Quote Originally Posted by birdgirl73
Do even the least bit of reading about lung physiology and function, and you'll see that the gas exchange and/or absorption of anything you breathe in occurs instantly. It literally occurs with the initial expansion of those little alveoli, the tiny air sacs where the chemical exchange occurs. Holding a hit doesn't do anything to make you higher, just like holding a breath doesn't do anything to make you absorb more oxygen from the air you breathe.
Are you sure about that last sentence. Because if I hold my breath as opposed to taking a deep breath and exhaling right away I can wait much longer till I need to inhale again.

Also couldn't there be multiple chemical exchanges in one alveoli as you are holding your breath? or in this case holding in weed smoke?