Yes, it is perfectly safe to use a ResMed AirSense or other CPAP machines without water in the humidifier chamber, but it may be less comfortable. The water is only there to provide heated humidification to prevent your nose and throat from drying out. If you choose not to use water, you should ideally turn the "Humidity Level" to "Off" in the settings menu to prevent the heating plate from warming up unnecessarily, which can sometimes cause a faint "burning" smell or wear down the empty plastic tub over time. Many travelers in 2026 prefer using their CPAP without water to avoid the hassle of finding distilled water or to prevent spills during transport. However, if you live in a very dry climate or wake up with a "dry mouth" or nosebleeds, you will likely find the therapy much more effective with the humidifier active. The machine itself will continue to deliver the prescribed air pressure safely regardless of the water level.