AAON, Inc. designs, manufactures and sells semi-custom heating, ventilation and air conditioning equipment for commercial and residential use. Its products include rooftop units, chillers, packaged outdoor mechanical rooms, air handling units, makeup air units, energy recovery units, condensing units, geothermal heat pumps, self-contained units and coils. The company was founded by Norman H. Asbjornson on August 18, 1987 and is headquartered in Tulsa, OK.