The three measurements on a cold-chain manager's desk are not three numbers that rule on their own. Each answers a different question: what condition did the product leave in, how long did the door event last, and when did the sensor show a defined condition was exceeded? Read each result with method, sampling, sensor location and logging interval.
Three measurements rise above the data pile when the cold chain basics are translated into field decisions.
1. Product measurement before loading
Before loading, define the product, packaging and measurement point. Select the probe or sample method under the product and site procedure. Record the number and selection of samples: puncturing packaging is not suitable for every product, and one pack may not represent the shipment.
Air, package surface and product readings describe different things. Record the sample choice, measurement point, device ID and time. This observation describes the load at departure; it does not by itself prove what will happen during transport.
2. Door-event minutes
Record the opening and closing times at each stop to show route context. Total open minutes are not a measurement of the product's actual heat load; interpret them with ambient conditions, load, opening size, unit operation and how long the door stayed open. The same minute total can have different effects under different air and load conditions.
3. Time outside the defined condition
Preserve out-of-range readings with their temperatures and timestamps. FAO/WHO §13.2.1 relates time-temperature control to product characteristics, shelf life, packaging and intended use. Minutes outside a limit alone do not quantify damage or diagnose a fault.
Read the logging interval correctly
Hypothetical example: a five-minute logger is within limits at 12:00 and high at 12:05. A transition occurred between those samples, but its exact start, the intervening peak and total time above the limit are unknown; multiple crossings are possible. Do not fill a missing interval with zero excursion time.
| Observation | Field to record | Use |
|---|---|---|
| Product start | Product/lot, sample method, point, device and time | Review starting dispatch condition |
| Door event | Stop, opening-closing minutes, ambient and activity | Compare route context |
| Thermal excursion | Sensor ID, logging interval, time window and values | Investigation and defined procedure |
| Decision | Product, record, owner and basis | Separate monitoring from release |
Use the same fields for each shipment:
- product or sample measurement method and sampling plan
- start and end minutes for each door event
- sensor ID, location, logging interval and raw file
- procedure used for excursion review and product decision
If one measurement is missing, record the gap and do not derive a definite result from the other two. Link it to the cold-chain incident and corrective-action guide. Monitoring data directs the next review; release or discard follows the defined quality process.
