Exhalation is the third phase of respiration and it is normally a passive act. However, the yogic act of recaka should be a slow, controlled process. Some say it should be twice as long as the puraka.
A controlled and focused rechaka helps prepare the individual for the yogic limb that follows pranayama: pratyahara (withdrawal of the senses). If the practitioner observes and focuses on their breathing, it helps switch off other senses and mental processes.
Slow rechaka also helps to maintain the elasticity of the lungs. It offers some major benefits for the brain, as well. The slow respiration requires the help of the cerebral cortex, which sends impulses to the respiratory center. These impulses overflow into the hypothalamus (a center of emotion) and quiets that area, providing a soothing effect.