It has been reported that continuous positive airway pressure therapy introduces negative nasal side-effects including sneezing, itching, nasal dryness, nasal congestion and/or a runny nose. As these symptoms are suggestive of nasal dysfunction, heated humidification is often used to fully saturate and heat the inhaled air to core body temperature. It is expected that this relieves the nasal mucosa from having to supply, or recover, heat and moisture from inspired and expired air. This review summarizes the current in vitro and in vivo knowledge relevant to nasal air-conditioning, and identifies further investigations necessary to improve our understanding the changes that occur during nasal continuous positive airway pressure therapy. Investigations into nasal airway fluid transportation, airflow regulation and heat and fluid supply may lead to a therapy temperature/pressure/humidification algorithm that optimizes these parameters for a prescribed therapy pressure. Optimization could lead to a reduction in titration pressure and improved treatment compliance.