What is the physics of backflow incense burners off smells with it?

What I mean is why backflow incense smells different when smokes goes down and why the normal rising smoke smells great. Example 2 incense burners have a incense cone, 1 intended for smoke to go down and the other to have smoke rise normally. The backflow one smells bad and the rising one doesn't, what's... show more What I mean is why backflow incense smells different when smokes goes down and why the normal rising smoke smells great. Example 2 incense burners have a incense cone, 1 intended for smoke to go down and the other to have smoke rise normally. The backflow one smells bad and the rising one doesn't, what's the physics in that what creates that off smell and can it be resolved
0