Dry Ice for shipments of chilled cargo


Shipments of perishable goods are extremely time-sensitive and must be managed at all stages of handling and transport correctly. Airfreight is often used as a solution for transporting perishable goods to avoid the long transit time of seafreight; shipments can conceivably arrive on the other side of the world the next day, not the next month!

But how is temperature control managed on an aeroplane compared to a mammoth container ship ? On a container ship reefer containers are plugged into power to maintain required temperature; probes inside the container will measure the temperature of the packed cargo and also ambient air temperature where required. This onboard temperature control, together with powered reefer plugs at the terminals, means that temperature can be controlled and monitored from the time the container is packed to when it is destuffed.

On an aeroplane, the first factor is of course space. The cargo must be packed into dedicated smaller airfreight containers, as seafreight containers are simply too big. An airfreight container is usually only big enough to carry about 1.3 ton of packed product, yet you can literally walk into a shipping container and walk about 10 paces from end to end without ducking your head.

  This demonstrates the main outcome of airfreight; you send smaller shipments more often. True, there are dedicated “super” planes where the nose lifts up and you can drive a tank onto them without touching the sides . But the majority of the flights used for perishable goods are also commercial flights with passengers aboard. The flights are literally packed with cargo and travellers.

The smaller size of the airfreight containers means that the cooling mechanism will need to focus on non-electric cooling as opposed to a traditional powering found in reefer plugs and gensets ( diesel powered “generators” to allow cooling of containers whilst being trucked ) than that found in a seafreight container. We must look to alternative means to maintain temperature once the product is removed from powered temperature control.

The way in which dry ice prevent spoilage of chilled cargo is through replacing oxygen  with carbon dioxide ( CO2 ). The indirect fumes from the dry ice will keep the cargo chilled.

With regards to dangerous goods regulations, unless the dry ice is being used to refrigerate another dangerous good then a separate dangerous goods declaration is not required. The package containing the dry ice would need to be appropriately marked with UN number, net weight and packaging group ; this information would also be included on the air waybill.

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