants: temperature distribution studies in a retort at minimum and maximum load.

PQ — does it consistently make good product?

PQ runs the equipment under normal production conditions — real materials, approved procedures, trained operators — and demonstrates consistent acceptable output, typically across consecutive batches or lots.

Example: three consecutive lots of gummy production on a depositing line, each meeting weight and content-uniformity specs, run by the regular shift crew following the approved batch record. PQ is where the equipment, the people, and the procedure prove they work together.

How the three connect

Each phase's output is the next phase's input: IQ establishes the qualified installation that OQ challenges; OQ establishes the proven operating range that PQ runs within. That's why the sequence matters — PQ performed on an installation that was never qualified proves nothing about the equipment, only about those particular batches. Traceability from requirement to IQ to OQ to PQ is what an auditor follows, line by line.

The mistakes that waste the most time

• Testing the same attribute in all three phases. If fill accuracy was proven in OQ across the range, PQ should confirm consistency — not repeat the range study.
• Running PQ before OQ deviations are closed. A failed OQ test that gets "explained away" poisons everything downstream.
• One batch called PQ. A single successful run is a demonstration, not qualification. Consecutive batches exist to prove consistency.
• Confusing calibration with OQ. Calibration proves an instrument reads correctly; OQ proves the equipment operates correctly. Both needed, not interchangeable.
• No acceptance criteria before testing. Criteria written after the results are just descriptions of what happened.

Where to start

List your GMP-critical equipment. For each, confirm a user requirement exists, check whether IQ/OQ/PQ documentation is complete and current, and flag anything modified since qualification — that's your requalification list. Our equipment qualification practice builds the full package: protocols, execution, and the traceability that ties it together.