Also see: Temperature mapping: Tips, frameworks, and pitfalls

What is GDP temperature mapping, and when is it required?

GDP requires documented evidence that storage areas maintain labelled conditions under representative use. Temperature mapping is the study that profiles a space to locate hot and cold spots, characterize variability, and justify monitoring placement. EU GDP (2013/C 343/01) and WHO TRS 961 both require mapping before first use of a warehouse or controlled area, and risk-based requalification when conditions change.

In practice, this often means performing mapping urgently before a facility goes live or running harmonized requalification across multiple sites.

Inspector insight: Regulators expect mapping before use, under representative conditions, and RP sign-off on the protocol and results.

Also read: Good distribution practice (GDP): Guidelines for pharma logistics

How do you design a GDP-ready mapping protocol that passes inspection?

A strong protocol prevents rework and audit findings. It should define the intent of the study, the risk-based design, and how results become operational controls. GDP-compliant protocols are risk-based and clearly documented.

What to include in a defensible protocol:

• Objective and scope: Define the area, labelled range(s), and boundaries. State the study type: initial qualification, seasonal, or requalification.
• Roles and approvals: Name the author, executor, analyst, QA reviewer, and RP approver. Add signatures and dates.
• Risk assessment: Document layout, HVAC, doors, heat sources, historical alarms, and product risk. Link risks directly to sensor count and placement.
• Acceptance criteria: Define labelled ranges, justified excursions, or variability limits, with rationale.
• Measuring equipment: List logger models, calibration status, points, and certificate IDs. Confirm traceability to ISO 17025 standards.
• Sensor plan: Show how many loggers you will use, where, how they are mounted, and why those locations represent worst case.
• Test conditions and duration: Describe steady-state runs and challenge tests (door openings, controlled power interruption) when appropriate.
• Data integrity: State sampling rate, synchronization, time-stamping, audit trail, and secure archiving in line with Annex 11 and 21 CFR Part 11.
• Deviations and change control: Define how to handle missing loggers, clock drift, or setup errors, and how to assess impact.
• Analysis and reporting: Define statistics, charts, and how findings translate into permanent monitoring placement and alarm strategy.

Real-world example: A logistics forwarder in Germany used a 72-hour steady-state study plus a dock-door challenge. Results were tied to a monitoring placement matrix and signed by the RP. The facility passed a GDP inspection with no findings and was cleared for use by a pharma client.

Inspector insight: Inspectors often ask: Does your protocol justify sensor count, placement, and acceptance limits based on risk? Is RP approval documented?

Also read: 7 GDP requirements for pharmaceutical warehouses

How many loggers and what grid should you use in a warehouse?

Data logger density is not fixed. WHO TRS 961 suggests an Electronic Data Logging Monitor (EDLM) grid of 5–10 m spacing in small/medium facilities, but this should be adapted based on risk, geometry, and HVAC complexity. Some organizations standardize grids across multiple warehouses, while others focus on cost-effective minimum coverage.

Also read: Where to place data loggers during temperature mapping?

Risk-based placement guidance:

• Cover the extremes: Place loggers at suspected hot and cold spots, including diagonal corners, far-from-HVAC points, and near large doors or docks.
• Profile airflow influences: Place sensors around HVAC inlets/outlets and known heat sources.
• Respect vertical variation: Add sensors at different heights when stratification is possible.
• Balance sample size and cost: Use replicates in the largest or most variable zones to confirm repeatability.

Tip: Start with a draft grid from risk assessment, run a short pilot, then refine the grid for the full study.

Inspector insight: WHO and EMA expect logger placement to be justified by a written risk assessment, not just copied from a template.

Also see: Step-by-step guide: Temperature mapping for GDP pharmaceutical warehouses

What acceptance criteria should you set for GDP mapping?

Acceptance criteria anchor your pass/fail decision and future monitoring limits. They must reflect labelled ranges and product stability, not device tolerances. USP <1079> stresses the role of Mean Kinetic Temperature (MKT) in evaluating excursions.

Good practice when defining criteria:

• Align to labelled conditions: Keep the space within its intended range for the study duration.
• Use rational exceptions: If product stability supports brief excursions, define maximum temperature, duration, and frequency.
• Quantify variability: Define acceptable spread (for example, max ΔT across sensors) if product safety could be impacted.
• Translate to monitoring: Convert mapping acceptance into alarm thresholds and delays for permanent sensors.

Example: An ambient warehouse (15–25 °C) with high dock traffic allowed brief excursions up to 27 °C for ≤15 minutes, supported by stability data. Permanent alarms were set tighter than the labelled range, with short delays near the dock to prevent nuisance alarms.

