An apparatus for ductlessly circulating large volumes of air in industrial facilities and the like includes an upstanding structure which defines a vertically extending chamber. Openings are provided in lower and upper portions of the structure and communicate the chamber with lower and upper strata of ambient air. A blower assembly is housed within the structure intermediate the lower and upper openings. In operation, the apparatus is positioned substantially centrally in a room, and the blower assembly is energized to move air upwardly through the chamber. The lower and upper openings are arranged such that air from the lower strata is drawn substantially radially toward the lower openings, and such that air discharging from the upper openings into the upper strata moves substantially radially outwardly toward walls of the room. The effect of this type of operation is to establish a primary substantially toroidal air flow circulation beside the apparatus, and to induce the establishment of a secondary substantially toroidal air flow circulation above the apparatus. The primary and secondary circulation torri promote a thorough intermixing of air from all parts of the room and promote temperature uniformity throughout the room. In the preferred embodiment, the apparatus is portable and its upstanding structure is provided by a stacked array of lower, intermediate and upper modules or sections. A heater assembly for selectively supplementally heating air in the chamber is preferably housed in an intermediate one of the modules or sections.