In passive containers the most common cause of lost time is not the box itself but the preparation. Conditioning has three parts, and the measure for each is written in the approved packout instruction for the product.
| Part | What is done |
|---|---|
| Coolant | Frozen through, for the time stated in the instruction |
| Box | Held before shipping in an environment at the target temperature |
| Product | Kept ready at the starting temperature the instruction gives |
A pack frozen on the outside and still liquid inside carries only part of its phase-change energy and runs out earlier than expected. A box standing at warehouse temperature also spends the first hours of cold on its own walls; holding the box in the target environment beforehand prevents that loss and buys measurable time.