What decides the outcome is whether the transit is longer or shorter than the packaging's holding window. Two days in a thick-walled container with eutectic plates and two days in a thin carton do not give the same result. The window depends on the product's acceptance temperature, the pack-out configuration and the outside temperature, so a number of days alone does not decide.
The clock starts when the coolant is placed or the product leaves controlled conditions, not when the carrier accepts the parcel. The time counted is not just time in the vehicle either: the accepting branch, transfer hub, customs, delivery branch and failed delivery attempts all count, and it ends when the receiver puts the goods into controlled storage. The carrier's quoted transit time can be shorter than this total; a hub or customs wait can exceed the window even when it fits inside the quoted number of days.
Example: a pack leaves controlled conditions on Tuesday at 10:00, the receiver takes delivery on Wednesday at 16:00 and puts it into controlled storage at 16:30, so the time is 30 hours 30 minutes. The tracking screen shows only 30 hours. Record event times rather than a day count.
When choosing the window, base it on the longest and hottest lane. WHO's shipping container qualification guidance (Supplement 13, written for pharmaceuticals) recommends selecting the worst-case lane and requalifying when the route or duration changes.
If the time exceeds the window, do not release the product automatically; assess product temperature, logger data and pack condition together. A smell check or re-cooling does not bring back lost temperature history. FAO's corrective-action guidance separates the assessment of affected product from correcting the process.
You will find how to verify the duration in how many hours a cold chain box lasts and what to record during a delay in the cold-chain emergency plan.
