An enclosure having a base with a chamber for holding water, right and left side panels, front and rear frames for supporting grilles or other air passages, and a top panel. At least the base, the side panels and the top panel are blow molded as separate components each having an exterior wall and an interior wall, each wall having a contour which differs from that of the other wall, each wall having an inner surface and an outer surface, and each wall connected at its periphery to the other wall.