The nasal cavity has the functions of breathing, filtering dust, regulating negative pressure in the chest, heating and humidifying the air, and smelling, as follows: 1. Breathing: The nasal cavity is connected to the outside world, and the outside air is inhaled through the nasal cavity into the lungs and trachea. 3, regulate the negative pressure in the chest: to facilitate the exchange of air in the lungs, mainly the nasal resistance in the nasal cavity to play a role. 4, heating and humidification of the air: the nasal cavity has more mucous membrane and submucosa blood vessels, the air can play the function of humidification, heating, especially in winter, heating function has a very good effect, if the nasal cavity is blocked, the loss of humidification If the nasal cavity is blocked, the humidifying function is lost and the air goes in directly from the mouth, which can easily lead to throat discomfort.5. Sense of smell: the nasal olfactory area can smell the odor in the air, and if there is a lesion in the olfactory area, this function may disappear.