The reasons that the smoke cannot backflow:
1. Only use Backflow Incense Cones can backflow effect make.
2. Make sure the hole on the bottom of the incense cone lines up with the hole on the burner.
3. The incense holder must work in a flat table and windless environment to maximize the effects of the flowing smoke.
4. The hole in the top of the incense burner was clogged with stains. Please clean the ashes after the incense burns, make sure the hole is not blocked.
5. There is No smoke flow from the bottom initially, after about 1-2 minutes, the smoke will change direction and slowly flow out from below.
6. The incense contains particles which heavier than air. As long as there is no wind in the room and no hot air which will rise with the smoke, the smoke will sink.
7. Continuously use will cause the hole a high temperature, it will affect the smoke backflow effect.