Temperature mapping tells you whether a storage area actually holds the conditions on its label. It sounds routine, and the study itself mostly is. The decisions around it are where programmes go wrong: where to put the sensors, how long to run, which season to map in, and what to do when the results are not what you hoped.
What mapping is for
A warehouse or cold room is not one temperature. It has hot spots near the roof and doors, cold spots near cooling units, and areas that change with the season, the stock level and how often doors open. Mapping finds those variations so that you can place routine monitoring sensors in the right places and decide where product can safely be stored.
WHO guidance on temperature mapping of storage areas is the most widely used reference, and EU GDP expects it before a storage area is used and again after significant changes.
Planning the study
- Sensor placement. A grid in three dimensions, with extra sensors near doors, walls, the ceiling, cooling and heating units, and anywhere product will be stored.
- Duration. Long enough to capture normal operation, including weekends and working days. Several days is the usual minimum.
- Season. For ambient warehouses, map in summer and winter, because the extremes are what matter.
- Load. Mapping an empty room tells you something, but conditions with racking full of stock are what product will experience.
- Calibrated loggers. Calibrated across the range you expect, with certificates on file.
Reading the results
Look for three things: whether any location went outside the limits, where the warmest and coldest points were, and how the space behaved during events such as a door left open or a power interruption. The hot and cold points become candidates for permanent monitoring sensors. Locations that went out of limits become places where product should not be stored, or problems to fix before the area is used.
Monitoring is not mapping
A frequent finding is a monitoring system with sensors placed for convenience, at eye level near the office door, rather than at the points mapping identified as worst case. The monitoring system then reports comfortably in-range numbers while product on the top racks experiences something else. Use the mapping to decide sensor placement, and document that link.
The monitoring system itself is a computerised system that needs validation: alarms, data retention, audit trail and access control. That part is often overlooked because it was bought as facilities equipment.
Vehicles and shipping lanes
The same thinking extends beyond the warehouse. Vehicles used to move temperature-sensitive product, and the routes they take, can be mapped and qualified in a similar way, with attention to loading positions, door openings during deliveries, and seasonal conditions on the route.
For shipping lanes, many companies rely on qualified packaging plus monitoring data from real shipments. Either way, the principle is the same: know where the risk sits, put the monitoring there, and use real data to show the conditions hold.
When to map again
After changes to the building, the racking layout, or the heating, ventilation or cooling. After a significant excursion that suggests the space behaves differently from what the last mapping showed. And on a periodic basis, with the interval justified by risk. Our piece on requalification triggers applies the same thinking to equipment, and our equipment qualification page covers our approach.
Where to go next
Explore GxP Copilot for AI-native validation, TraceDraft for source-traceable clinical documentation, or book a demo to see either on your own data.