Packing and stowage
Frozen cargo is usually pre-cooled to the correct transport temperature, so it is only necessary for air to circulate around the load. A block that has no spacing between any of the packages or pallets requires only air can circulate under, over and to each side and end of the stow, but not through the load as it is necessary for chilled products.
Fruit and meat for example require air circulation both around the product and through the load to remove respiratory heat, water vapor and gases such as carbon dioxide and ethylene.