A question which is at present still open to debate is that of allocating the stowage space on board ship which is optimum for the particular cargo. Present practice is to allocate stowage space with regard to optimum packing and unpacking technology, the only restrictions applying in the case of hazardous goods of the IMDG code and of refrigerated containers, which naturally have to be allocated the spaces provided for them.
Other requirements relating to maintaining cargo quality, such as radiation protection, shipment below deck, protection from heat sources etc., are given little consideration. Opinions will have to change if goods of vegetable origin are to be transported by container in any considerable quantity. The current practice of allocating containers to stowage spaces must of course be accepted for the majority of industrial goods, but is inadequate for sensitive goods.
Fig. 54 shows the different stowage spaces available on board a container ship. The significant difference with regard to cryptoclimate depends on whether the containers are stacked below deck or on the upper deck. None of the containers shipped below deck are exposed to radiant input and they are all protected during the voyage from spray and rainwater.
The daily variation in temperature of the ambient air is considerably more stable than on deck. A disadvantage is the low level of air movement, since the hold ventilation stream has little effect on a closed standard container, though a perceptible air exchange does occur in passively (naturally) ventilated containers. On the other hand, however, open containers packed with moisture-sensitive goods may also be transported below deck, such as citrus fruits on flatracks in the ventilated holds of ro/ro ships.
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