In pranayama, we always breathe through the nose (unless stated for specific practices). This has so many benefits to it and is by far the healthiest and most natural way for the body to breathe. From the perspective of natural physiology, mouth breathing usually only takes place as a secondary respiratory function when an exceeding demand for air isn’t being met by nasal breathing. Mouth breathing should only really occur when there is an excessive athletic demand, nasal congestion or some medical cause.
Mother nature ingeniously put tiny hairs in the nasal cavity to catch dirt and particles entering with the incoming air. Nothing’s left to chance in nature when it comes to the importance of filtering the air for breathing. Mother nature then created a second line of defence, called cilia, a sticky surface in the lining of the nose designed to catch finer dust and germs before entering the lungs. The nasal air way is responsible for around 90% of the respiratory system’s air-conditioning process, being to control the temperature and cleanse the air in preparations for the sensitive lungs. As critical as it is to breathe clean air through the nose, there are a number of other fascinating reasons that mother nature designed us to breathe through the nose.