What GDP expects from temperature mapping

The EU GDP guideline places temperature mapping under premises and equipment: an initial temperature mapping exercise should be carried out on the storage area before use, under representative conditions, and mapping should be repeated according to the results of a risk assessment or whenever significant modifications are made.

What follows from that

• 'Before use' means the study is part of qualification, not a later check.
• 'Representative conditions' is the argument for loaded studies and for considering seasons.
• Repeat mapping is triggered by change (racking, HVAC, layout) and by a documented risk assessment.
• Monitoring equipment should be placed according to the mapping results, at the areas of greatest variation.

The guideline states expectations, not methods. The method — sensor count, duration, analysis — comes from technical guidance such as the WHO supplement and from the organisation's own protocol.

The four words that carry the obligation

The GDP guideline is short on method and precise on intent, and almost the whole obligation sits in four phrases. Reading them literally is the difference between a study that satisfies an inspector and one that does not.

Mapping decides where the monitors go

The guideline's next requirement is the one that makes the study useful rather than ceremonial: temperature monitoring equipment is located according to the results of the mapping exercise. That is a direct, checkable link, and it is the first thing an inspector will test — pull the mapping report, find the hot spot, then walk to the monitoring sensor and see whether it is anywhere near it.

A very common failure is a monitoring probe installed by the refrigeration contractor at commissioning, in the most convenient place for cabling, and a mapping study performed two years later that identifies a hot spot three aisles away. The study then has to end with a recommendation to move the sensor, and somebody has to actually move it. A mapping report whose recommendations were never implemented is worse than no report, because it documents that you knew.

What GDP does not specify, and where the method comes from

• Sensor count, positions, duration and sampling interval are not in the guideline. They come from technical guidance — WHO Technical Supplement 8 is the usual reference — and from your own protocol.
• Acceptance criteria are not in the guideline either. They come from the label conditions of the products stored.
• The re-mapping interval is not specified. You set it from a documented risk assessment, and three years for a stable ambient store with one year for a cold room is a defensible pair; the same number for both, with no rationale, is not.
• Transport is covered separately. Vehicles and shipping containers used for temperature-sensitive products need their own qualification, and the ambient variation there is far larger than in any building.

Significant modification is broader than it sounds: racking layout, HVAC or refrigeration replacement, a change in door or dock usage, a new product with tighter limits, and a change in how the space is loaded all qualify.