Mr. Brown and his wife said they had ridden out the tornado in a storm cellar, Iistening to the sound of screeching metal and smelling the odor of gas.

WSJ: After Oklahoma Tornadoes, Rescue Efforts Focus on Survivors

Aside from its unpleasant odor, the toxic gas-a natural byproduct of organic and inorganic wastes-can corrode metal.

FORBES: Germ Warfare