For best effect burn indoors away from any breeze or sudden air movement. We advise that you suitably protect any furniture that the backflow burner is placed on, as it is normal for a light oily residue to be left behind on the burner. The residue can be easily wiped off the burner with a damp cloth. As with any burning product please use with caution. It is normal for the cones to take up to 10 minutes after being lit to start to create the smoking/mist effect.