How do humidifiers work and what is the daily output of water? Are they silent?
A. There are two basic types of CPAP humidifiers: passover and heated. In the case of the passover models, air passes over the surface of the water in the humidifier and gains humidity. A passover humidifier is completely silent and actually slightly decreases the noise transmitted through the hose. The amount of water used per night is a function of the temperature and humidity of the air coming from the CPAP, the water temperature in the humidifier, the amount of air flow, and the amount of water surface area the humidifier provides. Most users will find they have used 1/4 to 1/2 cup during a night. This is usually enough to keep the airway moist and comfortable. A heated humidifier greatly improves the amount of water vapor being delivered to the user.
