Studies show that about 85% of people only breathe out of one of their nostrils at a time. There is a nasal cycle which rotates between the two every ~4 hours. – WTF Fun Facts
Source: https://www.ua-magazine.com/good-to-know-most-people-only-breathe-out-of-one-nostril-at-a-time/#.XdwqOdXgpPY
