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What Kinds of Natural Gases Do We Breathe Every Day?

The main gases in the air we breathe are nitrogen and oxygen. The two minor gases are carbon dioxide and argon. The atmosphere also contains water vapor, which varies greatly with temperature and location. At least 11 other naturally occurring gases exist in the atmosphere in trace amounts. The composition of the atmosphere changes with the weather, season, time of day, elevation, latitude and longitude.

  1. Nitrogen

    • Nitrogen makes up the greatest portion, about 78 percent, of the air we breathe. It is a colorless, odorless and tasteless gas. The molecules of nitrogen gas consist of two nitrogen atoms held together by a strong bond. Nitrogen gas is inert or unreactive with other substances. It is non-flammable and will not support combustion. Because of its unreactivity, nitrogen gas is used to safeguard explosives, to keep foods fresh in packages and to prevent fires in some manufacturing processes. An atmosphere of mostly nitrogen will suffocate humans and animals because of their need for oxygen.

    Oxygen

    • Molecular oxygen is made up of two oxygen atoms. It is a colorless, odorless and tasteless gas and makes up about 21 percent of the air we breathe. Oxygen in the air derives from photosynthesis by plants. Green plants convert carbon dioxide to oxygen. Oxygen is essential for life on Earth. Unlike nitrogen, oxygen gas supports fires. It also reacts with metals to cause rusting and corrosion. The oxygen concentration decreases with higher elevation, because the concentration of oxygen is dependent on atmospheric pressure, which declines with higher elevations.

    Carbon Dioxide

    • Carbon dioxide is a slightly acidic, colorless and odorless gas. The carbon dioxide molecule is made up of one carbon atom and two atoms of oxygen. Carbon dioxide represents only about 0.03 percent by volume of the air we breathe, but it is essential for photosynthesis by plants and respiration by humans, animals and other life forms. Plants convert carbon dioxide into food such as glucose and release oxygen into the air. During respiration, food compounds plus oxygen generate energy and carbon dioxide. Carbon dioxide is also important for human health by maintaining or buffering the acidity (pH) of the blood. The concentration of carbon dioxide is lower during the growing season and higher the rest of the year.

      High concentration of carbon dioxide contribute to global warming. Currently, the amount of carbon dioxide in the air is more than 20 percent greater than what it was a century ago. The increase is largely due to human activities such as deforestation and burning of fossil fuels.

    Argon

    • Argon is a colorless, odorless, stable gas. It makes up about 1 percent of the air we breathe. Argon has no known health effects on people or animals. Because of its unreactivity and heat-shielding ability, it is widely used in the metal industry.

    Other Gases

    • The air we breathe contains at least 11 other gases in trace amounts. These gases include ammonia, ozone, carbon monoxide and sulfur dioxide; the inert gases helium, krypton, neon and xenon; the light, reactive hydrogen gas; and the greenhouse gases methane and nitrous oxide.

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