how much argon do we breathe
Vote for this answer. I'd assume that the amount of each element we breathe in would be similar to the amount in which they are present in our atmosphere, which would mean 78% of it is nitrogen, 21% is oxygen, 0.9% is argon, and so on... When we exhale, however, we probably let out a lot less molecular oxygen and a lot more carbon dioxide (in the form of carbon + oxygen).