FRESH AIR AND HEALTH
How much Air we Breathe.—At every breath we take in about one pint of air. We breathe eighteen times each minute. Nine quarts of air therefore pass in and out of the lungs every minute. Air once breathed is not fit to breathe again. It contains waste and carbon dioxide which weaken the body.
If you breathe three full breaths into a wide-mouthed jar or bottle, it will contain so much of the carbon dioxide that a lighted candle or splinter will at once go out when thrust into the jar. A cat shut in a tight box two feet square and one foot high will die in less than a half hour.
Many years ago when the British and Hindoo soldiers were fighting each other, the Hindoos made prisoners of 146 of the British and locked them in a room about one half as large as a common schoolroom. There were only two small windows. During the night 123 of these men died because of the bad air.
Fig. 64 —The direction of the flame of the candle shows how the fresh air enters and the bad air leaves a room.
How much Air should enter a Room.—The air laden with waste coming out of the lungs quickly mixes with the other air of the room. In this way all of the air in the room soon becomes impure. Forty children will give out nearly two barrels of air in one minute. In another minute this air has made all of the other air in the room unclean. It can still be breathed, but it makes children feel drowsy and lazy and may cause headache. They then do poor work.
To keep the air pure in a room, fresh air must be let in from the outside. If there are many in the room, the openings must be large or fans on a wheel must be used to force the air in. In the New York schools a little over a cubic yard of fresh air is forced into the room for each child every minute.
How to get Fresh Air into a Room.—When air is warmed it becomes lighter and rises. In many public buildings, fresh air heated by a furnace is forced into the rooms through pipes entering several feet above the floor. By a fan or heated flue the impure air is sucked out of the room through openings near the floor.