Airman 1st Class Michael Jackson, 36th Medical Operations Squadron Bioenvironmental Engineering technician, demonstrates how to secure a M50 gas mask at Andersen Air Force Base, Guam, Oct. 19, 2017. This process involves testing that each mask maintains a tight seal during several movements and breathing techniques. The mask is used during training and in chemical, biological, radiological and nuclear (CBRN) environments where air filtration may be required to breathe. (U.S. Air Force photo/Airman 1st Class Gerald R. Willis)