The Air Around Us

What’s in air—and why it matters.

- Emily Floess

The three pictures above were taken on the same airplane ride. What do you notice? I took the first picture just outside Kathmandu, Nepal. The air is thick with dust. The second picture has a view of the Himalayas, the mountain range including the tallest peak in the world, Everest. The air is clear, and you can see the blue sky. In the third picture, outside Delhi, India, pollution fills the air.

How does the air look outside your window today?

The Chemistry of Air

Air is useful, especially if you like breathing. Air contains the oxygen (O2) we need. However, air is only 21 percent oxygen. Much of the rest of air—78 percent—is nitrogen (N2). Most nitrogen remains in the air. A small amount changes to different forms and goes from the air to the soil. Nitrogen is important. Plants need it to produce proteins. Animals and humans eat these plants. However, too much nitrogen is considered pollution. Human actions can unbalance levels in the environment. Farmers treat crops with nitrogen-based fertilizers. Burning wood or coal releases nitrogen into the air.

Air contains some carbon dioxide (CO2) too. Humans and animals breathe the gas out. The process of burning carbon-containing materials in the presence of oxygen also produces carbon dioxide.