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pensire to place hot-water receivers in the form of a drum, or of pipes such as are often used in heaters, into which hot-water pipes should be tapped, and then carried vertically in the foul-air flue leading from the rooms, thus securing a change of air at all times and without expense.
In this way, also, baths might be supplied, which would be of great service for soldiers' hospitals. Ventilation being, as has been said, much more important at night, when all the men of one mess are together, than during the day, when most of them are out of doors, the registers
-the regulation of which should only be made by the order and under the direction of the adjutant of the week—will serve to check or prevent escape of air during the day, so as to accumulate heat in the flues for the night.
HOSPITALS. 82. General plans and dimensions to be adopted for the ventilation of hospitals. It is only proposed in what follows to give the proportions of the principal parts of the flues and pipes which it is necessary to use for the ventilation of hospital-wards, in order to secure the removal of vitiated air and the introduction of fresh air.
These proportions apply also to the different plans which local condi. tions may cause the architect to adopt.
The amount of air to be renewed in the sick-rooms may vary, according to circumstances, from 2,000 to more than 3,500 cubic feet an hour for each bed; 2,800 will here be taken as a basis for the calculations.
When local conditions permit, the foul air should be drawn off through descending passages; openings into them being made behind the head of the beds, at the floor-level, but in the vertical walls, to be in number at least equal to one for every two beds in ordinary hospitals, and one to each bed in lying-in hospitals.
When a hot-water heating-apparatus is used, and when the plans adopted as well as the proximity of chimneys permit, the waste heat from the small heaters and hot water tanks used in the hospital should be made use of to assist the draught.
But it is not necessary that the use of these little reservoirs, which have but a small capacity, should lead to the exclusive adoption of the up-cast draught, as L. Davoir has done, and which is less advantageous.
83. Advantages of the down-cast draught.-It will be remembered that the arrangements required by the down-cast draught lessen very much the weakening of the walls by the passage of ventilating-flues.
Thus, for a building with rooms on three floors, as in the case of Lariboisière Hospital, the piers of the third story are not pierced for any flue, because their own commences at the floor; those of the second story are only pierced by a single flue coming from the third floor; and those of the ground floor only contain the two flues belonging to the second and third stories.
The thickness of the walls being greater at the lower stories, the flues would always be proportionally less injurious with descending draughts
than with ascending draughts, the latter requiring the largest number of flues to be made in the upper stories, where the walls are thinnest.
Figs. 27, 28, which represent only the general features, show the ad
vantages presented by down-cast draughts over up-cast draughts as regards the weakening of the walls by the ventilating-flues. The downdraught, besides, as we have said, renders it easy, in order to give due force to the draught, to make use of the entire height of the main ventilating-chimney, to the bottom of which the flues are connected. It forms a very economical means of utilizing the heat expended in producing it.
For a building of a construction similar to that of Lariboisière Hospital, where the piers at the ground floor have a mean width of 10 feet and a thickness of 2 feet 7 inches, or 26 square feet of sectional area, if the two flues are carried from the second and third stories to the base. ment, they require, at most, in the walls—including the partition between them and even the interior brick lining—a space 2x1' +1"=2' 1" broad, and 9"+2"=11" deep, or a total sectional area of 1.9 square feet; that. is to say, one-fourteenth of the total sectional area of the pier, which could
not have any effect on the stability of a well-constructed building with a good foundation.
On the contrary, if the ventilating flues be carried upward, the piers of the third floor, wbich are only 10 feet by 2 feet=20 square feet in sectional area, would be pierced by three flues, making a channel 3x1'+3" =3' 3" broad, by 11" deep, or 2' 9" sectional area, equal to one-seventh that of the masonry. This would not be admissible.
In cases where the flues for the introduction of fresh air have also to be provided for in the piers, though this can sometimes be avoided in hospitals the wards of which contain only twelve or fourteen beds, it will be seen, then, that the en feebling of the walls by the passage of all the flues will not endanger the solidity of properly-built walls.
