As air is breathed in, it passes off through the back of the nose where dust and gases are filtered.Two tubes branch off from the windpipe and go to each lung.When you breath out(exhale), carbon dioxide is released-a natural by-product.How most creatures breath is quite similar eapect for that of birds.Technically speaking, even plants have respiration systems, but they exhale oxygen and inhale carbon dioxide.This is why plants are so important to our environment.They breathe in the harmful carbon dioxide that other mammals breath out.