Air is the mixture of gases in our atmosphere. It is mainly nitrogen (seventy eight percent) and oxygen (twenty one percent).
The rest is chiefly argon. There are also tiny amounts of carbon dioxide, neon, helium, hydrogen, ozone, krypton, methane and xenon. The air also contains water. It is this which forms rain clouds. Factories and house produce smoke and dust which goes into the air.
These can be harmful and are known as air pollution. Almost all the living things on Earth need air. Animals breathe in air to obtain the oxygen they need to stay alive. Plants take carbon dioxide out of the air for photosynthesis.