VENTILATION – Tropical Hygiene

The Objects of Ventilation are:
1. To remove the products of burning and breathing from the room.
2. To replace them with pure air.

PURIFICATION OF AIR

The air is rendered pure by:
1. The action of plants and trees (see page 7). 2. The falling of rain. This washes away dust (suspended impurities), both organic and inorganic, and makes the air fresh.
3. The oxygen in the air, which changes the organic impurities in the air and renders them harmless.
4. The sun. Nearly all germs exposed to its direct rays are soon killed.

Hot Air Rises.-Another natural property of gases made use of in ventilation is the fact that hot air rises. When gas is heated it expands and becomes lighter than the colder gas around. The air near fires, and air that has been breathed out, is foul or dirty air. It is lighter than pure air because it is warm. The dirty air in a room rises and finds its way out through any hole in the wall or in the ceiling. Cool pure air from outside takes its place. The fact that warm air rises also causes winds (see page 196).

METHODS OF VENTILATION

Ventilation may be artificial or natural. Artificial ventilation which is used for cinemas and other halls depends on fans and pumps which force the air to circulate by mechanical means.
1. The pure air may be forced into the room, usually by electric fans.
2. The bad air may be sucked out of the room. Here again fans are used and the impure air is driven through tubes near the roof.
3. As commonly used, electric fans and punkahs can hardly be called methods of ventilation. They set the air of the room in motion and in tropical houses produce a refreshing current of air, but they do not of themselves drive out the bad air and supply pure.
4. Air-conditioning is the name given to the perfected system of ventilation by which air is warmed or cooled, moistened or dried, to produce conditions regarded as ideal for human comfort and health. In the tropics, air-conditioned rooms tend to be a little chilly; they should not be made quite as cool and dry as would be ideal in other parts of the world.

Natural Means of Ventilation.-In the tropics we make use of the natural properties of air, aided by simple apparatus.
The ventilation of houses in Europe is, in one sense, more difficult than in the tropics, where the temperature of the air is much the same inside the house as outside and so we may admit a breeze without troubling about draughts. In Europe the temperature outside might be, say, 32°, and the inside temperature 65° or 70°. Fresh air must be allowed in, and all the fresh air available is cold; if a current of it blew steadily on to anyone, he would possibly get a chill. Therefore special means have to be used to see that the incoming air is either warmed or directed away from people inside.
Most tropical houses are so built that sufficient ventilation can be obtained by means of the doors and

SPACE FOR OVERHANGING ROOF

windows. Most of the houses have an opening between the top of the walls and the eaves of the roof. This space provides an outlet for bad air; the inlets are the doors and windows. This simple method of opening doors and windows and allowing the breeze to flow through is very effective. t ons scot at deoseb
The winds can purify the air in the house only if the building is properly arranged. The rooms themselves must have a certain amount of window area. This is regulated by law; the windows must be one-tenth the area of the floor. This is a minimum figure and better houses have twice as much window space. The windows should be at opposite sides of the room to allow the breeze to pass through the room. When the house consists of several rooms, they must be placed so that as many of them as possible have the wind blowing through them (see Fig. 5).

Objections are sometimes made to this use of windows:

(1) At night the house would not be safe from thieves were windows and doors open. That is true, but health is so important that some plan must be found. Let the door be locked at night, and the windows made, not of plain wood or glass, but of strong wire. Expanded metal or arc mesh is now largely used and will protect from thieves and yet allow air to pass through. Jalousies are better than plain wood. Many houses have two sets of shutters to the windows; one made of wire or glass, opening inwards, and the other made of wooden louvre or jalousy, opening outwards. medol bannsle
(2) But it may be asked, What about tornadoes or hurricanes? The windows must be shut. But the violent rain only lasts a short time, and the windows should be opened when it is over. Moreover in ordinary storms the rain often comes from one side of the house only, and the other side is not affected. 1 to nobelins7

