Two Main Lung Functions
Air-flow to the alveoli is necessary for gas exchange. The natural heating and humidifying functions of the airway assist with maintaining clear and patent airways by promoting mucociliary clearance and reducing bronchoconstriction associated with airway cooling.
Primary mechanical defense mechanisms are sneezing, coughing, gagging and the use of natural filters, i.e. nasal hairs. The second line of defense is the mucociliary transport system which traps and neutralizes inhaled contaminants (in mucus) and transports them up and out of the airway, keeping the lung free from infection-causing pathogens. This critical defense system is very sensitive to humidity.
Humidity is also crucial to mucociliary health.