GRAND FORKS AIR FORCE BASE, N.D. – Staff Sgt. David Helmbrecht, 319th Security Forces Squadron, and his military working dog Avar search an office building for explosives during an exercise March 19. Military working dogs are trained to search for drugs, explosives or as patrol dogs. Some, like Avar, are trained as both an explosives detector and patrol dog (U.S. Air Force photo/Senior Airman James Croxon).