A system and method for collecting x-ray exposure data in an x-ray detector include scanning pixels in an x-ray detector to determine exposure levels. In the system, a tube is arranged rotatable in a rotatable distributor body in the air distribution device, which distributor body are connected to tubes, and which distributor body includes rotating means, and when the distributor body is rotated, tubes are moved from a position above one hole in the holding plate to another hole in the holding plate. The allocation of space includes discovering free space in all the higher layers in the logical storage hierarchy.