A one-way pneumatic delivery system includes a plurality of sending units in fluid communication with a receiving unit via a duct system. Each of the sending units and the receiving unit include a door that selectively prevents fluid communication into the duct system. When the carrier is inserted in one of the sending units, a power unit applies a vacuum to the duct system and the doors of the other sending units and of the receiving unit are sealed. The power unit both decelerates the carrier prior to its reception in the receiving unit and is configured to prevent the insertion of foreign objects into the vacuum source. A second embodiment is presented wherein the power unit is disposed in an upside-down configuration above a ceiling.