A good and simple test for impure air is to take a clear glass bottle with a glass stopper, holding about 10 oz., and wipe it carefully inside and out. On entering a room, the air of which you wish to test, stuff a linen cloth into the bottle and rapidly withdraw it, so as to allow the air of the room to enter the bottle. Then carefully place a tablespoonful of clear lime water in the bottle, and replace the stopper. Shake it for a few minutes; then, if the air is pure, the lime water will remain clear. If bad, and loaded with carbonic acid, the lime water will become turbid, or even milky. This is because lime and carbonic acid together form chalk, which gives the milky appearance. It must be remembered that this test has no reference to the ammonia which often exists abnormally in the bad air of towns, nor does it indicate the presence of disease germs or poisons due to paint, wall-paper, &c.
A fire in an open fireplace is a good ventilator in a way. We may ventilate a room easily by raising the lower window sash, and by placing inside the frame a piece of wood 3-4 in. high, and 1 in. in thickness, and reaching from one side of the frame to the other. When the inside sash is brought down to rest on this piece of wood, it is thus raised 3-4 in. A current of fresh air moves inwards and upwards to the ceiling between the sashes, and if a piece of wood or glass, sloping upwards, be attached to the top of the lower sash, the current of air will be sent upwards to the ceiling, whence it will diffuse itself through the room.
Draughts must be avoided; and it is wonderful how easily they may be prevented. Pettenkofer has shown that if air at ordinary temperatures does not move at a greater rapidity than 1½ ft. per second, its movement is not felt. What is needed, therefore, is some kind of screen that will not prevent the entrance of air, but that will break its force, divide its currents, and make it flow unfelt into the room.
Perhaps the simplest plan of effecting this is the following: Open your window at the top to whatever degree is necessary to prevent closeness in the room, but if there is a draught open it wider still; place a little loosely-packed cotton-wool between the upper and lower sash, and in the open space above the upper sash place a strip of perforated zinc, with its lower edge turned upwards, so as to direct the draught towards the ceiling. If there is still too much draught, open it still wider, but fasten in front of the perforated zinc a screen of gauze containing loosely-packed cotton-wool. It is noteworthy that there must be a sufficient current to carry the air upwards along the slanting piece of zinc, and towards the ceiling, otherwise, as Corbett has pointed out, the cold air will trickle over the edge and cool the feet of the inmates of the room.
In the hot months it is worth while to bear in mind the plan adopted by Martin in order to keep the rooms of the sick in a state of freshness. This consists in opening the windows wide, and then hanging wet cloths before them. The water, as it vaporises, absorbs the heat, and lowers the temperature of the apartment by several degrees, while the humidity which is diffused renders the heat much more supportable. By adopting this plan, the inmates find themselves, even in the height of summer, in a freshened atmosphere, analogous to that which prevails after a storm. This fact is well known to and utilised by the natives of India. Another plan is to close all windows facing the sun and cover them with blinds or curtains, to exclude the sun’s rays and the heated external air. Carpets may be replaced by matting, and the latter may be sprinkled with plain or perfumed water.
In very cold weather it is equally desirable to close all cracks and chinks against the influx of draughts. Cracks in floors, around the skirting board, or other parts of a room, may be neatly and permanently filled by thoroughly soaking newspapers in paste made of 1 lb. flour, 3 quarts of water, and a tablespoonful of alum, thoroughly boiled and mixed. The mixture will be about as thick as putty, and may be forced into the cracks with a case knife. It will harden like papier-maché. Old windows that do not close tightly may be remedied by smearing the edge on which they close with putty, and that of the sash with chalk, and then closing them as firmly as possible. The putty will fill up the crevices, and the excess pressed out at the sides may be removed with a knife, whilst the chalk prevents adhesion to the sash.
A system in very general use is Moore’s patent glass louvre ventilator, consisting of a number of louvres (or slips of glass), which can be opened to any angle up to about 45°, thus always directing the incoming current of air upwards. They are easily regulated and secured by a cord, which when released allows the louvres to close practically air-tight. Moore’s circular glass ventilator, which consists of (usually five) pear-shaped openings, neatly cut in the window square, and fitted with a circular glass cover with corresponding holes working on a centre pivot, are also very effective for admission or extraction of air. Moore’s sliding ventilator consists of oblong vertical holes, with the cover sliding between guides horizontally, the principle being the same as in the circular ventilator, but it is more suited for the top of shop fronts or shallow fanlights. These are all made by J. Moore and Sons, Sekforde Works, St. James’s Walk, Clerkenwell Green, E.C.
Another simple method of admitting fresh air to a room consists in leaving an aperture in the external wall, at a level between the ceiling of one apartment and the floor of the room immediately above, then to convey the fresh air through a channel from the external wall to the centre of the ceiling of the apartment below, where the air can be admitted by an opening, and dispersed by having a flat board or disc to impinge against, suspended 4 in. or 6 in. below the opening of the ceiling, and so scattered over the room. The cold air, however, thus admitted, plunges on the heads of the occupants of the room and mixes with the hot air which has risen near the ceiling. A top window-sash lowered a little to admit fresh air has the same disagreeable effect, the cold air being drawn towards the floor by the chimney draught, and leaving the hot air to stagnate near the ceiling. In any siphon system placed vertically the current of air will enter by the short arm, and take its exit by the long arm, and thus the chimney flue acts as the long arm of a siphon, drawing the fresh air from the nearest opening. Fresh air may be introduced through perforations made in the woodwork of the bottom rail of the door to the room, or through apertures in the outer wall, admitting the fresh air to spaces behind the skirting board, and making the latter perforated. The only objection to this plan is the liability for vermin to lodge between the skirting board and the wall. This may be prevented by covering the outside apertures with perforated zinc, but such covering also helps to keep out the full supply of fresh air.
Butler recommends, while admitting the cold air through side walls near the floor level, and allowing the foul air to escape at the ceiling, that the fire draught should be maintained quite independent of the air inlet to the room, the requisite amount of air for combustion being supplied by a separate pipe led through the hearthstone with its face towards the fire, the latter acting as a pump, which is sure to procure its own allowance from the nearest source; thus the draught which would otherwise be felt by the fire drawing its supply from the inlet across the room is considerably reduced. The foul air may enter the ceiling in the centre, and be conducted by an air-flue either to the outside or to the chimney. The chimney is the best extractor, as its heated condition greatly favours the ventilating power.
Dr. Arnott was one of the first to draw attention to the value of a chimney as a means of drawing off the foul air from the interior of an apartment. He invented a ventilator consisting of a well-balanced metallic valve, intended by its instantaneous action to close against down draught and so prevent the escape of smoke into a room during the use of fires. If the fire is not alight, what is known as the register of the stove should be closed, or a tight-fitting board placed in front of the fireplace, with the adoption of all chimney-ventilators fixed near the ceiling.