The "belch" is a huge exhaust of smoke...if you were watching the SI during the first heating cycle (until the light turns off), you would know if it belched. The sound of it is quite scary! For me, I would typically see the belch when the SI gets to around 180F, and it only happens on the first cycle. Since I have switch to smokinlicious wood, I have not had a belch. Good wood with a high moisture content is the key to avoiding the belch.