Q:

What gases do we breathe in and out?

A:

Quick Answer

The gases that humans breathe in are nitrogen, oxygen, argon and carbon dioxide, with nitrogen in the largest proportion and carbon dioxide in the smallest proportion. The gases that humans breathe out are the same, although more carbon dioxide and less oxygen is present.

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Full Answer

Earth's atmosphere at sea level is approximately 78 percent nitrogen gas by volume. The second most common gas is oxygen, which makes up 20 to 21 percent of the atmosphere by volume. Other gases are present in much lower proportions, with argon making up around 1 percent and carbon dioxide around 0.5 percent. Trace amounts of hydrogen, ozone, water vapor and noble gases such as helium and neon are also present.

The exact proportions of gases vary according to elevation, location and humidity. Areas with higher humidity have a greater proportion of water vapor. The proportion of oxygen decreases with elevation, and regions with a large industrial presence tend to have higher proportions of carbon dioxide and various pollutants, such as sulfur dioxide. The only gases significantly taken in through human respiration are oxygen and carbon dioxide. When gases are inhaled, oxygen is absorbed to the bloodstream; when gases are exhaled, carbon dioxide is removed from the body.

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Related Questions

  • Q:

    What gases do humans exhale?

    A:

    Humans exhale oxygen, carbon dioxide and nitrogen. Humans inhale these same gases, though in different proportions to exhalation; that is, oxygen is exchanged for carbon dioxide during breathing.

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  • Q:

    What are the two most abundant gases in the atmosphere?

    A:

    The two most abundant gases in the Earth’s atmosphere are nitrogen and oxygen. The atmosphere contains approximately 78 percent nitrogen and about 21 percent oxygen. The Earth’s atmosphere also contains lesser amounts of other gases, such as argon, carbon dioxide, hydrogen and neon.

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  • Q:

    Why do people breathe out carbon dioxide?

    A:

    People and animals breathe in oxygen and breathe out carbon dioxide because of a process called cellular respiration. During cellular respiration, oxygen is combined with food nutrients and water in order to produce usable energy in the form of adenosine tri-phosphate (ATP). The byproduct of this process is carbon dioxide, which is removed from the body through breathing.

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  • Q:

    What are the four most common gases in dry air?

    A:

    Dry air is composed primarily of nitrogen, oxygen, argon and carbon dioxide. Nitrogen and oxygen comprise approximately 99 percent of the atmosphere. The other gases are present in minute amounts, each of them equaling less than 1 percent.

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