Heated humidification in CPAP therapy is often not enough to prevent side effects like dryness of nasal mucosa and xerostomia, especially in cases of mouth breathing or mask leakage. Additionally a higher level of humidification in lower ambient room temperature can lead to condensation and irritating noises. Compliance of affected patients decreases considerably. Regarding this, devices with humidifier and additional heated tubing are developed to automatically regulate optimal humidification and temperature right up to the mask. The efficacy of a system with controlled heated humidification and heated tubing in nasal masks under various conditions like leakage and different pressure levels is object of this study.