Inspector insight: Inspectors look for acceptance criteria that are tied to labelled ranges and stability data, not arbitrary thresholds.

Also read: Continuous mapping for GDP compliance

How long should a mapping run, and what challenge tests should you include?

Duration must capture normal variability. WHO TRS 961 recommends at least 48 hours, with seasonal studies where ambient influence matters. Runs that are too short risk missing cycles; runs that are too long waste resources.

Designing duration and tests:

• Steady-state window: Capture weekday and weekend patterns where relevant. Many warehouses use 48–72 hours; complex HVAC may need longer.
• Door-opening study: Simulate realistic traffic to locate worst-case dock zones.
• Controlled power interruption: Use only where safe and pre-approved; valuable for resilience validation.
• Seasonal studies: Use winter/summer studies for ambient stores influenced by external conditions.

Operational tip: Enterprises with multiple sites should standardize scripts and evidence tables to reduce QA oversight and ensure harmonization.

Inspector insight: Authorities want justification for duration and conditions. Seasonal mapping is expected if ambient variation could impact quality.

Also read: Good distribution practice (GDP): Guidelines for pharma logistics

How often should you re-map under GDP, and what triggers requalification?

GDP does not prescribe a fixed interval. Inspectors expect risk-based requalification, defined in your QMS and signed off by the RP. ISPE and EMA highlight requalification after changes or when monitoring indicates risk. Some organizations define harmonized frequencies (e.g., every 2–3 years), while others trigger requalification mainly at go-live or after modifications.

Risk-based re-mapping triggers:

• Facility or layout changes: New racking, stock changes, or expanded zones.
• HVAC or controls changes: Repairs, upgrades, or altered control strategies.
• Operational shifts: Increased throughput, new shifts, or high door activity.
• Adverse trends: Alarm clusters, excursions, or rising variability in monitoring.
• Seasonal extremes: Winter/summer differences in ambient warehouses.

Example: After an AHU replacement, a facility re-mapped only the zones with past variability. The RP approved the limited scope because monitoring showed stability in other zones.

Inspector insight: Regulators expect a written requalification policy with risk-based triggers. No fixed calendar interval is mandated.

Also read: Continuous mapping for GDP compliance

How should mapping results drive permanent monitoring and alarms?

Mapping is only valuable if it informs ongoing monitoring. EMA guidance requires mapping results to justify probe placement and alarm setup. Use results to position sensors at worst-case locations and set alarm thresholds that reflect operational reality.

From mapping to monitoring:

• Place monitors at extremes: Convert hot/cold spots into permanent probe locations.
• Set risk-based alarm limits: Base thresholds on labelled ranges, with delays to reduce false alarms.
• Document ownership: Assign alarm acknowledgment, deviation investigation, and CAPA sign-off.
• Validate systems: Ensure Annex 11/21 CFR Part 11 controls (audit trails, access control, e-signatures).

Inspector insight: Inspectors want to see an explicit linkage between mapping results and monitoring placement. They often request the monitoring placement matrix during audits.

Also read: Guide: GDP monitoring requirements

What common pitfalls cause GDP observations – and how do you avoid them?

Most GDP inspection findings come from poor documentation or weak justification, not failed conditions. Common audit risks include scattered calibration records, unclear logger rationale, or lack of linkage to monitoring placement.

Frequent pitfalls and fixes:

• Unjustified sensor placement: Fix with a written risk assessment linking hazards to each logger.
• Missing calibration evidence: Fix with a certificate index linking device IDs to locations and dates.
• Data integrity gaps: Fix with synchronized clocks, audit trails, and secure exports.
• No link to monitoring: Fix with a monitoring placement matrix and updated alarm strategy.

Inspector insight: Common GDP findings include missing calibration certificates, incomplete risk assessments, and no documented link between mapping and monitoring.

Also read: 7 GDP requirements for pharmaceutical warehouses

References and further reading

• EU GDP guideline (2013/C 343/01): Mapping before use, risk-based requalification.
• WHO Technical Report Series 961, Annex 9: Temperature mapping guidance for storage and transport of medicines.
• USP <1079> series: Good storage and shipping practices; MKT for excursion evaluation.
• ISPE Good Practice Guide (CTC, 2nd ed.): Lifecycle, risk-based mapping and monitoring.
• EMA GDP Q&A and inspection reports: Current inspector interpretation and common deficiencies.
• MHRA GDP blog and inspection updates: Practical examples of observations and inspector expectations.