Spent the weekend reading about gas grills and propane. The only question that was left unanswered was was about oxygen flowing into the hose and back into the tank. Apparently it doesn't do so due to the pressure of the propane pushing out and not allowing oxygen in. But what about when the tank is running low on propane? Wouldn't the varying pressure or weak pressure allow oxygen to flow back into the tank? Just a bit paranoid about this being a possibility if a flame is lit while the tank's propane is finishing.