Air is composed of two gases, oxygen and hydrogen, and it is the oxygen we take into our lungs with every breath that is so essential to life. The red blood which the heart pumps through arteries to every part of the body, comes back to the lungs by the veins as purple blood loaded with impurities, and especially with a gas which is poisonous to life.
In the lungs it meets the oxygen breathed in from the outer air, and the oxygen purifies and revitalizes the blood, which passes on to the heart to be pumped round the body once more on its life-sustaining mission.
The poison gas, called carbonic acid gas, which the venous blood unloads in the lungs, is breathed out into the air, and is thus got rid of with every breath.
Now we can understand the double evil of breathing for any length of time the air of a closed up and crowded room. First, we gradually exhaust the oxygen in the limited amount of air we breathe, until we are not getting sufficient oxygen to purify and revitalize the circulating blood.
Secondly, we are filling the air of the room at every breath we breathe out with that poisonous carbonic acid gas; and this gas we take in again into our lungs with every inspiration. The result is that the circulating blood becomes loaded with poison, which gradually reaches and poisons the whole system.
The first effects of this poison are sleepiness, headache and lassitude, which will pass off as soon as we get into the open air. But people who habitually live in stuffy, unventilated rooms and an impure atmosphere, eventually become liable to all kinds of diseases arising from poisoned blood and deranged lungs.
We can now understand the importance of ventilation. The windows and ventilators of the rooms we live in must be kept open, so that a current of pure air will always be passing through, driving the stale, used up air out, and replacing it with clean air full of oxygen.
It is especially important that bed-rooms should be kept well-ventilated at night, for to sleep in a shut-up room is simply to be slowly poisoned. And the more we can spend our time right out in the open air, the better it will be for our health.
The dreaded disease called phthisis, or consumption of the lungs, is largely the result of constantly breathing bad air; and the open air treatment is the only real cure for it.