NATURAL HISTORY BUILDING 95 



openings are uniformly 12 inches across, the size of the outlets where 

 they join the duct decreases in the direction of the fan, in order to 

 effect an approximate uniformity of outflow of air from all parts of 

 the room. Each branch is also provided with a damper. The main 

 duct leaves the room at its northwest corner, crosses the ceiling of the 

 adjoining corridor alongside one of the large girders, and enters a 

 flue back of the west freight elevator, in which, at this point, there 

 is a 2- foot Sturtevant full-housed blower fan, operated by a 1|- horse 

 power motor. The discharge passes up the flue, which measures 

 approximately 2 by 4 feet, and escapes through a ventilator at the 

 roof. By this arrangement the entire body of air in the room may 

 be changed every 47 minutes. 



Toilet rooms. — The general toilet rooms are all ventilated by means 

 of separate fans. Each of the public rooms in the ground story near 

 the north entrance has a flue connected to the space back of the closets, 

 giving direct ventilation from each of them, and a register for room 

 ventilation on the wall near the ceiling, both uniting in a vertical 

 flue leading to the attic space above. Here, on each side, a small 

 full-housed American Blower fan driven by a ^ horse power motor 

 discharges the air through an Emerson ventilator in the roof. The 

 two rooms in the third story of the middle wing near the rotunda are 

 similarly ventilated by fans of the same size and character, located 

 immediately over each toilet, but the air, instead of passing directly 

 through the roof, is discharged into the exhaust spaces of the attics 

 of the east and west wings. The two rooms in the ground story of 

 the east and west wings are each adjacent to one of the flues in the 

 wall structure surrounding the rotunda. The fans are at the base of 

 these flues, but, as the flues are cut off by diaphragms at the first 

 floor level, the discharge is provided for by means of 15-inch galvan- 

 ized iron ducts which run to the roof and terminate in Emerson 

 ventilators. 



Enghie and hoiler rooms. — For the ventilation of the engine room 

 there are two 3-foot Blackman fans located in a galvanized iron duct, 

 4 feet 6 inches square, near the ceiling of the reserve coal vault at 

 the east entrance and discharging through a grilled opening in the 

 window between the two doors. The air is drawn over the top of the 

 boilers through a duct at the ceiling of the adjoining corridor, meas- 

 uring there 10 by 2 feet but changing in general form though not 

 in capacity inside of the boiler room. Between and above the boilers 

 a galvanized iron partition with a door opening into the engine room 

 prevents the removal of any air from the boiler room itself, except 

 through an opening in the side of the duct controlled by a damper. 

 This arrangement gives positive ventilation to the engine room by 

 withdrawing the air from the top of the boilers after it has entered 

 the extreme western end of the room. Further aid to the ventilation 



