It should be noted, they started putting the fuel pump in the tank just about the same time they stopped venting them so there is not really that much oxygen in a fuel tank. It is mostly just fuel vapor. If I would be afraid, it would be a cool tank that was almost empty. As the tank cooled and the fumes condensed it would pull in more air.
Just about the time you are totally convinced his is safe, you think about TWA 800.
