FRESH AIR
It is now generally known that an abundant supply of moving, pure, fresh air is the proper and simple solution of the problem of the hygiene of the air.
Oxygen is the element of the air which sustains life. We inhale about seven pounds per day, two pounds of which are absorbed by the body. The air becomes dangerous, or infected, when the oxygen in the air is decreased to only 11 or 12 per cent., and when the oxygen reaches 7 per cent. death occurs from asphyxiation.
The human body requires about three thousand cubic feet per hour, and the great problem of ventilation is to give this amount of pure air, moving, and with the proper amount of moisture.
It is a common belief that with each breath we take we are filling our lungs with fresh air. This is not the case, for we never do get our lungs filled with fresh air. What really happens is that we ventilate a long tube which has no intercommunication whatever with the blood. Most of the time our lungs are filled with impure air, and we simply exchange a part of it for fresh air.