Airman 1st Class Timothy Lawrence checks the protective mask of Senior Airman Karleigh Campbell. U.S. Air Force Airman 1st Class Timothy Lawrence (right), avionics test station and components apprentice, 28th Maintenance Squadron, checks the protective mask of Air Force Senior Airman Karleigh Campbell, temporary duty technician, Air Force Financial Services Center, during a chemical, biological, radiological, nuclear and explosive defense training class at Ellsworth Air Force Base, S.D., on Jan. 26, 2009. The mask protects the face, eyes and respiratory tract against all known chemical and biological agents. SHARE: Download: Full Size (0.05 MB) Credit: VIRIN: 372607-Q-ZSW28-835.jpg Photo Gallery