One evening last fall in Heiskell, Tennessee, Michael Robinson was battling a house fire when he saw a fellow firefighter struggling to pick himself up off the ground. The man, who was wearing 70 pounds of gear, was delirious from heat and overexertion. Robinson rushed to his side, removed him from the area, and cooled him down as best he could with wet towels. Very slowly, the firefighter’s core temperature returned to normal, and eventually he recovered. But, Robinson says, the outcome could have been much worse.