A layer of foil is placed on top of the tobacco, and on top of that goes a few hot coals. The number of coals depends on the size of the coals and the size of the bowl. The coals heat up the tobacco (or fruit), causing it to smoke. What is happening to the tobacco in the bowl is more like smoldering than the burning that takes place with smoking cigarettes or cigars.
To smoke the hookah, you take hold of the hose and suck. This works because when you suck on the hose, it lowers the air pressure within the hookah's vase and draws the smoke down to it, even though the hose has no direct contact with the tobacco bowl itself. The smoke comes down from the bowl through a metal stem running through the center of the hookah. The bottom of the stem sits in a vase, which is filled with enough water to submerge it. When you draw the smoke from the bowl, it emerges from the stem underwater.
Place a hookah screen over the clay bowl. Use foil if no screen is available. Cut a small portion of foil the size of the bowl and wrap it over the head tightly. Poke several holes with a toothpick to allow the air to get through the tobacco.
Put the clay bowl on top of the grommet of the hookah pipe. Insert the hose into the side opening of the pipe.Light your coals. Use a blow torch to light natural coals, or a lighter or matches to quick light coals. Hold the coal with a pair of metal tongs and place the flame on the coal until the coal is completely lit and glowing red.Place the coal on top of the foil or screen covered clay bowl. Break up the coals with the tongs and evenly distribute the pieces over the surface of the clay bowl. Set the wind cover over the coal to protect the coal from falling down and to keep it lit.Suck the nozzle of the hose gently to pull steam through the pipe up to the tobacco. Inhale smoke slowly to prevent choking.
That eventually turns the water brown, and some claim this removes harmful impurities from the smoke. The smoke then rises up out of the water, collecting in the vase's air space. At the top of the vase is the opening for the hose, and it is from here that smoke is drawn up through the hose, into the mouthpiece and into the smoker.
This is an optional feature that not all hookahs have. The release valve allows you to clear stale smoke out of the vase. Blowing into the hookah reverses the effects of smoking on it, so the air pressure increases instead of decreases. That pushes a ball bearing in the release valve into the open position so smoke can be discharged from the hookah without having to disassemble it.