Our world is enveloped by a layer of atmosphere around 15 kilometers thick layer of the atmosphere consists of nitrogen, oxygen, water vapor and dust. And the microorganisms in the amount of these gases. Gas, the most important of its existence. Life on Earth is oxygen and the layer of the atmosphere with enough oxygen. To live with a thickness of only 5-6 kilometers. This usually consists of various gases is relatively stable nitrogen 78.09%, 20.94% oxygen, carbon dioxide and noble gases. 0.97% for a fixed amount of gas that we hold as fresh air, but whenever a component of climate change to the amount of dust, gas, odor, smoke, vapor, vapor, soot, and the radioactivity in the atmosphere since. too many of us call such conditions as "bad air" or "air pollution".