The compound in which each house is built must also be properly planned. If everybody buys a small piece of land and builds a house to cover it, the wind will have no chance to ventilate the houses. In some areas laws have been made that only a certain part of the land bought may be covered with buildings. This gives a good chance to put the latrine, the kitchen and the dust bin some distance from the house. Around such a compound a fence which allows wind to pass is, of course, better than a wall.
Town planning is so arranged that the wind can circulate among the houses. Regulating building in

this way has improved many tropical towns, and nowadays the chiefs of towns which do not come under the regulations sometimes ask to have their towns planned for them.
The planting of bushes and trees is clearly a very useful way of purifying the air; but they must be so arranged that the wind has free access to the houses. Trees that are well grown, for instance, should have their lower branches cut away.

Ventilation of Modern Houses.-Tropical towns now have some houses built on the European plan; certain internal rooms may have need of special ventilation. There are also churches, halls and schools which, when crowded with people and artificially lighted at night, need ventilating apparatus. We give here a few of the methods used in the ventilation of modern houses.

(a) One or more of the panes may be changed for louvre slips which may be opened or closed by a lever These are best made with glass.
(b) A hinged pane may be inserted. This will direct air from outside up into the room.
(c) Many small tropical houses with board windows and doors can be greatly improved by the extremely simple step of cutting off a few inches of the door and window, top and bottom. Nobody can claim that this will help thieves to enter, but bad air can get out and the breeze can get in through such openings.

(d) Sheringham’s Valve.-This is simply an iron box fixed into the wall just below the ceiling. One side is hinged and can be opened or shut as required. The opposite side is of iron gauze through which the outer air passes. The air is thus filtered and passed upwards.

It is very efficient and is specially suitable for large
rooms.
The Effect of Lights and Heating.-Kerosene lamps, candles and coal gas use up oxygen in burning and produce CO, and water vapour. It has been calcu- lated that a candle burning uses up half as much air as a man. A kerosene lamp equals a man, and gas- lamps equal more than two men. If, therefore, we have lamps burning in our rooms more fresh air will have to be supplied.
Electric Lamps do not use up oxygen and are there- fore very good. They do not make the air moist and only heat the room slightly.
Fires in a room also use up oxygen but do good; the CO, produced goes up the chimney, and the air is not spoiled much. Fires also are powerful aids to ventilation and tend to purify the air in this way.

Other Methods of Heating.-1. Hot-water Pipes. In cold countries rooms are often warmed by means of pipes carrying hot water or steam. Here no CO, is added by the heating.
2. Closed Stoves. These burn coal or coke and usually have a bad effect on the air of the room. The air becomes too dry, and often a stuffy smell is pro- duced because of the charring of particles of matter in the air. Again, carbon monoxide has been known to escape from them and kill people. This may be overcome by good ventilation, but still the closed stove tends to spoil the air.
Overcrowding. We are now able to understand one danger of having our rooms full of people. In tropical countries the rooms have so many doors and windows that there is little chance of having insufficient air during the day. Besides, the heat gives us a warning; we would not allow ourselves the discomfort of overcrowding. At night, however, there is a danger. The custom is to close tightly all doors and windows for fear of thieves. Many people sleep in the same room, and as they are unconscious and do not notice the badness of the air they think nothing is wrong.
The effects of overcrowding, however, are very serious. If the air cannot be changed sufficiently to allow every person sufficient fresh air, it follows that they must breathe the same air over and over again. What are the consequences?

1. They get insufficient oxygen. The blood there- fore is not well purified. The ” soldiers” of the bodily town are badly fed and get weak; disease becomes more likely. This may not take place in one night, or even in a month or year, but the effect will surely be seen in time. People who live and sleep in overcrowded rooms are generally feeble.
2. They run a great risk of catching infectious diseases from each other, especially those which are air-borne like sore throats, measles, mumps and influenza. Tuberculosis, meningitis and pneumonia are often caught through overcrowding.

NEXT >>>