Excerpts from the report Preface: This report extends and brings up to date the information in Marketing Research Report No. 178, "Aeration of Grain in Commercial Storages," published in September 1957. The main purpose of this revision is to present new information obtained from research studies and industry experience since September 1957. Major revisions were made in the sections on ducts for flat storages to present information relating to designs of duct systems for the large, peak-loaded flat storages now in use. Some revisions were made in the recommended allowable air velocities within ducts and in the fan horsepower and static pressure charts. Additional examples of steps in designing aeration systems and some new illustrations were also added. This publication covers: (1) The design, selection of equipment, and installation of grain aeration systems; (2) the operation of such systems; (3) ownership and operating costs; and (4) examples of installations.