Chilled and frozen transport look like the same job with a different dial setting, but the temperature bands, the failure modes and the margin for error differ enough that a carrier good at one can be mediocre at the other without noticing.
The bands, side by side
| Chilled | Frozen | |
|---|---|---|
| Typical carriage band | 0°C to +5°C | −15°C |
| Margin above product damage | A few degrees | Ten degrees or more |
| Main transit risk | Drifting warm on long or busy rounds | Slow thaw from unit failure going unnoticed |
| Recovery after a door opening | Minutes | Minutes, but from a deeper base |
| What kills product | Time above band, cumulative | Any genuine thaw, once |
Why chilled is the harder discipline
Frozen product carries its own thermal reserve. A pallet at −20°C takes a long time to warm anywhere near danger, so brief door openings on a multi-drop round barely register in the product. Chilled has no such buffer. The band is five degrees wide and the product often sits within two or three degrees of its limit, so a chilled round with many stops demands tighter door discipline and smarter load sequencing than the equivalent frozen work.
That’s also why chilled disputes are more common at goods-in. The air probe shows a spike from a door opening, someone reads it as a band breach, and the conversation starts. Air temperature is not product temperature; on chilled work you need the full trace to show the recovery pattern, because the numbers sit so much closer together.
Why frozen punishes inattention
Frozen fails differently. The product forgives door openings but not equipment. A refrigeration unit that falters on a frozen load starts a slow, one-way process, and a carrier who only glances at temperatures at the start and end of a run can miss hours of drift. Continuous monitoring exists for exactly this: the difference between catching a failing unit at −14°C and discovering a soft load at the door.
Both on one vehicle
Plenty of orders span both bands. Dual-zone vehicles run a frozen compartment and a chilled compartment behind the same doors, each monitored separately. The practical benefit is one delivery instead of two; the evidential benefit is that each band keeps its own clean record.
What to ask a carrier, whichever band you ship
Ask how temperature is recorded: continuously and per consignment, or occasionally and per vehicle. Ask how quickly they can hand you the trace for one specific delivery. And ask what their team does when a unit deviates in transit. The answers tell you whether the cold chain is a system or a hope.
