This is the cleanable version of the water chamber tub for the ResMed AirSense 10 series of CPAP, Elite, AutoSet, and AirCurve VPAP machines. For best results and to promote longer life, use distilled water and empty your tub nightly. Humidifiers are used in conjunction with CPAP (continuous positive airway pressure) devices to prevent dryness and irritation that could be caused by pressurized air. The typical water chamber tub has a life span of 3-12 months depending on proper care. Avoid using tap water which can lead to mineral build-up.