Abstract: An air flow producer of non-rectangular shape is adapted for installation in a rectangular opening of a drop ceiling. In preferred form, the producer has a circular housing with an open bottom covered with a grill. A fan with a rotary blade assembly is mounted in the housing to produce a downward air flow, and a circular metal band surrounding the rotary blade assembly defines an air discharge zone centered in the grill and an annular air intake zone surrounding the discharge zone. Flow rates are optimized by positioning the band close to the grill. The grill is preferably integrally molded with a rectangular flange that seats in the drop ceiling opening. The flange supports the housing from the framework and closes the opening to prevent the producer from drawing air from the plenum above the drop ceiling.