English: Lt. Col. Aaron B. Holland, director, Facilities Department, listens to the instructions of Sgt. William W. Patnode, Chemical Biological Radiological Nuclear chief, Headquarters Battalion, near the end of training during a Field Protective Mask Confidence Exercise at the base gas chamber Dec. 2. The required annual training helps Marines gain confidence in thier ability to use the protective mask. The chamber Dec. 2 was the first time many of the Marines trained with the new M50 Joint Service General Purpose gas mask .