Diana Craig

But it wasn’t until the appearance of primitive bacteria, millions of years ago, that the vital component of the air we breathe first materialized.
Using the power of the sun in a chemical process called photosynthesis, these bacteria absorbed carbon dioxide from the atmosphere and gave off a new gas: oxygen.

To compensate and reduce stress on the plane’s fuselage, the pressure inside the cabin is lowered.

It contains the highest density of air, holding about half of the planet’s atmospheric gases.