The Cilia are tiny hairs the protect your nose (or nasal passageway) and other parts of the respiratory tract by filtering out dust and other foreign particles that try to enter your body when you breathe.
The respiratory system is also lined with a mucous membrane that acts as a secondary defense towards foreign objects that the Cilia fail to catch. Things like pollen or smoke. The Cilia and mucous act together to clear your system from foreign objects. The hairlike structures help move particles trapped in the mucous out of the nose.