The air outlet port uses a one way valve so water does not enter the machine.
Compatible Hose Options: the humidifier is compatible with a standard 22mm hose, slim 15mm hose or a slim 15mm heated hose. Dry Box Technology: when used with the DreamStation machine, dry box technology works to reduce the chance of water damage by trapping water in the unit walls so it does not reach the machine and humidifier connection.