The HDD’s spindle structure relies on air pressure within the enclosed space to hold the heads at their proper airborne height as the disk turns around. An HDD needs a certain variety of air pressures in turn to operate correctly. The links to the outside environment and pressure happens because of a small gap in the enclosure which is approximately 0.5 mm in diameter. More often than not, through a carbon filter on the inside. If the air pressure is extremely small, in that case there is not sufficient lift for the flying head. The head becomes too close to the disk, and there is a possibility of head crashes and data loss. Specifically manufactured sealed and pressurized disks are desired for reliable high-altitude function.