GDP-compliant reefer temperature mapping for pharmaceuticals

Pharmaceutical companies are increasingly reconsidering sea freight for cold chain logistics due to rising air freight costs, sustainability targets, and improved reefer container technology. If you want to use reefer containers without risking product or audits, this guide shows exactly how to plan and execute GDP-compliant reefer temperature mapping, plus where it differs from trucks and warehouses.

This guide covers:

• What is reefer temperature mapping?
• Why consider reefer containers for pharmaceutical cold chain?
• How to perform GDP-compliant reefer temperature mapping
• How should sensors be placed inside a reefer?
• Common issues in reefer temperature mapping and how to prevent them
• How is reefer mapping different from truck or warehouse mapping?

Also see: Temperature mapping and validation solutions for reefers

How to perform GDP-compliant reefer temperature mapping

Pharmaceutical reefer temperature mapping verifies that a refrigerated shipping container can maintain uniform and stable product temperatures throughout its interior during transit. The process confirms performance during normal operation and recovery after stress events. Results are documented in an audit-ready report to support IQ, OQ, and PQ qualification. For process basics, see the ultimate mapping guide.

The key steps of reefer temperature mapping

The sequence below condenses a standard GDP reefer mapping checklist. It is route-aware and avoids common rework. If you need the full, tactical version, use the dedicated reefer mapping checklist and our on-site or remote options on wireless data loggers.

• Scope and criteria: Define temperature ranges and acceptance limits based on product stability data and risk assessments. Link these to your URS and regulatory standards.
• Risk and route profile: Document ports, dwell times, shore power usage, and climate zones to guide stress scenarios and loading plans.
• Equipment and sampling: Use ISO 17025-accredited calibration for all loggers and set justified intervals of 1–5 minutes. See ISO 17025.
• Unit readiness: Confirm PTI results, seals, drains, fans, ventilation settings, and pre-cooling before installing sensors.
• Placement and documentation: Position sensors to capture length, width, and height gradients – plus door, supply-air, return-air, and airflow-shadow areas. Photograph and record each location; see data logger placement guide.
• OQ challenges: Maintain steady state for defrost cycle coverage, then simulate door openings and brief power losses with defined recovery targets.
• PQ in real conditions: Run a loaded study on a representative shipping lane, logging ambient and operational data. Repeat on seasonal or route changes with elevated risk to maintain reefer container qualification for GDP.
• Analysis and reporting: Quantify uniformity, drift, and any temperature excursions. Relate hot or cold spots to airflow or handling practices and document CAPA in an audit-ready report.

How should sensors be placed inside a reefer during mapping studies?

Incorrect sensor placement can hide hotspots and weaken audit evidence in cold chain validation for reefers. Strategic positioning is crucial due to moving air, door-end exposure, and multi-climate voyages. Cover the evaporator end, center, and door end at multiple heights and near walls – and add supply and return air points for unit performance insight.

For a full guide, see "Where to place data loggers during temperature mapping?".

Common issues in reefer temperature mapping and how to prevent them

Most deviations in sea freight reefer mapping trace back to preventable issues. Address them early to improve study outcomes.

• Door-end exposure: Door openings during port or customs create temperature spikes. Mitigation: Test door openings during OQ and use pallet patterns to protect door-end product in PQ.
• Airflow shadows: Product stacked against walls or ceilings disrupts circulation. Mitigation: Keep T-bar floor channels and wall clearances open.
• Inadequate sampling: Long voyages require high-resolution data. Mitigation: Use justified 1–5 minute intervals and confirm logger memory capacity.
• Missing ambient context: Without external and unit air data, root cause analysis is weak. Mitigation: Log ambient, supply, and return air alongside internal sensors.
• Weak documentation: Missing sensor IDs, placement photos, or approvals weaken audit evidence. Mitigation: Follow ultimate mapping guide and store documentation in your QMS.

How is reefer mapping different from truck or warehouse mapping?

While truck and warehouse mapping are well established, reefer containers bring added challenges: multi-week voyages, route variability, and limited in-transit intervention. Acceptance criteria and stress events must reflect these constraints. If your network uses multiple transport modes, align your reefer mapping with truck mapping and warehouse protocols for consistent evidence.

Why invest in GDP-compliant reefer validation in logistics?

GDP-ready reefer capacity is scarce. Cold chain validation for reefers lets you win higher-value pharmaceutical contracts and offer cost-effective shipping options. Shippers lower landed costs while maintaining compliance; container owners tap into high-margin pharma markets.

Glossary: 4 key terms of reefer mapping

• GDP: "Good Distribution Practice" are standards for maintaining medicine quality during transport.
• IQ OQ PQ: Installation, Operational, and Performance Qualification – validation stages.
• Reefer container: Refrigerated shipping container for temperature-sensitive goods.
• Temperature mapping: Validation process to confirm uniform conditions in a controlled space.

Also see: The Eupry Glossary: Key GxP terminology explained

Next steps

If you want to self-execute, use a mapping kit and wireless temperature data loggers. For a turnkey solution, have the Eupry team design your URS and complete IQ/OQ/PQ - see IQ OQ PQ.

Ready to start? Contact our Eupry team today, and we will help you find the best solution for you.

Also see: Temperature mapping and validation solutions for reefers