Sitali Pranayama, popularly called the Cooling Breath exercise, is applied to calm and cool down the body. Alternatively, the exercise can be used to combat thirst and hunger.
This Yogic Pranayama breathing technique is sometimes also called the Tongue Hissing exercise because of the sound the breath makes when you inhale.
To perform Sitali Pranayama, you slowly and deeply inhale air through a protruding, rolled (curled) tongue that is folded as a tube (or through pursed lips if not otherwise possible).
Because of letting air pass over the moist tongue, the air is fresh and cool and refreshes the throat, while reducing internal heat of the body.
After each inhalation, the tongue is pulled inwards and the mouth is closed. One typically breathes out slowly and fully through the nostrils.
To achieve the desired effects the exercise can be done for several minutes.