a pneumatic conveying system for particulate material . an upper vessel includes an inlet for the material . an intermediate housing is open to and located under the inlet . a primary check valve is located in the intermediate housing and will receive the material from the inlet . a lower housing is located beneath the intermediate housing . the lower housing includes a secondary check valve therein which receives the material from the primary check valve . a material exit is located below the secondary check valve . each of the check valves includes an opening through which the material may flow . this opening is oblique to vertical , and a movable closure member is connected to alternatively open or seal the opening . pressurized air is supplied to the check valves in an alternating manner . air pressure delivered through the air inlet associated with the intermediate housing causes the closure gate of the intermediate housing to close and the closure gate of the lower housing to open , thus carrying particulate material received by the intermediate housing to the lower housing and out through the exit port to a material conveying conduit . air pressure delivered through the air inlet associated with the lower housing causes the closure gate of the lower housing to close and the air stream to travel through the exit port of the lower housing , thus carrying any residual particulate material from the lower housing out through the exit port to a material conveying conduit .