This dishwasher safe humidifier chamber is constructed of strong Lexan (polycarbonate resin thermoplastic) and has a stainless steel heat transfer plate. The chamber is easy to remove and replace and it includes built-in overfill protection which prevents humidifier water from damaging the CPAP! Along with the unique baffle design, the water chamber allows the airflow to collect more humidity. DeVilbiss designed the chamber to hold enough water for a full night's sleep. At the humidifier's highest setting, you can still expect a full 8 hours of humidification.