Pharmaceutical refrigerator mapping proves that a fridge maintains +2 °C to +8 °C uniformly and predictably under real use. It is typically performed during PQ, with elements also tested in OQ. This guide focuses on refrigerator‑specific mapping so you can meet GDP, GMP Annex 15, USP <1079>, WHO TRS 961, and DIN 13277 expectations without wasting resources.

Also see: CQV validation: Commissioning, qualification & validation guide for pharma facilities

What is pharmaceutical refrigerator mapping?

Pharmaceutical refrigerator mapping is a structured study that documents how temperature is distributed and controlled inside the unit. It identifies hot and cold spots, tests recovery after disturbances, and provides evidence for correct logger placement for ongoing monitoring.

Also read: Guidelines for temperature mapping

When is refrigerator mapping required?

You must perform mapping before first use and whenever risk factors change. GDP and GMP Annex 15 require documented evidence that the unit performs as intended. Common triggers include relocation, major service, configuration changes, or repeated excursions.

• Before use: Conduct initial mapping as part of PQ to establish baseline performance.
• After change: Remap after moves, repairs, firmware updates, or load profile changes.
• Risk‑based cadence: Use periodic mapping based on product criticality, historical stability, and environment.

Also read: Regulations for temperature compliance

How many sensors should be used and where should they be placed?

There is no universal number of sensors. Auditors expect a defensible, risk‑based plan that covers extremes and representative zones. In small under‑counter fridges, a 9‑point grid is common; larger cabinets may require 15–21 sensors or more.

• Cover extremes: Corners, top/bottom, front/back, and the geometric center.
• Door influence: Near the door and furthest airflow point to capture warm‑up risk.
• Airflow features: Near fan outlets/returns and areas shielded by shelves.
• Load representation: Adjacent to high‑mass products or fluid packs if used.
• Probe handling: Use calibrated probes; avoid wall contact; record placement with photos and grid maps.

Also read: GxP temperature mapping equipment and services

How do you define acceptance criteria for refrigerator mapping?

Acceptance criteria must reflect product risk and SOPs, covering uniformity, stability, recovery, and alarms. Standards such as USP <1079>, DIN 13277, and WHO TRS 961 provide benchmarks.

• Uniformity: Maximum temperature difference between hottest and coldest point.
• Stability: Maximum drift at the control point over time.
• Recovery: Maximum time to return in‑range after disturbance.
• Alarm behavior: Document thresholds, delays, and evidence of notifications.
• Data integrity: Confirm time sync, sample rate, raw data retention, and reporting.

Also read: Temperature monitoring systems

How often should you re-map a pharmaceutical refrigerator?

There is no fixed global frequency. Regulators expect a documented, risk‑based interval plus remapping after significant changes. Change control and periodic review help determine adequacy of evidence.

• Risk‑based frequency: Define by product criticality, historical excursions, ambient volatility, and maintenance history.
• Seasonal effects: Consider seasonal mapping if ambient variation is significant.
• Change triggers: Relocation, repair, controller updates, or repeated alarms.

Also read: Continuous temperature mapping solution - how does it work?

How do you implement continuous mapping for refrigerators?

Continuous mapping uses a subset of loggers from mapping studies as permanent monitors at risk zones. This provides ongoing evidence and may reduce or eliminate the need for periodic re‑mapping.

• Risk‑zone coverage: Keep loggers in hot/cold spots and door‑influenced areas.
• Integrated alarms: Use alarms at extremes; trend the rest for verification.
• Centralized records: Store raw data, certificates, and deviation handling in one system.

Learn more about the continuous mapping framework.

What should a refrigerator mapping report include?

Auditors expect traceable documentation from protocol to conclusion. A well‑structured report accelerates inspections and avoids findings.

• Approved protocol: Scope, responsibilities, acceptance criteria, references.
• Equipment traceability: Logger IDs, calibration certificates, sample rates, and placement.
• Execution record: Dates, ambient conditions, load, deviations, and corrective actions.
• Results and analysis: Uniformity, stability, recovery, and alarms with graphs.
• Conclusions: Fitness for use, storage limits, and re‑mapping triggers.

Operational examples: common pitfalls and fixes

These refrigerator‑specific issues often appear in audits and can be resolved with documented actions.

• Door heat plume: Warm air near the door causes alarms. Fix: Shorten door time, relocate products.
• Shelf shadowing: Dense packages create micro‑zones. Fix: Adjust shelving and airflow gaps.
• Auto‑defrost spikes: Defrost peaks exceed limits. Fix: Adjust alarm delays; document recovery.
• Firmware change: Updates shift control bands. Fix: Apply change control and re‑map.
• Certificate gaps: Missing calibration certificates. Fix: Use ISO 17025-accredited calibration.

Also read: Monitoring systems for GMP and GDP compliance