300 WARMING AND VENTILATION. 



sectional area for each bed ; and as it is admitted that in common hos- 

 pitals it will be sufficient to have one flue to every two beds, it will be 

 necessary to have 98 square inches sectional area, or to make the flues, 

 say, 9 inches deep by 11 inches broad. 



For lying-in hospitals the volume of air to be renewed being 3,500 

 cubic feet an hour to each bed, or 98 cubic feet a second, the sectional 

 area of the flues should be .43 square foot, or 62 square inches. 



In the first collecting-pipes, which unite the flues by groups, a mean 

 velocity of from 3 to 4 feet a second is allowed, and the sectional area 

 may be calculated on this basis and according to the number of beds 

 which it is necessary to ventilate. 



The second collecting-pipes, if any are formed to receive the vitiated 

 air from the preceding, should be proportioned by supposing a mean 

 velocity of from 4i to 5 feet a second. 



87. VentilatingcMmney. — Finally, in the main ventilatingchimney, it 

 is granted that the mean velocity should be about 6 feet a second, and 

 that in the upper part it should be at least 6^ feet a second, in order 

 not to be checked by gales. 



At the bottom of the chimney there should be an iron grate, sur- 

 rounded by a brick rim, completely isolated from the walls, in order that 

 the air coming in from the collecting-pipes may partly circulate around 

 it, and only become warmed to a moderate though sufficiently high tem- 

 perature. 



In every case, there should be arranged a direct passage opening to 

 the outside at the base of the chimney, through which the fireman may 

 feed the fire. 



If obliged to perform the work in the foul-air gallery, he would run 

 the risk of being suflbcated, or at least of experiencing much discomfort. 



The mean interior temperature of the. chimney should in all cases ex- 

 ceed that of the external air by a constant difference of 36° to 45°, in 

 order to give to the draught the same force at all times. The ventilat- 

 ing-fire should be much more energetic in summer than in winter. 



Similar methods proportioned upon the same data should be adopted 

 in cases where the arrangement of the different wards leads to the use 

 of a single ventilatingchimney for a large number of buildings. 



Means for maintaining the regularity of the fire will be given further 

 on. 



88. Cases icherc the foul air may he drawn off at the floor-level. — When 

 the general plan adopted for the building includes a veranda on one side, 

 the foul air may be drawn off at each story, to avoid the necessity of 

 making vertical flues in the walls, by placing the ventilating-chimney 

 at some point in the veranda, and carrying the ventilating-pipes into it, 

 iflacing them between the floor-beams. (Fig. 29.) 



A similar arrangement will render it easy to improve the ventilation 

 by using a part of the heat from the kitchen and bath boilers, the hos- 

 pital-stoves, smoke-flues, kitchen-ranges, &c. 



