Ucchwasa and Nihshwasa are the inhaling and exhaling of prana vayu. This comes under svarodaya vijnanam or swasa sastram – science of breathing in Hindu religion. Inhaling of prana vayu is known as nihshvasa and exhaling is ucchvasa. Exhaling and inhaling seem simple, however, they contain secrets, according to this shastra. Our success, failure, pleasure or pain depends of svasa shastra. Prana and apana vayu are symbolically called aswini devas in Vedas. They are ever young, unaffected by old age, disease or death. They are the divine physicians.
Our body is living only because of these two vital airs. When they leave the body, we die. So it is apt to say symbolically that these two vital airs are Ashwini Kumaras, or divine doctors. Not only these two divine persons but also many gods live in our body, ‘pancha indriya’ or devas states Yajur Veda. A sage called Cyavana is called the body. When we become old, we are afraid of it and we want to look young. This is possible with the help of the twin gods.
Everyone breathes twelve or thirteen ucchvasa and nihshvasa every minute. In twenty four hours, 21,600 ucchvasa nisvasa take place in a human body. If uccvasa nihsvasa fall below twelve per minute, the life span increases, i.e., if a person control breath, the life span increases. We do not inhale simultaneously through the nostrils. Breath enters through the left and goes out through the right nostril. Sometimes it enters through the right nostril and leaves through the left. The left nostril is called ida and the right nostril is called pingala.
When air enters through ida it is swara and when it enters through pingala it is called udaya. In a day very often svara and udaya take place, and for a few minutes air goes through both nostrils and comes out through both. According to this Shastra, when air goes through ida, auspicious ceremonies are to be performed. When the breath enters through pingala, we can start performing difficult things. If a person breathes through both nostrils, he should avoid doing good actions. To know through which nostril we are breathing there is a shloka.
Adou chandrah sitepkashe bhaskarastu sitetara pratipathou dinanyahuh streethi trini kramodaye
Left nostril – Chandra nadi
Right nostril – Surya Nadi.
Dangers are also predictable if we observe our breath. On the first day of the bright half of a month, if a person starts to breathe through the right nostril, it foretells some diseases and some unhappy news. His is sure to get diseases relating to heat. In the dark half of the month, if air enters through left nostril, diseases relating to cold are foretold. If a person breathes through the left nostril for four hours continuously, gain or good fortune is foretold.