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.