WARMING AND VENTILATION. 325 



winter to a temperature of about 68°. The doors of adjoining boxes 

 being usually contiguous, it will be well to place a hot-air opening in 

 tlie corridors before each pair of doors, so that during the momentary 

 opening of one of these doors warm air may enter into the correspond- 

 ing box. The same plan may be carried out by each door in the pas- 

 sage-way ; but it is necessary that these hot-air openings be placed in 

 vertical planes, and not at the floor-level. The passage-ways should 

 have two doors opening outward and inward, and between them should 

 be a hot-air opening. 



126. Removal of foul air. — This air should be drawn out of the room 

 by veutilating-openings at the back of the boxes or galleries, or in the 

 risers of the amphitheater. The clear surface of these openings should 

 be calculated on the condition that the air shall enter with a velocity of 

 28 or 30 inches a second. 



Each box or each pair of adjoining boxes of the same tier should have 

 a special ventilating-pipe. The section of these pipes should be calcu- 

 lated on the condition that the air drawn out should have a velocity of 

 3 feet a second. For the first, second, and third galleries, these pipes 

 should be carried to the ventilator above the chandelier. 



For the parquet, the orchestra, and the lower boxes, and, if possible, for 

 the first gallery, the foul-air pipes should descend. In the parquet and 

 the orchestra, gratings arranged around the whole lower circumference 

 of the partitions, together with other openings placed on top or on the 

 sides of pipes carried along by the feet of the seats, will serve to direct 

 the foul air in an interjoist placed under the floor. This interjoist, made 

 high enough to be cleaned, should be divided in large theaters into two 

 parts by a longitudinal division in the mean plane of the edifice. 



Each of these parts should communicate with a separate veutilating- 

 chimney, of which the opening should be either in the basement or at 

 the height of the floor of the passage-ways in the parquet. 



In no case should the ventilating-openings be placed at the floor-level, 

 as has nevertheless been done at the Lyric Theater. 



The foul air drawn ofl' from the lower boxes and the first gallery 

 should likewise be carried underneath by means of special pipes, after- 

 w^ard united in collecting-pipes terminating at the base of the chimneys 

 just referred to. 



The dimensions of these pipes should be determined on the condition 

 that the velocity in them should be from 3 to 4 feet a second. 



In small theaters, a single chimney will usually suffice for all the gal- 

 leries. The calculation of the dimensions to be given to the foul-air 

 openings should be made for each gallery separately, from the corre- 

 sponding number of spectators. 



The cast-iron smoke-pipes of the heaters should be carried into the 

 ventilating-chimneys, keeping them separate throughout their whole 

 height ; and at the lower part of the chimney a grate should be placed, 

 to be used whenever required, to increase the draught, especially in sum- 



