Humidification adds moisture to the CPAP air, reducing irritation to the nasal passages caused by the increased airflow.
CPAP air is an irritant - to one degree or another - to everyone. In some cases the irritation dries out the nasal passages and may cause bleeding. It may also cause swelling, excess mucous, congestion or sneezing. The irritation may create a very fertile ground for infections to begin. The irritation may be cumulative, building up over time. The only way to reduce the irritation is to add moisture.
Humidification is therefore a critical part of CPAP Therapy.