This was copied from the old forum:
"I believe the Dovetec is positive draft, that is, the combustion air is forced into the burn area and then exhausted, unlike more modern units where there is a draft inducing fan on the BACKSIDE of the combustion area, drawing out the products of combustion and venting them. That's why you are getting charred corn in the auger tube. If you were burning pellets, you'd have a full fledged burn back. Corn don't combust as readily as pellets do. "
A few homes have burned down due to fire traveling up the feed chute and igniting the pellets in the chute as well as in the hopper.
Hope this makes sense!