In the country the balance ordained in nature has its compensating power. The poisonous carbonic acid thrown off by lungs and body is absorbed by vegetation whose food it is, and which in every waving leaf or blade of grass returns to us the oxygen we demand. Shut in a close room all day, or even in a tolerably ventilated one, there may be no sense of closeness; but go to the open air for a moment, and, if the nose has not been hopelessly ruined by want of education, it will tell unerringly the degree of oxygen wanting and required.
It is ordinarily supposed that carbonic-acid gas, being heavier, sinks to the bottom of the room, and that thus trundle-beds, for instance, are especially unwholesome. This would be so, were the gas pure. As a matter of fact, however, being warmed in the body, and thus made lighter, it rises into the common air, so that usually more will be found at the top than at the bottom of a room. This gas is, however, not the sole cause of disease. From both lungs and skin, matter is constantly thrown off, and floats in the form of germs in all impure air. To a person who by long confinement to close rooms has become so sensitive that any sudden current of air gives a cold, ventilation seems an impossibility and a cruelty; and the problem becomes: How to admit pure air throughout the house, and yet avoid currents and draughts. "Night-air" is even more dreaded than the confined air of rooms; yet, as the only air to be had at night must come under this head, it is safer to breathe that than to settle upon carbonic acid as lung-food for a third, at least, of the twenty-four hours. As fires feed on oxygen, it follows that every lamp, every gas-jet, every furnace, are so many appetites satisfying themselves upon our store of food, and that, if they are burning about us, a double amount of oxygen must be furnished.
The only mode of ventilation that will work always and without fail is that of a warm-air flue, the upward heated air-current of which draws off the foul gases from the room: this, supplemented by an opening on the opposite side of the room for the admission of pure air, will accomplish the desired end. An open fire-place will secure this, provided the flue is kept warm by heat from the kitchen fire, or some other during seasons when the fire-place is not used. But perhaps the simplest way is to have ample openings (from eight to twelve inches square) at the top and bottom of each room, opening into the chimney-flue: then, even if a stove is used, the flue can be kept heated by the extension of the stove-pipe some distance up within the chimney, and the ascending current of hot air will draw the foul air from the room into the flue. This, as before stated, must be completed by a fresh-air opening into the room on another side: if no other can be had, the top of the window may be lowered a little. The stove-pipe _extension_ within the chimney would better be of cast-iron, as more durable than the sheet-iron. When no fire is used in the sleeping-rooms, the chimney-flue must be heated by pipes from the kitchen or other fires; and, with the provision for _fresh_ air never forgotten, this simple device will invariably secure pure and well-oxygenated air for breathing. "Fussy and expensive," may be the comment; but the expense is less than the average yearly doctor's bill, and the fussiness nothing that your own hands must engage in. Only let heads take it in, and see to it that no neglect is allowed. In a southern climate doors and windows are of necessity open more constantly; but at night they are closed from the fear referred to, that night-air holds some subtle poison. It is merely colder, and perhaps moister, than day-air; and an extra bed-covering neutralizes this danger. Once accustomed to sleeping with open windows, you will find that taking cold is impossible.
