The Trion 500 atomizing humidifier is a self contained cold steam humidifier unit. It can be attached to ductwork so it injects cold steam into the duct system or wall mounted so it blows moisture directly into the air. This second applicaton is common for humidors across the planet. The Trion 500 was replaced by the Trion 707U recently. The Trion 707U comes with a nozzle extension so it can be mounted on the backside of a wall with the nozzle protruding through the wall should you desire. Periodic maintenance on this device consists of taking it apart and cleaning it.