when youre hitting a bong (unless its a slide carb) theres a little hole on the back now if you want to hit the bong you have to hold the hole or you wont get shit... and when you fill the chamber with smoke you let go of the carb and instead of pulling in air from the bowl (which brings in smoke obviously) youre inhaling from the carb which is just air that "shotguns" the smoke into your lungs clearing the chamber