It is taken up by the system along with the oxygen, and yet is not the oxygen.

The Hebrew writer of the book of Genesis knew the difference between the atmospheric air and the mysterious and potent principle contained within it.

He speaks of neshemet ruach chayim, which, translated, means "the breath of the spirit of life." In the Hebrew neshemet means the ordinary breath of atmospheric air, and chayim means life or lives, while the word ruach means the "spirit of life," which occultists claim is the same principle which we speak of as Prana.
Prana is in the atmospheric air, but it is also elsewhere, and it penetrates where the air cannot reach.

The oxygen in the air plays an important part in sustaining animal life, and the carbon plays a similar part with plant life, but Prana has its own distinct part to play in the manifestation of life, aside from the physiological functions.
We are constantly inhaling the air charged with prana, and are as constantly extracting the latter from the air and appropriating it to our uses.

Prana is found in its freest state in the atmospheric air, which when fresh is fairly charged with it, and we draw it to us more easily from the air than from any other source.