Hey Bill and Terry , Thanks much for the nice comment.
" Did I notice a hole in the line for air and a valve near the tractor? "
The hole in the line lets in close to the amount of mixing air the tractor will need. The valve is for fine adjustment.
" Also, when you disconnected the gas hose from your truck, Is it important to seal the truck up right away as to not get oxygen creeping into the system while the hearth is still hot? "
As long as the gasifier is warm there will be a light positive pressure through the system . When the gasifier cools of enough that the air flow might seep back in the gasifier there will be no fire. Each time I shut down I try to remember to close the intake air but often I forget . I do try to remember venting the hopper before sticking the lighting torch in at next light up. .