Most of the time, the air inside the mask will equalize from small amounts of air coming from your nose during respiration. It is a good idea to consciously breathe out through your nose every 1 meter/3 feet during descent. If you feel any pressure on your face, breathe out through your nose. If this does not work, ascend 1 meter/3 feet and try again. Rarely, mask squeeze can cause blood vessels in the eyes or face to burst. This looks much worse than it really is, but a trip to the doctor is recommended as a safety precaution.