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.
THE VALUE OF DEEP BREATHING Deep breathing is undoubtedly extremely beneficial.

Most of us, due largely to the fact that Nature leaves a considerable margin of safety, are able to carry on our ordinary activities without the requisite ventilation of the lungs, especially if we do not exercise.