How do they smoke

I have had the question of how the German Smoking figures smoke. They are designed so the top part lifts off where I placed a bottle cap to put the cone incense in. When you light the incense, the smoke rises and comes out a hole drilled in the upper body and head. The next question that usually comes up is fire hazard. When you light the incense, wait until the flame goes out and start smoking to place the top part back on, the cones do not put out that much heat and don't burn for that long before they will go out.