Question

Why should one breathe by nose and never by mouth

Answer 1

Certain individuals, whether children or adults, have a tendency to breathe through the mouth instead of the nose. ... Exhaling through the nose, which is smaller than the mouth, creates greater air pressure and therefore a slower exhalation. This gives the lungs extra time to extract a greater amount of oxygen.

Answer 2

Becoz nose can purify the air but mouth cannot.