Never. The nasal cavity warms, moistens, and filters the air before it enters the lungs. It also produces nitric oxide, an important gas for the body [1]. The m

Never. The nasal cavity warms, moistens, and filters the air before it enters the lungs. It also produces nitric oxide, an important gas for the body [1]. The mouth does none of these things. [1] https://en.wikipedia.org/wiki/Biological_functions_of_nitric_oxide https://en.wikipedia.org/wiki/Biological_functions_of_nitric...