[The respiratory system--its self-cleaning system. General mechanisms of clearance]

The behaviour of particles and deposition in different parts of respiratory system are described. Listed are factors which contribute to the deposition of particles in the lungs and upper areas of the respiratory system. The general mechanisms of lung clearance and their action such as cough, mucociliary transport, alveolar clearance and immunological system are reported. Particularly is stressed the necessity of coordination of all defense mechanisms in order to maintain normal respiratory function.