Abstract: An air exhaust box, for mounting in an exterior building wall and connecting to at least one exhaust duct, includes: a housing having side walls, a rear wall and a front exhaust opening; the front opening having a mounting flange surrounding a periphery of the opening and extending outwardly from the side walls; the rear wall having an inlet opening greater than a predetermined maximum dimension; each of the side walls being joined to the rear wall at an angle less than 90 degrees; and a duct adapter having a cover removably mountable to the rear wall with removable fasteners, the cover having an outer dimension larger than said maximum dimension of the inlet opening and a rearwardly projecting duct sleeve with an inner opening of size between said maximum dimension and a minimum dimension.

Abstract: A recessed fan inlet cover, for covering an enclosure inlet opening of an exhaust fan enclosure to provide an air flow channel into the fan enclosure while impeding sound emission from the fan enclosure, the fan inlet cover comprising: a cover frame having an outer peripheral edge extending outward of the enclosure inlet opening and having an inner edge defining a substantially planar frame surface, the frame having an upwardly recessed mounting surface joined to the inner edge with an arcuate wall, the mounting surface having an intake opening; and a cover plug mounted to the recessed mounting surface downwardly spaced from the mounting surface, the plug having a substantially planar plug surface co-planar with said frame surface, the plug having an outer peripheral edge with an inwardly projecting lip, the plug having a sound absorbing layer on an upper surface opposite said planar plug surface; wherein an air flow channel is defined between said arcuate wall and said lip.