Abstract: An elongated hollow housing is provided including air inlet means at one end, air outlet means at the other end, intermediate length air filtering panel means within the housing intermediate the air inlet means and the air outlet means, an electric motor mounted within the other end of the housing and including a rotatable output shaft portion extending toward the air inlet means end of the housing and a pair of axial flow impellers mounted on the rotary output shaft within the housing on opposite sides of the air filtering panel means. The air filtering panel means comprise separate air filtering panels mounted within the housing on opposite sides of the motor output shaft and one peripheral side wall of the housing includes a removable portion thereof registrable with the air filtering panels enabling removal and replacement of the latter through the aforementioned opening when the removable periperal side wall portion is removed.