Reefer shipping fails in the gaps, not in the container. The box holds temperature reliably; what goes wrong is the hour on an unplugged chassis, the pre-cooling that never happened, or a setpoint entered as a shipping instruction that nobody converted correctly. Specify all nine of these in writing and most reefer problems disappear.
The nine
| # | Specify | Why it matters |
|---|---|---|
| 1 | Setpoint, with units | State Celsius or Fahrenheit explicitly. Unit confusion is a real and expensive failure mode |
| 2 | Chilled or frozen | Different equipment behaviour, different tolerances, different risk if it drifts |
| 3 | Ventilation setting | Respiring produce needs fresh air exchange; frozen cargo needs it closed. Wrong setting spoils the load |
| 4 | Humidity control | Required for some produce and pharma, irrelevant and costly for others |
| 5 | Pre-cooling | Whether the container is pre-cooled, and whether the cargo is pre-cooled — see below |
| 6 | Controlled atmosphere | Oxygen and CO2 levels for long-transit produce; specialist equipment, book early |
| 7 | Data logger | Who supplies it, where it sits in the load, and who gets the download |
| 8 | Genset requirement | Road legs need a generator unless the chassis provides power. This is where cold chains break |
| 9 | Plug-in commitments | Named responsibility and maximum unplugged time at every handover |
A reefer container does not pre-cool your cargo
The single most common misunderstanding. A refrigerated container is designed to hold cargo at temperature by circulating air, not to pull warm cargo down to setpoint. Load produce warm and the unit will run continuously, never reach setpoint through the middle of the pallets, and deliver a partially spoiled load with a temperature trace that looks like equipment failure.
Cargo must be pre-cooled to its carrying temperature before loading, at the packhouse. Specify it, and ask for evidence.
Stow the load so air can move
Reefer airflow runs from the floor T-bar decking, up through the cargo, and back along the ceiling. That means:
- Never block the floor channels. Cargo sits on the decking so air passes underneath.
- Stay below the red load line. Cargo stacked into the return-air path starves the far end of the container.
- Block-stow chilled produce to force air through the cargo rather than around it; frozen cargo is stowed tight to hold its own cold mass.
- Keep the rear doors clear — the last metre is where temperature deviations show first.
Where cold chains actually break
Not at sea. The container is plugged in and monitored for the whole ocean leg. The failures cluster at:
- The gate. Container unplugged for the road leg without a genset booked.
- Terminal dwell. Waiting for a plug point at a busy terminal, or after a missed connection.
- Customs inspection. Cargo opened and held, sometimes in ambient conditions.
- Delivery. Doors open on the dock while the consignee finds space.
Which is why free time matters more for reefers than for dry cargo, and why demurrage exposure is a temperature risk as well as a cost risk — estimate it here and read delivery appointment scheduling.
Documentation and compliance
Perishables and pharma carry documentation beyond the standard set: health or phytosanitary certificates, and for pharma, evidence of an unbroken chain. Build the extra lead time into your plan — the import documentation checklist covers the baseline. Note also that reefer capacity is genuinely scarce on some lanes and around peak seasons, so book earlier than you would for dry cargo (see the closure calendar).
Before you book
- Put the setpoint, units, ventilation and humidity in the booking, not in an email thread.
- Confirm pre-cooling of cargo and container, and who is responsible for each.
- Book the genset for every road leg explicitly.
- Agree maximum unplugged time at each handover, in writing.
- Specify data loggers and who receives the download on arrival.
- Ask what happens, and who pays, if the unit alarms in transit.
Reefer work rewards specialists. Find forwarders who handle temperature-controlled cargo on your lane, or post your requirements and let them quote against the specification above.
