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room. If there are several outlet tubes in a room they should all commence at the same distance from the floor, be of the same height (or the discharge will be unequal), and have the same exposure to the sun and wind.
Simple ridge openings may be used in one-story buildings with slanting roofs; they ventilate thoroughly, but snow sometimes drifts in. The discharge of outlets is much more certain and constant if the air be warmed. The chimney with open fire is an excellent outlet-So good that in dwelling-houses if there are proper inlets, no other outlet need be made. Every room and dwelling-house should have an open fire-place. When rooms are large and more crowded, other outlets are needed. The heat of the fire in such rooms may be utilized by surrounding the smoke flues with foulair shafts.
Plans of Pipes.-Of the various plans proposed for air-tubes and shafts, Dr. Parkes recommends McKinnell's circular tube. *
See Figs. 1 and 2. It consists of two cylinders, one encircling the other, the area of the inner tube and encircling tube being equal. The inner one is the outlet tube; it is so because the case of the other tube maintains the temperature of the air in it; and it is also always made rather higher than the other; above it should be protected by a revolving cowl. The outer cylinder, or ring, is the inlet tube; the air is taken at a lower level than the top of the outlet tube; when it enters the
room it is thrown up toward the ceilFig. 1.
ing, and then to the walls by a flange
placed at the bottom of the inner tube; the air then passes from the walls along the floor toward the centre of the room and upward to the outlet shaft. Both tubes can be arranged to
close by valves. If there is a fire in the room both tubes may become inlet tubes ; to prevent this the outlet tube should be closed. The movement of air by this plan is imperceptible and it is an admirable plan for square rooms or small churches ; for long halls it is less adapted. The tubes may be of any size, from six inches for ordinary living rooms, to seven or eight feet, for churches. The two tubes after passing out of the room may be carried in different directions, care being taken that the inner tube is the largest. An advan
tage would be gained if the two tubes Fig. 2.
could be kept together some distance, as the hot air of the inner tube would , transmit heat to the incoming air, or that it would enter the room at a higher temperature than it otherwise would.
Ventilation by the open fire place is admirably illustrated by Burn in his little work on “Sanitary Science," page 82.
The withdrawal of pure air is illustrated by Fig. 3 copied from Mr. Burn's work. An opening is made at a in the breast of the chimney b of the fireplace c.
Fig. 4 shows the ordinary kind of ventilation carried on in which there is a fire-place a. The currents are mostly drawn by this along the floor from the door b as shown by arrow c. The arrows d e indicate the currents from windows in close proximity to the fireplace, but the air lying near the ceiling, as at f f and g, is rarely influenced by the draught of a fire-place a even when there is an opening in the breast as at a in Fig. 3.
Probably the best plan of ventilation by open fire-places is that known as the Galton, a description of which was given by our Secretary in his
last report, and which is here reproduced :
Vertical section through chimneys
These grates are built into the chimney (Fig. 5)—this is a very delicate job and requires an expert in the building of fireplaces and chimneys—and are of iron, but have a lining of fire-clay. From the throat of this grate an iron pipe rises some ten feet, (just above the ceiling C), terminating in a flue, which runs the remainder of the chimney, and should terminate in a cap.
The air admitted from the outside at the base of structure A, is warmed by contact with the heated sides and back F of the grate, then after being still further heated by surrounding the iron pipe in its ascent, is delivered into the ward from a lowered opening or register R, placed just beneath the ceiling C. The opening at A should be carried to the outer air by a pipe or flue.
Edward Smith, a member of the Royal College of Physicians, in his standard work on Foods gives the following general directions for ventiiation:
Ist. Inhabited rooms should if possible have external walls on two sides, so that air may be admitted through both.
2d. The openings should be small and many, rather than few and large, defend
ed by perforated zinc, and placed as disFig. 5.
tant as possible from those who inhabit the room. Hence the cornice above and the skirting below are convenient protections, but rooms of less than ten feet in height are not easily ventilated without draughts. The connection between the inside and outside of the room should not be direct, but at an angle so that a direct current may not be produced.
3d. Such ventilations as direct the current to the ceiling are useful in a degree, but the cold air thus admitted will descend before the air is warmed.
4th. Channels which are divided by a perpendicular diaphragm on the theory that there will be an ascending current in one and a descending current in the other, are for the most part based on a fallacy, and when the heat of the air is very great there will be an upward and downward current in both.
