Most fires can be put out by removing one of the four things necessary to keep it burning: fuel, oxygen, the chemical reaction that started it, or heat. This usually means dousing it with water for non-chemical or non-electrical fires, smothering it so it burns up all of the usable oxygen, or removing it from the heat source. But wouldn't it be terrifying if none of these worked? If a fire just kept burning "forever" no matter what?