Thermal mapping—the scientific process of documenting the temperature and humidity distribution within a three-dimensional space—is not a “one-and-done” task. It is a recurring requirement that spans the entire lifecycle of a facility or equipment. In the Philippines, the timing of these studies is further complicated by the country’s distinct seasonal shifts.
Here are the essential milestones and triggers that dictate when your company must initiate a thermal mapping study.
1. The Commissioning Phase: New Facilities and Equipment
The most critical time to conduct thermal mapping is before a single product enters a new storage area. This is part of the Qualification Lifecycle (IQ, OQ, PQ).
- Installation Qualification (IQ): Mapping confirms the unit is installed correctly with adequate airflow.
- Operational Qualification (OQ): Performed on an empty room or unit. This determines the baseline performance of the HVAC or refrigeration system without the thermal mass of products.
- Performance Qualification (PQ): Performed on a fully loaded room. This is arguably the most vital test, as it identifies how air circulates around actual stock—revealing “dead zones” where air becomes stagnant and warm.
Rule of Thumb: Per WHO Supplement 8, you should never store Time- and Temperature-Sensitive Pharmaceutical Products (TTSPPs) in a new area until the mapping report is finalized and approved.
2. Seasonal Extremes: The Tropical “Worst-Case” Scenarios
In temperate countries, mapping is done in summer and winter. In the Philippines, companies must adapt to the “Wet” and “Dry” extremes.
The Hot Dry Season (March – May)
During the Philippine “Summer,” the external heat load on a warehouse is at its peak.
- Why Map Now? This is the ultimate test of your refrigeration system’s capacity. Mapping during this period ensures that even when the outside air is at its hottest, the internal “Hot Spots” remain within the acceptable range (e.g., 2°C to 8°C).
The Monsoon / High Humidity Season (July – October)
While temperatures may be slightly lower, humidity levels are extreme.
- Why Map Now? High humidity creates a “Latent Heat” load. Mapping during the rainy season identifies if your dehumidification systems are adequate and if condensation is forming on walls or products, which can lead to mold and packaging degradation.
3. Following Significant “Change Control” Events
Any change to the physical or mechanical environment of a storage area requires a re-mapping to ensure the “validated state” hasn’t been compromised.
- HVAC / Refrigeration Repairs: Replacing a compressor, changing a fan motor, or upgrading the control system can alter airflow patterns.
- Structural Modifications: Adding a new door, partition, or changing the insulation in a warehouse wall creates new thermal risks.
- Racking Layout Changes: If you install new high-density racking or move existing shelves, you are fundamentally changing the “Obstruction Map” of the room. This can create new “Hot Spots” that were not present in previous studies.
4. Periodically: The “Pulse Check” for Stability
Even if nothing changes, mechanical systems naturally “drift” over time.
- The 2-3 Year Standard: For established facilities, WHO Annex 9 advises a re-mapping every 2 to 3 years. This accounts for the gradual wear and tear of insulation and the declining efficiency of older cooling units.
- Risk-Based Frequency: Companies handling ultra-sensitive biologics or high-risk vaccines often choose an annual mapping cycle to minimize the risk of a catastrophic excursion.
5. After a Major Power Failure or Equipment Malfunction
In the Philippines, brownouts and power surges are common. If a facility experiences a prolonged power outage, a “Recovery Mapping” or “Power Failure Test” is often required.
- The Goal: To scientifically document the “Holdover Time”—exactly how many minutes or hours your room stays within the safety range once the power is cut. This data is essential for your disaster recovery plan.
Summary: Thermal Mapping Trigger Checklist
| Trigger Event | Type of Mapping Required | Recommended Duration |
| New Warehouse / Cold Room | Empty (OQ) and Loaded (PQ) | 7–10 Consecutive Days |
| New Fridge / Freezer / Incubator | Empty and Loaded | 24–72 Hours |
| Seasonal Peaks (Summer/Rainy) | Standard Operational Load | 7 Days |
| Post-HVAC Repair | Targeted Performance Test | 3–5 Days |
| Relocation of Equipment | Re-qualification (OQ/PQ) | 24–72 Hours |
| Periodic Validation | Standard Operational Load | 3–7 Days |
Conclusion: Data-Driven Compliance
Conducting thermal mapping at the right time is the difference between an audit-ready business and one that is exposed to massive liability. By aligning your mapping schedule with new installations, seasonal extremes, and significant repairs, you create a “Thermal History” that proves your commitment to product safety.
In the 2026 Philippine market, where FDA scrutiny is increasing, your mapping report is your strongest evidence that you are in control of your environment, no matter how hot it gets outside.