5th. An air flue by the side of the chimney flue, into which the exit tubes lead, will act in some degree so long as there is fire in the chimney to rarify the air ; but if archimedean screw can be placed at the top of such a flue, it will produce an upward current when there is no fire, provided there is wind to move it. This apparatus may be attached to any air flue placed in any position.
6th. The use of the chimney flue as an exit for the air is liable to allow the
smoke to enter the room through it when there is a down draught, notwithstanding the excellent contrivances which have been devised to prevent the return current.
7th. Whenever it is proposed to renew air, means for supplying a larger quantity of air should be provided, or the attempt at ventilation will be ineffectual.
8th. It is often desirable to warm as much of the air which is admitted as possible, and for that purpose stoves have been designed with an exit from a special channel into the room.
The idea advanced in the last rule of Dr. Smith may be carried out by placing the stove or heating apparatus in the cellar, or one room of the cellar. By this method the warmed air may be carried through every room in the building to the roof, where it makes its exit through a cowled flue.
Dr. John S. Billings, of the United States Army, says, in his work on Heating and Ventilation : "For an ordinary room in a dwelling-house which is to be heated by indirect radiation--that is by warm air, it will be necessary in order to secure satisfactory warming, when the temperature of the external air is below the freezing point and the room has the usual proportion of external wall and window surface, that the amount of air supply shall be about one and one-half times the cubic contents of the room. I would advise that heating surface, foul and fresh air flues and registers, be provided for an air supply of one cubic foot per second per head for rooms which are to be occupied constantly."
F. Schumann, civil engineer of the U.S. Treasury, in his Manual on Heating and Ventiation, says: "Currents in ventilated rooms are either directed upward or downward ; in the upward direction the pure air is admitted at or near the fioor, the impure air passing off at or near the ceiling; in the downward direction the pure air is admitted at or near the ceiling or through inlets through the wall near the floor, and the impure air passing off through the floor or openings in the walls near the floor." "Public places where large crowds assemble should have the upward direction. Smaller rooms, offices, dwellings, etc., may be ventilated downward." The pure air inlets should be distributed equally around the room, with the outlets for impure air in such position as to cause the currents to sweep the entire room, being careful not to place an outlet directly over an inlet.
"In the upward movement the inlets may be in the floor, in risers of platforms, sides of walls near the floor. In stationary desks in front of stationery benches etc., the outlets may be in the cornice or ceiling, or sides of walls near the ceiling. This method requires no change with seasons, the fresh air entering the same way in summer that it does in winter, when the room is heated.
"In the downward movement on the other hand the fresh air in summer may be admitted at or near the floor and passed off near the ceiling. Where windows are available and so placed that currents pass through the room no other provision need be made for summer ventilation."
Velocity of currents per second.-When entering at or near the ceiling, and not less than twelve feet above the floor, and descending 1.8 feet; when the openings are the same as above and horizontal 4.0 feet; when entirely at or near the floor, (maximum) 2.0 feet; in ducts, shafts, etc., 3 to 10.0 feet.
“In cold weather, when the temperature of a room is higher than the external air, the air should be admitted
at the bottom and passed off at the top Ceiling Fresh Air | Fcul Air
of a room ; in warm weather, when the
temperature of the room is lower than External! Room
the external air, the pure air should Air warmer
come in at the top and pass off at the
bottom of the room.
"The movement as shown in figure 6, can be reversed by either the vacu
um or plenum method (heat or fan), Fig. 6. The arrows show the direction of currents. when desirable, but they should coin
cide with and assist nature (grayKEL
ity) it being more economical where ventilation is required. The vacuum movement is represented by figure 7, which represents a section through a building showing downward and upward movement of air cur
A room to contain not more than from 15 to 2 per cent. of vitiated air must be supplied with from 5.6 to 49 times more fresh air than is vitiated plus that quantity required for illuminating purpose,
An adult man vitiates per hour............................215 cubic feet. Every cubic foot of gas burned. ................. 8.5 cubic feet. Every pound of oil burned..................................... 150 cubic feet. Every pound of candles (6 to a pound).................. 160 cubic feet.
The sources of heat in units in rooms per hour are:
By an adult..
600 15,000 to 18,000
2,400 430 to 515 454 to 545
In order to give a better idea of proper methods of heating and ventilation of a dwelling, for heating is inseparably connected with ventilation, I would recommend the publication of the plans of a dwelling house, as