Abstract: A ventilator for supplying breathable gas to a patient includes an external housing; an internal housing suspended within; a gas flow generator within said internal housing; a gas inlet conduit extending between a first gas inlet opening in said external housing and a second gas inlet opening in said internal housing, and a gas outlet conduit extending from a first gas outlet opening in the internal housing via a second gas outlet opening in the external housing and to a patient interface means adapted for introducing the breathable gas into the airway of said patient. One or both of the gas inlet and outlet conduits exhibit a first substantially rigid conduit section and a second membrane conduit section with a membrane wall portion separating a volume of breathable gas within the gas inlet conduit and/or gas outlet conduit from a volume of ambient air within the external housing.