The Stadler Form humidifiers use different techniques. The Oskar humidifier uses cold water and the Fred humidifier uses hot steam. When choosing the one for you, make sure that the type of Stadler Form humidifier fits your situation. For example, a steam humidifier isn't a good choice if you have small children or pets running around. In addition, it's important that the Stadler humidifier is powerful enough to humidify the room.