This section of the book is from the "Household Companion: The Family Doctor" book
In the sick-room the things to be done are, to have the air changed constantly, and at the same time to prevent direct draughts upon the patient's bed. If there are several windows, all but the one nearest the bed may be open a little-at top and a little at bottom; more or less according to the weather. In warm weather, of course, everything may be opened wide all the time.
With only one window in a room, as already said, there ought to be another outlet for air, such as a transom over a door; or, in the absence of this, the door itself may be left open. This will require attention to the air of the room, or passage, communicating by that door with the room. If the air of the house is foul, that will hurt the condition of the sick-room, when the door of the latter is left open. Yet, somehow, both an inlet and an outlet are needed, to change the air of the room.
In very cold weather, when it is impossible safely to have (as is always best) a constant and considerable movement of air through the room, the next best thing will be to have chosen times of airing it thoroughly. Cover the patient with extra blankets or coverlids, protecting even the head and face for the time; and then open the window or windows and doors wide for a few minutes. Upon closing them, see that the patient keeps his extra cover until the room is warm enough again.