A flask and a transport container answer the same need at two different scales, and that difference decides how many degrees the food shows at handover. In a classic flask the air between two walls is removed, which almost stops heat loss by conduction and convection, and a reflective surface reduces the radiation that remains. A transport container has no vacuum; the thickness and material of its foam wall slow the heat.
| Food flask | Insulated transport container | |
|---|---|---|
| Insulation method | Vacuum wall | Foam wall |
| Scale | One or a few portions | A shipment, tens of litres |
| What goes inside | The food directly | Standard pans and trays |
| Washing and tracking | Each flask separately | One container |
For a single meal, field staff and short distances a flask is enough and practical. Dozens of portions a day, multi-stop distribution or hot and cold groups travelling together call for a transport container; going out to fifteen addresses with fifteen flasks is possible, but each is filled, washed and tracked separately.
Two figures are enough to decide: how many litres and how many hours per run. With those the answer emerges by itself; without them, run a delivery trial with the real load and record filling, loading, access at stops, cleaning time and product temperature at handover.