I experience the same thing when I smoke certain strains, which strains they are I have no clue... Even after cardiovascular activities I REALLY notice how low the oxygen in the air seems to be.

Also when trying to meditate I can tell that the 21% of oxygen in the atmosphere is pretty low, but juuuuust high enough to keep us alive.

OSHA claims anything below 19.5% is deficient. That's cutting it pretty close!
GreenDestiny Reviewed by GreenDestiny on . Strange Feelings Of Breath The sensation that I've been noticing the last 2 weeks or so (whenever I smoke) is annoying and disconcerting. A few minutes after smoking, I begin to feel like normal inhalation of air does not satisfy my body's craving for oxygen. I can't really explain it, I feel like I can't inhale deeply enough to get that satisfaction of having taken a breath. My solution and the only method that seems to counter this feeling at all has been to inhale slowly through my nose until my lungs are FULL, Rating: 5