When a door opens, the air in the body warms briefly and settles back once it closes; that is the normal ripple of an operation. If the same vehicle waits two hours on the dock with its doors open, the product itself warms and the situation changes. Two things define a break: the temperature leaves the product's own range, and it stays outside long enough to matter.
Understanding what the cold chain is first makes the rest of the assessment easier: temperature, time and product can then be read as parts of the same system.
The range is written per product, because the same temperature means different things to different goods.
| Product | Written limit | Source |
|---|---|---|
| Raw milk, at the processing plant | 6 °C or below | Turkish Regulation on Specific Hygiene Rules for Food of Animal Origin |
| Frozen fishery products, in transport | -18 °C or below; short fluctuations not exceeding 3 °C are accepted | same regulation |
| Immunization programme vaccines | between 2 and 8 °C | WHO immunization handbook |
Most loggers measure air, while the product's own temperature changes far more slowly, in proportion to its mass. An air alarm is therefore not proof that the product deviated too, but thermal lag is no reason to ignore it either. Warming air is a warning, warming product is a result, and the lag between them is the time left to intervene. If the logger measured air only, no definite statement about product temperature is written; sensor position, load and packaging are assessed together.
The first bad value in a record is only the first observed bad value. If the last good reading is 10:00, the first bad one 10:10 and the deviation is noticed at 10:17, there are three separate times, and the product may have been exposed from the last good reading until someone acted. The gap between readings is not treated as safe; it is written down as the possible start. A missing record does not show that nothing happened, it only leaves timing and exposure uncertain.
When refrigeration restarts or the air returns to the band, the operation has recovered, but the product is not automatically acceptable. The event record, root cause and corrective action sit in one file, while the release, quarantine or disposal decision is made separately. The decision note lists the observed values, the unknowns, the action taken and the final status of the product. For the prevention side, see the steps in cold-chain break prevention.
A product label, an approved transport procedure and a customer contract can set different limits, so the one used at delivery should be written down beforehand. If the contract puts the acceptance threshold at 4 °C, the number discussed at delivery is 4. What delays a break is the thermal barrier around the product: an insulated container and the eutectic plate inside it lengthen the time an excursion needs to turn into a break. GEBHARDT eutectic plates or dry ice hold the cold chain for up to 24 hours.
