Air - The Thing Which Keeps us Alive Could Mean our Demise

Air is all around us all the time. It surrounds us every single minute of our lives, from start to finish: literally. Air is extremely important, and without it life may never even have come into existence. Air is mixture which helps us do things such as breathe, make fires and fly aeroplanes. One tiny change in the composition of air and we might have had very different lives, if none at all!  

A common misconception is that air is just one ‘element’. This is completely untrue! Air is not on the periodic table (you can check if you like). Air isn’t even one simple compound. In fact, air is actually a mixture of a variety of different elements and compounds in gaseous form, the most notorious of which being oxygen. However, this is not the gas in most abundance, in fact if it was we would most probably be dead, as pure oxygen is poisonous!

Air is actually made up mainly of nitrogen (around 78%), oxygen generally only makes up about 20-21% of air. There are also small amounts (around 1%) of noble gases such as argon and helium in the air. Finally, air contains substances essential for plant life: carbon dioxide (0.03%) and water vapour (0.97%, but it can vary!) Plants need carbon dioxide and water for the process of photosynthesis, where they convert these substances to glucose and oxygen in the process of photosynthesis. You may have heard of humidity levels. Since the amount of water in the air can vary, this can raise or drop humidity levels. It can go from 4% to 0.5%!

Air however does not only contain these set substances. It also contains minutely small amounts of other substances such as aerosols (which are tiny particles of dust from the ground or from volcanic ash.) If you can imagine zooming up into the sky, the composition of air there would be very different. There lies the notorious gas known as ozone, which environmentalists are currently making a big fuss about (due to the theory of global warming). There is also a lot more helium and hydrogen up there, as they are lighter elements, less dense than the others, so when they float up the others sink down.

You have probably heard of air pressure as well. This is just basically the weight of the air pushing down on everything on the earth – including us! Air pressure is measure in something called Pascal units which is just how many kilograms of ‘weight’/’force’ (measured in Newtons – “N”) act over 1 m² of area. So if 3kg of air was pressing down on 1 m² of area then the air pressure would be 3 Pascals. However the real pressure of the air comes nothing close to that. In fact for every 1 m² of area on the earth, air pressure results in a force equivalent to the weight of a large elephant pushing down on it! You may ask why we aren’t crushed by this force. This is because the blood in our bodies pushes out with an equivalent pressure and the two cancel out. This also explains why when we enter different areas of pressure, for example when flying on a plane, sometimes people get nosebleeds as the difference in pressure causes the blood vessels to expand and burst. Imagine if you entered a vacuum (space) without a special suit, you would just burst due to the pressure of your blood being too strong for your body to withstand!