Although the right and left halves of the nose are separated by a septum, their operation is coordinated In medicine, this relationship between the structures is called reciprocal. Many people do not notice it, but the right and left halves of the nose usually pass air unevenly - one better, the other worse, and about every 2 to 4 hours they switch roles. This process is called the "nasal cycle." It is assumed that this happens so that one half of the nose "rests." Indeed, in the half that breathes worse, even the beating of the mucus cilia slows down or stops altogether.