An airflow problem is not only a stack-height problem. Discharge, the path through or around the load and return air must be read together. A road trailer duct and return, a maritime reefer container's T-floor and unit end, and a fixed cold store with an evaporator are not checked with the same assumption.
Find the equipment air path first
Before loading, mark discharge direction, return opening, floor duct or under-rack clearance on the equipment drawing. A pallet blocking the ceiling, return or unit end can reduce airflow to part of the load even when the room display looks correct. Clearance follows equipment, cargo and operating drawings; there is no universal hand-width or 10 cm rule.
| Check location | Possible obstruction | Action |
|---|---|---|
| Road trailer discharge and return duct | Pallet, curtain, top load or blocked return | Open the corridor from the unit drawing and recheck restraints |
| Reefer container T-floor and unit end | Cargo above the load line, beyond the T-bar footprint or air escaping through uncovered floor | Respect load limits and cover open floor according to carrier loading instructions |
| Fixed cold-store evaporator | Rack, carton or load extending into the air curtain | Clear discharge and return using the equipment plan |
| Packaging inside the pallet | Closed vents or packaging not designed for airflow | Use only packaging instructions for ventilated products |
| Restraint point | Strap, corner protector or load bearing against it | Do not cut restraints blindly to create airflow; obtain approval |
Match package vents to product instructions
Vent holes help crates or packaging designed for air movement through the product. Plastic wrapping can restrict that circulation. Perforated film, top-only banding or aligned holes is not a solution for every package or product. Follow the packaging instructions before changing film or vents, and maintain load stability.
Do not place warm cargo in a random zone
Unchilled cargo placed among prepared stock can add heat and block a cold-air path. A separate receiving or preparation area is appropriate only when its equipment, airflow capacity and product procedure support it. A cold store is not a rapid cooling tunnel for warm cargo under every condition.
Measurement points do not diagnose the cause
Door-side, unit-distant, top-load and pallet-centre points can show different conditions. Comparing more than one record helps select an area for investigation; a difference between loggers alone does not prove a stacking fault. Record sensor position, product temperature and air temperature separately.
Why might an open reefer floor need covering?. Hapag-Lloyd's loading guide says to respect the load line and T-bar floor boundary and cover free floor space with suitable board or dunnage. This limits air returning through open space instead of circulating through the load. Blocking the channels themselves differs from covering unused floor above them as instructed. This maritime reefer arrangement does not transfer directly to a road trailer.
The final check should record equipment type, discharge and return points, obstruction, change made and responsible person. The refrigerated trailer stacking plan helps with dimensions and load distribution, while the container pallet calculation helps organise geometric candidates; neither replaces an actual airflow check or carrier approval.
