system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: why are we told to breathe in through your nose and out through your mouth if all the oxygen gets in your blood stream in the lungs either way? Would it not be better to just breathe in and out of your mouth for the most oxygen?
gpt
The nose warms, filters and moistens the air so that it’s ready for the lungs.

The mouth just draws in air without warming, filtering or moistening the air.

Breathing through your nose reduces the amount of dust and crud that gets in your lungs.