Senior Airman David Skannal checks a photo ionization detector before inspecting inside the center wing fuel tank of a KC-135 Stratotanker Jan. 9 at March Air Reserve Base, Calif. The photo ionization detector is an atmospheric monitor used to evaluate the air inside fuel tanks. Airman Skannal is a fuel cell technician from the 452nd Maintenance Squadron. (U.S. Air Force photo/Val Gempis)