Server racks for hot aisle-cold aisle server rooms

A standard server rack is modified to be able to detect if a blanking panel is missing from an unoccupied slot. Detection can be achieved electrically by providing switch elements in the holes on the rack siderails, whose switching state depends on whether a fastening pin is in the hole. A blanking panel, when fitted to a particular slot, thus switches the switch elements for that slot, which can be detected by a make/break circuit including the switch elements. Alternatively, detection of a missing blanking panel can be achieved optically by arranging a bank of forward pointing optical sensors at the back of the server rack, which point forward to detect the presence of a blanking panel. The optical sensors are distributed vertically so that at least one optical sensor covers each slot.