The best air filter in this world is the human nose. Human nostrils are lined up with hair responsible for blocking germs and dust. Grooves in the nasal cavity make air swirl like stream currents. This is when the inhaled hair is moistened and warmed so that the sensitive tissues of the lungs can be protected. It is during this filtration process that the mucus lining of the nasal cavity captures cold viruses and pollen which cannot be stopped by hair in the nostrils.