An air diffuser device suitable for use in an air diffuser system for a centrifugal pump the pump including a pump casing with a pumping chamber therein, an impeller mounted within the pumping chamber for rotation about a rotation axis, the impeller including a front side and a rear side. The air diffuser system comprises one or more passages extending through the impeller from the front side to the rear side, the or each passage having a first opening at the rear side and a second opening at the front side of the impeller. The air diffuser device comprises a main body having a seal side and an impeller side, and at least one channel extending through the main body from the seal side to the impeller side, the or each channel having an intake opening at the seal side, a discharge opening at the impeller side, and a base wall extending through the main body, the base wall having a leading end portion at the seal side, and a trailing end portion at the impeller side, the discharge opening being in fluid communication with the first opening of the passage in the impeller when installed.