Why should we only breathe through nose

Because while breathing through our nose, thanks to the hair we have around our nostrill walls, air is purified which maintains our lungs cleaner and healthier. When we breathe through our mouth, air is not purified so dust goes in which can cause damage to our throat and lungs.

Hope it helped,

BioTeacher101

answer; /// i do believe its (heredity); good luck

i am going to guess that it is co2.