84. Cases where the walls have not sufficient thickness.—When the nature of the materials used or local circumstances do not permit of giving the walls sufficient thickness to allow of cutting flues in them with safety, ventilating-shafts may be made projecting from the walls in the interior of the rooms, making them of light brick work. Then, to diminish as little as possible the available breadth of these rooms, and to prevent hurting their appearance, the depth of these flues should be restricted by making them occupy almost the entire breadth of the piers.
85. Arrangement of the ventilating shafts.—The necessary arrangements should be made to prevent ventilating shafts or flues from being crossed by the beams or joists of the floor, which can easily be avoided by the use of trimmers.
If there are no cellars under the buildings, which is not indispensable, sufficiently large vaults should be made to give the necessary area of passage-ways, and these should be covered on top, as well as the floor of the first story, with a coating of tar.concrete, to protect it from moisture. Ifany difficulty be encountered in carrying the ventilating-fues below the floor of the first story, they may stop at this floor. It is only in exceptional cases, or in buildings already constructed presenting peculiar obstacles, that the flues should be carried from below upward in the upper floors or in the roof.
In every case, the discharge-fues corresponding to beds placed on different floors one above another, should be kept separate in their vertical course and not united in groups in partial horizontal conductors, unless separated by partitions for an extent of 10 or 12 feet beyond the outlet of those which are the nearest to the main ventilating-chimney, in order to prevent as far as possible the establishment of communications from one story to another.
86. Dimensions of ventilating-flues and collecting pipes.—The sectional area to be given to the first ventilating-passages should be calculated on
2800_78 the basis of the renewal of 2,800 cubic feet of air an hour, or = .78 cubic foot a second for each bed, and at a mean velocity of 2.3 feet a second, which would give 19 = .34 square foot, or 49 square inches of
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 41 to 5 feet a second.
87. Ventilating-chimney.-Finally, in the main ventilating.chimney, 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, surrounded 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 temperature.
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 suffocated, or at least of experiencing much discomfort.
The mean interior temperature of the chimney should in all cases exceed that of the external air by a constant difference of 360 to 450, in order to give to the draught the same force at all times. The ventilating-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 ventilating-chimney for a large number of buildings.
Means for maintaining the regularity of the fire will be given further on.
88. Cases where the foul air may be 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, placing them between the floor-beams. (Fig. 29.)
A similar arrangement will render it easy to improve the rentilation by using a part of the heat from the kitchen and bath boilers, the hospital-stoves, smoke-flues, kitchen-ranges, &c.
In such a case, each ward would have a main ventilating.chimney carrying off the foul air from each story in flues separated from each
other as far as to the top of the upper story. At the bottom of each of the col.
lecting-flues may be kept a little auxilFIG. 29
iary heater, to be used only when neces. sary in order to obtain a sufficiently powerful draught.
It should also be understood that in every case the interior surface of the flues should be covered with as smooth a coating as possible, to diminish the resistance to the motion of the air, and that the openings should be arranged so as to permit of cleaning the flues at least twice a year, in order to remove the cob. webs and other obstacles which would interfere with the circulation of air.
In general, it would be well to place on top of the ventilating-chimney a cowl, which the wind would keep with its mouth away from the wind, so that strong winds would assist the draught, instead of checking it, as they would do without this precaution.
The proportions and the general arrangements which bave been indicated should also be observed when it becomes necessary to draw off the foul air either at the level of the floors, as just mentioned, or at the top of the buildings, as
will often occur, especially in the case of existing buildings.
Whenever local conditions permit, the smoke-flues of the heating-ap. paratus should be carried up in the main ventilating.chimney, in order to use the heat they give out. They should be made of cast iron and kept separate.
89. Utilization of the waste heat of laundries and kitchens.—The furnaces of the laundry-boilers should, if possible, be placed at the base of the ventilating-chimney, in order to assist the ventilation by means of the heat given out in the furnaces by the gaseous products of combustion.
90. Application of the preceding rules.—Let us take the case of a hospital of 100 beds, containing two wards, with but one ventilating-chimney, hav. ing two stories, containing together 50 beds in each ward there being four halls with 12 beds, and two rooms with one bed each. Under ibese conditions, each ball will contain six beds on each side,