Composition of Air
Pure air is a mixture of several gases that are invisible and odourless. It consists of about 78% nitrogen, 21% oxygen, and less than 1% of argon, carbon dioxide, and other gases — as well as varying amounts of water vapour. Adults breathe in about 10-20 cubic metres of air every day. That’s about 20,000 breaths. Children breathe almost twice that amount because they are smaller, and their respiratory systems are still maturing.
What is Atmosphere?
The atmosphere is a mixture of gases that surround the earth. It is the air we breathe, the wind and rain, and the clouds in the sky. It is life giving, retaining heat and blocking out harmful rays (ultraviolet radiation) from the sun. The atmosphere is about 1,000 kilometres thick, and is made up of invisible layers that circle the planet. We live in the lowest and thinnest layer, called the troposphere, which is only about 14 kilometres thick.
The bottom two kilometres of the troposphere are really our “home.” Most of the air and weather are there, along with most air pollutants. Two kilometres aren’t very much. It would take just two minutes to drive that distance, at 60 km per hour.
Above the troposphere is the stratosphere. This is the relatively quiet, stable band of air in which the ozone layer is found and where our emissions of greenhouse gases and ozone-depleting substances go. There is no exact place where the atmosphere ends; it just gets thinner and thinner, until it merges with outer space.