Abstract: Means for venting the interior of the developer housing in a xerographic type copying or printing machine to control pressures therein comprising, a cover sealingly attached over a portion of the developer housing exterior and cooperative therewith to form an elongated relatively shallow exhaust chamber substantially coextensive with the developer housing, an exhaust port in the developer housing adjacent each end communicating the interior of the developer housing with the exhaust chamber, a discharge opening in the cover adjacent the center thereof, and filter means for trapping toner in the discharge opening; pressure air from the interior of the developer housing discharging through the exhaust ports and exhaust chamber to the discharge opening and the exterior, the sharp bends imposed on the air stream passing into, through, and out of the exhaust chamber causing toner entrained with the air stream to be separated from the air stream and deposited within the chamber for later removal.