No other natural environment on earth is as rich in oxygen.

Every part of your body needs blood that is rich in oxygen.

However, because oxygen-17 and oxygen-18 are also present in natural oxygen this led to 2 different tables of atomic mass.

This test shows how well the lungs are taking in oxygen.

Think if the air were very high in oxygen what would happen when you light a cigarette?

The sudden increase in oxygen led to an explosion of life across the globe.

I felt the blood bathing in oxygen inside her lungs.

Here was the source of the atmosphere's increase in oxygen.

At a guess, maybe a little high in oxygen.