it works like this i believe...when you seal off the chamber with your mouth and inhale, it creates a vacuum inside the bong and in order to equalize the pressure, air is forced from the outside, causing the flame to be sucked onto the weed, which produces the smoke, which is then sucked through the bowl, into the chamber, it bubbles up from under the water, the bubbles pop and out comes cool, smooth smoke, straight into your lungs.