Whenever a container is loaded and sealed, some moisture invariably becomes trapped either in airborne form (depending on the external ambient and relative humidity) or being present in timber packing or dunnage materials, the container floor or the cargo itself. This "invisible" captured water can amount to many litres when relative humidity is high, just about all of which precipitated when the container travels between equatoria/tropical and temperate zones. It is by preventing this release as condensation - or in the worse instance as " container rain" - which will do damage to the cargo.
There were more than 650 million TEU containers were shipped by sea in 2013, a third of these containers were shipped from China. It's estimated that the cargoes in 20% of these were in danger of being damaged by humidity. As a result, manufacturers, shipping lines and customers losed billions of dollars in the year.