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
WTF Fun Fact – Nasal Cycle
They can also have a deviated septim. The middle part of your nose flops over back and forth depending on positioning of the head and blocks one nostril.