21% of the air we inhale is oxygen
yes!
Exhaled air contains 16% oxygen and 21% when inhaled.
If you're talking about the level in the air, which I assume you are, it's because as we exhale, the oxygen we inhaled is replaced with carbon dioxide, which trees "breathe" in. Trees, or any plant, then releases oxygen after it completes photosynthesis with the carbon dioxide.
i forgot
The concentration of oxygen inhaled depends upon the prescribed flow rate and the ventilatory minute volume (MV).
About 21%.
oxygen:)
About 21%
cells
(cellular) respiration
The gas we take in when we inhale is oxygen.
Exhaled air has more carbon dioxide and less oxygen than does inhaled air.