An evaporative humidifier uses fans to blow air across water-moistened pads or filters. This cools down warm room air which then increases its relative humidity. On the other hand, steam appliances work by boiling water into steam through heating coils that are powered either electrically or via propane (liquefied petroleum gas). They don’t require any moisture pads because they rely on condensation of vaporized liquid particles in order to generate humidity levels.