criteria were received in November 1949, requesting the ventilation of the communications buildings (Station No. 69 on Runit, Aomon, and Engebi), The equipment and materials used in design of the ventilating systems for these stations were high quality, standard design products, with the exception of special wall fittings designed to fit particular buildings. The ventilation of Station 69 was accomplished by mounting a centrifugal fan complete with weatherproofed hood and fungusproof and moistureproof motor outside the station, and blowing air into the metal ducts, All supply and exhaust ducts that penetrated the concrete walls were flanges; cast iron wall fittings were supplied with blind flanges so that the stations could be sealed before test. The exhaust ducts consisted of lightweight steel pipe terminated above the earth fill over the station in a welded 180° long radius ell. Ventilation systems for Stations 54, 55, and 57 on Runit and Engebi and station 56 on Aomon were designed similar to those stations described above except that the duct work did not penetrate the concrete walls of the stations, The duct work located inside the station was connected to the supply fan mounted outside, with a removable, flexible, metal air tube that could be connected only when the door of the station was open, Preliminary design for the ventilating system of Stations 30la through k was started in March 1950 to determine the amount of ventilation required to maintain a maximum temperature of 120°F in the stations for a period of 20 seconds after the ventilating system was out of operation, As a result of a conference with representatives of Sandia Corporation in April 1950, it was decided that the ventilation would be maintained as long as possible from the available power supply. this conference, the following ventilation system was designed: After _ An industrial type centrifugal blower with fungusproof moistureprcof, motor and weatherproof cover was mounted on the roof of each station, Filtered air was supplied through welded, light wall steel pipe into the station, The exhaust duct was constructed of similar material, Flanged cast iron wall fittings were used where the supply and exhaust ducts penetrated the concrete walls. Each station had two solenoidoperated butterfly valves, one on the air supply and one on the exhaust, The solenoids were actuated to close the valves at H-hour minus 5 seconds, The valves were constructed of cast iron suitable for high humidity salt air at atmospheric temperature, The maximum leakage specified was not to exceed one-half of one percent. The exhaust systems for removal of sulphuric acid fumes from Stations 23a, on Engebi, Aomon, and Runit; Station 23b on Engebi, and Station 25 on Engebi were designed for standard equipment, except the fan, which was provided with an explosionproof motor and nonsparking wheel, Inside the station, a removable section of duct work was provided adjacent to the wall fitting to allow installation of the blind flange before experiment time, 5-261