Smoke contains particles heavier than air. As long as there is no wind in the room and it is isolated from the hot air rising around the combustion heating, the hot air will not rise with the flue gas and the flue gas will sink. There are more impurities in the smoke, that is to say, more impurity particles can be produced when incense is lit. The proportion of smoke particles is greater than that of air, and the smoke sinks.
Extended data
Reflux fragrance, also known as dirty fragrance, is named because of its high tar content and the smoke generated in the combustion process flows from high to low like water. Reflux furnace has holes or slots for the small holes of tower incense, which is also beneficial to the downward flow of flue gas.
There is a small hole in the special tower incense, which is conducive to the downward flow of smoke. After setting the incense burner, light the heavy smoke incense. Don't put out the flame at once. Let the flame burn slightly for 4-6 seconds, and then see it burn completely. Fan out the flame and put it into a special reflux furnace. At first, there will be no cigarette butts coming out from the bottom. After about a minute or two, the cigarette changed direction and slowly flowed out from the bottom.
Reflux incense burners all use special "tower incense", which can spread more impurity particles when burning. This backward incense burner has existed for a long time, and I have to admire the wisdom of the ancients. Reflux incense is mostly conical and hollow, and it is generally equipped with a special incense burner when used. There are holes or grooves on the incense burner to facilitate the downward flow of smoke.
Baidu encyclopedia-Dao Liu Xiang