Our world is wrapped by a layer of the atmosphere around the thick layer of the atmosphere is approximately 15 km to it. Oxygen, nitrogen, steam, gas, dust and microbes in the amount of these gases. The most important gas towards the existence of life on Earth is oxygen gas and oxygen layer of the atmosphere with enough gas. Personal lives are just 5-6 km in thickness only. Which are the different components of the gas constant is rather nitrogen 78.09% oxygen, gas gas, 20.94% carbon dioxide and 0.97% inert gas in a fixed quantity of gas, it is regarded as the fresh air, but whenever a change to the air component has a quantity of dust. I smell gas, steam fog of smoke. Carbon particles and radiation in more Samak check too. We call it "bad weather conditions," or "air pollution".