Crews at Fairchild Air Force Base are changing the way they handle petroleum fires to avoid contaminating the area's water supplies. The base has stopped using a pair of flame-smothering chemicals to protect ground water both on and off the installation. You would assume that with all the re-fueling that Fairchild does, the most likely contaminant out there would be gas for jet engines. But a more recent concern is two chemicals used to snuff out petroleum fires. When a B-52 crashed at Fairchild back in 1994, the fire department doused the flaming wreckage with foam. A lot more of the perfluorooctanesulfonic acid ended up on the ground when firefighters practiced using the foam.