Inhaling through the nostrils is preferred over inhaling through the mouth because

It is preferred to inhale through an individual’s nostrils than through mouth respiration because it allows better conditioning of the air being inhaled. Base on a research, individuals who have proper knowledge on nasal breathing and performs nasal breathing during an exercise expels more expired air or also known as CO2 (Carbon Dioxide). Mouth respiration may cause an increase in pH and Vocal effort, which is why nasal breathing is preferred more than mouth respiration.