302 WARMING AND VENTILATION. 



and there will be three ventilating-flues, 100 square inches in sectional 

 area, or 8^ x 12 inches. 



The vertical flues should be carried under the floor of the ground- 

 story, and joined to the first horizontal collectors intended to furnish 

 passage to the air brought by the first, and each should carry off 12 x .78= 

 9.36 cubic feet a second with a velocity of 3.28 a second. They should 



9 36 

 then have a section of -i--,=2.86 square feet, or be 1 foot 8 inches 

 o.jJ8 



square, for example. 



One of these flues, which would also ventilate the two single-bed bed- 

 rooms, or 14 X. 78=10.92 cubic feet, should have a sectional area of 



- "^ =3.34 square feet, or should be 1 foot 8 inches by 2 feet. 

 3.28 

 If these pipes do not lead directly to the foot of the chimney, and if 

 the general arrangements adopted render it necessary to carry the first 

 collecting-pipes into a second collector, the volume of air which the lat- 

 ter will be obliged to pass will be 50 x. 78=39 cubic feet, with a velocity 



39 

 of 4.6 feet a second. Its transverse section will then be equal to -7—,= 



4.0 



8.50 square feet, and it may have the dimensions 2 feet 10 inches by 2 



feet 10 inches. 



If the main ventilating-chimney should have to carry off the foul air 



of both wards, or that from 100 beds = 280,000 cubic feet an hour, or 78 



cubic feet a second, with a mean velocity of C feet a second, its internal 



78 

 sectional area should be—. =13 square feet, and its mean internal diam- 



b 



eter 4 feet. At the upper part, this diameter should be reduced to 3 feet 

 10 inches to make the velocity there (U- ii*et a second. 



91. Introduction of fresh air. — Tlio oiicnings for the introduction of 

 warm or cold air should always be plact'd near the ceiling, and distrib- 

 uted as uniformly as possible throughout the whole extent of the halls 

 in the proportion of one to every two beds if possible, or at least one to 

 every four beds. 



When they are made in the walls, they should be furnished with regis- 

 ters in the form of slats inclined 20° or 25° to the horizon in order to 

 force the air in that direction toward the ceiling. 



The transverse section of the vertical or other flues should be calcu- 

 lated so that the air will traverse them with a velocity not exceeding 3 

 or 4 feet a second. That of those through which the air flows immedi- 

 ately into the room should be determined by the condition that the 

 entering velocity should not exceed 3 or 4 feet a second. 



In the case where the air flows from above vertically downward, 

 through openings in the ceiling itself, which may take place where 

 double floors are used or where a loft serves as an air-chamber, the sum 

 of the clear sectional area of the passages should be calculated on the 

 condition that the velocity should not exceed 18 inches or 2 feet a 

 second. 



