Choosing monitoring locations from mapping results
Permanent monitoring sensors go where the mapping showed the worst case — the hot spot, the cold spot and the slowest-recovering position — not where the cable is shortest.
The purpose of a mapping study is to find where a space behaves worst. Routine monitoring is then placed at those positions so that if the worst location is within limits, everything else is too. A monitoring sensor placed at the control probe's position typically shows the best-controlled point in the room — the least informative place to look.
Selection rules
- Hot spot (highest mean or maximum) and cold spot (lowest mean or minimum) from the loaded mapping.
- Positions with the slowest recovery after door openings or defrost.
- Each distinct zone if the space has more than one HVAC regime.
- Product-height positions, not ceiling or floor, unless product is stored there.
Record the rationale
A monitoring plan should show, for each sensor, which mapping position it corresponds to and why. When the space changes and is re-mapped, the plan is reviewed against the new results.
Frequently asked questions
- Can the mapping loggers stay in place as the monitoring system?
- They can, if they are calibrated for that role, connected to alarms, and their data are captured in a compliant system. Usually dedicated monitoring sensors are installed at the chosen positions.
- How many monitoring sensors does a cold room need?
- At least two (hot and cold spot) for a small unit; larger rooms add sensors per zone and near doors. The mapping results and risk assessment set the number.
References
- [1]EU Guidelines on Good Distribution Practice of medicinal products for human use (2013/C 343/01)
- [2]WHO Technical Supplement 8 to TRS 961 Annex 9: Temperature mapping of storage areas (2015)
- [3]WHO Technical Supplement 16 to TRS 961 Annex 9: Environmental temperature monitoring systems for fixed storage areas
General technical guidance written against the cited sources. It is not regulatory or legal advice and does not replace the applicable standard, guideline or a qualified reviewer's judgement.
Have a question on this topic?
Ask ValiTrac AI and see the evidence and calculation behind the answer.
Ask ValiTrac AIFree calculator: MKT & logger data check
Paste logger readings and get MKT per ICH Q1A(R2) alongside min, max, mean and out-of-limit runs with durations.
Open the calculatorRelated articles
Sensor placement principles for mapping studies
Place sensors where product is, where risk is, and where the monitoring probe might go — and write down why.
Alarm limits vs acceptance limits: setting them correctly
Acceptance limits come from the product; alarm limits sit inside them to give time to act; alert (warning) limits sit inside those. Uncertainty and delay decide the gaps.