Quote Originally Posted by alwaystrippin
hmm do u understand that just inhaling and exhaling your own air from inside a bag is real bad for your lungs!!! why would smoke be any better?? and besides all the thc u need is in the first hit anyways....so yes as you said this was a stupid question>
Repeatedly, but not necessarily once or twice.

Its because when you breath in your own exhaled air, you absorb more carbon dioxide into your bloodstream than you need which raises the pH (turns it into a base). When your blood becomes basic then your central nervous system decides that you must not need to breath as rapidly if you have to so much CO2 in your blood, because when you exhale the CO2 is usually stripped from red blood cells and blood plasma. Also, basic blood denatures the protein enzymes and messenges sent by your brain which interferes with your body's natural processes which can lead to you fainting or going unconcious.
Plus, when you're burning plant material you are inhaling carbon minoxide which you want to avoid reinhaling or inhaling it at all. Recurculating that exhaled air makes sure that whatever CO molecules didn't make it into your blood on the first inhale, will have a greater chance when they pass once more into your lungs.