Temperature monitoring during transport

EU GDP chapter 9 requires that the required storage conditions are maintained during transport, and that temperature-sensitive products are shipped with monitoring where the route or product warrants it. In practice most cold-chain shipments carry a single-use or reusable logger.

Practical rules

• Position the logger where the shipper qualification showed the worst case, not on top of the outer packaging.
• Use loggers whose calibration covers the transport range, with a documented interval.
• Start the logger with a recorded time and, if possible, a stabilisation period before packing.
• On receipt: download, review against limits, and file the trace with the shipment record.
• Excursions: quarantine, assess with product data, document the decision.

Where loggers are reused, their calibration and battery status become part of the dispatch checklist.

Where the logger goes

The position is decided by the shipper or vehicle qualification, not by convenience, and the two differ more than people expect. A logger taped to the outside of a carton measures the vehicle; a logger on top of the load in a trailer measures the warmest air; a logger among the product measures something close to what the product experienced. Only one of those is evidence about the shipment.

Reviewing the record on receipt

The record is only a control if someone reads it before the product moves. That means a defined step at goods-in: download or read the logger, compare against the product's limits, and either release or quarantine — before the pallet goes to a storage location, not after.

An excursion found at that point is a deviation with a decision attached. Assessing it means comparing the actual time-temperature profile against the stability data for that product, which is a judgement for quality, not for the receiving team. What the receiving team owns is the quarantine and the record.

Cargo temperature monitoring by mode

Road, air and sea freight fail in different places, and a transport monitoring plan that treats them alike will be wrong about at least two of them. The duration differs by two orders of magnitude, and so does the question of who is holding the cargo when the excursion happens.

A reefer container keeps its own record, and so does a temperature-controlled trailer. Both are equipment monitoring: they describe the box, not the pallet inside it, and they do not replace a data logger travelling with the load. The container record is still worth collecting, because when the two disagree the difference is usually the thing you needed to know.

Data loggers, recorders and indicators

These are not interchangeable, and the choice made at dispatch decides which questions can be answered on arrival.

• A chemical or mechanical indicator shows that a threshold was crossed. It gives no profile and no timing, so it can tell you a shipment is suspect and can never tell you whether it is acceptable.
• A single-use electronic data logger records a full time-temperature profile and is read on arrival, usually as a PDF generated by the device itself. This is the common choice for pharmaceutical shipments.
• A reusable data logger does the same and moves calibration status, battery and memory onto the dispatch checklist, where they are easy to forget.
• Real-time telemetry reports in transit over cellular or satellite, which converts the record into an intervention: a lane that is going wrong can be stopped, rerouted or met at the airport rather than written up afterwards.

The distinction matters most when an excursion is found. Assessing one means comparing the actual profile against the product's stability data, and an indicator leaves you with nothing to compare. The cheapest device is the one that forces you to destroy the consignment.

Assessing the record on arrival

Three numbers do most of the work, and they answer different questions. Total time out of range measures how much of the journey was non-compliant. The longest single excursion, with its magnitude, is what gets read against the stability data, because fifteen minutes at 12 C and six hours at 12 C are not the same event. Mean kinetic temperature summarises the cumulative thermal history over a long or multi-leg journey.

Choosing between them is where transport reviews go wrong in both directions. MKT is the right summary for a three-week sea crossing and the wrong one for a sharp spike on a two-day road leg, where it will average a genuine problem into an acceptable-looking figure. A single excursion magnitude is the right summary for the spike and says nothing useful about the crossing. Report whichever one the journey shape calls for, and say which you used.

The operational details that go wrong

• Calibration covering the transport range. A logger certified from 0 to 10 °C does not cover a summer trailer that reached 34 °C, and that is the reading the decision turns on.
• Start delay. A logger activated in a 20 °C dispatch office records the office for twenty minutes unless a start delay is configured, and that spike then has to be explained on every shipment.
• Battery and memory checked at dispatch. For reusable loggers this belongs on the dispatch checklist alongside calibration status, because a flat logger produces no record and no warning.
• Clock set and time zone recorded, especially on international lanes where the receiving site reads the file in a different zone.
• A defined route for the file: who downloads it, where it is stored unchanged, and how it links to the delivery record. A logger in a drawer is not a record.