Nasal Breathing: How Air Is Conditioned Before Reaching the Lungs

Inhaled air enters the nasal cavity, where three critical processes occur:

1. Warming – Rich vascular plexus (Kiesselbach's plexus, turbinates) raises air to near body temperature.
2. Humidification – Mucosal secretions saturate air to ~100% relative humidity.
3. Filtration – Vibrissae (nose hairs) trap large particles; mucociliary blanket captures smaller particles, pathogens, and allergens, transporting them to the pharynx for swallowing.

Air composition: ~78% N₂, 21% O₂, 0.9% Ar, 0.04% CO₂. The nose processes ~10,000 L/day, protecting delicate alveolar tissue and optimizing gas exchange.