Carbon Dioxide (CO2) and Human Body

Carbon Dioxide (CO2) is a Result of Burning of any fuel, such as coal, gas, oil, or wood. As it burns sends out forth gases into the surrounding atmosphere.

These gases, like air, are invisible, and were unknown to us for a long time. Oxygen-Carbon-Dioxide-and-Human-Body

The main gas formed by a burning substance is called carbon dioxide (CO2) because it is composed of one part of carbon and two parts of oxygen.

This gas has the characteristic of being the most widely distributed gaseous compound of the entire world;

it is found in the ocean depths and on the mountain heights, in brilliantly lighted rooms, and most abundantly in manufacturing towns where factory chimneys constantly pour forth hot gases and smoke.

Wood and coal, and actuality, all animal and vegetable matter, contain carbon, and when these substances burn or decay, the carbon in them unites with oxygen and forms carbon dioxide.

Carbon dioxide is an end product in living beings that get energy from breaking down sugars, fats and amino acids with oxygen as part of their metabolism, in a process known as cellular respiration.

This is a form of oxidation or burning that occurs daily in the human body to provide the heat necessary for bodily warmth and the energy required for thought and action.

Oxygen is essential to burning, and the food fires within the body are kept alive by the oxygen taken into the body at every breath by the lungs. We see now one reason for an abundance of fresh air in daily life.

The food which we eat is either animal or vegetable, and it is made ready for bodily use by a slow process of burning within the body; carbon dioxide accompanies this bodily burning of food just as it accompanies the fires with which we are more familiar. The carbon dioxide thus produced within the human body escapes into the atmosphere with the breath.

We see that the source of carbon dioxide is practically inexhaustible, coming as it does from every stove, furnace, and candle, and further with every breath of a living organism.

Danger of Carbon Dioxide

When carbon dioxide occurs in large quantities, it is dangerous to health, because it interferes with normal breathing, lessening the escape of waste matter through the breath and preventing the access to the lungs of the oxygen necessary for life.

Carbon dioxide is not poisonous, but it cuts off the supply of oxygen, just as water cuts it off from a drowning man. However, if there is not enough ventilation or oxygen present, CO is produced instead.

Low levels of CO can cause such vague sicknesses as depression, fatigue and headaches. More severe poisonings can cause dizziness, confusion, irregular heartbeats, convulsions, unconsciousness and even death.

Since every man, woman, and child constantly breathe forth carbon dioxide, the danger in overpopulated rooms is great, and proper ventilation is of vital importance.


In estimating the quantity of air necessary to keep a room well aired, we must take into account the number of lights (electric lights do not count) to be used, and the number of people to occupy the room.

The average house should provide at the minimum 600 cubic feet of space for each person, and in addition, arrangements for allowing at least 300 cubic feet of fresh air per person to enter every hour.

What Becomes of the Carbon Dioxide?

When we reflect that carbon dioxide is constantly being supplied to the atmosphere and that it is injurious to health, the question naturally arises as to how the air remains free enough of the gas to support life.

This is largely because carbon dioxide is an essential food of plants. Through their leaves plants absorb it from the atmosphere, and by a wonderful process break it up into its component parts, oxygen and carbon.

They reject the oxygen, which passes back to the air, but they retain the carbon, which becomes a part of the plant structure. Plants thus serve to keep the atmosphere free from an excess of carbon dioxide and, in addition, furnish oxygen to the atmosphere.

While it is true that carbonic acid possesses properties that render it unfit to be breathed, it is, despite this, useful of extremely agreeable effects, when brought into the stomach. It forms the sparkling property of mineral waters, and fills the bubbles that rise when beer or cider is fermenting.

Pure atmospheric air is best adapted to a healthy action of the system. As the air cannot be maintained pure under all circumstances, the question may be asked,

To what degree may the air be vitiated and still sustain life? And what is the smallest quantity of pure air a human body needs each minute to maintain good health?

  • 1%, as can occur in a crowded auditorium with poor ventilation, can cause drowsiness with prolonged exposure.

  • At 2% it is mildly narcotic and causes increased blood pressure and pulse rate, and causes reduced hearing.

  • At about 5% it causes stimulation of the respiratory center, dizziness, confusion and difficulty in breathing accompanied by headache and shortness of breath. In addition at this concentration panic attacks may occur.

  • At about 8% it causes headache, sweating, dim vision, tremor and loss of consciousness after exposure for between five and ten minutes.

Although the human body requires oxygen for metabolism, low oxygen levels do not stimulate breathing.

Rather, breathing is stimulated by higher carbon dioxide levels. As a result, breathing low-pressure air or a gas mixture with no oxygen at all (such as pure nitrogen) can lead to loss of consciousness without ever experiencing air hunger.

These is especially dangerous for high-altitude pilots and also make sense why flight attendants instruct passengers, in case of loss of cabin pressure, to apply the oxygen mask to themselves first before helping others — otherwise the person risks going unconscious.

The necessity of fifteen or twenty times the amount of air actually taken into the lungs arises from the circumstance, that the expired air mixes with the surrounding air that has not been inhaled.

The amount of air the human body needs varies from person to person depending on size, age, habits, and body condition. A tall person, who has a large quantity of blood, requires more air than a small man with a less amount of circulating blood.

Individuals, whose work is active, require more air than sedentary or lazy persons, because the waste of the system is greater. So do the young require more air than an adult of the same weight, because he consumes more food than a grown-up person?

Air, in which lamps will not burn with brilliancy, is unfitted for respiration. In jammed rooms, not ventilated, the air is impure, not only by the low level of oxygen and the accumulation of carbonic acid, but as well by the excretions from the skin and lungs of the audience.

The bedrooms also should be so ventilated that the air in the morning will be as pure as when going to rest in the evening. Diverse bedroom apartments of twelve feet square and seven feet high are considered spacious for two persons, and good accommodations for four to lodge in.

An apartment of this size contains 1008 cubic feet of air. Allowing ten cubic feet to each person per minute, two occupants would vitiate the air of the room in fifty minutes, and four in twenty-five minutes. When lodging-rooms are not ventilated it is strongly recommend early rising.

While staying in a room, we are insensitive of the gradual vitiation of the air. This is the result of the decreased sensibility of the nervous system, and gradual adaptation of the organs to blood of less stimulating oxygen. This condition is well illustrated in the hibernating animals.

We are insensible of the impure air of unventilated bedrooms, until we leave them for a walk. If they have been closed, we are made sensible of the quality of the air, as soon as we re-enter them, because the system has regained its usual sensibility while inhaling a purer atmosphere.

Breathing produces approximately 2.3 pounds (1 kg) of carbon dioxide per day per person.

Adaptation from: A Treatise On Anatomy, Physiology, And HygieneBy Calvin Cutter, M.D.

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