Morning Mr. Don,
I think because of the deep char bed ours it will tolerate having the lid open much longer than an imbert. If the gasifier is at the state where it is producing more pressure than the motor is taking this means oxygen will not be trapped in the hopper after loading. If the hopper is blowing smoke out vs drawing in air . If oxygen is trapped there might be a small burp.
But even on an imbert I’m sure it could be open for a little while.