portions 94 and a pair of vertical reinforcing portions 96 top and bottom side walls 98 and 100 and left and right side walls 102 and 104 for purposes later described a mounting tab 106 having a circular opening 108 formed therethrough projects upwardly from the top housing wall 98 adjacent its rear side edge additionally a spaced pair of tabs 110 project downwardly from the bottom housing wall 100 adjacent its rear side edge according to an important feature of the present invention the upper fan assembly 40 also includes a pair of uniquely configured vibration isolation members 112 and 114 which as viewed in fig3 have vertically elongated configurations each of the vibration isolation members 112 114 is preferably molded from a suitable elastomeric material such as rubber or neoprene and includes upper and lower pocketed sections 116 118 which are interconnected by an elongated joining strip 120 each of the upper and lower sections 116 118 has a pair of generally triangularly shaped front and rear side walls 122 and 124 joined to the opposite side edges of a pair of perpendicular horizontal and vertical side walls 126 and 128 the four walls of each of the upper and lower sections 116 118 define therein a pocket 130 which with the upper fan assembly components is their illustrative fig3 orientations open outwardly toward one of the corner portions 70 72 74 76 of the fan frame 64 the vibration isolation members 112 114 are installed on the fan frame 64 simply by moving them inwardly toward the fan frame as indicated by the arrows 132 in fig3 to snugly position each of the.