The Aprilaire 800 humidifier requires regular maintenance consisting of replacing the steam canister as it scales up with mineral deposits from your water supply. The Aprilaire Model 800 Steam Humidifier is a self-contained device that takes tap water and boils it, using electrode technology, to create steam. The humidifier generates steam by energizing two electrodes that extend into a canister of water. Current flowing between the electrodes causes the water to boil, creating steam. The steam flows through a steam hose and is injected into a moving airstream by the way of a distribution tube. The steam flows out of the distribution tube into the duct work through a series of small tubelets which create an even, drip-free transfer of steam into the moving airstream.