the perforated floor of the grain storage chamber of a grain tower fans propel air from outside the grain tower into such air chambers the fans are contained within the tower at bulkheads which divide ones of the air chambers each into a relatively larger air distribution chamber and a relatively smaller air intake chamber the distribution chamber communicates through the perforations in the perforate floor to aerate grain within the grain compartment the intake chamber is partly bounded by a portion of the peripheral wall of the tower the fans draw outside air through limited openings in the tower peripheral wall into such intake chambers application_number US 6495779 A description fig1 discloses the lower portion of a grain tower 10 embodying the invention grain towers are normally tall circular cross section cylindrical structures diameters ranging from 20 feet to 72 feet and heights to 100 feet or more are common conventionally construction is of reinforced concrete cast in place in fig1 tower 10 includes a circular base slab 12 of heavy for example 27 inches thick reinforced concrete supported on the ground the cylindrical reinforced concrete peripheral wall 13 of the tower 10 extends upward from base slab 12 and carries a conventional roof structure not shown closing the top of the tower suitable hatchways or the like not shown are conventionally provided in or adjacent such roof for adding grain to the tower in the preferred embodiment shown a grain aeration.