Examines air flow into air-conditioned buildings caused by opened external doors in summer. Firstly the wind velocity through open doorways was measured using puffs of smoke inentrance hallways, finding that velocities varied from 104 ft/min to 350 ft/min with a mean of 265 ft/mins. Then tests were made on the air inflow when a swing door was opened and closed. Finally tests were made of the air flow due to operating revolving doors. Results for various types of entrances are displayed in a table.