In an EPS box the pack position is not chosen from the idea that cold air falls. The box gains heat through its base, sides, lid and sun-facing surface, and the vehicle floor and opening frequency change that load from route to route. The aim of the layout is a thermal condition that repeats at every loading for a defined product and route.
Measure the box and the load first
Take usable internal length, width and height instead of the outside dimension, and note lid projections, base thickness and corner radius separately. Mark the space taken by packs and separators first, then fit the product packages in their actual orientation. A litre calculation does not show that a corner or the space under the lid is usable. A dry fit tests whether things fit; thermal performance is measured separately.
Write the starting condition into the pack-out record: product and lot, loading temperature, sensitivity to freezing and surface contact, package type, total mass and loading order. For freeze-sensitive goods a fully frozen pack does not touch the product directly; a separator keeps the distance, and overcooling of the surface next to a pack is assessed together with warming in the far areas.
Model, count and position are defined together
Record the pack model, target regime and dimensions. There is no gram-per-litre ratio or plate count that holds for every route; the quantity follows from box geometry, product starting temperature, ambient conditions, total duration and opening pattern. Show top, side and bottom positions in a numbered diagram. GEBHARDT eutectic plates must be completely frozen before use, and when freezing an air gap is left between the plates so that cold air circulates freely.
Closure and route
The instruction includes lid orientation, seal or taping method, a latch check and which side of the box faces the sun or the vehicle floor. Write the ambient range, total duration, depot dwell, transfer or delay scenario, and the number and length of openings separately; a target duration alone does not cover a delay scenario.
| Measurement area | Risk sought |
|---|---|
| Product surface near a pack | Local overcooling or freezing |
| Area away from packs | Insufficient temperature holding; the warmest point is not assumed before it is measured |
| Load next to the lid or wall | Closure and ambient effects |
| Inner region of the load | Temperature difference within the load; one central reading may not represent all of it |
Do not put the logger against a pack or the cold source; the record looks good but does not represent the product. FAO's HACCP monitoring guidance asks for a method and frequency planned to catch a deviation before it passes the limit and recommends continuous recording where possible; it sets no legal temperature limit for a particular product.
For pharmaceutical transport, WHO's supplement on qualification of shipping containers has the operational qualification protocol define the pack-out arrangement and the location of temperature monitoring devices; if the design or packaging is modified the work is repeated, and re-qualification is considered when components, route or duration change. It is pharmaceutical guidance, not food law or a fixed test count for every EPS box.
A change calls for a new trial
When packs, load, separators, box, closure or route change, first check whether the change stays within the limits of the earlier trial; try the new configuration if needed, and redetermine the risky points if the geometry changed. If the temperature leaves the accepted range, adding packs and carrying on is not an option: according to FAO corrective action restores control of the process and also decides what happens to the affected product (expert evaluation, reprocessing, diversion to another use, destruction).
To make the instruction repeatable, photograph the empty box, the pack and separator layer, the loaded state and the closed lid; label packs A1, A2 and sensors S1, S2. For separator choice see what goes between an ice pack and the product, for measurement and proof proving the cold chain, and for requirements writing a cold-chain transport case specification.
