How are `CO_2` and dust particles removed from air before subjecting air to liquefaction

How are dust particles that enter the respiratory system in the air expelled?

How is SO_2 an air pollutant?

Assertion :- Trachea is lined by ciliated epithelium. Reason :- The co-ordinated movements of cilia in the trachea help in removing dust particles and some of the foreign substances inhaled alongwith atmospheric air.