This gives the air time to heat up and become moisturized. It also gives the millions of cilia (tiny hairs) in our nasal passages time to collect all the nasty germs and particulate that might be in the air we’re breathing. This is what our lungs function optimally with—highly conditioned and clean air.
Breathing through your nose also creates negative pressure in and positive pressure out, which helps tone the soft tissue in our nasal passages and throat, pulling it back and opening the airway up even further. This guards against the muscle and soft tissue atrophy that can lead straight to obstructive sleep apnea.
On the other hand, when you open your mouth and inhale, there is no filter between what comes in and your lungs, and no negative/positive pressure being created. It’s straight‑up throat and trachea, and those are short tubes compared to the sophisticated labyrinth of your nasal cavity.
In a world where forest fires, pollution, and airborne viruses are becoming increasingly commonplace, our nose is truly our first line of defense.