posted by Eva .
Will we ever run out of air?
Air is stuck to the planet by gravity, it won't leave. Two things are adding to the air all the time too, the planet is always releasing gasses from volcanoes and volcanic vents, and there are some meteors that are mostly ice that evaporate when they hit tie air.
Probably not, at least in our lifetime. Global heating may cause plants to die, and then we could run out oxygen, but we just don't know yet.
And don't forget the loss of Rain Forests..They generate a lot of oxygen. As they are destroyed, we will be choking ourselves for oxygen.
As Ken pointed out volcanoes replenish the atmosphere. There is another import effect which protects the atmoshere: The Earth's magnetic field. The magnetic field deflects high energy charged particles from the Sun. Without this field the atmosphere would be slowly stripped away by the solar wind.
The Earth's magnetic field is generated in the liquid outer core of the Earth. Some time in the future the Earth's interior will have cooled down to such an extent that there will be much less volcanic activity and also the outer core will have solidified. From then on the Earth will start to lose its atmosphere.
We know that this happened on Mars a few billion years ago.