Flyingman: I was a Firefighter/EMT. We called this "Big Bang" a smoke explosion. They are closely related to a back draft. When my SMO45 was new I had a big "Big Bang" on Thanksgiving morning. That bang actually shook the house and had every dog in the neighborhood going nuts. I figured I would have a round smoker full of turkey pieces parts. I turned the smoker off and waited a little while before opening the door. The turkey was fine. I checked the smoker with a square and everything was nice and square. I fired the smoker back up and we had a great thanksgiving. I did keep a closer watch on the smoker for a while. I did get to see the smoker do a couple of smaller bangs. Just before the bang I watched the smoker "Breath". The smoke would be rolling out of the vents and then the smoke would reverse stream and suck back into the smoker. When the smoker got a big enough gulp of air it would bang. All of this eventually went away as the smoker got well seasoned.