Apparatus for generating a supply of air at positive pressure for the amelioration or treatment of a respiratory disorder includes a first chamber, a second chamber, at least one inlet tube structured and configured to allow ambient air to enter the first chamber, at least one flow tube structured and configured to allow air to pass from the first chamber to the second chamber, and a blower structured and configured to produce a flow of air at positive pressure. The blower is positioned in the first chamber and structured and configured to receive air from the second chamber. The blower includes a housing structured and configured to sealingly separate air flow through an interior of the housing from the first chamber. The at least one inlet tube is axially spaced from the at least one flow tube.