As he does not want to put patients abroad at risk, Klose has to test the cooling devices in an independent study before the armed forces can use them. Therefore, he and Putzker have tested different insulating boxes and cooling devices in the past years. Again and again, in various combinations, they stuffed the boxes and placed them in a climatic chamber. They stayed there at minus ten or plus 40 degree for two to five days. The best outcomes were achieved when box and cooling devices were pre-cooled at four degree and then a bundle of 40 blood units per box was enclosed by paraffin cooling devices on every side. „The cooling devices form a cube in the end“, Klose describes.
Paraffin that is mainly known as ceraceous part of candles has several states of aggregation. The freezing point is at four degree, here fluid paraffin becomes solid. That is exactly the temperature that blood units ideally keep during their transportation and at which the sensitive cells feel good.
Before packing, the insulating box has to be lined with bubble wrap – to defend from percussions. If, finally, the boxes are transported in the cabin or the cockpit of a plane, and not in the cargo hold, the air pressure is balanced and the cells have a really good chance to arrive alive. Klose observed: at a constant outdoor temperature of 40 degree, following the European guidelines, blood has 36 hours to reach the blood storage with this method. With ice, in contrast, the units would have been too warm already after twelve hours.